Chapter 24 - The Digestive System

Question 1

GI Track performs which 6 basic functions?

Answer 1

1. Ingestion
2. Secretion
3. Mixing and Propulsion
4. Digestion

Question 2

Parasympathetic NS

Answer 2

“Rest and Digest”

• Sublingual, submandibular and parotid glands
• Liver, gallbladder and bile ducts
• stomach
• pancreas
• small intestine
• large intestine

Question 3

Sympathetic NS

Answer 3

“Fight or Flight”

• liver, gall bladder and bile
• stomach
• pancreas
• small intestine
• large intestine

Question 4

Enteric NS

Answer 4

Independent nerve network within wall of GI tract

• Capable of continued function without input to CNS
• 2 Networks
  1. Myenteric plexus
  2. submucosal plexus

Question 5

Somatic NS

Answer 5

Skeletal Muscle
- Voluntary chewing and swallowing food

External anal sphincter
-voluntary control of defecation

Question 6

3 Phases of Digestion

Answer 6

1. Cephalic Phase
2. gastric phase
3. Intestinal Phase

Question 7

Cephalic phase…

Answer 7

In the mouth …

1. Mechanical
2. Chemical (Salivary Amylase, Lingual Lipase)
3. Deglutition (Voluntary swallowing followed by Pharyngeal stage - involuntary movement of bolus through pharynx to esophagus)
4. Esophageal stage (bolus moves from esophagus to stomach - peristalsis)

Question 8

Gastric Phase …
Mechanical Digestion
Chemical Digestion
Absorption in the Stomach

Answer 8

Bolus reaches stomach! 
Mechanical Digestion in stomach: 
1. Peristalsis (15 - 25 seconds, propulsion and retropulsion)
2. Chyme 
3. Gastric emptying (2 -4 hours) 

Chemical Digestion:
Parietal cell: HCL and Intrinsic factor

Chief cell: Pepsinogen and gastric lipase

G cell: Gastrin

Epithelial cells in stomach impermeable to most materials except:
Water ,Ions, Short-chain FA, Drugs, Alcohol

Question 9

Function of stomach:

Answer 9

Mixing chamber, Storage

Question 10

Neural regulation of stomach:

Answer 10

Parasympathetic and Enteric branches

Question 11

Hormone in stomach:

Answer 11

Gastrin

Question 12

Secretion of HCl in Gastric phase

Answer 12

1. H+ formed from H2O and CO2
2. Proton pump transports H+ out of cell and K+ into cell
3. Cl- and K+ diffuse out of cell through channels
4. Bicarbonate leaves cell in exchange for Cl- via antiporters

Question 13

Functions of HCl

Answer 13

• kills microbes
• partially denatures proteins
• activates pepsin
• stimulate secretion of hormones that promotes flow of bile and pancreatic juices

Question 14

Gastric juice is made up of..

Answer 14

• HCl (released by Gastrin)
• Intrinsic factor (absorption of Vit B12)
• Pepsinogen (+ HCl = pepsin)
• Gastrin (Releases HCl)
• Gastric Lipase
• Lingual Lipase
• Salivary amylase

Question 15

Rate of gastric Emptying…

Answer 15

(Fast) Carbohydrates, Protein, Lipids (Slow)

Question 16

Intestinal Phase

Answer 16

1. Chyme enters small intestine
2. Digestion and Absorption
   `

Question 17

Enterogastric reflex

Answer 17

• Food entering small intestine inhibits gastric motility and decreases gastric emptying

1. Segmentation
2. Migration motility complex

Question 18

Chemical Digestion in intestine..

Answer 18

Contributing sources:

1. Pancreas
2. Liver
3. Small Intestine