Lecture 2

Question 1

GI tract wall consists of 4 layers

Answer 1

1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa

Question 2

Mucosa

Answer 2

—innermost layer; epithelial tissue, lamina propria, muscularis mucosae

Question 3

Submucosa

Answer 3

—connective tissue with blood vessels, lymphatics, and nerves

Question 4

Muscularis

Answer 4

—longitudinal and circular layers of smooth muscle
- Stomach has additional oblique layer

Question 5

Serosa

Answer 5

—outermost layer; thin layer of connective tissue

Question 6

Mechanical digestion

Answer 6

—uses force generated by muscles to digest nutrients
Begins with chewing (mastication) in the mouth
Muscularis layer is involved in mechanical digestion
Peristalsis—wave-like contraction

Question 7

Chemical digestion

Answer 7

—utilizes enzymes and other secretions to break down ingested material
Other secretions come from salivary glands, stomach, liver, pancreas, and gallbladder

Question 8

Nerve Supply

Answer 8

Central nervous system initiates activities such as salivation
Also responsible for sight, taste, smell, and feel of ingested materials
Enteric nervous system innervates GI tract
Myenteric plexus controls movements of muscularis
Submucosal plexus controls digestive secretions
Autonomic nervous system
Sympathetic—decreases GI motility and secretion
Parasympathetic—increases GI motility and secretion

Question 9

Blood supply

Answer 9

Provides nutrients & removes wastes from GI tract and accessory organs
Absorbs protein & carbohydrate nutrients
Lipids absorbed by unique lymphatic capillaries called lacteals
Hepatic portal system
Veins that drain intestine carry absorbed nutrients to liver first
Liver processes and detoxifies incoming nutrients before they enter general circulation