Digestive System

DIGESTIVE SYSTEM

I. Overview

A. Alimentary canal (gastrointestinal tract)

1. Organs include: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anal canal, anus

2. Accessory organs: tongue, salivary glands, teeth, gall bladder, pancreas, liver

B. Processes of Digestion

1. Mechanical digestion -

2. Chemical digestion -

3. Movements of food through the alimentary canal

a. Peristalsis -

b. Segmentation -

4. Absorption of nutrients

5. Elimination

II. Histological Organization of the Digestive Organs

A. Layers of the Wall

1. Mucosa -

a. Epithelium

b. Lamina propria

c. Muscularis

2. Submucosa -

3. Muscularis Externa

4. Serosa (visceral peritoneum)

III. Digestive Organs

A. Mouth and Oral cavity (food mass is a bolus when chewed and swallowed)

1. Tongue

a. Filiform papillae-
b. Fungiform papillae-
c. Foliate papillae -
d. Circumvalate papillae -

2. Palate

3. Salivary Glands

a. Parotid gland -

b. Submandibular gland -

c. Sublingual gland -

d. Salivary secretions -

4. Teeth

a. Deciduous: I2/2, C1/1, P0/0, and M2/2
b. Permanent: I2/2, C1/1, P2/2, and M3/3
c. Tooth anatomy
d. Mastication

B. Pharynx

1. Oropharynx

2. Laryngopharynx

C. Esophagus

1. Esophageal hiatus

2. Hiatal hernia

3. Deglutition

4. Lower Esophageal (Cardiac) sphincter

D. Stomach

1. Gross anatomy

a. Regions: cardia (or "cardiac"), fundus, body, pylorus

b. Rugae

c. Greater and lesser curvatures

d. Greater and lesser omentum

e. Pyloric sphincter

f. Pyloric stenosis of the newborn

2. Gastric juices

a. Gastric Pits

b. Gastric glands

c. Cell Types of the Gastric Gland

CELL TYPES	FUNCTIONS
Mucous Neck Cells
Parietal Cells
Chief Cells

3. Regulation of gastric secretions

HORMONE	PRODUCED BY	TARGET	FUNCTION
Gastrin
Cholycystokinin (CCK)
Secretin
Gastric Inhibitory peptide

4. Why is there little nutrient absorption occurring in the stomach?

5. Mixing and emptying the stomach

a. 3 Layers of smooth muscle in the muscularis

b. What kind of foods spend the most time in the stomach?

c. What kinds of foods spend the least time in the stomach?

E. Small Intestine

1. Parts of the small intestine:

a. Duodenum
b. Jejunum
c. Ileum

2. Structure of the wall

a. Factors that increase the surface area for absorption:

1. Plicae circulares -

2. Villi -

3. Microvilli -

b. Lacteals

c. Lining epithelium (many goblet cells)

d. Intestinal movements

1. Segmentation
2. Gastroenteric reflex
3. Gastroileal reflex

3. Chemical Digestion in the Small Intestine:

ENZYME	FUNCTION
Peptidases
Sucrase
Maltase
Lactase
Lipase

4. Intestinal Hormones

HORMONE	ORIGIN	TARGET	FUNCTION
Gastrin
Secretin
Cholecystokinin (CCK)
Gastric Inhibitory Peptide (GIP)

5. Absorption in the small intestine

Proteins -->

Carbohydrates -->

Lipids -->

F. Pancreas

1. Retroperitoneal organ

2. Acinar cells

3. Pancreatic juice

ENZYME	FUNCTION
Pancreatic Amylase
Pancreatic Lipase
Nucleases
Trypsin
Chymotrypsin
Carboxypeptidase

4. Regulation of pancreatic secretions

a. Secretin - stimulates bicarbonate release

b. Cholecystokinin (CCK) - stimulates pancreatic juice release

G. Liver

1. Anatomy of the Liver

a. Two main lobes

b. Falciform ligament

c. Round ligament

d. Each lobe made up of lobules (functional units of the liver)

e. Histology of the liver

1. hepatocytes
2. central vein
3. bile canaliculi
4. portal triad (branch of Portal vein, hepatic artery and bile duct)
5. Kupffer cells (macrophages)
6. sinusoids

*Note: what is the direction of blood flow and bile flow through the liver lobule?

3. Bile

a. Composition - bile salts, cholesterol, water, bile pigments

b. Bile salts emulsify fats

c. Jaundice

d. Hepatitis

4. Functions of the Liver

5. Gallbladder

a. Function -

b. Ductile system:

c. Gallstones

*Q: What would happen if their was a lack of bile salts?

H. Large Intestine

1. Parts

a. Cecum -

b. Appendix -

c. Colon:

1. Haustra

2. Taeniae coli

3. Ascending colon

4. Transverse colon

5. Descending colon

6. Sigmoid colon

d. Rectum and Rectoanal canal

1. Hemorrhoids - inflamed rectal veins

2. Anus

3. Internal anal sphincter -

4. External anal sphincter -

2. Absorption in the Large Intestine:

a. Vitamins

b. Bilirubin Products

c. Bile Salts

d. Toxins

3. Unique Features of the Large Intestine

a. Gobs of goblet cells

b. Taeniae coli -

c. Haustra -

d. Epiploic appendages

4. Movements of the large intestine

a. Peristalsis

b. Mass movements

IV. Digestive Processes Wrap-Up

A. Digestion and absorption of Carbohydrates

B. Digestion and absorption of Proteins

C. Digestion and Absorption of Lipids

1. Lacteals

2. Chylomicrons

D. Absorption of Water

E. Absorption of Vitamins

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Last Updated 06/08/07