Digestive System of the Dog
Some vitamins, such as biotin and vitamin K K 2 MK7 produced by bacteria in the colon are also absorbed into the blood in the colon. Guyton and Hal Textbook of Medical Physiology 12th ed. This is especially important if the birds are to attain the expected productive performance. Can you guess where it ends up? Gastric juice mainly contains hydrochloric acid and pepsin. It passes through the posterior mediastinum in the thorax and enters the stomach through a hole in the thoracic diaphragm —the esophageal hiatus , at the level of the tenth thoracic vertebra T
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The structure of the cloaca is very similar to that of the intestine except that the muscularis mucosa disappears near the vent. It divides into three chambers, each separated by a constriction not readily defined:. The liver is a bi-lobed organ that lies ventrally below and posterior in rear of to the heart and is closely associated with the proventriculus and the spleen. The right side lobe is larger. The liver is dark brown or chocolate in colour except for the first days when it may be quite pale due to the absorption of lipids fats from the yolk as an embryo.
It weighs approximately 50 grams in adult birds. The capsule, or glissosis, is the membrane that covers the liver and is thinner than that of mammals. The gall bladder lies on the right lobe beneath the spleen. Two bile ducts emerge from the right lobe and one of these originates from the gall bladder and the second provides a direct connection from the liver to the small intestine. A system of ducts connects the right and left lobes.
The liver cells have a high rate of destruction and a good regenerative capacity re-growth ability. Notwithstanding this, in the normal animal, much of the organ is in reserve and can be removed or destroyed without causing undue stress. There are two blood supply systems. One originates from the coelic artery for normal maintenance of the liver as an organ and the second, called the hepatic portal system, transports the nutrients from the small intestine after absorption to the liver.
This latter system enters the liver via two veins one for each lobe. The two blood supply systems join together inside the organ. The liver is drained via the hepatic veins into the posterior vena cava hepatic — relating to the liver; vena cava — one of the main veins that enters the heart. The liver has a network of sinusoids empty holes in the tissues as in a sponge. The hepatic portal system, the capillaries of the arterial blood supply and the hepatic veins are in close association with each other in these sinusoids.
The liver consists of a series of tissue sheets that are two cells thick, with a sinusoid on either side of the sheet. Bile is made by the cells. The blood vessels, when they enter these sinusoids, become closely associated with them to provide for the easy transfer of material from one system to another. Minute canals called canaliculi that have the task of collecting and transporting the bile are associated with the cells in the tissue sheets.
These canals eventually join together to form the bile ducts with one going directly to the intestine and one to the gall bladder before it connects to the small intestine. This organ has three lobes that occupy the space between the two arms of the duodenal loop.
Two or three ducts pass the secretions of this organ into the distal end of the duodenum via papillae common with the ducts from the gall bladder and the liver. These are mainly associated with the production of hormones. In poultry the cells of the islets of Langerhans are less defined than those in mammals.
The functions of the pancreas are:. The pattern of food intake and its passage through the digestive system are the main factors that influence secretory and hence digestive activity. Probably because of the high metabolic rate of the fowl, a more or less continuous supply of food is required by the digestive system. This is provided for by the crop that acts as a reservoir for the storage of food prior to its digestion and consequently permits the fowl to eat its food as periodic meals.
There is quite wide variability between birds in relation to eating behaviour, even between those in the same flock. Some eat small amounts at short intervals while others eat larger amounts at wider intervals. The food is delivered into the crop for storage after the first few boli have passed into the proventriculus. The crop is quite distensible and will hold a large amount of undigested food that is then moved on as required by the proventriculus.
This function of the crop is less important when there is a plentiful supply of food available. There is no relationship between the length of time of food deprivation and the amount of food consumed. While there is a wide variation between the eating habits of different birds in the flock, fowls do tend to eat meals on about minute intervals through the daylight hours and, to some extent, during darkness. They tend to eat larger portions at first light and in the late evening.
Similar factors affect the rate of movement of the food through the digestive system with a meal of normal food taking approximately 4 hours to pass through in the case of young stock, 8 hours in the case of laying hens and 12 hours for broody hens. Intact, hard grains take longer to digest than the cracked grain and, quite often some whole grain will pass through unchanged. After ingestion, the food is mixed with saliva and mucous from the mouth and oesophagus and these secretions thoroughly moisten the food.
The enzyme amylase, which is produced by the salivary and oesophageal glands and found in the saliva and mucous, can now commence to breakdown the complex carbohydrates. However, the amount of enzyme action at this stage is minimal and the first major enzyme activity takes place in the proventriculus and in the gizzard. The secretions of the proventriculus, or glandular stomach as it is often called, include hydrochloric acid to lower the pH of the system and the food mixture, the enzyme pepsin that acts on protein, and the hormone gastrin that stimulates the production and release of gastric juice in the proventriculus and pancreatic juice from the pancreas.
The gizzard is a very powerful organ which physically breaks the food particles into smaller sizes to make the work of the enzymes easier. At the same time, the enzymes previously released into the food with the saliva and by the proventriculus are thoroughly mixed into the food which improves their opportunity to carry out their work. This breaking and mixing function of the gizzard is enhanced by the presence of insoluble grit such as stones. The food material enters the duodenum from the gizzard.
Enzyme activity in this region is, in the main, a continuation of the breakdown of proteins started in the gizzard. Pancreatic juice and bile from the liver enters via ducts located at the distal end of the duodenum at about the junction of the duodenum and the jejunum if it were differentiated. However, because of back flow of pancreatic juice and bile towards the gizzard, the actions of these secretions start earlier in the digestive process than would be expected by their entry point to the small intestine.
The wall has an outer layer of longitudinal muscles, the taeniae coli , and an inner layer of circular muscles. The circular muscle keeps the material moving forward and also prevents any back flow of waste. Also of help in the action of peristalsis is the basal electrical rhythm that determines the frequency of contractions. Most parts of the GI tract are covered with serous membranes and have a mesentery. Other more muscular parts are lined with adventitia. The digestive system is supplied by the celiac artery.
The celiac artery is the first major branch from the abdominal aorta , and is the only major artery that nourishes the digestive organs. There are three main divisions — the left gastric artery , the common hepatic artery and the splenic artery. Most of the blood is returned to the liver via the portal venous system for further processing and detoxification before returning to the systemic circulation via the hepatic veins.
The enteric nervous system consists of some one hundred million neurons  that are embedded in the peritoneum , the lining of the gastrointestinal tract extending from the esophagus to the anus. Parasympathetic innervation to the ascending colon is supplied by the vagus nerve.
Sympathetic innervation is supplied by the splanchnic nerves that join the celiac ganglia. Most of the digestive tract is innervated by the two large celiac ganglia, with the upper part of each ganglion joined by the greater splanchnic nerve and the lower parts joined by the lesser splanchnic nerve. It is from these ganglia that many of the gastric plexuses arise. Early in embryonic development , the embryo has three germ layers and abuts a yolk sac.
During the second week of development, the embryo grows and begins to surround and envelop portions of this sac. The enveloped portions form the basis for the adult gastrointestinal tract. Sections of this foregut begin to differentiate into the organs of the gastrointestinal tract, such as the esophagus , stomach , and intestines. During the fourth week of development, the stomach rotates. The stomach, originally lying in the midline of the embryo, rotates so that its body is on the left.
This rotation also affects the part of the gastrointestinal tube immediately below the stomach, which will go on to become the duodenum. By the end of the fourth week, the developing duodenum begins to spout a small outpouching on its right side, the hepatic diverticulum , which will go on to become the biliary tree.
Just below this is a second outpouching, known as the cystic diverticulum , that will eventually develop into the gallbladder. Each part of the digestive system is subject to a wide range of disorders many of which can be congenital. Mouth diseases can also be caused by pathogenic bacteria , viruses , fungi and as a side effect of some medications. Mouth diseases include tongue diseases and salivary gland diseases. A common gum disease in the mouth is gingivitis which is caused by bacteria in plaque.
The most common viral infection of the mouth is gingivostomatitis caused by herpes simplex. A common fungal infection is candidiasis commonly known as thrush which affects the mucous membranes of the mouth. There are a number of esophageal diseases such as the development of Schatzki rings that can restrict the passageway, causing difficulties in swallowing.
They can also completely block the esophagus. Stomach diseases are often chronic conditions and include gastroparesis , gastritis , and peptic ulcers. A number of problems including malnutrition and anemia can arise from malabsorption , the abnormal absorption of nutrients in the GI tract. Malabsorption can have many causes ranging from infection , to enzyme deficiencies such as exocrine pancreatic insufficiency.
It can also arise as a result of other gastrointestinal diseases such as coeliac disease. Coeliac disease is an autoimmune disorder of the small intestine. This can cause vitamin deficiencies due to the improper absorption of nutrients in the small intestine. The small intestine can also be obstructed by a volvulus , a loop of intestine that becomes twisted enclosing its attached mesentery. This can cause mesenteric ischemia if severe enough.
A common disorder of the bowel is diverticulitis. Diverticula are small pouches that can form inside the bowel wall, which can become inflamed to give diverticulitis.
This disease can have complications if an inflamed diverticulum bursts and infection sets in. Any infection can spread further to the lining of the abdomen peritoneum and cause potentially fatal peritonitis. Crohn's disease is a common chronic inflammatory bowel disease IBD , which can affect any part of the GI tract,  but it mostly starts in the terminal ileum.
Ulcerative colitis an ulcerative form of colitis , is the other major inflammatory bowel disease which is restricted to the colon and rectum. Both of these IBDs can give an increased risk of the development of colorectal cancer.
Ulcerative coliltis is the most common of the IBDs . Irritable bowel syndrome IBS is the most common of the functional gastrointestinal disorders. These are idiopathic disorders that the Rome process has helped to define. Giardiasis is a disease of the small intestine caused by a protist parasite Giardia lamblia. This does not spread but remains confined to the lumen of the small intestine. Giardiasis is the most common pathogenic parasitic infection in humans. There are diagnostic tools mostly involving the ingestion of barium sulphate to investigate disorders of the GI tract.
Gestation can predispose for certain digestive disorders. Gestational diabetes can develop in the mother as a result of pregnancy and while this often presents with few symptoms it can lead to pre-eclampsia.
From Wikipedia, the free encyclopedia. Redirected from Digestive system. See also gastrointestinal tract. For digestive systems of non-human animals, see Digestion.
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Robbins and Cotran pathologic basis of disease. The Journal of the American Medical Association. Retrieved 12 June The New England Journal of Medicine, The Functional Gastrointestinal Disorders. Diagnosis, Pathophysiology and Treatment. Anatomy of the mouth. Vermilion border Frenulum of lower lip Labial commissure of mouth Philtrum. Hard palate Soft palate Palatine raphe Incisive papilla.
Parotid gland duct Submandibular gland duct Sublingual gland duct. Oropharynx fauces Plica semilunaris of the fauces Uvula Palatoglossal arch Palatopharyngeal arch Tonsillar fossa Palatine tonsil. Anatomy of the gastrointestinal tract , excluding the mouth.
Muscles Spaces peripharyngeal retropharyngeal parapharyngeal retrovisceral danger prevertebral Pterygomandibular raphe Pharyngeal raphe Buccopharyngeal fascia Pharyngobasilar fascia Piriform sinus.
Sphincters upper lower glands. Suspensory muscle Major duodenal papilla Minor duodenal papilla Duodenojejunal flexure Brunner's glands. Ileocecal valve Peyer's patches Microfold cell. Ascending colon Hepatic flexure Transverse colon Splenic flexure Descending colon Sigmoid colon Continuous taenia coli haustra epiploic appendix. Anatomy of the liver, pancreas and biliary tree. Physiology of the gastrointestinal system. Submucous plexus Myenteric plexus.
Segmentation contractions Migrating motor complex Borborygmus Defecation. Diseases of the digestive system primarily K20—K93 , — Gastritis Atrophic Ménétrier's disease Gastroenteritis Peptic gastric ulcer Cushing ulcer Dieulafoy's lesion Dyspepsia Pyloric stenosis Achlorhydria Gastroparesis Gastroptosis Portal hypertensive gastropathy Gastric antral vascular ectasia Gastric dumping syndrome Gastric volvulus.
Coeliac Tropical sprue Blind loop syndrome Small bowel bacterial overgrowth syndrome Whipple's Short bowel syndrome Steatorrhea Milroy disease Bile acid malabsorption. Abdominal angina Mesenteric ischemia Angiodysplasia Bowel obstruction: Proctitis Radiation proctitis Proctalgia fugax Rectal prolapse Anismus. Upper Hematemesis Melena Lower Hematochezia. Peritonitis Spontaneous bacterial peritonitis Hemoperitoneum Pneumoperitoneum.
Stomodeum Buccopharyngeal membrane Rathke's pouch Tracheoesophageal septum Pancreatic bud Hepatic diverticulum. Urorectal septum Proctodeum Cloaca Cloacal membrane. Esophagogastroduodenoscopy Barium swallow Upper gastrointestinal series. Bariatric surgery Duodenal switch Jejunoileal bypass Bowel resection Ileostomy Intestine transplantation Jejunostomy Partial ileal bypass surgery Strictureplasty.
Appendicectomy Colectomy Colonic polypectomy Colostomy Hartmann's operation. Anal sphincterotomy Anorectal manometry Lateral internal sphincterotomy Rubber band ligation Transanal hemorrhoidal dearterialization.
Colonoscopy Anoscopy Capsule endoscopy Enteroscopy Proctoscopy Sigmoidoscopy Abdominal ultrasonography Defecography Double-contrast barium enema Endoanal ultrasound Enteroclysis Lower gastrointestinal series Small-bowel follow-through Transrectal ultrasonography Virtual colonoscopy.
Fecal fat test Fecal pH test Stool guaiac test. Artificial extracorporeal liver support Bioartificial liver devices Liver dialysis Hepatectomy Liver biopsy Liver transplantation Portal hypertension Transjugular intrahepatic portosystemic shunt [TIPS] Distal splenorenal shunt procedure. Frey's procedure Pancreas transplantation Pancreatectomy Pancreaticoduodenectomy Puestow procedure. Diagnostic peritoneal lavage Intraperitoneal injection Laparoscopy Omentopexy Paracentesis Peritoneal dialysis.
Inguinal hernia surgery Femoral hernia repair. Human systems and organs. Fibrous joint Cartilaginous joint Synovial joint. Skin Subcutaneous tissue Breast Mammary gland. Myeloid Myeloid immune system Lymphoid Lymphoid immune system. Genitourinary system Kidney Ureter Bladder Urethra. Medicine portal Metabolism portal. Retrieved from " https: Organ systems Digestive system Metabolism.
Anatomical terminology [ edit on Wikidata ]. Pharynx Muscles Spaces peripharyngeal retropharyngeal parapharyngeal retrovisceral danger prevertebral Pterygomandibular raphe Pharyngeal raphe Buccopharyngeal fascia Pharyngobasilar fascia Piriform sinus. Enteric nervous system Submucous plexus Myenteric plexus. From here, food travels to the esophagus or swallowing tube. The esophagus is a muscular tube extending from the pharynx to the stomach.
By means of a series of contractions , called peristalsis, the esophagus delivers food to the stomach. Just before the connection to the stomach there is a "zone of high pressure," called the lower esophageal sphincter; this is a "valve" meant to keep food from passing backwards into the esophagus.
The stomach is a sac-like organ with strong muscular walls. In addition to holding the food, it's also a mixer and grinder. The stomach secretes acid and powerful enzymes that continue the process of breaking down the food.
When it leaves the stomach, food is the consistency of a liquid or paste. From there the food moves to the small intestine. Made up of three segments, the duodenum, jejunum, and ileum, the small intestine is a long tube loosely coiled in the abdomen spread out, it would be more than 20 feet long.
The small intestine continues the process of breaking down food by using enzymes released by the pancreas and bile from the liver. Bile is a compound that aids in the digestion of fat and eliminates waste products from the blood. Peristalsis contractions is also at work in this organ, moving food through and mixing it up with digestive secretions. The duodenum is largely responsible for continuing the process of breaking down food, with the jejunum and ileum being mainly responsible for the absorption of nutrients into the bloodstream.
Three organs play a pivotal role in helping the stomach and small intestine digest food:. Among other functions, the oblong pancreas secretes enzymes into the small intestine. These enzymes break down protein, fat, and carbohydrates from the food we eat.
The liver has many functions, but two of its main functions within the digestive system are to make and secrete bile, and to cleanse and purify the blood coming from the small intestine containing the nutrients just absorbed. The gallbladder is a pear-shaped reservoir that sits just under the liver and stores bile.