7. System of reproductive organs Reproduction is one of the most important functions of the body and ensures procreation. To perform functions related to reproduction, dogs use the reproductive apparatus. The reproductive apparatus of a male dog. The male reproductive system consists of

8. System of internal secretion organs Internal secretion organs are glands that produce and release special substances - hormones - directly into the blood. A characteristic feature of hormones is their ability to exert

Diseases of the digestive organs L. V. Panysheva Diseases of the digestive organs occupy one of the main places among non-contagious diseases of dogs. Puppies especially often suffer from indigestion after weaning from their mother. A range of infectious diseases such as

Examination of the digestive organs Observing the intake of food and drink, one can notice a number of abnormalities. Many diseases begin with a partial loss of appetite or its complete loss. Lack of appetite occurs with fever, infectious, invasive diseases,

Chapter VIII Digestive System Food and Nutrition I have always liked the expression “We are what we eat”; this applies to cats and dogs just as much as it does to humans. The digestive system primarily suffers from poor food; other organs - liver, pancreas

9.2. Digestion process Features of digestion in the stomach. The stomach is the most expanded part of the digestive system. It looks like a curved bag that can hold up to 2 liters of food. The stomach is located asymmetrically in the abdominal cavity: most of it is on the left, and the smaller part is on the left

10 - gums
11 - sublingual-maxillary fold
22 - language
30 - tooth enamel
31 - tooth crown

The tooth consists of dentin, enamel and cement.

Dentine- tissue that forms the basis of the tooth.
Dentin consists of a calcified matrix penetrated by dentinal tubules containing processes of odontoblast cells lining the tooth cavity. The intercellular substance contains organic (collagen fibers) and mineral components (hydroxyapatite crystals). Dentin has different zones that differ in microstructure and color.

Enamel- a substance covering dentin in the crown area. Consists of crystals of mineral salts oriented in a special way with the formation of enamel prisms. Enamel does not contain cellular elements and is not tissue. The normal color of enamel is from white to cream with a yellowish tint (distinguishable from plaque).

Cement- tissue covering dentin in the root area. The structure of cement is close to bone tissue. Consists of cementocyte and cementoblast cells and a calcified matrix. Nutrition of cement occurs diffusely from the periodontium.

Inside the tooth there is cavity, which is divided into coronal cavity And root canal, opening with the above about aperture of the tooth apex. Fills the dental cavity dental pulp, consisting of nerves and blood vessels immersed in loose connective tissue and providing metabolism in the tooth. Distinguish coronal And root pulp.

Gum- mucous membrane that covers the dental edges of the corresponding bones, tightly fused with their periosteum.
The gum covers the tooth in the neck area. It is abundantly supplied with blood (tendency to bleeding), but relatively poorly innervated. The grooved depression located between the tooth and the free edge of the gum is called the gingival sulcus.

The periodontium, alveolar wall and gums form supporting apparatus of the tooth - periodontium.

Periodontium- provides attachment of the tooth to the dental alveolus.
It consists of the periodontium, the wall of the dental alveoli and the gums. The periodontium performs the following functions: supporting and shock-absorbing, barrier, trophic and reflex.

CHANGE OF TEETH

A dog's teeth, like those of most mammals, are diphyodont type, that is, during the life of the animal there is one change of teeth: the first generation - temporary, or baby teeth replaced by second generation teeth - permanent. In dogs, only P1 teeth do not change; they erupt along with the baby teeth and remain permanent.

Table Timing of teething in dogs
(according to J. Hozgood et al., 2000).

Changing teeth (general X-ray)

TYPES OF TEETH

Dogs are heterodont animals, i.e. have teeth of different structures depending on the functions they perform. The following types of teeth are distinguished: incisors, fangs And permanent teeth: premolars (false, small molars), or premolars And truly indigenous, or molars that do not have milk precursors.

Teeth arranged in order in a row form topand lower dental arches (arcades) . The upper arcade is represented by 20, and the lower by 22 teeth (10 and 11 on each side, respectively).

Anatomy of the incisors of the upper arcade

Incisors

Between the margin and the canine of the upper arch, as well as the canine and the first premolar of the lower arch, there are spaces - diastemas, which ensure the closure of the canines.

The molars of each arcade increase in size distally to the largest secant teeth, also called predatory. Molars have a different structure on the upper and lower arches, and therefore their structure will be considered separately.

Premolars - 4 on each side.
P I - has 1 (rarely 2) crown tubercles and 1 root.
P 2.3 - the crown has 3 teeth: a large medial one and 2 smaller distal ones; the tooth has 2 roots - medial and distal;
P 4 - the crown has 3 tubercles: large medial
both distal and lesser lingual; There are 3 roots, they correspond to the tubercles in location.

Molars - 2 on each side. Their longitudinal axes are parallel to each other and perpendicular to the median plane.

M 1 - the crown has 6 tubercles: 2 large buccal, middle - lingual and 3 small between them. The tooth has 3 roots: powerful lingual
and 2 smaller buccal ones - medial and distal.
M 2 - the crown has 4-5 tubercles: 2 buccal (medial and distal) and 2-3 lingual. There are 3 roots, their location is similar to that of M 1.

P 1-4 are similar in structure to those of the upper arcade, with the exception of slightly longer and narrower roots.
The lower P 1 is sometimes referred to in the literature as a wolf tooth.

Molars- 3 on each side.

M 1 is the largest of the molars. The crown has 5 cusps: medial, 2 distal and 2 middle between them: powerful buccal
and a smaller lingual. 2 roots: medial and distal.

M 2 - the crown has 3-4 tubercles: 2 medial and 2 distal. The tooth has 2 roots, identical in size: medial and distal.

M 3 is the smaller of the molars; the crown usually has 1 or 2 cusps. There is one root, rarely two.

DENTAL FORMULA

Recording teeth in the form of a number series, where each number indicates the number of teeth of a certain type on one side of each arcade in the direction from the median plane is called dental formula.

The dental formula is:
baby teeth D: ICP/ICP
molars: P: IСРМ/IСРМ.

Dog teeth formulas:
D: 3130/3130
R: 3142/3143.
Thus, 28 milk teeth (here we should not take into account the first premolars, which are essentially permanent teeth, although they erupt with the milk shift) and 42 permanent teeth.

In medical dental practice, the dental formula is written according to the following scheme: D: PCI|ICP/PCI|ICP; R: МРCI|ICРМ/ МРCI|ICРМ the number of teeth is reflected in the entire arcade, and not just on one side. In this case, the dog’s dental formula will look like D: 313| 313/ 313|313; R: 2413|3142/3413|3143.

This form of recording the dental formula seems to be the most rational. Using this type of notation, you can briefly designate any arcade tooth. For example, the permanent lower left second premolar is designated as P|P2, the deciduous upper right tooth as DI1|-, or OP for short]. The entry D|Р1 is erroneous,
since there is no primary first premolar in dogs.

BITE
The closure of the dental arcades is called occlusion, or occlusion.

When the dog's jaws close, the upper incisors come in front of the lower ones in such a way that the lingual surfaces of the former are in free contact with the vestibular (vestibular) surface of the latter, and the fangs freely enter the corresponding diastema, forming a so-called lock. This occurs because the upper dental arcade is slightly wider than the lower one (anisognathous arcades). Teeth touching are called antagonists.

The bite can vary depending on the shape and size of the jaws and incisal bone, the direction of growth of the incisors and canines, which in turn is determined by the breed, type of constitution of the animal, age and other factors.

The physiological occlusion options are:

Orthognathia or the scissor bite described above. Characteristic for dogs with gentle, strong and strong rough types of constitution. Is normal for most breeds. With this type of bite, wear of the incisors occurs most slowly.

If the lower incisors are located behind the upper ones, but are separated from them at some distance, such a bite is called undershot.
In this case, the mesial surface of the upper canines and the distal surface of the lower canines are worn down due to friction.
Such a bite may be caused by abnormalities in bone development (elongated upper jaw and/or shortened lower jaw - microgenia) or dental growth. It is more common in dogs of dolichocephalic breeds with a sharp muzzle. It is found in puppies with a massive head in the cheekbones and a wide lower jaw in the branches. As a rule, with the completion of the formation of the skeleton, the bite in such puppies is restored to a scissor or straight bite.
For adult dogs of most breeds it is considered a defect, as it significantly complicates eating and reduces the animal’s performance. In addition, with underbite, the fangs of the lower jaw do not form a lock, but injure the palate.

Progenia or snack- The lower incisors are located in front of the upper ones. Significant shortening of the bones of the facial region with a normal or elongated lower jaw causes the advancement of not only the lower incisors, but also the canines - a bulldog bite. It is standard for breeds such as English and French bulldogs, pugs, boxers and some others, provided that the incisors and canines of the lower jaw do not protrude beyond the upper lip.

Straight bite (pincer-shaped)- the incisors touch the edges.
This bite is typical for dogs of coarse and coarse loose constitution types with a massive lower jaw. For some breeds, a direct bite is allowed by the standard unconditionally or from a certain age. For example, the FCI-335 standard for the Central Asian Shepherd Dog breed (came into force on March 22, 2000) states: “scissor bite, straight or close bite (without waste), regardless of age.” With a straight bite, the incisors grind down most quickly.

Gradual wear of enamel and dentin with age - physiological process. At correct bite Under physiological loads, adequate compensatory changes occur in the dental organ, ensuring the full functioning of worn teeth.

DATES FOR TEETH ABRASION

The timing of crown wear in dogs, as in other animals, depends on many factors. These include, first of all, bite. As stated above, with a scissor bite, grinding of the incisors and canines occurs much more slowly than with a straight (pincer) and other bite options.
We should not forget that in addition to the described types, there is a great variety of pathological forms of occlusion, in which the grinding of individual teeth occurs inappropriately for age.

Also, the intensity of crown abrasion is determined by feeding conditions, such as: consistency of food (dry or wet food); the depth of the dish from which the dog takes food, and the material from which it is made (does the dog have the ability to physiologically capture food and not injure its teeth). The habit of some dogs to chew and carry hard objects greatly affects the time it takes for the incisors and other teeth to wear down.

Special meaning for erasing teeth have individual characteristics microstructure and chemical composition of enamel and dentin. Such deviations can be either congenital (hereditary factor, use of teratogenic drugs in pregnant dogs, severe feeding disorders and diseases during pregnancy) or acquired (disease and other infectious diseases during the period of teeth change, taking tetracycline drugs in young animals, excess fluoride in the body (dental fluorosis), the use of aggressive chemicals (mineral acids) for treating the oral cavity, etc.

Taking into account the above factors, it becomes obvious that it is impossible to establish a strict relationship between the degree of abrasion of individual teeth and the age of the animal. The exception is animals under the age of 10-12 months, in which the order of eruption permanent teeth is quite stable, and after its completion (6-7 months) until 10-12 months, the final advancement of the crowns of permanent teeth into the oral cavity occurs.
Over 1 year, the correlation of erasure with age is very conditional.

Below are approximate dates changes in the dental apparatus in dogs.

Shamrocks begin to wear off at around 2 years of age. First, they are ground down on the lower incisors, by 3 years - on the upper hooks, by 4 years - on the middle ones, and by 5-6 years, trefoils, as a rule, are absent on all incisors, except for the upper edges.

From 5-6 to 10-12 years, the lower incisors move forward with varying intensity (the lower hooks are usually the first to move forward), the canines and large tubercles of the molars wear down.

In dogs older than 10-12 years, the crowns of the lower toes are usually almost completely worn out. The crowns of other teeth are slightly evenly ground down. If the animal does not suffer from periodontal disease (which is rare in dogs) home care), then natural tooth loss begins by the age of 14-17 years.

Note that with periodontitis and periodontal disease, complete loss of teeth can occur by the age of 8-10 years.

A more reliable criterion for determining the age of a dog is the relative size of the tooth cavity. With age, there is a gradual decrease in the cavity of the tooth until it is completely obliterated in old dogs. This parameter is practically not influenced by external and internal factors and can be the basis for the development of a method for determining age.
To determine the size of the tooth cavity, it is necessary to take an x-ray. Using this technique, it will be possible to determine the age from an x-ray or a section, having only one tooth at your disposal.

MECHANICAL DIGESTION

Digestion in the oral cavity occurs mainly mechanically; when chewing, large fragments of food are broken into pieces and mixed with saliva. Chewing is especially important for the absorption of plant-based ingredients, since nutrients are often encased in cellulose-containing membranes that are resistant to digestion. These membranes must be broken down before the nutrients inside can be used.

Mechanical digestion also increases the area exposed to digestive enzymes.

FOOT OF ORAL CAVITY

STRUCTURE

The floor of the oral cavity is covered with mucous membrane, located below the free surface of the tongue and on the sides of its body, it is a slit-like space under the sublingual mucosa. Sagittally, the floor of the mouth is divided by a fold of the frenulum of the tongue.

On the sides of the body of the tongue, the mucous membrane of the bottom with a thick submucosal layer forms folds into which multiple short ducts open sublingual salivary gland. Lateral to the frenulum of the tongue there are small sublingual (hunger) warts. They are the openings of the excretory ducts mandibular
and long duct sublingual salivary glands.

SALIVARY GLANDS

1 - parotid gland
2 - mandibular gland
3 - sublingual gland
7 - zygomatic gland

Maxillary (mandibular) salivary gland located behind the branch of the lower jaw, ventral to the parotid salivary gland, reaches the neck, where it lies between the maxillary veins.
It is large, oval in shape, yellowish-waxy in color and larger than the parotid gland. Its excretory ducts follow in the intermaxillary space over the premaxillary muscle medially from the sublingual salivary gland into the hungry warts. The gland secretes a serous mucous secretion.

Parotid salivary gland lies more ventral auricle, comparatively small sizes. The excretory duct passes across the masticatory muscle and opens into the buccal vestibule with a low salivary papilla.

Sublingual salivary gland lies under the mucous membrane on the sides of the body of the tongue. Divided into multi-channel, which big amount, the ducts open on the lateral surface of the sublingual fold, and single-duct- one duct - in a hungry wart. Produces a mucous secretion.

ENZYMATIVE DIGESTION

Saliva is secreted into the oral cavity by four pairs of salivary glands.
Typically, a small amount of saliva is present in the mouth, but the amount may be increased by the sight and smell of food. This effect, called the “taste reaction,” was first studied by academician I.P. Pavlov.

Salivation continues as food enters the oral cavity, and its effect is enhanced by the chewing process.
Saliva is 99% water, while the remaining 1% is mucus, inorganic salts and enzymes.
Mucus acts as an effective lubricant and promotes swallowing, especially dry food. Unlike humans, the saliva of cats and dogs lacks the starch-digesting enzyme amylase, which prevents the rapid hydrolysis of starch in the oral cavity.
The absence of this enzyme is consistent with the observed behavior of dogs, which tend to swallow without chewing all but the hardest pieces of food, and the behavior of cats, characteristic of carnivores, which tend to consume foods with a low starch content.

LANGUAGE

Language- a muscular, movable organ lying at the bottom of the oral cavity.

Language structure

The papillae of the mucous membrane of the tongue perform the function of a taste analyzer; its surface provides thermoregulation of the dog’s body, and also performs the function of touch.

Curving like a spoon, the tongue serves to receive water.

In terms of external shape, dogs' tongues are long, wide and thin. The skeleton of the tongue makes up the inner surface of the lower jaw, as well as the hyoid bone.

Language structure

2 - muscles of the tongue
3 - body of tongue
4 - root of tongue

In the language there are: root, body And top.

Root The tongue is located between the molars and is covered with the mucous membrane of the palatoglossal arch.
Body The tongue lies between the branches of the lower jaw; the back and lateral surfaces are distinguished on it. There are many papillae on the back. The dorsum of the tongue is concave and divided by a deep sagittal groove extending to the apex of the tongue. On the sides of the back, the lateral surfaces of the body of the tongue converge into its frenulum.

tip of tongue- its most mobile part, expanded and flattened, has a ventral surface free from the frenulum. The dorsal surface of the apex is noticeably wider than its dorsum.
In the thickness of the apex of the tongue lies a specific intralingual cartilage (a remnant of the intralingual bone), which supports the dog’s protruding tongue and helps with the intake of liquid food.

PAPIPLES OF THE TONGUE

The papillae of the tongue are divided into mechanical And taste.

Mechanical:

1. Thread-like
Cover the entire dorsal surface of the tongue, long, thin
and soft.
2. Conical
Located in the area of ​​the root of the tongue instead of threadlike ones.

Flavoring(contain taste nerve receptors - taste buds):

1. Mushroom
Scattered over the entire surface of the back of the tongue among the threadlike ones.
2. Roll-shaped (grooved).
They lie on the border of the body and the root of the tongue in 2-3 pairs. They are large, round in shape, with a groove around each one. In the latter, the mucous glands open.
3. Leaf-shaped
They lie on the sides of the root of the tongue in front of the palatoglossus arches. Oval in shape, 0.5 - 1.5 cm long, divided into segments - “leaves”. Contains serous-mucous glands.

GLANDS OF THE TONGUE

The glands of the tongue are parietal, they are scattered over the entire surface and edges of the tongue, lie deep in the mucous membrane, and secrete a mucous secretion.

MUSCLES OF THE TONGUE

The tongue is based on striated muscle tissue. Its muscle fibers are oriented in three mutually perpendicular directions: longitudinal (front to back), transverse (right to left) and oblique (top to bottom) and form differentiated muscles, which are divided into the muscles of the tongue and the hyoid bone.

The basis of the language is lingual muscle. It is built from vertical, oblique and longitudinal muscle fibers running from the hyoid bone to the tip of the tongue.
Function: changes the shape (thickness, length, width) of the tongue in different directions.

Lingual lateral muscle. It starts from the lateral surface of the middle segment of the hyoid bone and follows the lateral surface of the tongue to its apex.
Function: with bilateral action pulls the tongue back, with one-sided - turns it in the corresponding direction.

Sublingual - lingual muscle. It begins on the body and laryngeal horns of the hyoid bone, ends in the thickness of the tongue medially from the lateral lingual muscle, lateral from the genioglossus.
Function: pulls the tongue back, flattens the root of the tongue when swallowing.

Genioglossus muscle. It begins on the mental angle of the lower jaw and branches fan-shaped in the midsagittal plane from the apex to the middle of the body of the tongue.
Function: flattens the tongue, moves it forward.

MUSCLES OF THE HYPOGLOUS

The geniohyoid muscle is fusiform and runs from the chin of the lower jaw to the hyoid bone.
Function: pulls the hyoid bone and with it the tongue forward. Provides maximum extension of the tongue when lapping or licking.

Transverse premaxillary (hyoid) muscle. It extends from the mental angle of the lower jaw, along the dental edge along the line of its muscular attachment to the tendon suture of the submandibular space and ends on the body and large horns of the hyoid bone.
Function: raises the tongue when chewing. Presses back to the hard palate.

Stylohyoid muscle - from the greater and lesser horns of the hyoid bone.
Function: brings the branches together when swallowing.

Hornohyoid muscle - follows from the laryngeal horns of the hyoid bone to its lesser horns.
Function: pulls up named branches.

Hyoid retractor muscles - the sternohyoid and sternothyroid muscles retract the hyoid bone during swallowing.

2. Pharynx (Pharynx)

Throat - pharynx - a tube-shaped movable organ in which the digestive tract crosses, going through the pharynx from the oral cavity to the pharynx and further to the esophagus and the respiratory tract - through the choanae to the pharynx and further to the larynx.

1 - esophagus
2 - throat
4 - trachea
5 - larynx
6 – epiglottis

STRUCTURE

The pharyngeal cavity is divided into two different parts: the upper - respiratory - nasopharynx and the lower - digestive - (larynx), which are limited from each other by the velopharyngeal arch. The velopharyngeal arches converge before the beginning of the esophagus, forming the esophagopharyngeal border.

The respiratory part of the pharynx, located under the base of the skull, serves as a continuation of the nasal cavity behind the choanae. It is lined with single-layer columnar ciliated epithelium, while the digestive part is lined with squamous stratified epithelium. The pharyngeal openings of the auditory (Eustachian) tubes open into the lateral parts of the nasopharynx, which connect the nasopharynx with the tympanic cavity of the middle ear (pharyngitis can provoke otitis media).

The anterior section of the digestive part of the pharynx borders the pharynx, from which it is separated by the velum palatine and, thus, serves as a continuation of the oral cavity, and is therefore called the oral cavity. At the back, it abuts the anterior surface of the epiglottis. Then, located on top of the larynx, the pharynx continues back to the entrance
into the esophagus. This part of the digestive section of the pharynx is called the laryngeal part, since the entrance to the larynx opens into it from below. Thus the pharynx has 7 holes.

On the dorsal wall of the pharynx in the area of ​​the fornix is ​​the pharyngeal tonsil.

The pharynx is located between the middle segments of the hyoid bone, they cover the organ from the sides, and the upper (proximal) segments of the hyoid bone suspend it from the mastoid part of the petrous bone.
Contraction of the pharyngeal muscles underlies the complex swallowing act, which also involves the soft palate, tongue, larynx, and esophagus.

Radiography: X-ray control
performing endoscopy of the pharynx area

At the same time, the pharyngeal levators pull it upward, and the compressors consistently narrow its cavity backwards, pushing the food bolus into the esophagus. At the same time, the larynx also rises, the entrance to it is tightly covered by the epiglottis, due to pressure on it with the root of the tongue. In this case, the muscles of the soft palate pull it upward and caudally in such a way that the velum palatine lies on the velopharyngeal arches, separating the nasopharynx.
During breathing, the shortened velum palatine hangs obliquely downward, covering the pharynx, while the epiglottis, built of elastic cartilage, directed upward and forward, provides access to a stream of air into the larynx.

The outside of the pharynx is covered with connective tissue adventitia.
It is attached to the base of the skull through the basilar pharyngeal fascia.

The basis of the pharynx is made up of three pairs of constrictors (narrowers) and one dilator (dilator). These paired muscles form a middle sagittal tendon suture on the upper wall of the organ, extending from the velopharyngeal arch to the esophagus.

1. Cranial (rostral) constrictor of the pharynx - consists of paired muscles: velopharyngeal and pterygopharyngeal.

The velopharyngeal muscle makes up the lateral walls of the cranial part of the pharynx, as well as the velopharyngeal arch, starts from the palatine and pterygoid bones and ends at the tendinous pharyngeal suture.
Function: brings the mouth of the esophagus closer to the root of the tongue.

The pterygopharyngeal muscle tendinously begins on the pterygoid bone and ends in the caudal part of the pharynx. Merges with the velopharyngeal muscle.
Function: pulls the pharyngeal wall forward.
The main function of the anterior pharyngeal constrictor is to block the entranceinto the nasopharynx and expansion of the esophagus.

2. The middle constrictor of the pharynx (hypoglossal muscle) is formed by: the cartilaginous and oropharyngeal muscles (belong to the group of muscles of the hyoid bone) - it follows from the laryngeal horns of the hyoid bone to the tendon suture of the pharynx.
Function: pushes the food bolus towards the esophagus.

3. The caudal constrictor of the pharynx is formed by: the thyropharyngeal muscle, going from the thyroid cartilage of the larynx to the tendinous suture, and the annular pharyngeal muscle, going from the annular cartilage to the pharyngeal suture.
Function: pushes the food bolus towards the esophagus.

Pharyngeal dilator - follows from the medial surface of the middle segment of the hyoid bone under the middle and caudal constrictors to the lateral surface of the pharynx.
Function: expands posterior section pharynx after swallowing, narrows the nasopharynx.

3. Esophagus (Oesophagus)

Esophagus- is the initial part of the foregut
and in structure it is a typical tube-shaped organ. It is a direct continuation of the laryngeal part of the pharynx.

The mucous membrane of the esophagus along its entire length is collected
into longitudinal folds, which straighten as the food bolus passes. The submucosal layer contains many mucous glands that improve the sliding of food. The muscular lining of the esophagus is a complex multi-level striated layer.

STRUCTURE

The outer membrane of the cervical and thoracic parts of the esophagus is connective tissue adventitia, and the abdominal part is covered with visceral peritoneum. The attachment points of the muscle layers are: laterally - the arytenoid cartilages of the larynx, ventrally - its annular cartilage, and dorsally - the tendon suture of the larynx.

Schematic representation of the esophagus

Along the way, the diameter of the esophagus is uneven: it has 2 expansions and 2 narrowings. In medium-sized dogs, the diameter at the inlet is up to 4 cm, and at the outlet up to 6 cm. There are cervical, thoracic and abdominal parts of the esophagus.

The total length of the esophagus is on average 60 cm, and the average diameter of the collapsed esophagus is about 2 cm. Topographically, the esophagus is divided into cervical, thoracic and abdominal parts. The cervical part is long and makes up about half the length of the esophagus. Directly behind the pharynx, it is located above the semi-rings of the trachea
and under the prevertebral layer of the fascia of the neck (surface plate).

Then, at the level of the 4-6 cervical vertebrae, the esophagus makes a bend, descending to left side from the trachea, and follows into the entrance to the chest cavity. This feature of the topography allows you to avoid tension on the organ in the thoracic part during movements of the head and neck, at the same time, it should be taken into account during medical manipulations on the organ.

In the chest cavity in the mediastinum, the esophagus accompanies the trachea on the left, and then in the region of its bifurcation (bifurcation) again lies on the trachea. The thoracic part of the esophagus first passes over the base of the heart to the right of the aortic arch, then through the esophageal opening of the diaphragm, located at the level of the third intercostal space, slightly to the left. Behind the diaphragm, in the abdominal cavity, the short abdominal part of the esophagus forms the entrance to the stomach or cardiac opening (cardia).

FUNCTIONS

There is no secretion of digestive enzymes in the esophagus, however, the epithelial cells of the esophageal mucosa secrete mucus, which serves to lubricate the food coma during the process of peristalsis, automatic wave-like muscle contractions that are stimulated by the presence of food in the esophagus and ensure its movement through the digestive canal. The process of moving food from the mouth to the stomach takes only a few seconds.

4. Stomach (Ventriculus)

The dog's stomach is single-chamber, intestinal type. It is an extension of the digestive tube behind the diaphragm.

Appearance of an isolated stomach

1 - pyloric part of the stomach
2 - cardiac part of the stomach
3 - fundic part of the stomach
4 - exit of the duodenum
5 - cardial opening (entrance of the esophagus)

The external ventral flexure of the stomach is commonly called great curvature, and the dorsal small bend between the entrance and exit from the stomach is small curvature. The anterior surface of the stomach between the lesser and greater curvatures faces the diaphragm and is called diaphragmatic, and the opposite posterior surface is called visceral. It faces the intestinal loops.

From the outside great curvature the greater omentum is attached to the stomach - gastric mesentery. It is very extensive, covering the entire intestine up to the hypogastrium like an apron and forming an omental sac. On the left surface of the greater curvature, in the fold of the omental sac, the spleen is adjacent to the stomach.
It is connected to the greater curvature of the stomach gastrosplenic ligament, in which numerous vessels are located. This ligament is a continuation of the mesentery of the stomach - the greater omentum.

The entrance to the omental sac is located between the caudal vena cava and the portal vein of the liver, medial to the right kidney. Small seal located on the lesser curvature, it is short and consists of gastrohepatic ligament. In the cranial direction it merges with esophagohepatic ligament, and in the caudal - with hepatoduodenal ligament. The above ligaments, in addition to the gastrosplenic ligament, perform only a mechanical function.

Endoscopy: appearance stomach is normal

Endoscopy: appearance of the stomach.
Ulcerative gastritis

(various projections)

TOPOGRAPHY OF THE STOMACH

The stomach is located in the left hypochondrium in the region of the 9th - 12th intercostal space and the xiphoid cartilage (epigastrium); when filled, it can extend beyond the costal arch and descend onto the ventral abdominal wall.

In large dogs, this anatomical feature underlies the pathogenesis of non-contagious diseases of the stomach - its acute dilatation or volvulus.

PARTS OF THE STOMACH

It is customary to distinguish three parts of a single-chamber stomach: cardiac, fundus (fundic), pyloric, which differ not only in structure, but also in the specialization of the glands. The cardial part of the stomach is thicker and less blood-supplied compared to its other parts; this fact must be taken into account when performing surgical interventions.

The cardiac part is an extension behind the entrance
into the stomach and makes up 1/10 of the area of ​​its greater curvature. The mucous membrane of the cardiac part of the intestinal type is pinkish in color, rich in parietal cardiac glands, which secrete a serous-mucosal secretion of an alkaline reaction.

The middle part of the stomach behind the pars cardia on the side of the greater curvature is called the fundus of the stomach. It is the main part of the stomach where food is deposited in layers. There is located bottom gland zone(aka functional or bottom). In dogs, it occupies the left half of the greater curvature of the stomach.

The zone of the fundic glands is distinguished by a dark coloration of the mucosa, and is also equipped with gastric pits - the mouths of the parietal glands. The right half of the stomach is occupied zone of pyloric glands. The gastric mucosa, when unfilled, is gathered into folds. Only in the area of ​​lesser curvature are they oriented from the entrance to the stomach to the pylorus.

The pyloric part of the dog's stomach has a powerfully developed constrictor (narrower), which circumferentially covers it 5 - 7 cm from the entrance to the duodenum and ensures the evacuation of food from the stomach to the intestine.

MININGS OF THE STOMACH

The mucous membrane is white, lined with stratified squamous epithelium, collected in numerous longitudinal folds. The well-developed submucosal layer contains mucous glands.

The muscular lining of the stomach is made of smooth muscle tissue and has three layers of fibers: longitudinal, circular and oblique.

Longitudinal fiber layer thin follows from the esophagus to the pylorus. Circular layer located predominantly in the bottom
and pyloric parts of the stomach. It forms the pyloric constrictor.

Oblique layer predominates in the left half of the stomach; in the area of ​​the circular layer it doubles (into internal and external).

The serous membrane of the stomach passes from the lesser curvature into the lesser omentum, and from the greater curvature into the splenic ligament and greater omentum.

EMBRYOLOGY

During embryonic development, the stomach, as part of a straight digestive tube, undergoes two 180-degree rotations. One in the frontal plane counterclockwise and the other in the segmental plane.

FUNCTIONS

The stomach performs several functions:

It serves to temporarily store food and controls the rate at which food enters the small intestine

The stomach also secretes enzymes necessary for the digestion of macromolecules

The stomach muscles regulate motility, allowing food to move caudally (away from the mouth), and aid digestion by mixing and grinding food.

The dog's stomach is large in size; its maximum volume can approach the volume of the entire large and small intestines. This is due to the dog’s irregular feeding and eating food “for future use.”
It is known that a dog can also use its stomach as a temporary reservoir for storing food: for example, when feeding older puppies, the bitch regurgitates the food she has obtained for them.

PHASES OF STOMACH SECRETION

Gastric secretion is regulated by complex processes of nervous and hormonal interaction, thanks to which it is carried out at the right time and in the required volume. The secretion process is divided into three phases: cerebral, gastric and intestinal.

Brain phase

The medullary phase of secretion is initiated by the anticipation of food intake and the sight, smell and taste of food, which stimulates the secretion of pepsinogen, although gastrin and hydrochloric acid are also released in small quantities.

Gastric phase

The gastric phase is initiated by mechanical stretching of the gastric mucosa, a decrease in acidity, as well as products of protein digestion. In the gastric phase, the main secretion product is gastrin, which also stimulates the secretion of hydrochloric acid, pepsinogen and mucus. Gastrin secretion slows down sharply if the pH drops below 3.0 and may also be controlled by peptic hormones such as secretin.
or enteroglucagon.

Intestinal phase

The intestinal phase is initiated by both mechanical distension of the intestinal tract and chemical stimulation with amino acids and peptides.

5. Small intestine (Intestinum tenue)

STRUCTURE

The small intestine is a narrowed section of the intestinal tube.

The small intestine is very long, representing the main part of the intestine and ranges from 2.1 to 7.3 meters in dogs. Suspended on a long mesentery, the small intestine forms loops that fill most of the abdominal cavity.

The small intestine emerges from the end of the stomach and is divided into three different sections: the duodenum, the jejunum, and the ileum. The duodenum accounts for 10% of the total length of the small intestine, while the remaining 90% of the length of the small intestine consists of the jejunum and ileum.

BLOOD SUPPLY

The wall of the thin section is richly vascularized.

Arterial blood flows through the branches abdominal aorta- the cranial mesenteric artery, and to the duodenum also via the hepatic artery.

Venous drainage occurs in the cranial mesenteric vein, which is one of the roots of the portal vein of the liver.

Lymphatic drainage from the intestinal wall occurs from the lymphatic sinuses of the villi and intraorgan vessels through the mesenteric (intestinal) lymph nodes into the intestinal trunk, which flows into the lumbar cistern, then into the thoracic lymphatic duct and cranial vena cava.

INNERVATION

The nervous supply of the thin section is represented by branches vagus nerve and postganglionic fibers of the solar plexus from the semilunar ganglion, which form two plexuses in the intestinal wall: intermuscular (Auerbach) between the layers of the muscular layer and submucosal (Meissner) in the submucosal layer.

Control of intestinal activity by the nervous system is carried out both through local reflexes and through vagal reflexes involving the submucosal nerve plexus and intermuscular nerve plexus. Intestinal function is regulated by the parasympathetic nervous system, the center of which is its medulla oblongata, from where the vagus nerve (10th pair of cranial nerves, respiratory-intestinal nerve) extends to the small intestine. Sympathetic vascular innervation regulates trophic processes in the small intestine.

TOPOGRAPHY

The thin section begins from the pylorus of the stomach at the level of the 12th rib, is covered ventrally by the leaves of the greater omentum, and is limited dorsolaterally by the thick section. There are no clear boundaries between the sections of the small intestine, and the identification of individual sections is mainly topographical in nature.

Only the duodenum is most clearly distinguished, which is distinguished by its large diameter and topographic proximity to the pancreas.

Contrast barium radiography of the small intestine

MININGS OF THE INTESTINAL

DEFINITION

The functional features of the small intestine leave an imprint on its anatomical structure. There are mucous membrane and submucosal layer, muscle (external longitudinal and internal transverse muscles) And serosa intestines.

INTESTINAL MUCOSA

The mucous membrane forms numerous devices that significantly increase the absorption surface.
These devices include circular folds, or Kirkring folds, in the formation of which not only the mucous membrane is involved, but also the submucosal layer and villi, which give the mucous membrane a velvety appearance. The folds cover 1/3 or 1/2 of the circumference of the intestine. The villi are covered with a special bordered epithelium, which carries out parietal digestion and absorption. The villi, contracting and relaxing, perform rhythmic movements with a frequency of 6 times per minute, due to which they act as a kind of pumps during suction.

In the center of the villus there is a lymphatic sinus, which receives fat processing products. Each villus from the submucosal plexus contains 1-2 arterioles, which break up into capillaries. Arterioles anastomose with each other and during absorption all capillaries function, while during a pause there are short anastomoses. Villi are thread-like outgrowths of the mucous membrane, formed by loose connective tissue rich in smooth myocytes, reticulin fibers and immunocompetent cellular elements, and covered with epithelium.
The length of the villi is 0.95-1.0 mm, their length and density decreases in the caudal direction, that is, in the ileum the size and number of villi are much smaller than in the duodenum and jejunum.

HISTOLOGY

The mucous membrane of the thin section and villi is covered with a single-layer columnar epithelium, which contains three types of cells: columnar epithelial cells with a striated border, goblet exocrinocytes (secrete mucus) and gastrointestinal endocrinocytes.

The mucous membrane of the thin section is replete with numerous parietal glands - the common intestinal, or Lieberkühn's glands (Lieberkühn's crypts), which open into the lumen between the villi. The number of glands averages about 150 million (in the duodenum and jejunum there are 10 thousand glands per square centimeter of surface, and 8 thousand in the ileum).

The crypts are lined with five types of cells: epithelial cells with a striated border, goblet glandulocytes, gastrointestinal endocrinocytes, small borderless cells of the crypt bottom (stem cells of the intestinal epithelium) and enterocytes with acidophilic granules (Paneth cells). The latter secrete an enzyme involved in the breakdown of peptides and lysozyme.

LYMPHOID FORMATIONS

The duodenum is characterized by tubular-alveolar duodenal, or Bruner's glands, which open into crypts. These glands are a continuation of the pyloric glands of the stomach and are located only on the first 1.5-2 cm of the duodenum.

The final segment of the thin section (ileum) is rich in lymphoid elements, which lie in the mucous membrane at different depths on the side opposite to the attachment of the mesentery, and are represented by both single (solitary) follicles and their clusters in the form of Peyer's patches.
Plaques begin in the final part of the duodenum.

The total number of plaques is from 11 to 25, they are round or oval in shape, length from 7 to 85 mm, and width from 4 to 15 mm.
The lymphoid apparatus takes part in the digestive processes.
As a result of the constant migration of lymphocytes into the intestinal lumen and their destruction, interleukins are released, which have a selective effect on the intestinal microflora, regulating its composition and distribution between the thin and thick sections. In young organisms, the lymphoid apparatus is well developed, and the plaques are large.
With age, a gradual reduction of lymphoid elements occurs, which is expressed in a decrease in the number and size of lymphatic structures.

MUSCULAR TRANSCRIPT

The muscular coat is composed of two layers of smooth muscle tissue: longitudinal And circular, and the circular layer is better developed than the longitudinal one.

The muscularis propria provides peristaltic movements, pendulum movements, and rhythmic segmentation that propel and mix the intestinal contents.

SEROSA

The serous membrane - the visceral peritoneum - forms the mesentery, on which the entire thin section is suspended. At the same time, the mesentery of the jejunum and ileum is better expressed, and therefore they are combined under the name mesenteric colon.

FUNCTIONS OF THE SMALL INTESTINE

In the small intestine, food digestion is completed under the action of enzymes produced by the wall (liver and pancreas) and parietal (Lieberkühn and Brunner) glands, absorption of digested products into the blood and lymph, and biological disinfection of incoming substances.
The latter occurs due to the presence of numerous lymphoid elements enclosed in the wall of the intestinal tube.

The endocrine function of the thin section is also great, which consists in the production of some biologically active substances by intestinal endocrinocytes (secretin, serotonin, motilin, gastrin, pancreozymin-cholecystokinin, etc.).

PARTS OF THE SMALL INTESTINE

It is customary to distinguish three sections of the thin section: the initial segment, or duodenum, the middle segment, or jejunum, and the final segment, or ileum.

DUODENUM

Structure
The duodenum is the initial section of the thin section, which is connected to the pancreas and the common bile duct and has the form of a loop facing caudally and located under the lumbar spine.

The length of the intestine is on average 30 cm or 7.5% of the length of the thin section. This section of the thin section is characterized by the presence of duodenal (Bruner's) glands and a short mesentery, as a result of which the intestine does not form loops, but forms four pronounced convolutions.

Barium contrast radiography
duodenum:

Topography
The cranial part of the intestine forms S-shaped, or sigmoid gyrus, which is located in the pylorus region, receives the ducts of the liver and pancreas and rises dorsally along the visceral surface of the liver.

Under the right kidney, the intestine makes a caudal turn - this cranial gyrus of the duodenum, and goes to descending part, which is located in the right iliac. This part passes to the right of the root of the mesentery and under the 5-6 lumbar vertebrae passes to the left side transverse part, dividing the mesentery into two roots in this place, and forms caudal gyrus of the duodenum.

The intestine is then directed cranial to the left of the mesenteric root as ascending part. Before reaching the liver, it forms duodejejunal gyrus and passes into the jejunum. Thus, a narrow loop of the anterior root of the mesentery is formed under the spine, containing the right lobe of the pancreas.

JEJUNUM

Structure
The jejunum is the longest part of the small section and is about 3 meters, or 75% of the length of the small section.
The intestine got its name due to the fact that it has a half-dormant appearance, that is, it does not contain voluminous contents. The diameter exceeds the ileum located behind it and is distinguished by a large number of vessels passing through a well-developed mesentery.
Due to its considerable length, developed folds, numerous villi and crypts, the jejunum has the largest absorption surface, which is 4-5 times greater than the surface of the intestinal canal itself.

Topography
The intestine forms 6-8 skeins, which are located in the region of the xiphoid cartilage, the umbilical region, the ventral part of both ilia and the groins.

ILEUM

Structure
The ileum is the final part of the thin section, reaching a length of about 70 cm, or 17.5% of the length of the thin section. Externally, the intestine is no different from the jejunum. This section is characterized by the presence of a large number of lymphoid elements in the wall. The final section of the intestine has thicker walls and the highest concentration of Peyer's patches. This section runs straight under the 1st-2nd lumbar vertebrae from left to right and in the area of ​​the right ilium flows into the cecum, connecting with it by a ligament. At the point where the ileum enters the cecum, the narrowed and thickened part of the ileum forms ileo-cecal valve, or ileal papilla, which has the appearance of a relief ring-shaped damper.

Topography
This section of the small intestine received its name due to its topographic proximity to the iliac bones, to which it is adjacent.

WALL GLANDS. LIVER.

Liver- the largest gland in the body, it is a parenchymal organ of dark red color, weighing 400-500 g, or 2.8-3.4% of body weight.

Five tubular systems are formed in the liver:
1) bile ducts;
2) arteries;
3) branches of the portal vein (portal system);
4) hepatic veins (caval system);
5) lymphatic vessels.

STRUCTURE OF A DOG'S LIVER

The shape of the liver is irregularly rounded with a thickened dorsal margin and sharp ventral and lateral margins. The pointed edges are dissected ventrally by deep grooves into lobes. The surface of the liver is smooth and shiny due to the peritoneum covering it, only the dorsal edge of the liver is not covered with peritoneum, which in this place passes onto the diaphragm, and thus is formed extraperitoneal field liver.

Under the peritoneum there is a fibrous membrane. It penetrates the organ, divides it into lobes and forms perivascular fibrous capsule(Glisson's capsule), which surrounds bile ducts, branches of the hepatic artery and portal vein.

The anterior surface of the liver - the diaphragmatic surface - enters the niche formed by the dome of the diaphragm, and the posterior surface - the visceral surface is in contact with organs located in the vicinity of the liver.

The dorsal margin has two notches: on the left - esophageal depression, and on the right - vena cava gutter. Located on the ventral edge cutting of the round ligament. In the center visceral surface located surrounded by connective tissue gate of the liver- this is the place where the vessels and nerves penetrate, where the common bile duct exits and where the hepatic lymph nodes lie.

The falciform ligament, which is a duplicate of the peritoneum passing from the diaphragm to the liver, is a continuation round ligament- remnant of the umbilical vein, divides the liver into two lobes: right- large and left- smaller. Thus, the entire portion of the liver located to the right of the round ligament is the right lobe.

On the right side of the liver lies the gallbladder. The area of ​​the liver between the gallbladder and the round ligament is middle share. The middle lobe of the portal of the liver is divided into two sections: the lower one is called square fraction, and the top one is caudate lobe. The latter consists of caudate process, which has renal depression, And mastoid process, which occupies the lesser curvature of the stomach. Finally, the left and right lobes are divided
into two parts each: lateral and medial.

Thus, the liver has six lobes: right lateral, right medial, left lateral, left medial, quadrate and caudate.

The liver is a polymer organ in which several structural and functional elements can be distinguished: hepatic lobule, sector (a section of the liver supplied by a branch of the portal vein of the 2nd order), segment (section of the liver supplied by a branch of the portal vein of the 3rd order), hepatic acinus (adjacent sections two adjacent lobules) and the portal hepatic lobule (areas of three adjacent lobules).

The classic morphofunctional unit is the hepatic lobule, which is hexagonal in shape, located around the central vein of the hepatic lobule.

The hepatic artery and portal vein, having entered the liver, are repeatedly divided into lobar, segmental, etc. branches all the way
before interlobular arteries and veins, which are located along the lateral surfaces of the lobules along with interlobular bile duct, forming hepatic triads. From these arteries and veins branches arise that give rise to sinusoidal capillaries, which flow into the central veins of the lobule.

The lobules consist of hepatocytes, which form trabeculae in the form of two cellular cords. One of the most important anatomical features The liver function is that, unlike other organs, the liver receives blood from two sources: arterial blood through the hepatic artery, and venous blood through the portal vein.

BILIARY TRACT AND BILE FORMATION

One of the most important functions of the liver is the process of bile formation, which led to the formation of the bile ducts. Between the hepatocytes that form the lobules, there are bile ducts that flow into the interlobular ducts, which, in turn, form two hepatic duct, coming out of each lobe: right and left. Merging, these ducts form the common hepatic duct.

The gallbladder is a reservoir for bile, in which bile thickens 3-5 times, since it is produced more than is required for the digestion process. The color of gallbladder bile in dogs is red-yellow.

The bladder lies on the quadrate lobe of the liver high from its ventral edge and is visible from both the visceral and diaphragmatic surfaces. The bubble has bottom, body And neck. The wall of the bladder is formed by the mucous membrane, a layer of smooth muscle tissue and is covered on the outside by peritoneum, and the part of the bladder adjacent to the liver is made up of loose connective tissue. The cystic duct originates from the bladder and contains spiral fold.

As a result of the fusion of the cystic duct and the common hepatic duct, the common bile duct is formed, which opens
into the S-shaped gyrus of the duodenum next to the pancreatic duct at the apex major papilla duodenum. At the point where it enters the intestine, the duct has bile duct sphincter(sphincter of Oddi).

Thanks to the presence of the sphincter, bile can flow directly into the intestines (if the sphincter is open) or into the gallbladder (if the sphincter is closed).

TOPOGRAPHY OF THE LIVER

The liver is located in front of the stomach and is in contact with diaphragm. Lies almost symmetrically in both hypochondriums. Caudal edge The liver corresponds to the costal arch; only in old animals the liver can protrude beyond the costal arch.
On X-ray and ultrasound examination, the distance between the caudal edge of the liver and the diaphragm should be five times the length of the second lumbar vertebra.

The liver is held in its position by the ligamentous apparatus, which includes round ligament liver - connects the ventral edge of the liver with umbilical ring, the connection continues in falciform ligament, attaching the liver to the diaphragm; the liver is also connected to the diaphragm using the coronary ligament, the left triangular ligament; The liver is connected to the right kidney by the hepatorenal ligament, to the stomach by the hepatogastric ligament, and to the duodenum by the hepatoduodenal ligament.

The liver receives blood supply through the hepatic arteries and portal vein, and venous outflow occurs through the hepatic veins into the caudal vena cava.

The innervation of the liver is provided by the vagus nerve through the extra- and intramural ganglia and the sympathetic hepatic plexus, represented by postganglionic fibers from the semilunar ganglion. The phrenic nerve takes part in the innervation of the peritoneum covering the liver, its ligaments and the gallbladder.

LIVER FUNCTIONS

The liver is a multifunctional organ that takes part in almost all types of metabolism, plays a barrier and disinfecting role, is a depot of glycogen and blood (up to 20% of blood is deposited in the liver), and performs a hematopoietic function in the embryonic period.

The digestive function of the liver is reduced to the process of bile formation, which promotes the emulsification of fats and the dissolution of fatty acids and their salts. Dogs secrete 250-300 ml of bile per day.

Bile is a mixture of bicarbonate ions, cholesterol, organic metabolites and bile salts. The basis on which bile salts work is fat. Bile salts break down large fat particles into small droplets, which interact with various lipases.

Bile also serves to excrete organic residues, such as cholesterol and bilirubin, during the breakdown of hemoglobin. Liver cells produce bilirubin from the blood and actively secrete it into bile. It is due to this pigment that bile acquires its yellow color.

Three-dimensional structure of a bile salt
indicating the polar and non-polar sides

WALL GLANDS. PANCREAS

The pancreas is a large, loose parenchymal organ, consisting of individual lobules united by loose connective tissue. By weight, iron is 30-40 g, or 0.20-0.25% of body weight, and the color is pale pink.

According to the structure of the iron, it belongs to the complex tubular-alveolar glands of mixed secretion. The gland does not have clear contours, since it does not have a capsule, is stretched along the initial section of the duodenum and the lesser curvature of the stomach, covered with peritoneum ventro-caudally, the dorsal part is not covered with peritoneum.

The pancreas consists of exocrine lobules and endocrine parts.

Anatomically, the gland is divided into body, which is located in the S-shaped gyrus of the duodenum, left the lobe or gastric lobe, which is adjacent to the lesser curvature of the stomach, lies in the duplicate of the omentum and reaches the spleen and left kidney, and right lobe, or duodenal blade, which lies in the duplicate of the mesentery of the duodenum and reaches the right kidney.

In dogs, the right lobe is highly developed, so the gland has an elongated (ribbon-like) shape bent at an angle. The gland has a main (virzung) pancreatic duct, which leaves the body of the gland and opens next to the bile duct at the top of the duodenal papilla (sometimes the duct may be absent),
and 1-2 accessory (Santorini) ducts, which open at a distance of 3-5 cm from the main one.

The blood supply to the gland is provided by the branches of the splenic, hepatic, left gastric and cranial mesenteric arteries, and venous outflow occurs into the portal vein of the liver.

Innervation is carried out by branches of the vagus nerve and the sympathetic plexus of the pancreas (postganglionic fibers from the semilunar ganglion).

FUNCTIONS OF THE PANCREAS

The pancreas is responsible for both exocrine and endocrine functions, but in the context of this section, only exocrine digestive functions are considered.
The exocrine pancreas is responsible for secreting digestive secretions and large volumes of sodium bicarbonate ions, which neutralize the acidity of the chyme that comes from the stomach.

Secretion products:

Trypsin: Breaks down whole and partially digested proteins into peptides of various sizes, but does not cause the release of individual amino acids.
- chymotrypsin: breaks down whole and partially digested proteins into peptides of various sizes, but does not cause the release of individual amino acids.
- carboxypeptidases: cleaves individual amino acids from the amino terminus of large peptides.
- aminopeptidases: cleaves individual amino acids from the carboxyl end of large peptides.
- pancreatic lipase: hydrolyzes neutral fat into monoglycerides and fatty acid.
- pancreatic amylase: hydrolyzes carbohydrates, converting them into smaller di- and trisaccharides.

6. Large intestine (Intestinum crassum)

The large intestine is the final section of the intestinal tube, averages 45 cm in length and is divided into the cecum, colon and rectum. It has a number of characteristic features, which include relative shortness, volume, low mobility (short mesentery), and the presence of a blind outgrowth - the cecum - on the border with the thin section.

1 - stomach
2, 3, 4, 5 - duodenum
6 - jejunum
7 - ileum
8 - cecum
9, 10, 11 - colon
12 - rectum

The blood supply to the colon is provided by the branches of the cranial and caudal mesenteric arteries, and the rectum is supplied by three rectal arteries: cranial(branch of the caudal mesenteric artery), middle and caudal(branches of the internal iliac artery).

Venous drainage from the cecum, colon and cranial portion of the rectum occurs into the portal vein of the liver. From the middle and caudal portions of the rectus cat into the caudal vena cava, bypassing the liver.

Innervation of the thick section is provided by branches vagus(transverse position of the colon) and pelvic nerves(blind, most of the colon and rectum). The caudal part of the rectum is also innervated by the somatic nervous system through the pudendal and caudal rectal nerves of the sacral spinal plexus. Sympathetic innervation is carried out through the mesenteric and rectal plexuses, which are formed by postganglionic fibers of the semilunar and caudal mesenteric ganglia.

Muscle control from the nervous system is carried out both through local reflexes and through vagal reflexes involving the submucosal nerve plexus and the intermuscular nerve plexus, which is located between the circular and longitudinal muscle layers. Normal bowel function is regulated by the parasympathetic nervous system. Control is directed from the medullary part of the vagus nerve to the anterior part and from the nuclei sacral region spine
through pelvic nerve To peripheral department large intestine.

The sympathetic nervous system (control directed from the ganglia in the paravertebral sympathetic trunk) plays a less important role. The processes of local control and coordination of motility and secretion of the intestine and associated glands are of a complex nature, involving nerves, paracrine and endocrine chemicals. The nervous supply of the small section is represented by branches of the vagus nerve and postganglionic fibers of the solar plexus from the semilunar ganglion, which form two plexuses in the intestinal wall: intermuscular (Auerbach's) between the layers of the muscular layer and submucosal (Meissner) in the submucosal layer.

Control of intestinal activity by the nervous system is carried out both through local reflexes and through vagal reflexes involving the submucosal nerve plexus and intermuscular nerve plexus.
Bowel function is regulated by the parasympathetic nervous system. Control is directed from the medullary portion of the vagus nerve to the small intestine. The sympathetic nervous system (control directed from the ganglia in the paravertebral sympathetic trunk) plays a less important role.
The processes of local control and coordination of motility and secretion of the intestine and associated glands are of a more complex nature; nerves, paracrine and endocrine chemicals take part in them.

The loops of the large intestine are located in the abdominal and pelvic cavities.

MEMBRANES OF THE LARGE INTESTINE

The structure of the colon consists of several layers: mucous membrane, submucosal layer, muscular layer (2 layers - outer longitudinal layer and inner circular layer) and serosa.

The epithelium of the cecum does not contain villi, but has numerous goblet cells on the surface that secrete mucus.

The mucous membrane does not have villi or circular folds, which is why it is smooth. Villi are present only in the embryonic state and disappear soon after birth. This is sometimes observed in some dogs in the first days of life, and in most individuals by the end of the second week.

The following types of cells are distinguished in the mucous membrane: intestinal epithelial cells with a striated border, goblet enterocytes, borderless enterocytes - the source of restoration of the mucous membrane, and single intestinal endocrinocytes. Paneth cells, present in the small intestine, are absent in the large intestine.

The intestinal (Lieberkühn) glands are well developed, lie deep and close to each other, and there are up to 1000 glands per 1 cm2.

The openings of the liberkühn glands give the mucous membrane an uneven appearance. In the initial part of the thick section, there is an accumulation of lymphoid elements that form plaques and lymphatic fields. An extensive field is located in the cecum at the confluence of the ileum, and plaques are located on the body of the cecum and at its blind end.

The muscular layer in the thick section is well developed, which gives the entire thick section a thick appearance.

FUNCTIONS OF THE THICK SECTION

Undigested food debris enters the large intestine and is exposed to the microflora inhabiting the large intestine. The digestive capacity of the large intestine of dogs is negligible.

Some excreta (urea, uric acid) and salts of heavy metals, water is intensively absorbed mainly in the initial part of the colon. The thick section is functionally more an organ of absorption and excretion than of digestion, which leaves an imprint on its structure.

PARTS OF THE LARGE INTESTINE

The large intestine consists of three main parts: cecum, colon And rectum.

CECUM

Structure
The cecum is a blind outgrowth at the border of the thin and thick sections. The iliac foramen is well marked and represents an obturator mechanism.
The exit cecumcolic opening is not clearly defined and does not have a locking mechanism. The cecum in dogs is greatly reduced. It has the appearance of a convoluted appendage, making from 1 to 3 curls, its walls are enriched with lymphoid elements, but the intestine does not have a vermiform appendage, characteristic of higher primates. Depending on the size and number of curls, 5 types of dog cecum can be distinguished.

Topography
The intestine hangs on the mesentery on the right in the lumbar region under the 2-4 lumbar vertebrae, its length ranges from 2 to 16 cm, or 11% of the length of the thick section.

The cecum forms a pouch, closed at one end, located below the junction of the large and small intestine. In cats, the cecum is a vestigial organ, while in dogs the size of the cecum is significant.

COLON

Structure
The colon makes up the main volume of the thick section.
It reaches about 30 cm in length, or 66.7% of the total length of the thick section. The intestine is very narrow (narrower than the duodenum), but thick-walled. The shape forms a rim located in the frontal plane, under the spine, which in appearance resembles a horseshoe.
The colon consists of three relatively straight sections: the ascending colon, the transverse colon
and the descending colon, which continues into the rectum.

Topography
The colon begins on the right in the lumbar region and runs in the dorsal part of the right ilium in a straight line to the diaphragm as the ascending colon.
Behind the diaphragm (in the hypochondrium) it forms a transverse bend - the transverse colon and, moving to the left side, runs caudally in the dorsal part of the left iliac as the descending colon. Having reached the left groin, the sigmoid colon forms a sigmoid bend and passes into the rectum.

RECTUM

Structure
The rectum is the final segment of the large intestine. The length of the rectum is about 10 cm, or 22.2% of the length of the colon. The intestine is suspended on the mesentery, and in the pelvic cavity it is surrounded by loose connective tissue (pararectal tissue).

In the pelvic cavity, the intestine forms a poorly developed ampulla.
The rectum has smooth, elastic and thick walls, with a uniformly developed muscle layer. The mucous membrane is collected in longitudinal folds and contains modified Lieberkühn glands and numerous mucous glands that secrete large amounts of mucus.
There are many venous plexuses in the submucosal layer, due to which water and aqueous solutions from the rectum are well and quickly absorbed.

Topography
Lies under the sacrum and the first caudal vertebrae, ending with the anus.

Anus
The perineal part of the rectum is called the anal canal. The mucous membrane of the rectum 2-3 cm before the anus ends with the anorectal line, caudal from which the stratified squamous epithelium begins. In this area, two ring-shaped zones are formed. The inner zone is called the columnar zone of the anus, the longitudinal folds of which are called the anal columns. Between them, depressions are formed - anal sinuses, in which mucus secreted by the anal glands accumulates.

The outer zone is called the intermediate zone, which is separated from the skin zone of the anus by the anal cutaneous line.
In the latter, the circumferential glands and paranal sinuses open. The rectum and anus have their own muscular apparatus, which in the anal area is represented by two sphincters: external and internal. The first is an accumulation of smooth muscle tissue around the anus, formed from the muscular layer of the rectum, and the second is striated muscle. Both sphincters function synchronously.

A number of muscles extend from the anus to the sides:

The rectal-tail muscle is represented by a longitudinal layer of the rectal musculature, which passes from the walls of the rectum to the first caudal vertebrae;
- levator anus - originates from the ischial spine and goes from the side of the rectum to the muscles of the anus;
- suspensory ligament of the anus - originates from the 2nd caudal vertebra and in the form of a loop covers the rectum from below; built of smooth muscle tissue; in males it becomes a retractor of the penis; and in females it ends in the labia.

INTESTINES

The absolute length of the intestines of dogs is 2.3-7.3 meters. The ratio of body length to length is 1:5. There are small and large intestines.

Small intestine

It begins at the level of the pylorus of the stomach and is divided into three main parts: the duodenum (the first and shortest part of the small intestine, into which the bile ducts and pancreatic ducts exit; the length of this section of the small intestine in dogs is 29 cm), the jejunum (2-7 m ) and ileum. The ribbon-shaped pancreas (weighing 10-100 g) lies in the right hypochondrium and secretes several liters of pancreatic secretion into the duodenum per day, containing enzymes that break down proteins, carbohydrates, fats, as well as the hormone insulin, which regulates blood sugar levels. The liver with the gall bladder in dogs is located in the right and left hypochondrium; blood flowing through the portal vein from the stomach, spleen and intestines passes through it and is filtered. The liver produces bile, which converts fats for absorption into the blood vessels of the intestinal wall.

The intestinal mucosa is more specialized for the digestion and absorption of food. Epithelial cells lining the inner surface of the small intestine are called enterocytes. The mucous membrane is collected in folds called villi. Each villi is well supplied with blood vessels and has a dead-end lymphatic vessel. These vessels transport absorbed nutrients from the small intestine to the liver and other parts of the body. The duodenum has a relatively porous structure and is capable of secreting a large volume of fluid into the lumen. The degree of permeability decreases accordingly in the jejunum, ileum and large intestine, where only fluid resorption takes place. This preserves fluid in the body and prevents diarrhea.

The bulk of proteins is digested in the small intestine to amino acids under the action of pancreatic enzymes. They are absorbed into enterocytes through specific transporters, and then transported to the liver through the portal vein. Carbohydrates (dogs get most of their carbohydrates in the form of starches) are broken down in the small intestine into glucose and other monosaccharides by pancreatic enzymes. In enterocytes, glucose is rapidly released into the bloodstream and transported to the liver through the portal vein. Dietary fats mainly consist of triglycerides, which can be easily broken down by bile salts into glycerol and fatty acids and absorbed, while cholesterol and phospholipid can be digested by dogs, but not as efficiently. This occurs under the influence of bile secreted by the liver and stored in the gallbladder. Since the cell membrane of enterocytes consists of lipids, the absorption process occurs passively and is often accompanied by the absorption of vitamins dissolved in fats. Inside the enterocytes, fatty acids are converted to triglyceride and attached to lipoproteins to form chylomicrons, which are excreted into the milk duct for transport to the main circulatory system and subsequently to the liver and other tissues.

Thus, any disruption of the small intestine (for example, rotavirus infection) can cause diarrhea and anorexia (loss or lack of appetite) due to the virus damaging the enterocytes of the villous apex). Well-digestible foods are necessary to reduce the cost of enzymes and increase the absorption area, which simultaneously achieves good level nutrient consumption. Eating small amounts of food does not overload the digestive and absorption capabilities of the intestines and reduces the risk of diarrhea.

Colon

This section of the intestine consists of the cecum (its length in dogs is 6-12 cm, lies under the 2-4th lumbar vertebrae and widely communicates with the colon); colon (located in the lumbar region and forms an arch) and rectum (lies at the level of the 4-5th sacral vertebra, has a powerful muscular structure) intestines. There are no villi on the mucous membrane of the large intestines. There are crypts - depressions where the intestinal glands are located, but there are few cells in them that secrete enzymes. The columnar epithelium of the mucous membrane contains many goblet cells that secrete mucus. Feces are formed in the large intestines.

In the large intestine, the final hydrolysis of nutrients occurs with the assistance of enzymes of the intestinal tract and enzymes of microorganisms. The most active activity of the intestinal microflora is observed in the colon: absorption of water and electrolytes, which is necessary for the formation of feces and the prevention of dehydration; fermentation of food residues by abundant bacterial flora (from nitrogen-rich food residues, bacteria produce large amounts of ammonia, which is absorbed and enters the liver through the portal vein, where it is processed into urea, which is excreted by the kidneys). Due to strong peristaltic contractions, the remaining contents of the large intestine enter the rectum through the descending colon, where feces accumulate. The release of feces into the environment occurs through the anal canal (anus). The anus has two sphincters: deep, made of smooth muscle fibers, and external, made of striated muscles. In dogs, there are two depressions on its sides - the right and left sinuses, into which the paranal glands open, secreting a thick secretion that emits a specific odor.

Thus, once in the oral cavity, the food is ground and chopped, rather than chewed with the teeth. Then it is moistened with saliva and enters the stomach through the pharynx and esophagus, where the process of its decomposition into simpler substances begins. Absorption of nutrients occurs in the intestines, and undigested food remains, mainly fiber, are excreted through the rectum.

Respiratory system

This system ensures the entry of oxygen into the body and the removal of carbon dioxide, that is, the exchange of gases between atmospheric air and blood. In pets, gas exchange occurs in the lungs, which are located in the chest. Alternate contraction of the inspiratory and expiratory muscles leads to expansion and contraction chest, and with it the lungs. This ensures that air is drawn in through the air passages into the lungs and expelled back out. Abbreviations respiratory muscles controlled by the nervous system.

While passing through the airways, the inhaled air is moistened, warmed, cleared of dust, and also examined for odors using the olfactory organ. With exhaled air, some water (in the form of steam), excess heat, and some gases are removed from the body. Sounds are produced in the air passages (larynx). The respiratory organs are represented by the nose and nasal cavity, larynx, trachea and lungs.

NOSE AND NASAL CAVITY

The nose together with the mouth make up the front section of the head in animals - the muzzle. The nose contains a paired nasal cavity, which is the initial section of the airways. In the nasal cavity, the inhaled air is examined for odors, heated, humidified, and cleaned of contaminants. Nasal cavity communicates with the external environment through the nostrils, with the pharynx - through the choanae, with the conjunctival sac - through the nasolacrimal canal, as well as with the paranasal sinuses. On the nose there are apex, dorsum, sides and root. At the top there are two holes - nostrils. The nasal cavity is divided by the nasal septum into right and left parts. The basis of this septum is hyaline cartilage.

The paranasal passages communicate with the nasal cavity paranasal sinuses. The paranasal sinuses are air-filled and mucous-lined cavities between the outer and inner plates of some flat bones skulls (eg frontal bone). Because of this message inflammatory processes from the mucous membrane of the nasal cavity can easily spread to the sinuses, which complicates the course of the disease.

LARYNX

The larynx is a section of the respiratory tube that is located between the pharynx and trachea. In a dog it is short and wide. The unique structure of the larynx allows it to perform, in addition to conducting air, other functions. It isolates the respiratory tract when swallowing food, serves as a support for the trachea, pharynx and the beginning of the esophagus, and serves as a vocal organ. The skeleton of the larynx is formed by five movably interconnected cartilages, on which the muscles of the larynx and pharynx are attached. This is an annular cartilage, in front and below it is the thyroid cartilage, in front and above there are two arytenoid cartilages, and below it is the epiglottic cartilage. The laryngeal cavity is lined with mucous membrane. Between the vocal process of the arytenoid cartilage and the body of the thyroid cartilage on the right and left there is a transverse fold - the so-called vocal lip, which divides the laryngeal cavity into two parts. It contains the vocal cord and vocal muscle. The space between the right and left vocal lips is called the glottis. The tension of the vocal lips during exhalation creates and regulates sounds. Dogs have large vocal lips, which allows your four-legged pet to make a variety of sounds.

TRACHEA

The trachea serves to conduct air to and from the lungs. This is a tube with a constantly gaping lumen, which is ensured by rings of hyaline cartilage that are not closed at the top in its wall. The inside of the trachea is lined with mucous membrane. It extends from the larynx to the base of the heart, where it divides into two bronchi, which form the basis of the roots of the lungs. This location, which occurs at the level of the 4th rib, is called the tracheal bifurcation. The length of the trachea depends on the length of the neck, and therefore the number of cartilages in dogs ranges from 42 to 46.

LUNGS

These are the main respiratory organs, directly in which gas exchange occurs between the inhaled air and the blood through the thin wall separating them. To ensure gas exchange, a large contact area is required between the airways and bloodstreams. In accordance with this, the airways of the lungs - the bronchi - like a tree, branch repeatedly to the bronchioles (small bronchi) and end with numerous small pulmonary vesicles - alveoli, which form the lung parenchyma (parenchyma is a specific part of the organ that performs its main function). Blood vessels branch parallel to the bronchi and entwine the alveoli with a dense capillary network, where gas exchange takes place. Thus, the main components of the lungs are the airways and blood vessels. Connective tissue unites them into a paired compact organ - the right and left lung. The right lung is slightly larger than the left, since the heart, located between the lungs, is shifted to the left (Fig. 14). The relative weight of the lungs is 1.7% relative to body weight.

The lungs are located in the chest cavity, adjacent to its walls. As a result, they have the shape of a truncated cone, somewhat compressed from the sides. Each lung is divided into lobes by deep interlobar fissures: the left - into three, and the right - into four. Frequency breathing movements in dogs depends on the load on the body, age, health status, temperature and humidity of the environment.

Normal number of inhalations and exhalations (respirations) healthy dog fluctuates within significant limits: from 14 to 25-30 per minute. This range width depends on a number of factors. Thus, puppies breathe more often than adult dogs because their metabolism is more active. Bitches breathe more frequently than males. Pregnant or nursing dogs breathe more frequently than non-pregnant dogs. The breathing rate can also be affected by the breed of the dog, its emotional state, and the size of the dog also affects it. Small breed dogs breathe more often than large ones: miniature pinscher, the Japanese Chin breathes 20-25 times per minute, and the Airedale - 10-14 times. This is due to different rates of the metabolic process, and, as a consequence, greater loss heat.

Breathing largely depends on the dog’s body position. Animals breathe easier when they stand. In case of diseases accompanied by damage to the heart and respiratory organs, animals take a sitting position, which helps to facilitate breathing.

Rice. 14. Topography of the dog's lungs, right view: 1 - trachea; 2,3,4 - cranial middle lobe of the lung; 5 - heart; 6 - diaphragm; 7 - dorsal edge of the lung; 8 - basal edge of the lung; 9 - stomach; 10 - ventral edge of the lung

The breathing process is also affected by the time of day and season. At night, when at rest, the dog breathes less frequently. In summer, when the weather is hot, as well as in stuffy rooms with high humidity, breathing becomes more frequent. In winter, dogs' breathing at rest is even and imperceptible. Muscle work sharply increases the dog's breathing. The factor of the animal's excitability is also of certain importance. The appearance of a stranger or a new environment can cause rapid breathing.

Urinary system

These organs are designed to remove end products of metabolism in the form of urine from the body (from the blood) into the external environment and to control the water-salt balance of the body. In addition, the kidneys produce hormones that regulate hematopoiesis (hemopoietin) and blood pressure(renin). Therefore, dysfunction of the urinary organs leads to serious illnesses and often to the death of animals.

The urinary organs include paired kidneys and ureters, an unpaired bladder and the urethra. In the main organs - the kidneys - urine is constantly produced, which is discharged through the ureter into the bladder and, as it fills, is released out through the urethra. Per day adult dog a small breed excretes 0.04-0.2 liters of urine, and an adult dog of medium and large breeds - from 0.5 to 1.5 liters. Urine pH ranges from 4.8 to 6.5 depending on feeding. In males, this canal also carries sexual products and is therefore called the urogenital canal. In females, the urethra opens into the vestibule of the vagina.

KIDNEYS

The kidneys are organs of dense consistency, red-brown in color, smooth, covered on the outside with three membranes: fibrous, fatty, serous. They are located in the lumbar region under the first 3 lumbar vertebrae. These are quite large organs, identical on the right and left, having a bean-shaped, somewhat flattened shape. Near the middle of the inner layer, vessels and nerves enter the kidney, and the ureter emerges. This place is called the renal hilum. On the section of each kidney, the cortical, or urinary, cerebral, or urinary, and intermediate zones are distinguished (Fig. 15).

The cortical zone is darker and lies superficially. The medullary zone is lighter, located in the center of the kidney and is shaped like a pyramid. The apex of the pyramid forms the renal papilla, of which the dog has only one. Between these zones, in the form of a dark stripe, there is an intermediate zone, where the arcuate arteries are visible, from which the interlobular arteries separate towards the cortical zone. Along the latter are located the renal corpuscles, consisting of a glomerulus - a glomerulus (vascular glomerulus), which is formed by the capillaries of the afferent artery and capsule. The renal corpuscle, together with the convoluted tubule and its vessels, constitute the structural and functional unit of the kidney - the nephron. In the renal corpuscle of the nephron, liquid - primary urine - is filtered from the blood of the vascular glomerulus into the cavity of its capsule. During the passage of primary urine through the convoluted tubule of the nephron, most (up to 99%) water and some substances that cannot be removed from the body, such as sugar, are absorbed back into the blood. This explains the large number of nephrons and their length. The primary urine then enters the straight canaliculus and directly enters the renal pelvis (dogs do not have renal calyces), located at the hilum of the kidney, from which secondary urine enters the ureter.

Rice. 15. Kidney: 1 - renal lobule; 2 - cortical zone; 3 - border zone; 4 - renal papilla; 5 - brain

URETERS

The ureter is a typical tube-shaped paired organ: its wall is formed by three membranes. Its diameter is small. The ureter starts from the renal pelvis, and, covered by the peritoneum, goes into the pelvic cavity, where it flows into the bladder. In the wall Bladder it makes a small loop that prevents urine from flowing back from the bladder into the ureters without interfering with the flow of urine from the kidneys to the bladder.

BLADDER

The bladder is a reservoir for urine continuously flowing from the kidneys, which is periodically excreted through the urethra. It is a pear-shaped membranous muscle sac. It distinguishes between the apex facing the abdominal cavity, the body and the one directed towards the pelvic neck. In the neck area, the bladder muscles form a sphincter that prevents the voluntary release of urine. The empty bladder lies at the bottom of the pelvic cavity, and when full, partially hangs into the abdominal cavity.

URINE CHANNEL, OR URETHA

This organ serves to remove urine from the bladder and is a tube made of mucous and muscular membranes. The internal end of the urethra begins from the neck of the bladder, and the external opening opens in males on the head of the penis, and in females on the border between the vagina and its vestibule. The auricular part of the long urethra of males is part of the penis, and therefore, in addition to urine, it removes sexual products. The urination center is located in the lumbosacral region of the spinal cord and is connected to the brain

Reproductive organ system

The system of reproductive organs is closely connected with all systems of the body, in particular with the excretory organs (these two systems have a common terminal excretory duct and common rudiments of some other organs). Its main function is to continue the look. The genital organs of males (males) and females (females) are different, so we will consider each system separately.

GENITAL ORGANS OF MALES

The genital organs of male dogs are represented by paired organs: testes (testes) with appendages, vas deferens and spermatic cords, accessory sex glands; and unpaired organs: the scrotum, genitourinary canal, penis and prepuce.

Testes

The testis is the main reproductive organ of males, in which the development and maturation of sperm occurs (Fig. 16). It is also an endocrine gland - it produces male sex hormones - sperm. The testis is ovoid in shape, suspended on the spermatic cord and located in the cavity of the saccular protrusion of the abdominal wall - the scrotum. Closely associated with it is its appendage, which is part of the excretory duct. In the epididymis, mature sperm can remain quite immobile long time, they are provided with nutrition during this period, and when animals mate, they are thrown into the vas deferens by peristaltic contractions of the muscles of the appendage. The appendage has a head, body and tail.

In males, the testes are relatively small, and the appendage is highly developed: its head and tail are equally thick.

Rice. 16. Position of the testis in a dog: 1 - scrotum; 2 - testis; 3 - head; 4 - body; 5 - tail appendage; 6 - vas deferens; 7 - vaginal membrane; 8 - spermatic cord

Scrotum

The scrotum is the container of the testis and its appendage, which is a protrusion of the abdominal wall. The temperature in it is lower than in the abdominal cavity, which favors the development of sperm. In male dogs, the scrotum is located closer to anus. The skin of this organ is covered with small hair and has sweat and sebaceous glands.

The muscular-elastic membrane is located under the skin and forms the septum of the scrotum, as a result of which the organ cavity is divided into two parts. The muscular formations of the scrotum ensure that the testis is pulled towards the inguinal canal at low external temperatures.

Vas deferens, or vas deferens

The vas deferens is a continuation of the epididymis duct in the form of a narrow tube of three membranes. It starts from the tail of the appendage. As part of the spermatic cord, it is directed through the inguinal canal into the abdominal cavity, and from there to the pelvic cavity, where it forms an ampulla. Behind the neck of the bladder, the vas deferens connects with the excretory duct of the vesicular gland into a short ejaculatory canal, which opens at the beginning of the genitourinary canal.

Spermatic cord

The spermatic cord is a fold of the peritoneum that contains vessels, nerves going to the testis and lymphatic vessels leaving the testis, as well as the vas deferens.

Urogenital canal, or male urethra

Serves to remove urine and sperm. It begins with the urethral opening from the neck of the bladder and ends with the external urethral opening on the head of the penis. The initial, very short part of the urethra - from the cervix to the confluence of the ejaculatory canal - conducts only urine. The wall of the male urethra is formed by a mucous membrane, a spongy layer and a muscular layer. The mucous membrane is collected in folds. The spongy layer has a network of veins with extensions - lacunae. When the spongy layer is filled with blood, the lumen of the urethra opens and sperm comes out.

Accessory sex gland

This is the unpaired prostate gland. It is complex in structure, and its excretory ducts open into the pelvic part of the genitourinary canal. The secretion of this gland activates sperm motility.

Penis

The penis performs the function of introducing male sperm into the female genitals, as well as removing urine from the body. It consists of the cavernous body of the penis and the penile (udal) part of the urogenital canal. The penis is divided into root, body and head. The root and body are covered from below with skin, the latter extends to the head, forming a fold at the transition to it - the prepuce, or foreskin. During sexual arousal, the cavities of the penis fill with blood, as a result of which the penis lengthens, thickens and becomes dense, that is, it becomes erect.

Prepuce

When the penis is not erect, the prepuce completely covers the head of the penis, protecting it from damage. It is pulled onto the glans penis by the prepuce cranialis muscle and pulled back by the penile retractor. In males, the head of the penis is long and cylindrical. The urethra opens at the end of the head. The head is based on bone. Its length in large dogs reaches 8-10 cm. The amount of sperm secreted by a male dog fluctuates around 15 ml. There are about 6000 sperm in 1 mm3 of sperm. Inside the uterus, sperm exist for 8-12 hours.

After the birth of puppies, the absolute weight of the testes increases 16-17 times in the first 6 months of life, and the weight of the accessory sex glands increases, especially during puberty. Sexual and physiological maturity is the ability of animals to produce offspring. It is characterized by the release of sperm in males, the formation of sex hormones that determine the development of secondary sexual characteristics. Sexual and physiological maturity occurs at 6-8 months.

GENITAL ORGANS OF BITCHES

The genital organs of bitches include paired organs: ovaries, fallopian tubes; and unpaired: uterus, vagina, vestibule of the vagina and external genitalia (Fig. 17). In dogs, the length of the fallopian tube is 4-10 cm.

Rice. 17. Female genital organs from the dorsal surface of the dog: 1 - ovary; 2 - oviduct; 3 - uterine horn; 4 - body of the uterus; 5 - cervix; 6 - external opening of the uterus; 7 - vagina; 8 - vaginal vault; 9 - vestibular-vaginal fold; 10 - external opening of the urethra; 11 - vestibule of the vagina; 12 - small vestibular glands; 13 - clitoris; 14 - labia; 15 - bladder

Uterus

It is a hollow membranous organ in which the fetus develops. During childbirth, the latter is pushed out by the uterus through the birth canal. The uterus is divided into horns, body and cervix. The horns on top start from the fallopian tubes, and below they grow together into the body. The uterine cavity passes into the narrow canal of the cervix, which opens into the vagina. The body and cervix of the non-pregnant uterus lie in the pelvic cavity, next to the bladder, and the horns hang into the abdominal cavity. The entire uterus is located in the abdominal cavity, mostly on the right. The dog's uterine horns are long, straight and thin, and the body is short.

Vagina

It is a tubular organ that serves as an organ of copulation and is located between the cervix and the urogenital opening. In dogs, it is 2 times longer than the vestibule.

Vaginal vestibule

The vestibule of the vagina is a common area of ​​the urinary and genital tracts, an extension of the vagina behind the external opening of the urethra. It ends with the external genitalia.

Veterinary guide for dog owners
M. V. Dorosh