Outline-3, BIO 2320, Digestive System (pancreas through large intestine)

L. Pancreas (Accessory)

1. Position

Posterior, inferior to stomach

2. Pancreatic duct

Pancreas to duodenum

3. Islets

Endocrine cells

4. Pancreatic Juice

a. Acinar Cells [99%]– Exocrine cells

b. Bicarbonate (pH 8)

c. Pancreatic Amylase (Carbohydrate Enzymes)

d. Protein Enzymes

1. Trypsin

2. Chymotrypsin

3. Carboxypolypeptidase

e Lipase

f. Controls of Release

The following increase pancreatic juice release:

1. Secretin

2. Cholecystokinin

3. Neurally (Vagus nerve)

M. Liver(Hepato-) (Accessory)

1. 4 Lobes; Right & Left Lobes are large-separated by Falciform Ligament

2. Hepatocyte

3. Common Bile Duct– Hepatic ducts and gall bladder ducts join and empty into duodenum

4. Blood supply

Quite large

5. Bile Production [600-1000 ml/day]

a. Liver Cells

b. Gall Bladder –Stores bile

c. Bile composition

1. Water

2. Bilirubin

Break down product of hemoglobin

3. Bile salts –Emulsification

Breaks fat into smaller particles

d. Enterohepatic circulation

Bile salts released into duodenum are reabsorbed in ileum and returned to liver

e. Rate of secretion

The following increase bile secretion:

1. Increased Enterohepatic circulation, increased hepatic blood flow

2. Vagus nerve

3. Secretin

4. Cholecystokinin

6. Other Liver functions

a. Metabolic Regulation – Blood filtering, monitoring

b. Blood Regulation – Clotting factors, blood protein production

c. Phagocytose old WBC, RBC

d. Detoxification, Storage of poison

e. Stores Glucose (glycogen), Fat, Protein, Cu,

Fe, Vitamins

N. Small Intestine[3-5 hours]

1. Duodenum (1′), Jejunum (8′), Ileum (12′)

2. Microstructure

a. Villi and Microvilli

b. Blood vessels & Lacteals

3. Intestinal Secretions/Juice (2-3 l/d)

– Duodenal (Brunner’s) glands

Protective mucus

 Intestinal glands make isotonic juice containing enzymes

4. Motility

a. Segmentation


b. Peristalsis

Wave like weak contractions for movement of chyme

5. Absorption

a. Definition

Nutrients pass from GI tract into bloodstream or lymph vessel, 90% absorption occurs in small intestine

b. Villi & microvilli

Increase surface area for absorption!

c. Active transport, diffusion, facilitated diffusion, cotransport

d. Carbohydrate

– Glucose

e. Proteins

f. Lipids

1. Emulsification

2. Lipase

3. Micelles [fat + bile salt]

4. Chylomicrons [more breakdown within epithelial cells, bile recirculated]

5. Lacteals


g. Vitamins

Vitamins ADEK absorbed along with fat, Vitamins BC absorbed along with water

h. Water & Electrolytes (ions in solution)

1. 200-400 ml water/hour by osmosis (9 liters/day)

2. Sodium

3. Calcium; Vit. D dependent

O. Large Intestine[3-5 hrs; 5′]

1. Cecum

a. Ileocecal sphincter (valve)

b. Appendix

2. Colon

a. Ascending

b. Transverse

c. Descending

d. Sigmoid

3. Rectum

4. Anus

5. No Villi

6. Goblet Cells

Make mucus

7. Taeniae coli

Flat muscular bands

8. Haustra

Pouches formed by contraction of Taeniae coli muscles

9. Motility

a. Peristalsis

b. Haustral churning

c. Mass peristalsis [3-4x/d]

Drives contents into rectum

d. Gastroileal reflex [activates mass peristalsis]

e. Defecation reflex

Relaxation of internal anal sphincter

f. Anal sphincters

Internal & external

10. Function

a. Some absorption (water)

b. Lubrication

c. Form & Store feces

d. Vitamin K & some B’s & absorption

e. Bacterial fermentation

Pancreas & Bile Secretion Video

Intestinal Motility Video

Summary of Digestive Organs Video