jejunum ileum

The digestive tract (also known as the alimentary canal) is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. The major functions of the GI tract are ingestion, digestion, absorption, and defecation.

MOUTH Teeth Oral Cavity Tongue TEETH

DENTITION Human being forms two sets of teeth during their life - temporary milk or deciduous teeth & permanent or adult teeth. This type of dentition is called DIPHYODONT. Each tooth is embedded in a socket of jaw bone. This type of attachment is called THECODONT. An adult human has four different types of teeth - Incisor, canine, premolar & molar. This type of dentition is called HETERODONT. DENTAL FORMULA - 2123 2123

TONGUE Tongue(Lower surface) Frenulum (Frenulum of the tongue: membrane that prevents a person from swallowing his or her tongue.)

Swallowing or deglutition Salivary glands helps soften & moisten the food Amylase (pH = 6.8) cleaves starch into maltose. Lysozyme acts as an antibacterial agent. Saliva moistens & lubricates food Breaks up food particle Breaks up food particles swallows Transports food Swallows food Transports food Swallowing or deglutition

Peristalsis Cardiac sphincter of Stomach

Cardiac Pyloric

Serosa Muscularis

Mucous cell - secrete mucus Peptic /Chief cells - secrete pepsinogen Parietal/oxyntic cells - secrete HCl & intrinsic factor

Parietal cells (oxyntic cells) Parietal cells (oxyntic cells). These are mainly found in the upper part of the gastric glands. These are rounded or pyramidal cells characterized by their round central nuclei and very acidophilic cytoplasm. The parietal cells are responsible for the synthesis and secretion of hydrochloric acid. In humans these cells are also responsible for synthesis of intrinsic factor, a glycoprotein essential for intestinal vitamin B12 absorption.

Stomach(pH = 1.8) Stores & churns food (food mixed with gastric juice is called Chyme). Pepsin cleaves proteins into proteoses & peptones HCl activates enzymes pepsinogen, prorenin, breaks up food, kills germs Mucus protects stomach wall Renin digest milk in infants. limited absorption

Small intestine - Duodenum, jejunum, ileum Mucosa has small finger-like folding called Villi. Each villi has a lacteal and blood vessels. Each villi is lined by brush border epithelial cells. In between the villi crypts are present called Crypts of Leiberkuhn which form intestinal glands. It secretes intestinal juice or Succus entericus.

Intestinal glands. These are simple tubular glands that open to the intestinal lumen between the base of the villi. The intestinal glands are sometimes called the crypts of Lieberkuhn. Secretory cells (Paneth cells) with large acidophilic granules are found at the base of the intestinal glands. Their function is still not fully understood, but it is known that they secrete lysozyme, which has anti-bacterial properties.

Brunners gland: (Purple spots) secrete alkaline fluid in response to parasympathetic stimulation. neutralizes acidic Chyme that enters the Duodenum from the Pyloric stomach

Liver is the largest gland of the body. It secretes bile juice which contains bile salts & bile pigments ( biliverdin & bilirubin). Bile juice is stored in the gall bladder Hepatic ducts Pancreas is a compound organ as it is both exocrine & endocrine. It secretes pancreatic juice Cystic duct Common hepato-pancreatic duct

The sphincter of Oddi refers to the smooth muscle that surrounds the end portion of the common bile duct and pancreatic duct. This muscle relaxes during a meal to allow bile and pancreatic juice to flow into the intestine. The sphincter of Oddi has three major functions: 1) regulation of bile and pancreatic flow into the duodenum, 2) diversion of hepatic bile into the gallbladder, and 3) the prevention of reflux of duodenal contents into the pancreaticobiliary tract. With the ingestion of a meal, the gallbladder contracts and there is a simultaneous decrease in the resistance in the sphincter of Oddi zone.

Breaks down & builds up many biological molecules. Liver Breaks down & builds up many biological molecules. Stores vitamin & iron. Destroys old blood cells. Produces bile containing bile pigment, bile salts, cholesterol, phospholipids. Gall bladder - Stores bile Pancreas Regulates blood glucose levels Bicarbonates neutralize stomach acid Enterokinase of the intestinal juice converts inactive trypsinogen to active trypsin Trypsin activates chymotrypsinogen & procarboxypeptidases Trypsin , chymotrypsin & Carboxypeptidase cleaves proteins into dipeptides. Amylase cleaves starch & glycogen into disaccharides Lipase cleaves lipids into di- & monoglycerides. Nuclease cleaves nucleic acid into nucleotides & nucleosides Small intestine - Completes digestion. Absorbs nutrients. Goblet cell secretes Mucus that protects gut wall Dipeptidases cleaves dipeptides into amino acid. Sucrases cleaves sucrose. Lactase cleaves lactose. Maltase cleaves maltose Lipase cleaves di- & monoglycerides into fatty acids + glycerol Nucleotidases & nucleosidases cleaves nucleotides & nucleosides into sugars & bases.

LARGE INTESTINE .

LARGE INTESTINE Regulates water, ions, & vitamins. Absorbs certain drugs. Secretion of mucus for lubrication. Stores waste APPENDIX Contains cells of the immune system ANUS Opening for waste elimination RECTUM Expels waste