Chapter 24 Notes Continued
The Digestive System

The Accessory Organs of the Small Intestine

6. Pancreas 

• hammer shaped
• head near duodenum, tail near spleen
• duct of Wirsung empties into the common bile duct
• exocrine secretions

- grape-like clusters called acini
- CCK controls digestive enzyme secretion

1. amylase
2. trypsinogen (inactive)
3. lipase

- secretin controls buffer secretion

4. sodium bicarbonate

• endocrine secretions
  - Islets of Langerhans secrete two hormones
  - blood glucose levels control these

5. insulin
6. glucagon

7. Liver

• largest organ
• four lobes: right, left, quadrate, caudate
• unit of the liver called a LOBULE
• chains of hepatic cells radiating around a central vein
• blood vessels at outer edge allow blood flow over each cell
• sinusoids are leaky capillaries
• kupffer cells are phagocytes
• without your hepatic cells you would:

- not have the energy to carry on

1. glycogenesis
2. glycogenolysis
3. gluconeogenesis

- waste away

4. synthesize lipoproteins
5. synthesize cholesterol for bile salts

- have a waste poor urine

6. deamination produces urea

- be killed by your bad habits

7. detoxifies alcohol and drugs

- have bad old erythrocytes

8. phagocytosis of worn out red blood cells

- bleed to death

9. synthesis of clotting proteins: fibrinogen and prothrombin

- lack fat-soluble vitamins

10. stores vitamins A,D,E, and K

• blood flow through the liver by the hepatic portal system
  - hepatic artery and hepatic portal vein
  - liver sinusoids (capillaries)
  - central vein
  - hepatic vein
  - inferior vena cava
• liver online histology

8. Gall Bladder

• bile manufactured by the liver
• separate system of ducts sends bile to the gall bladder
• bile is stored here until CCK signals gall bladder contraction
• bile contents include:
  - bile salts: cholesterol based to emulsify lipids in duodenum
  - bilirubin: waste product of heme from hemoglobin
  - products of detoxification
• pathway of bile from liver

- right and left hepatic duct
- common hepatic duct
- cystic duct
- GALL BLADDER for storage
- food enters intestines and gall bladder contracts
- cystic duct
- common bile duct
- duodenum
- online ducts

The Small and Large Intestines

9. Small Intestine

• major role in digestion and absorption
• duodenum-->jejunum-->ileum = 21 feet
• increased absorptive surface by

- villi contain capillary and a lacteal
- microvilli form a brush border

• secretions from intestinal crypts of Lieberkuhn include the following digestive enzymes

- dextrinase, maltase, sucrase, lactase
- peptidase
- nucleosidases, phosphatases
- lipase

• secretion of mucus increases and digestive enzyme decrease along the route of the small intestine
• ileum has lymphatic nodules called Peyer's patches
• online histology

10. Large Intestine

• the colon: ascending, hepatic flexure, transverse, splenic flexure, descending, sigmoid
• ileocecal valve prevents backflow
• 2X the diameter of the small intestine
• no villi, no enzymes
• taenia coli are three bands of longitudinal muscles, when contracted
  cause a puckering called haustra
• functions

- secretion of mucus and sodium bicarbonate to protect against acid producing bacteria
- water and electrolyte absorption
- manufacture of vitamins B and K by bacteria
- preparation of digested nutrients for elimination

0nline organs

11. Digestive tract valves