Lecture 11 Small Intestine Function

Question 1

What is the total length of the small intestine

Answer 1

6 metres

Question 2

What occurs in the duodenum

Answer 2

Gastric acid neutralisation
Digestion
Iron absorption

Question 3

What occurs in the jejunum

Answer 3

Nutrient absorption

Question 4

What occurs in the ileum

Answer 4

NaCl/H2O absorption

Chyme dehydration

Question 5

Villus cell absorbs

Answer 5

• NaCl
• Monosaccharides
• Amino acids
• Peptides
• Fats
• Vitamins
• Minerals
• Water

Question 6

Crypt cell secrete

Answer 6

Cl and water (water movs with Cl passively due to osmosis)

Question 7

Hoe does glucose, galactose, amino acids and nucleosides get into the cell

Answer 7

Na+ coupled secondary active transport

Question 8

Why is H20 important and where does it come from

Answer 8

A Maintains lumenal contents in liquid state
B Promotes mixing of nutrients with digestive enzymes
C Aids nutrient presentation to absorbing surface
D Dilutes and washes away potentially injurious substances
Secreted by crypts

Question 9

What are the distinct types of intestinal movement

Answer 9

Segmentation and Peristalsis

Question 10

Describe Segmentation

Answer 10

Most common during a meal

Contraction and relaxation of short intestinal segments which provides thorough mixing of contents with digestive enzyme

Question 11

How is segmentation contractions generated

Answer 11

• Initiated by depolarisation generated by pacemaker cells in longitudinal muscle
• Intestinal basic electrical rhythm (BER) produces oscillations in membrane potential to reach threshold and cause action potential which results in a contraction

Question 12

When does peristalsis occcur

Answer 12

Following absorption of nutrients segmentation stops and peristalsis starts

Question 13

What is Migrating Motility Complex and where does it start

Answer 13

Pattern of peristaltic activity travelling down small intestine (starts in gastric antrum)

Question 14

What is the Law of the Intestine

Answer 14

• If intestinal smooth muscle is distended (eg by bolus of chyme):
• Muscle on oral side of bolus contracts
• Muscle on anal side of bolus relaxes
• Bolus is moved into area of relaxation towards colon
• Mediated by neurones in myenteric plexus

Question 15

Describe the gastroileal reflex

Answer 15

Gastric emptying leads to an increase in segmentation activity in ileum
 Opening of ileocaecal valve (sphincter)
 Entry of chyme into large intestine
 Distension of colon
 Reflex contraction of ileocaecal sphincter (prevents backflux into small intestine)