Chapter 62: GI Function Basics (Discussion 8)

Question 1

Major Purpose of GI Tract

Answer 1

Intake H2O, electrolytes, and nutrients

Question 2

Functions of GI Tract (5)

Answer 2

1. Move food through tract
2. Secrete digestive substances/digestion
3. Absorb desired substances from digested products
4. Circulation of blood through GI organs
5. Regulation of functions through nervous/hormonal control

Question 3

Path through GI Tract

Answer 3

1. Mouth
2. Esophagus
3. Stomach
4. Small Intestine
   
   1. Duodenum
   2. Jejunum
   3. Ileum
5. Large Intestine
   
   1. Ascending
   2. Transverse
   3. Descending
   4. Sigmoid
6. Anus

Question 4

Layers of GI Wall - Nervous Regulation

Answer 4

1. Myenteric plexus: signal outer muscular layer
2. Submucosal plexus: signal inner layer
   
   1. Secretion/absorption
   2. Blood flow

Question 5

Para/Sympathetic Stimulation

Answer 5

Parasympathetic: acetylcholine –> excites GI function (motility and secretion)

Sympathetic: norepi/epi –> inhibit GI functions

Question 6

GI Reflexes

Answer 6

• Can excite or inhibit GI function
• Can act locally, systemically, or integrate with CNS

Question 7

GI Stimuli for Reflexes

Answer 7

Irritation of mucosa

Excessive distention of gut

Presence of specific chemicals

Question 8

Gastrin

Answer 8

Secreted by: stomach in response to meal ingestion

Stimulates: gastric acid secretion

Question 9

Cholecystokinin (CCK)

Answer 9

Secreted by: duodenum/jejunum in response to fat digestion

Stimulates: bile secretion into duodenum by the gallbladder

Question 10

Secretin

Answer 10

Secreted by: duodenum in response to (stomach) acid entering duodenum

Stimulates: pancreatic secretion of HCO3- into duodenum

Question 11

Blood Flow in GI

Answer 11

Blood from gut, spleen, & pancreas –> portal vein –> liver –> normal circulation

Liver cleans/digests particles absorbed to prevent poisoning

Non-water-soluble fats carried in lymphatics (bypasses liver)

↓ blood flow to gut can result in loss of cilia –> ↓absorption capacity

Sympathetic stim. –> shut off blood flow/activity in intestines –> shifts blood into systemic circulation