Small Intestine Function

Question 1

How long is the duodenum?

Answer 1

~25cm

Question 2

What is the function of the duodenum?

Answer 2

Neutralise acid
Digestion
Absorption of Fe

Question 3

What is the function of the jejunum?

Answer 3

~95% of nutrient absorption?

Question 4

What is the function of the ileum?

Answer 4

Absorption of NaCl to dehydrate Chyme

Question 5

What structures increase the surface area of the small intestine?

Answer 5

Folds
Villi
Microvilli

Question 6

What structure lies at the bottom of Villi?

Answer 6

Crypts

Question 7

What is the function of small intestinal crypts?

Answer 7

Growth of villi endothelial cells

Question 8

What are plicae circularis?

Answer 8

Circular folds inside the small intestine

Question 9

How tall are microvilli?

Answer 9

1um

Question 10

What types of cells are found on the surface mucosa of villus?

Answer 10

Simple columnar epithelium

Goblet cells

Question 11

What vessels are found within a villus?

Answer 11

Capillary networks

Lacteals

Question 12

What is the function of crypt cells of the small intestine?

Answer 12

Secretion of Cl and Water

Question 13

Why is Cl secreted by Crypt cells?

Answer 13

So water will follow the osmotic gradient and keep the mucus watery

Question 14

Villus cells absorb what?

Answer 14

Everything

Question 15

How is Sodium absorbed into the cell in the small intestine?

Answer 15

Coupled with:
Glucose/Galactose
AAs
Nucleosides

Question 16

How is Na taken from the small intestinal epithelial cells to the blood?

Answer 16

Na-K ATPase

Question 17

How much water is secreted by the small intestine each day?

Answer 17

1500ml

Question 18

What is the purpose of of secreting water into the small intestine?

Answer 18

Lumenal contents liquidity
Mixing of nutrients and enzymes
Dilutes injurious surface

Question 19

How is chloride taken from the blood into small intestinal epithelial cells?

Answer 19

2 Cl- ions coupled with 1 K+ and 1 Na+

Question 20

How does Cl- enter the lumen of the small intestine?

Answer 20

CFTR channel protein triggered by cAMP –> PKA

Question 21

What is the purpose of pumping Cl- into the small intestinal lumen?

Answer 21

Passive diffusion of water

Question 22

What types of movements occur in the intestines?

Answer 22

Segmentation

Peristalsis

Question 23

What is segmentation?

Answer 23

Contraction and relaxation lengthways up intestinal surface

Question 24

What is the purpose of segmentation?

Answer 24

Move chyme back and forwards, mixing contents with enzymes

Bringing chyme into contact with BBM

Question 25

How are segmentation contractions triggered?

Answer 25

Depolarisation generated by pacemaker cells (longitudinal muscle layer)

Question 26

Action potential frequency in the longitudinal muscle layer determines what?

Answer 26

Strength of contraction

Question 27

What determines the strength of segmentation?

Answer 27

Basic electrical rhythm | Distance down intestine (--> rectum)

Question 28

Is segmentation fast or slow?

Answer 28

Slow

Question 29

What is the effect of the Parasympathetic NS on segmentation?

Answer 29

Increased contractility

Question 30

What is the effect of the Sympathetic NS on segmentation?

Answer 30

Decreased contractility

Question 31

When does peristalsis begin?

Answer 31

When nutrients are absorbed (segmentation stops)

Question 32

What is the Migrating Motility Complex

Answer 32

Pattern of peristaltic activity from antrum to terminal ileum

Question 33

What causes the Migrating Motility Complex to stop?

Answer 33

Arrival of food into the stomach

Question 34

What is the purpose of the Migrating Motility complex?

Answer 34

Move undigested material into the large intestine | Limit bacterial colonisation of SI

Question 35

What is the function of Motilin?

Answer 35

Initiation of MMC

Question 36

What is the law of the intestine?

Answer 36

Muscle on oral side of bolus contracts | Muscle on anal side of bolus relaxes

Question 37

The law of the intestine is mediated by what?

Answer 37

Myenteric plexus

Question 38

What is the gastroileal reflex?

Answer 38

``` Gastric emptying increases segmentation Ileocaecal valve opens Chyme --> LI Colon distended Reflex contraction of Ileocaecal valve to prevent backflux ```