1. Lecture 22
Digestive System II

2. Small Intestine Site of greatest amount of digestion and absorption
Duodenum
Jejunum
Ileocecal valve
Ileum
Fig
Site of greatest amount of digestion and absorption
Divisions
Duodenum (“twelve finger widths”)
Jejunum (“empty”)
Ileum (“twisted”)

3. Small Intestine Secretions
Mucus
Protects against digestive enzymes and stomach acids
Digestive enzymes
Disaccharidases: Break down disaccharides to monosaccharides
Peptidases: Hydrolyze peptide bonds
Nucleases: Break down nucleic acids

4. Duodenum and Pancreas Duodenum 25cm in adult
Accessory glands empty secretions into duodenum
Fig

5. Histology of Small Intestine
Fig
Circular folds, villi and microvilli increase surface area
Epithelial cells produced by intestinal glands

6. Liver
Inferior
vena cava
Posterior
Caudate lobe
Left lobe
Right lobe
Inferior
vena cava
Left lobe
Hepatic
portal vein
Right lobe
Common
hepatic duct
Cystic duct
Gallbladder
Quadrate lobe
Gallbladder
(a) Anterior view
Anterior
(b) Posteroinferior view
Fig
4 Lobes
Ducts
Cystic duct joins with common hepatic duct to form common bile duct
Common bile duct joins pancreatic duct

7. Functions of the Liver Bile production Storage
Salts emulsify fats, neutralizes stomach acid
Stored in gall bladder
Gallstones can form as precipitate of cholesterol
Storage
Glycogen, fat, vitamins, copper and iron
Nutrient interconversion
Detoxification
Removal of ammonia and conversion to urea (eliminated by kidneys in urine)
Phagocytosis
Removal of worn-out and dying red and white blood cells, some bacteria
Synthesis
Blood proteins

8. Pancreas Anatomy Endocrine Exocrine Insulin Pancreatic juice
Digestive enzymes
Released in inactive form
Become active in duodenum
Digest protein, fats, carbohydrates, and nucleic acids

9. Review Question
Digestion of proteins is started in the ______________ and completed in the ________________.
Oral cavity, stomach
Stomach, small intestine
Esophagus, small intestine
Oral cavity, small intestine
Esophagus, stomach

10. Large Intestine Extends from ileocecal valve to anus
Transverse colon
Extends from ileocecal valve to anus
Consists of cecum, colon, rectum, anal canal
Movements sluggish (18-24 hours)
Descending
colon
Ascending
colon
Cecum
Sigmoid
colon
Vermiform
appendix
Ileocecal
valve
Cecum
Ileum
Vermiform appendix
Rectum
Anal canal
Fig

11. Movement in Large Intestine
Mass movements
Common after meals
Defecation reflex
Distension of the rectal wall by feces
Defecation
Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration (breathing in) and contraction of abdominal wall muscles
Rectal valve
Rectum
Anal canal
Veins
Internal
anal sphincter
Anus
External
anal sphincter
Fig

12. Points to Remember Stomach Small intestine Large intestine Mixes food
Protein digestion
Limited absorption (aspirin)
Small intestine
Receives secretions of liver and pancreas
Chemical and mechanical digestion
Transports undigested material
Large intestine
Absorb water
Form, store and expel feces

13. Questions?