Digestive System Pancreas – Large Intestine

Pancreas (accessory) Location Pancreatic duct Islets

Pancreas Pancreatic Juice Acinar Cells – exocrine Bicarbonate Pancreatic Amylase

Pancreas Protein Enzymes – Trypsin – Chymotrypsin – Carboxypolypeptidase Lipase

Controls of Juice Release Secretin Cholecystokinin Neurally – Vagus nerve stimulates release

Liver (accessory) Hepato- 4 lobes; Falciform ligament separates large R & L lobes Cells are hepatocytes Common Bile Duct (Hepatic duct + Gall bladder duct), which empties into duodenum

Liver Blood supply – enormous Bile Production – mls per day – Liver cells make bile, gall bladder STORES bile

Bile Composition Water Bilirubin (from Hb breakdown) Bile Salts function in Emulsification

Enterohepatic Circulation Bile salts secreted into duodenum, are reabsorbed in ileum and returned to liver

Bile Secretion Controls Enterohepatic Circulation Vagus Nerve Secretin Increased hepatic blood flow Cholecystokinin

More liver functions Metabolic regulation (blood filtering, monitoring blood) Clotting factors are made by liver Blood protein synthesis Phagocytosis of old WBC & RBCs Detoxification, storage of toxins Stores glucose (glycogen), fat, protein, Cu, Fe, Vitamins

SUMMARY of GI HORMONES GASTRIN – Made by pylorus cells – Increases gastric motility – Increases gastric secretions

SUMMARY of GI HORMONES SECRETIN – Made by duodenal cells – Decreases gastric motility & secretions – Increases pancreatic juice release – Increases bile secretion

SUMMARY of GI HORMONES CHOLECYSTOKININ – Made by duodenal cells – Decreases gastric motility & secretions – Increases pancreatic juice release – Increases gall bladder contraction

SUMMARY of GI HORMONES GIP (Gastric Inhibitory Peptide) – Made by duodenal cells – Decreases gastric motility & secretions – Promotes insulin release

Small Intestine 21 foot tube Duodenum – 1 foot Jejunum – 8 ft. Ileum – 12 ft.

Small Intestine Microstructure Villi Microvilli Blood vessels Lacteals

Small Intestinal Secretions 2-3 liters of “juice” per day Duodenal glands (Brunner’s) make protective mucus Intestinal glands make isotonic fluid containing some digestive enzymes

Small Intestine Motility Segmentation Peristalsis

Absorption Definition – 90% of all absorption occurs in SI Nutrients from SI to blood or lymph vessel Villi & Microvilli Processes include active transport, diffusion, facilitated diffusion, cotransport

Absorption Carbohydrates Proteins Lipids – Emulsification – Lipase – Micelles (fat + bile salt) – Chylomicrons – Lacteals

Absorption Vitamins (ADEK along with fat, B’s and C along with water)

Absorption Water & Electrolytes (ions in soln.) 9 liters/day by osmosis Sodium Calcium absorption is Vit. D dependent

Large Intestine Five feet long Cecum – Ileocecal sphincter = valve – Appendix

Large Intestine Colon – Ascending – Transverse – Descending – Sigmoid Rectum Anus

Large Intestine No villi Goblet cells make mucus Taeniae coli – flat muscular bands Haustra – pouches as taeniae coli contract

Large Intestine Motility Peristalsis Haustral churning Mass peristalsis drives contents into rectum Gastroileal reflex activates mass peristalsis Defecation reflex Anal sphincters – Internal and External

Large Intestine Functions Some water absorption Lubrication of contents Form and store feces Synthesis of Vitamin K and some B vitamins and absorption Bacterial fermentation