small intestine structure and function

Question 1

parts of small intestine

Answer 1

duodenum
jejunum
ileum

Question 2

approx length small intestine

Answer 2

~6m

Question 3

duodenum lenght and function

Answer 3

25cm

gastric acid neutralisation, digestion, iron absorption

Question 4

jejunum length and function

Answer 4

2.5m

nutrient absorption

Question 5

ileum length and function

Answer 5

3.5m

NaCl/H20 absorption –> chyme dehydration

Question 6

what does villus cell absorb

Answer 6

NaCl
monosaccharides
amino acids
peptides
fats
vitamins
minerals
water

Question 7

what do crypt cells secrete

Answer 7

Cl

water

Question 8

intestinal water secretion

Answer 8

~1500ml per day from epithelial cells lining crypts of Leiberkuhn

secreted osmotically as consequence of active secretion of chloride into intestinal lumen

Question 9

how is water important for normal digestive process

Answer 9

• maintains lumenal contents in liquid state
• promotes mixing of nutrients with digestive enzymes
• aids nutrient presentation to absorbing surface
• dilutes and washes away potentially injurious substances

Question 10

2 distinct types of intestinal motility

Answer 10

segmentation

peristalsis

Question 11

segmentation

Answer 11

contraction and relaxation of short intestinal segments
most common during meal

provides thorough mixing of contents with digestive enzymes and brings chyme into contact w absorbing surface

Question 12

generation of segmentation contractions

Answer 12

initiated by depol generated by pacemaker cells in longitudinal muscle layer

intestinal BER produces oscillations in membrane potential –> threshold –> AP –> contraction

Question 13

what determines strength and freqeuncy of segmentation contractions

Answer 13

strenght - AP frequency

frequency - BER

Question 14

parasympathetic NS effect on segmentation contractions

Answer 14

increase

Question 15

sympathetic NS effect on segmentation contractions

Answer 15

decrease

Question 16

migrating motility complex (MMC)

Answer 16

pattern of peristaltic activity travelling down small intestine (starts gastric antrum)
as one MMC ends another begins

arrival of food in stomach = cessation of MMC and initiation segmentation

Question 17

MMC acts to

Answer 17

move undigested material into large intestine

limit bacterial colonisation of small intestine

Question 18

which hormone is involved in initiation of MM C

Answer 18

motilin

Question 19

law of the intestine

Answer 19

if intestinal smooth muscle is distended by chyme

• muscle on oral side of bolus contracts
• muscle on anal side of bolus relaxes
• bolus is moved into area of relaxation towards colon

Question 20

gastroileal reflex

Answer 20

gastric emptying –> inc segmentation activity in ileum

• opening ileocaecal sphincter
• entry chyme large intestine
• distention colon
• relfex contraction of ileocaecal sphincter prevents backflux into small intestine