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Year 2 GI (JK) > Small intestine structure and function > Flashcards

Small intestine structure and function Flashcards

1
Q

What is the average total length of the small intestine?

A

6m

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2
Q

Why is it advantageous to have a long small intestine?

A

to prevent material passing through too quickly

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3
Q

What is the shortest and longest parts of the small intestine?

A

duodenum (25cm)
jejunum (2.5m)
ileum (3.5m)

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4
Q

What processes occur in the duodenum?

A

neutralisation, digestion and iron absorption

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5
Q

What processes occur in the jejunum?

A

95% nutrient absorption

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6
Q

What processes occur in the ileum?

A

NaCl/H2O absorption to dehydrate the chyme

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7
Q

Name 3 ways in which the surface area of the small intestine is increased

A

folds (plicae)

villi and microvilli

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8
Q

What are plicae?

A

corkscrew folds of the mucous membranes

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9
Q

What are the crypts of Lieberkuhn?

A

Short gland invaginations between the villi

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10
Q

Explain the structure of a villi and the components making it up

A

simple columnar epithelium
capillaries for exchange and lacteals for fat absorption
Goblet cells present for mucus secretion

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11
Q

What is the main difference between the villi and the crypts?

A

villi absorb and crypts secrete

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12
Q

What things does the villi absorb?

A

amino acids, fat, NaCl, minerals, vitamins, monosaccharides, water

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13
Q

What does the crypts secrete?

A

water and chloride

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14
Q

What are some molecules which are sodium coupled for transport?

A

glucose and galactose

amino acid, nucleotides, water soluble vitamins

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15
Q

How much water is secreted a day in the small intestine and from where EXACTLY?

A

1.5L

epithelial cells of the crypts of Lieberkuhn

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16
Q

What is the water secretion in the small intestine due to? (what drives it)

A

active chloride secretion into the lumen

17
Q

List the 4 things water is important for in the small intestine

A

wash away toxins
mixing
maintains liquid state of lumen
Aids nutrient presentation to the absorbing surface

18
Q

What is chloride coupled to for movement across the basolateral membrane?

A

sodium and potassium ie 2 chlorides transported at a time

19
Q

How is chloride expelled from the cell to the apical membrane and through what receptor?

A

adenylate cyclase catalyses ATP –> cAMP

turns on protein kinase A which turns on CFTR

20
Q

What are the 2 types of intestinal motility?

A

segmentation

peritalsis

21
Q

When is segmentation most likely to be occurring?

A

during a meal

22
Q

Briefly explain what segmentation is

A

the contracting of one part of the intestine and the relaxing of the part before and after the contraction which interchanges to give a mixing of the contents

23
Q

How is segmentation generated?

A

pacemaker cells depolarise cells in longitudinal muscle layer and the BER produces AP until contraction

24
Q

What determines the strength of contraction?

A

AP frequency

25
Q

BER decreases or increases from intestine to rectum?

A

decreases

26
Q

How does the nervous system stimulate the contraction of segmentation?

A

Para - vagus to increase
sympathetic - decrease
autonomic - no control

27
Q

When does peristalsis kick in?

A

After the nutrients have been absorbed

28
Q

What is the MMC?

A

Pattern of peristaltic activity from the gastric antrum

29
Q

When does another MMC start after the other?

A

When the one before terminates at the ileum

30
Q

If food enters the stomach what happens to peristalsis?

A

stops and segmentation begins

31
Q

What are the 2 roles of MMC?

A

move undigested eg cellulose material to the large intestine
prevent bacterial colonisation of the small intestine

32
Q

What is motilin and how is it increased?

A

A hormone which initiates MMC

nutrient content drops

33
Q

If the smooth muscle in the intestine is distended what are the 3 rules which happen?

A

muscle on anal side of bolus relax
muscle on oral side contract
bolus moved into relaxation toward colon

34
Q

What mediates the law of the intestine?

A

neurons in the myenteric plexus

35
Q

What is the general movement of a bolus in the intestine?

A

to the anal end

36
Q

What happens to a bolus once it has reached the ileum (gastroileal reflex)

A

peristalsis starts as the stomach is emptying
The ileocaecal sphincter opens and the chime enters the large intestine. This distends the colon and closes the valve behind it to prevent backflux.

Year 2 GI (JK) (39 decks)

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