Digestive system Flashcards
2 main parts of the digestive system
Alimentary canal
Associated glands
Constituents of saliva
water
salt
cells
mucins (slippery glycoprotein)
buffers
anti-microbial components- immunoglobulines and lysozymes.
Functions of Saliva
• Salivary amylase: Chemical digestion of polysaccharides (e.g. starch and glacogen) into smaller polysaccharides and disaccharide maltose.
• Water: Liquefy food and provide watery medium for chemical digestion. Aids in taste reception.
• Mucus: Lubrication of food which makes it easier for swallowing. Clean the mouth and protects the lining of the mouth from abrasion.
• Antimicrobial substances such as immunoglobulin and lysozymes: Protect against bacteria that enter the mouth.
• Buffers prevent tooth decay by neutralizing acid
Oral cavity is lined by?
Non-keratinized squamous epithelium
Types of cells present in gastric gland?
Mucus cells - secrete mucus
Chief cells - secrete pepsinogen
Parietal cells - Release hydogen ions and chloride ions separately into the stomach where HCl is formed.
Gastric juice mainly consist of?
Mucus, pepsinogen, HCl and intrinsic factor( glycol-protein secreted by chief cells)
Chemical digestion in the stomach
Pepsinogen is initially converted to pepsin by HCl
This activated pepsin intiates the protein digestion (churning action of the stomach facilitates it.)
Proteins are hydrolyzed to small polypeptides by pepsin.
Stomach
The stomach is a J- shaped dilated sac in the abdominal cavity. The inner surface of the stomach is highly folded and contains large number of pits that leads to gastric glands. Sphincters are found at the junctions between esophagus and stomach (cardiac sphincter) and stomach and the small intestine(pyloric sphincter). They are made up of circular smooth muscles. These sphincters help to regulate the passage of materials between these organs.
What is chyme?
Partially digested semisolid, acidic, food mass
Small intestine
Longest organ in the alimentary canal.
3 regions: duodenum, jejunum and ileum.
Surface area is greatly increased by permenant circular folds and villi.
Most of the digestion is completed in the duodenum while major sites of nutrition absorption are jejunum and ileum.
Highest absorption of water is found in the small intestine.
Intestinal glands
Crypts of Liberkuhn
How nutrients are absorbed in the small intestine
Products of fat digestion are absorbed into the lacteal of the villus while products of digestion of other nutrients are absorbed into blood capillaries. Blood capillaries are converged in to the hepatic portal veins and are transported to the liver and then to the tissues.
What are ulses in stomach
Wounds in stomach
Chyme is mixed with
Secretions from intestinal wall, pancrease and liver.
Glands of intestinal wall secretes
Disaccharidases
Dipeptidases
Carboxypeptidases
Aminopeptidases
Neucleotidases
Nucleosidaaes
Phosphotases
What are the hormones secreted by the duodenum which stimulates the release of pancreatic juice and bile
Secreton and cholecystokonin