Tenesmus of GI origin usually is associated with inflammatory disease of the rectum and anus. The small intestine say: Make a Purse-string Sphincter or Valve In the digestive system, there are a number of places along the way that are designed to help regulate when, what direction, and how fast, food travels. It develops in any condition that results in nutrient malabsorption or maldigestion or when an animal ingests a large amount of osmotically active substances that are not absorbed, eg, an overeating puppy. Oesophagus is a bng and narrow tube. There are often pieces of food in the gut corresponding to the shape of the jaw.
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Other factors that may cause abdominal pain include edema and failure of local blood supply, eg, in local embolism or twisting of the mesentery. Specific diseases cause diarrhea by varied and characteristic mechanisms, the recognition of which is useful in understanding, diagnosing, and managing GI diseases.
The major mechanisms of diarrhea are increased permeability, hypersecretion, and osmosis. Disorders of motility are often secondary. In healthy animals, water and electrolytes continuously transfer across the intestinal mucosa. Secretions from blood to gut and absorptions from gut to blood occur simultaneously. In clinically healthy animals, absorption exceeds secretion, ie, there is net absorption. If the amount exuded exceeds the absorptive capacity of the intestines, diarrhea results. The size of the material that leaks through the mucosa varies, depending on the magnitude of the increase in pore size.
Large increases in pore size permit exudation of plasma protein, resulting in protein-losing enteropathies eg, lymphangiectasia in dogs, paratuberculosis in cattle, nematode infections. Greater increases in pore size result in the loss of RBCs, producing hemorrhagic diarrhea eg, hemorrhagic gastroenteritis, parvovirus infection, severe hookworm infection. Hypersecretion is a net intestinal loss of fluid and electrolytes that is independent of changes in permeability, absorptive capacity, or exogenously generated osmotic gradients.
Enterotoxic colibacillosis is an example of diarrheal disease due to intestinal hypersecretion; enterotoxigenic Escherichia coli produce enterotoxin that stimulates the crypt epithelium to secrete fluid beyond the absorptive capacity of the intestines. The villi, along with their digestive and absorptive capabilities, remain intact.
The fluid secreted is isotonic, alkaline, and free of exudates. The intact villi are beneficial because a fluid administered PO that contains glucose, amino acids, and sodium is absorbed, even with hypersecretion. Osmotic diarrhea is seen when inadequate absorption results in a collection of solutes in the gut lumen, which cause water to be retained by their osmotic activity.
It develops in any condition that results in nutrient malabsorption or maldigestion or when an animal ingests a large amount of osmotically active substances that are not absorbed, eg, an overeating puppy. Malabsorption see Malassimilation Syndromes in Large Animals and see Diseases of the Stomach and Intestines in Small Animals is failure of digestion and absorption due to some defect in the villous digestive and absorptive cells, which are mature cells that cover the villi.
Several epitheliotropic viruses directly infect and destroy the villous absorptive epithelial cells or their precursors, eg, coronavirus, transmissible gastroenteritis virus of piglets, and rotavirus of calves. Feline panleukopenia virus and canine parvovirus destroy the crypt epithelium, which results in failure of renewal of villous absorptive cells and collapse of the villi; regeneration is a longer process after parvoviral infection than after viral infections of villous tip epithelium eg, coronavirus, rotavirus.
Intestinal malabsorption also may be caused by any defect that impairs absorptive capacity, such as diffuse inflammatory disorders eg, lymphocytic-plasmacytic enteritis, eosinophilic enteritis or neoplasia eg, lymphosarcoma. Other examples of malabsorption include defects of pancreatic secretion that result in maldigestion. Rarely, because of failure to digest lactose which, in large amounts, has a hyperosmotic effect , neonatal farm animals or pups may have diarrhea while they are being fed milk.
Reduced secretion of digestive enzymes at the surface of villous tip cells is characteristic of epitheliotropic viral infections recognized in farm animals. The ability of the GI tract to digest food depends on its motor and secretory functions and, in herbivores, on the activity of the microflora of the forestomachs of ruminants, or of the cecum and colon of horses and pigs.
The flora of ruminants can digest cellulose; ferment carbohydrates to volatile fatty acids; and convert nitrogenous substances to ammonia, amino acids, and protein. In certain circumstances, the activity of the flora can be suppressed to the point that digestion becomes abnormal or ceases. Incorrect diet, prolonged starvation or inappetence, and hyperacidity as occurs in engorgement on grain all impair microbial digestion. The bacteria, yeasts, and protozoa also may be adversely affected by the oral administration of drugs that are antimicrobial or that drastically alter the pH of rumen contents.
Signs of GI disease include excessive salivation, diarrhea, constipation or scant feces, vomiting, regurgitation, GI tract hemorrhage, abdominal pain and distention, tenesmus, shock and dehydration, and suboptimal performance. The location and nature of the lesions that cause malfunction often can be determined by recognition and analysis of the clinical findings. In addition, abnormalities of prehension, mastication, and swallowing usually are associated with diseases of the oral mucosa, teeth, mandible or other bony structures of the head, pharynx, or esophagus.
Vomiting is most common in single-stomached animals and usually is due to gastroenteritis or nonalimentary disease eg, uremia, pyometra, endocrine disease. The vomitus in a dog or cat with a bleeding lesion gastric ulcer or neoplasm may contain frank blood or have the appearance of coffee grounds.
Horses and rabbits do not vomit. Regurgitation may signify disease of the oropharynx or esophagus and is not accompanied by the premonitory signs seen with vomiting. Large-volume, fluid diarrhea usually is associated with hypersecretion eg, in enterotoxigenic colibacillosis in newborn calves or with malabsorptive osmotic effects. Blood and fibrinous casts in the feces indicate a hemorrhagic, fibrinonecrotic enteritis of the small or large intestine, eg, bovine viral diarrhea, coccidiosis, salmonellosis, or swine dysentery.
Black, tarry feces melena indicate hemorrhage in the stomach or upper part of the small intestine. Tenesmus of GI origin usually is associated with inflammatory disease of the rectum and anus. Small amounts of soft feces may indicate a partial obstruction of the intestines. Abdominal distention can result from accumulation of gas, fluid, or ingesta, usually due to hypomotility functional obstruction, adynamic paralytic ileus or to a physical obstruction eg, foreign body or intussusception.
Distention may, of course, result from something as direct as overeating. A sudden onset of severe abdominal distention in an adult ruminant usually is due to ruminal tympany. Ballottement and succussion may reveal fluid-splashing sounds when the rumen or bowel is filled with fluid. Varying degrees of dehydration and acid-base and electrolyte imbalance, which may lead to shock, are seen when large quantities of fluid are lost eg, in diarrhea or sequestered in intestinal obstruction or in gastric or abomasal volvulus.
Abdominal pain is due to stretching or inflammation of the serosal surfaces of abdominal viscera or the peritoneum; it may be acute or subacute, and its manifestation varies among species. In horses, acute abdominal pain is common see Colic in Horses. Subacute pain is more common in cattle and is characterized by reluctance to move and by grunting with each respiration or deep palpation of the abdomen. These are arranged in a single row on each Jaw. Sensory papillae are present. Tongue is narrow triangular and fleshy.
Its surface is covered with horny material and bears thorn-like projections which carry taste buds and mucous glands.
Tongue is highly specialized, fleshy and muscular and can be moved in different directions. It can be protruded out. Its surface is rugose being covered with numerous papillae along with taste buds. A pair of internal nostrils open into the roof of the buccal cavity anteriorly. Hard palate is present. A bony palate is wanting in birds but a pair of palatal folds and palatal groove between the two folds are present. Internal nostrils are located dorsal to the palatal folds. The nasal passages are separated from the buccal cavity by a bony palate.
The internal nostrils open into the pharynx nearer to glottis. A bony palate is present covering the roof of the buccal cavity. A bony palate is absent. But soft palate is formed of two membranous folds.
The palate is differentiated into anterior bony hard palate and a soft palate is formed of connective tissue. The soft palate is produced behind into a process — velum palati hanging down from the roof, which prevents the entry of food into nasal passage. Unicellular mucous glands are present and keep the buccal cavity always wet.
Unicellular mucous glands are absent in the epithelium of bucco-pharyngeal region. Uni cellular mucous glands are absent. But multi cellular serous glands are present.
Salivary glands are absent. But labial glands are open at the lips which do not play any role in digestion.
Salivary glands which open into the buccal cavity are lingual, mandibular, maxillary, cricoary tenoid, palatinal and sphenopalatinal glands. The multi cellular salaivary glands are four pairs. They are Infra orbital, parotid, sublingual and sub-maxillary glands. Pharynx is marked off. On the roof of pharynx near the junction of two jaws a pair of openings is called Eustachian apertures.
Pharynx is not sharply demarcated from the buccal cavity. It receives the openings of esophagus and the glottis. Esophagus is a narrow tube and straight extends through the neck.
Mucous glands are present. Oesophagus is a bng and narrow tube. It has thick walls. Mucous glands are absent. Oesophagus is a long thin walled tube. It is clearly marked off from the pharynx as well as stomach. The oesophagus is dilated into a thin-walled sac the crop. It secrete pigeon milk in both sexes and used to feed the young birds.
The wall of oesophagus is produced into the cardiac stomach to form cardiac valve. Stomach is a sac- like structure. Its anterior part is cardiac stomach and posterior part is pyloric stomach. At the end of pyloric stomach a small constriction is present. It possesses a pyloric sphincter. Stomach is divided into a glandular proventriculus and posterior muscular gizzard.
Gizzard acts like grinding apparatus. Stomach is divisible into cardiac, fundic and pyloric parts. Pyloric stomach contains pyloric valve. Intestine is differentiated into duodenum and ileum. Intestine very long and very much coiled because is a herbivorous animal