small bowel and large intestine

Question 1

what is the most important role of the small intestine

Answer 1

absorption of water, salts and nutrients

Question 2

where does the small intestine originate

Answer 2

stomach, before coiling around abdomen

Question 3

what holds the small intestine in place and what is its function

Answer 3

mesentery, which is a connective tissue and throws small intestine into folds; supports blood supply

Question 4

what does the small intestine meet in the lower right quadrant

Answer 4

large intestine

Question 5

sphincter at proximal end

Answer 5

pyloric sphincter

Question 6

sphincter at distal end

Answer 6

ileocaecal valve (prevents back flow of bacteria into ileum)

Question 7

3 portions of small intestine, length and key roles

Answer 7

duodenum (0.25m; digestion, gut regulation), jejenum (2.5m; absoprtion), ileum (3.75m; absorption)

Question 8

what does the epithelial layer have and why

Answer 8

finger-like villi projections to increase SA for absorption

Question 9

what are villi rich in and what are they innovated by

Answer 9

bloody supply, lymph drainage, motility; innovated by submucosal plexus

Question 10

what is the mucosa arranged in

Answer 10

circular folds

Question 11

name of mucosal invaginations in between villi

Answer 11

crypts of Lieberkuhn

Question 12

distinguishing feature of duodenum

Answer 12

coiled mucous-secreting Brunner’s submucosal gland; secretes bicarbonate-rich alkaline solution which open up into the base of the Crypts

Question 13

function of solution from duodenum

Answer 13

helps to neutralise acid chyme, protects lining of proximal small intestine, provides optimum pH for enzymes

Question 14

distinguishing feature of jejenum

Answer 14

large submucosal folds (plicae circularis); similar to folds in rest of the small intestine, but are considerably larger, closer together and more frequent (look more like frills than folds)

Question 15

distinguishing features of ileum

Answer 15

has up to 100 Peyer’s patches (aggregates of specialised lymphoid tissue key to immune response to gut-borne pathogens); more bacteria in colon so could migrate back up into small intestine

Question 16

what are Peyer’s patches in ileum able to do

Answer 16

initiate leukocyte and immunoglobulin responses to pathogens

Question 17

what do Payer’s patches in ileum contain

Answer 17

M-cells

Question 18

what do M-cells do

Answer 18

key for immunity

Question 19

what don’t M-cells possess

Answer 19

microvilli

Question 20

3 main functions of intestinal motility

Answer 20

mix ingested food with digestive secretions and enzymes, facilitate contact between contents and mucosal surface, propel contents along small intestine

Question 21

3 mechanisms to achieve motility functions

Answer 21

segmentation, peristalsis, migrating motor complex

Question 22

describe segmentation

Answer 22

less coordinated; alternative contraction and relaxation of non-adjacent segments of circular muscle in gut wall, so food is pushed backwards then forwards to mix it and break it down mechanically, with a minor effect of propulsion; more frequent in duodenum than ileum

Question 23

descibe peristalsis

Answer 23

more coodinated; sequential contraction of adjacent segments of circular muscle in gut wall, combined with contractions of longitudinal muscle, so that food is propelled distally in a 10cm long wave, with a minor effect of mixing

Question 24

describe migrating motor complex

Answer 24

periodic contractions from stomach to distal ileum during fasted state (restart when complete) - also present in fed state but less ordered; prevent colonic flora travelling backwards and help cleansing of residual food

Question 25

where are secretions that facilitate digestion in small intestine principally derived from

Answer 25

liver, gall bladder, pancreas, small intestine wall

Question 26

where do enzymes that cleave big nutrients into smaller nutrients operate and where are they released from

Answer 26

gut lumen, released from glandular organs

Question 27

where do enzymes that cleave dimeric nutrients into monomers for absorption operate and where are they released from

Answer 27

brush border of enterocytes, released from gut epithelium