Small intestine Structure and Function

Question 1

What is the function of the duodenum? What glands and where?

Answer 1

Neutralisation, digestion, iron absorption

Question 2

What is the function of the jejunum?

Answer 2

95% nutrients abssorption

Question 3

WHich is the longest part of the small intestine?

Answer 3

Illium (3.5m/6m)

Question 4

ROle of Ileum?

Answer 4

Mainly water and asalt resorption

Question 5

What 3 features help icrease srface area for aborption?

Answer 5

Plicae folds (in the surface)
Villi (Folds in the epithelium)
Microvilli (folds in the cell surface membrane)

Question 6

plicae circularis are what? What is their function?

Answer 6

Folds in the small intestine, work like a screw, to churn and move chyme around

Question 7

Where is the myenteric plexus located?

Answer 7

Between the circular and longitudinal muscle layers

Question 8

Where are the stem cells found in the small intestine?

Answer 8

At the bottom of the crypt

Question 9

What is the lymph structure reunning up the villi?

Answer 9

lacteal

Question 10

What is the feature of the small intestine that increases the surface area the most?

Answer 10

microvili

Question 11

What are the differenc ein function of the Villi and the Crypts?

Answer 11

Villi are for absorption and crypts are for secretion

Villi Absorption of:
NaCl
Monosaccharides
aminoacids
peptides
fats
vitamins
minerals
water

Crypt secretion of Cl and Water

Question 12

What molecules use Na+ coupled secondary active transport to get across the lumen?

Answer 12

monosaccharides (and galactose)
aminoacids
Nucleosides

Question 13

The small intestine secretes 1500ml/day. Which cells secrete this? How does it get into the lumen? Why is it important?

Answer 13

Crypt cells

Through active Chloride transport into the lumen pulling it in through osmosis

Maintains content in liquid state
helps enzyme mixing
helps presentation to absorbing surface
dilutes and washes away harmful substances

Question 14

How does Cl get into the intestial lumen?

Answer 14

Through a Na K coupled transporter (1 Na and 1 K drive 2 Cl the cell)

Question 15

What does adenylate cyclase do?

Answer 15

It turns ATP to cAMP

Question 16

What regulatess the Cl channe?

Answer 16

A chain of reactions through Adenylte cyclase ATP-> cAMP -> PKA -> stiulates CFTR open -> Cl out

Question 17

What happens in CF?

Answer 17

Fault in CFTR transporter, so no CHloride exiting cell, so no osmotic gradient for the water, so dried out digestiveness, -> malnourishment -> failure to thrive

Question 18

When does segmentation tak eplace? What is it?

Answer 18

When eating, basically churning up of food in the intestine like a washing machine, contracing and relaxing so all is mushed up togethter

Question 19

How are segmentation contractions genarated?

Answer 19

There is Basal peristaltic rhythm genarated by pacemaker cells in longitudinal muscle layer, but not enough to reach threshold. More AP =bigger contractions.

Question 20

What determines the the segmentation frequency?

Answer 20

BER (Basic Electrical Rhythm, set out by the pacemaker cells in the longitudinal layer)

Question 21

How does Chyme migrate to the large intestine through segmentation?

Answer 21

Because the BER decreases the further down the intestine you go, so it very slowly pushes the chyme down the way.

Question 22

What nerve stimulates an increase in contraction of segmentation?

Answer 22

Vagus (PArasympathetic)

Symathetic NS decreases contraction

Question 23

Does the nervous system affect the rhythm (basal segmentation)

Answer 23

No. Set by BER

Question 24

What does peristalsis happen for? What is the mMC? WHen does peristalsis happen?

Answer 24

To chivy along the left overs from digestion into the large intestine and down to the rectum

MMC = Migrating Motility Compplex

Peristalsis happens after we’ve finished eating and nutrients have been absorbed

Question 25

What does teh MMC act to do?

Answer 25

Limit amount of bact heading into small intestine. Move undigested material into large intestine.

Question 26

MMC initiated by what?

Answer 26

Motalin (Hormone)

Question 27

What is th elaw of the intestine?

Answer 27

That if a bolus of food is in the intestine,(causing expansion of smooth muscle) it will independantly (mediated by nerves in myenteric plexus) move the food towards the anus.

Question 28

What is the Gastrolial reflex?

Answer 28

Opening and closing of iliocecal valve (Sphincter) due illium segmentation (opening) and distension of colon (closing)