Accessory Organs Pancreas Liver and Gallbladder Pancreas Secretes

Accessory Organs Pancreas, Liver and Gallbladder

Pancreas • Secretes pancreatic juice into pancreatic duct then to the duodenum • Function: contains 4 classes of enzymes to break down substances. • Location: posterior to stomach; left side

Pancreatic Juice • Pancreatic amylase – splits starch and glycogen into disaccharides • Pancreatic lipase – splits triglycerides into fatty acids and monoglycerides • Proteinases (Trypsin, chymotrypsin, carboxypeptidase) – Breaks up peptide bonds • Nucleases – split nucleic acid molecules

Pancreatic Juice • Bicarbonate ions make pancreatic juice alkaline to neutralize acidic chyme

Pancreatic Secretion Regulation • During cephalic and gastric digestive phases parasympathetic impulses stimulate pancreatic secretion. • Secretin: hormone – causes release of pancreatic juice into duodenum – stimulates a bicarbonate-rich fluid. – Activated by the duodenum filling up with chyme

Figure 17. 25

Pancreatitis • Inflammation of pancreas • Caused by activation of enzymes in the pancreas gland – Trypsinogen------trypson

Liver • Largest internal organ • 2 lobed structure – Large right and small left • Each lobe is made up of Hepatic lobules: function unit of the liver Figure 17. 28

Liver • Lobes are divided into hepatic lobules – hepatic cells around a central vein – hepatic sinusoids lead to the hepatic portal vein – Kupffer cells remove bacteria by phagocytosis – bile canals lead to hepatic ducts which merge at the common bile duct Figure 17. 29

Liver Functions 1. Metabolism: • Carbohydrate metabolism – stores glycogen, regulates blood glucose levels • Lipid metabolism – synthesizes lipoproteins, regulates lipid metabolism • **Protein metabolism – deamination of amino acids, forming urea – transamination of amino acids – synthesis of plasma proteins • (clotting proteins)

Liver Functions 2. Stores minerals and vitamins – iron is stored as ferritin, Vit A, B 12 and glycogen 3. Detoxification of substances, including alcohol 4. Destruction of damaged red blood cells 5. Phagocytosis of foreign antigens – Contain Kupffer’s cells • Remove and destroy microbes, foreign matter and worm platelets and erythrocytes 6. Serves as a bile reservoir and Secretion of bile 7. Blood reservoir

Bile Composition Yellowish-green fluid secreted by hepatic cells • Contains water (90%), cholesterol, and electrolytes • Contains bile salts* – Emulsify (break down) fats – Makes cholesterol • Contains bile pigments – bilirubin, biliverdin – breakdown products of hemoglobin

Figure 17. 30

Jaundice • Abnormal Skin pigmentation • Excess bilirubin in the blood. (Bilirubin is produced by the normal breakdown of red blood cells. Normally bilirubin passes through the liver and is excreted as bile through the intestines)i • Jaundice occurs when bilirubin builds up faster than the liver can break it down and pass it from the body.

Liver Diseases • Cirrhosis • Jaundice

Gallbladder • Bile is produced by the liver and concentrated in the gall bladder. • Stores bile between meals Figure 17. 32

Gallbladder CCK • Cholecystokinin: released in response to proteins and fats in the small intestine, stimulates gall bladder contraction. • Bile leaves through the cystic duct to the common bile duct and is squirted into the duodenum of the small intestine.

Function of Bile Salts • Bile salts enhance absorption of fatty acids and fat -soluble vitamins. • Bile salts reduce surface tension and break fat into small droplets (emulsification). • Emulsification increases surface area so lipases can more easily digest fats. • The intestinal mucosa reabsorbs nearly all of the bile salts.

Blocked cystict duct

cholecystitis

Small Intestine • Extends from the pyloric sphincter to the large intestine • Three portions: duodenum, jejunum, ileum • Receives secretions from the pancreas and the liver • Complete digestion of nutrients in chyme, absorbs products of digestion, Figure 17. 33 transports residue to the large intestine

Figure 17. 33

Small Intestine • Double-layered folds of peritoneum – mesentery: supports intestinal nerves, blood and lymphatic vessels – greater omentum: drapes over the intestine • Inner intestinal wall has many tiny projections, the intestinal villi. Each contains blood vessels, nerves and a lacteal • Intestinal glands extend into the mucosa • Circular folds of the mucosa, plicae circulares, increase surface area

Figure 17. 35

Figure 17. 36

Figure 17. 37

Small Intestine Secretions • Mucus is secreted by goblet cells and glands in the submucosa • Intestinal mucosa have digestive enzymes on their luminal surfaces – peptidases: split peptides into amino acids – sucrase, maltase, lactase: split disaccharides into monosaccharides – intestinal lipase: splits fats into fatty acids and glycerol