Location of stomach• Stomach is situated on the left side of abdomen under diaphragm
• (in direction or location) from front to back in the median plane or in a plane parallel to the median.
Stomach wall• 3 layers• Outer layer of connective tissue• Middle layer of smooth muscles• Inner layer( mucosa) of connective tissue with many glands.
Middle layer• Outer longitudinal• Inner circular muscles• These muscle layers help in churning (mixing ,tossing and turning) and mixing of food with stomach secretions.• This mixture is called chyme
Mucosa• It has various tubular gastric glands which are composed of 3 kinds of cells.
Mucous cells• They secrete mucus• Mucous is thick secretion that covers the inside of stomach and stops digestion of lining of stomach wall
Parietal cells• Also called oxyntic cells• They secret HCl.• HCl is secreted in concentrated forms.• It adjusts the pH of stomach contents ranging from 2-3 so that pepsin can act on proteins.• It also makes food soft• It kills microorganism taken along with food
Zymogen cells• They secrete pepsinogen.• Pepsin is an enzyme.• Its inactive form is called pepsinogen.• Pepsinogen gets converted to pepsin only in acidic environment or after getting exposed to some already activated pepsin.• Pepsin hydrolyses protein to produce peptones and polypeptides.
Gastric juice• Secretions of all these cells is called gastric juice.
Digestion of carbohydrates• In the Mouth The process of digesting carbohydrates begins in the mouth. Our saliva contains an enzyme called amylase that starts breaking down the more complex carbs into simpler types.• In the Stomach Enzyme activity continues in the stomach, but slows down significantly as digestive acids are released into the stomach by the glands.
• The secretion of gastric juice is regulated by• 1. smell• 2.sight• 3.quality
• Chyme finally goes to duodenum through relaxed pyloric sphinter.