Small Intestine Function

Question 1

what is the average total length of the small intestine?

Answer 1

6 meters

Question 2

name three main functions of the duodenum

Answer 2

> gastric acid neutralisation
digestion
iron absorption

Question 3

what makes up the majority of the small intestine the jejunum or the ileum?

Answer 3

the ileum (3.5cm long)

Question 4

what part of the small intestine carries out the majority of nutrient absorption?

Answer 4

jejunum

Question 5

what is the function of the ileum?

Answer 5

NaCl/H2O absorption: chime dehydration

Question 6

what is the effect of the plica?

Answer 6

like a corkscrew they create a swirling pattern, so liquid swirls down the intestine

Question 7

where are gut cells born?

Answer 7

in the crypts between the villi

Question 8

what is contained in a villi?

Answer 8

> capillaries

> lacteals

Question 9

by how much do the plicae increase the surface area of the intestine?

Answer 9

3 times

Question 10

what structure increases the relative surface area of the intestine by 30 times?

Answer 10

the villi

Question 11

by how much do microvilli increase the relative surface area of the intestine?

Answer 11

600 times larger

Question 12

what do the villi cells absorb?

Answer 12

> NaCl
> monosaccharides
> amino acids
> peptides
> fats
> vitamins
> minerals
> water

Question 13

what do crypt cells secrete?

Answer 13

chlorine and water

Question 14

what is transported into the cell via sodium coupled secondary transporters?

Answer 14

> glucose
galactose
amino acids
nucleosides

Question 15

how much fluid does the small intestine secrete per day?

Answer 15

1500ml

Question 16

where does h2o secretion come from?

Answer 16

epithelial cells lining the crypts of lieberkuhn

Question 17

how is h2o secreted passively?

Answer 17

due to the active secretion of chloride into the intestinal lumen

Question 18

why is h20 secretion important for normal digestive purposes?

Answer 18

> luminal contents is maintained in a liquid state
promotes mixing of nutrients and digestive enzymes
aids presenting nutrients to absorbing surface
dilutes and washes away potential injurious substances

Question 19

name the transporter that transports chloride ion into the cell

Answer 19

sodium potassium chloride coupled transporter.

Question 20

how does potassium leave the cell in regards to chloride ion transport?

Answer 20

through leaky k channels

Question 21

how does sodium leave the cell in regards to chloride ion transport?

Answer 21

through sodium potassium channel

Question 22

how is chloride transporter into the lumen from inside the gut cell?

Answer 22

through CFTR channel. ATP is converted to cAMP via adenylate cyclase. PKA then switches on the transporter allowing ions to be transported across

Question 23

what are the two distinct types of movement in intestinal motility?

Answer 23

> segmentation

> peristalsis

Question 24

when does segmentation occur?

Answer 24

during a meal

Question 25

describe segmentation

Answer 25

there is contraction and relaxation of short intestinal segments. the contraction moves the chime into the relaxed segments which in turn contract and push the chime back. movement is quicker at the top of the intestinal tract so net movement is down.

Question 26

what initiates the generation of segmentation contractions?

Answer 26

pacemaker cells in the longitudinal muscle layer

Question 27

what produces oscillations in the membrane potential that brings the cell to threshold to allow the segmentation contractions?

Answer 27

the intestinal basic electrical rhythm

Question 28

what determines the strength of the contractions?

Answer 28

the frequency of the action potential

Question 29

what determines the frequency of segmentation?

Answer 29

the intestinal basic electrical rhythm

Question 30

what is the effect of parasympathetic stimulation by the vagus nerve of segmentation?

Answer 30

increase in contraction

Question 31

what Is the effect of the sympathetic system on segmentation?

Answer 31

decrease in contraction

Question 32

what is the effect of the autonomic nervous system of segmentation?

Answer 32

none

Question 33

when does peristalsis commence?

Answer 33

following the absorption of nutrients

Question 34

what is migrating motility complex?

Answer 34

the pattern of peristaltic activity travelling down the small intestine (beginning in the gastric antrum)

Question 35

where does the migrating motility complex end?

Answer 35

in the terminal ileum

Question 36

what does the migrating motility complex aim to do?

Answer 36

> move undigested material into the large intestine | > limit bacterial colonisation

Question 37

what hormone is involved in the initiation of migrating motility complex?

Answer 37

motilin

Question 38

describe the contraction and relaxation of muscle in the small intestine if the smooth muscle is distended

Answer 38

> muscle on the oral side of bolus contracts > muscle on anal side relaxes > bolus is moved into area of relaxation

Question 39

what neurons mediate peristalsis in the small intestine?

Answer 39

myenteric plexus

Question 40

describe the gastroileal reflex

Answer 40

> ileocaecal valve opens > chyme enters the large intestine > colon distends > reflex contraction of the ileocaecal sphincter preventing back flux into the small intestine