Animal anatomy, histology, pathological anatomy

Internal inspection.To open cavities and remove organs, the horse's corpse is placed in the right lateral or semi-lateral position, since in horses the main mass of the large intestine (colon) occupies the right half of the abdominal cavity. The left forelimb is cut off along with the scapula and scapular cartilage, and the left hind limb is cut off after opening the hip joint and cutting its round ligament. The mammary gland (in a female) and the external genitalia (in a male) are separated and examined.
Two incisions are made in the abdominal wall: the first longitudinal - along the white line from the xiphoid process of the sternum to the pubic fusion; the second - perpendicular to the first with the removal of two flaps of the left abdominal wall or along the bony arch of the ribs to the groin and the transverse processes of the lumbar vertebrae.
The abdominal cavity is examined, noting: the anatomical location of the organs, the contents of the cavity, the condition of the diaphragm, omentum and peritoneum. With setaria, small nematodes of the genus Setaria and villous growths (consequences of peritonitis of setaria origin) can be found on the serous membranes of the liver and spleen, peritoneum and between intestinal loops. It should be remembered that in horses, due to the long mesentery, there are often displacements (dystonia) of the intestine in the form of torsions, volvulus, and intussusception of individual areas. Prolapse and strangulation of the small intestine in the Winslow foramen of the omentum or inguinal ring with the development of congestive venous hyperemia and hemorrhagic infarction are also possible. The strangulated intestine is dark red in color, and in the area of ​​strangulation there is a white stripe - a strangulation groove.
Healing internal organs.The spleen is first removed from the abdominal cavity and examined to exclude septic diseases. In healthy animals, the follicles of the organ are almost invisible; the trabeculae have the appearance of whitish stripes and dots, thickened with anemia and atrophy.
After palpating the intestine for the presence of stones and examining its appearance, it is removed. To do this, grab the pelvic curve of the large colon with your hands, straighten it and place it parallel to the right limbs, and the small colon is brought out behind the back of the corpse to the ligament connecting the duodenum with the small colon. Place two ligatures on the duodenum at its exit from the stomach and in the area of ​​the ligament with the small colon, on the small colon in the area of ​​the said ligament, as well as between the small colon and rectum, on the ileum at the place of its confluence with the cecum, on esophagus between the diaphragm and the stomach. Ligatures are applied at a distance of 4–5 cm from one another after displacing the contents between them. The rectum is cut at the ampulla and separated along with the small colon from the mesentery to the place of its attachment. The jejunum and ileum are separated together, and the duodenum is left with the stomach.
The large intestine of horses is often parasitized by nematodes of the genus Delafondia, the larvae of which infect the anterior mesenteric artery, mesenteric and other arteries, attaching to the intima and causing the development of blood clots, aneurysms, thromboembolism and thromboembolic colic. Therefore, before removing the colon, the anterior mesenteric artery is opened.
The left kidney, adrenal gland, ureter and pancreas are first examined, and the kidney and adrenal gland are separated. Then an incision is made in the thoracic part of the aorta and continues through the diaphragm to the abdominal aorta.
The second major branch of the abdominal aorta after the worm is the anterior mesenteric artery and its branches, which are opened through the opening in the aorta. After this, the root of the mesentery of the large colon is crossed and removed.
The stomach is separated from the esophagus between the applied ligatures and after dissection of the round gastrophrenic ligament with the right kidney, it is removed separately or with the duodenum, liver and pancreas. After this, the right kidney and adrenal gland are removed. To check the patency of the common bile and pancreatic ducts in the area of ​​the S-shaped bend of the duodenum, a branch of button scissors is inserted into the duct of Vater and the duct is opened to the portal of the liver and, accordingly, to the portal of the pancreas.
Before opening, the chest is freed from soft tissues (muscles) and the ribs are sawed in two places: near the head of the ribs and at a distance of 5 cm from the sternum. In this case, the left wall of the chest cavity is easily separated and access to the chest cavity is opened.
The heart weight of a horse is 1.68–4.80 kg; length from the origin of the aorta to the apex is 19–24 cm, of the right ventricle – 13–20, of the left – 16–21 cm; the circumference at the level of the transverse furrow is 45–68 cm. The hole of the right heart allows 4–5 fingers to pass through, and the hole of the left heart allows 3–4 fingers of a man’s hand.
Horse urine contains large amounts of mucin. Therefore, the accumulation of cloudy mucous fluid in the renal pelvis is a normal phenomenon, and not a sign of catarrhal or purulent inflammation.
The oral cavity is opened by removing the left lower jaw. After separating the masseter, the left branch of the lower jaw is sawn close to its body. Using a cut parallel to the inner surface of the mandibular branch, the connection with the muscles is dissected, the cut is continued upward between the parotid salivary gland and the posterior edge of the jaw and ends by cutting the temporal muscle. After freeing the branch of the lower jaw from the joint in the joint using a knife, it is easily removed, and then the organs of the oropharynx and thoracic cavity are removed.
To open the skull, an isosceles triangle is cut out in the skull, the base of which passes at a distance of 2 cm from the brow ridges and the upper edge of the ocular processes of the frontal bones. The lateral sides of the triangle are directed from the ends of the transverse cut at the base of the same processes posteriorly, through the frontal, parietal, temporal and occipital bones and end in the foramen magnum, on the border of the upper edge of the occipital tuberosities.