Digestive system

The digestive system is made up of the gastrointestinal tract—also called the GI tract or digestive tract—and the liver, pancreas, and gallbladder. ... The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus.

1. DIGESTIVE SYSTEM Prof. Amol B Deore Department of Physiology MVPs Institute of Pharmaceutical Sciences, Nashik

2. COMPOSITION OF THE SALIVA Daily salivary secretion:1400 mL P H = 5.8 – 7.4 Water Mucus Mineral salts: Na + , K + , Mg +2 , Ca +2 , HCO 3 , SO 4 - 2 etc. Salivary amylase ( Ptyline ) Lingual lipase Lysozyme Antibodies Clotting factors Urea, uric acid Serum albumin, globulin

3. Digestion of carbohydrates SALIVARY AMYLASE Salivary amylase initiates the breakdown of complex sugars (polysaccharides) like starch , reducing them into disaccharide maltose .

4. Lingual lipase

5. Stomach juice break down proteins and other substances into simple soluble substances. The food remains in the stomach for upto three hours.

6. The stomach is divided in a four portions: the cardia, the fundus, the body, and the pylorus. The fundus and body are mainly storage areas, whereas most digestion takes place in the pylorus.

7. COMPOSITION OF GASTRIC JUICE P H : acidic < 4 Daily secretion: 1000-2000 mL per day Water Mineral salts Na + , K + , Mg +2 , Ca +2 , HCO 3 - , SO 4 -2 etc. Mucus Pepsinogen Gastric lipase Hydrochloric acid Intrinsic factor (glycoprotein)

8. intrinsic factor + vitamin B 12 Absorption of vitamin B12 in small intestine

9. COMPOSITION OF PANCREATIC JUICE Daily secretion : about 500 to 600mL P H : about 8 Water Mineral salts Pancreatic amylase Pancreatic lipase Proteolytic enzymes Trypsinogen & Chymotrypsinogen Carboxypeptidase Ribonuclease Deoxyribonuclease

10. Functions of pancreatic juice

11. GALLBLADDER

12. COMPOSITION OF BILE Daily secretion: about 500mL P H :- About 8.0 Water Mineral salts Mucus Bile salts: Sodium taurocholate, Sodium glycocholate , Bile pigment: Bilirubin Stercobillin Cholesterol

13. SMALL INTESTINE

14. Fig 9.8: anatomy of small intestine, villi & microvilli

15. The intestine wall is made up of four layers: Mucosa, submucosa, muscularis & serosa. Mucosa : the mucosa contains permanent circular folds (cavities), villi and microvilli which provide large surface area for digestion and absorption. The villi are tiny finger like projections of mucosa layer of the small intestine.

16. The villi enclose a blood capillary network and lymph capillaries called lacteals. Water-soluble nutrients are absorbed into the blood in the capillary networks. Fat-soluble nutrients are absorbed into the lymph in the lacteals of the villi. When chyme passes into small intestine it is mixed with pancreatic juice, bile and intestinal juice and is in contact with villi.

17. COMPOSITION OF INTESTINAL JUICE Daily secretion : about 2000 mL P H : 7.8 – 8.0 Water, Mucus, Mineral salts Na + , K + , Mg +2 , Ca +2 , HCO 3 - , SO 4 -2 etc Enzymes - Enterokinase or ( enteropeptidase ), - α- Dextrinase , Maltase, Sucrase , - Lactase, Peptidase, Nucleosidase

18. The liver consists of two large lobes, right and left, and fills the upper right and center of the abdominal cavity, just below the diaphragm. The structural unit of the liver is the liver lobule , a roughly hexagonal column of liver cells (hepatocytes ). Between adjacent lobules are branches of the hepatic artery and portal vein. The capillaries of a lobule are sinusoids , large and very permeable vessels between the rows of liver cells. The hepatic artery brings oxygenated blood , and the portal vein brings blood from the digestive organs and spleen. Each lobule has a central vein. The central veins of all the lobules unite to form the hepatic veins, which take blood out of the liver to the inferior vena cava

19. The cells of the liver have many functions ( which are discussed in a later section), but their only digestive function is the production of bile . Bile enters the small bile ducts, called bile canaliculi , on the liver cells , which unite to form larger ducts and finally merge to form the hepatic duct , which takes bile out of the liver. The hepatic duct unites with the cystic duct of the gallbladder to form the common bile duct , which takes bile to the duodenum.