small bowel and large intestine

Question 1

5 components of large intestine

Answer 1

colon, caecum, appendix, rectum, anal canal

Question 2

3 main functions of large intestine

Answer 2

reabsorption of water and electrolytes, elimination of waste, microenvironment for gut bacteria

Question 3

length and width of large intestine

Answer 3

150cm x 6cm - shorter and wider than small intestine

Question 4

blood supply of large intestine

Answer 4

middle colic artery (branch of superior mesenteric artery) and inferior mesenteric artery; region between two is sensitive to ischaemia

Question 5

what section does middle colic artery supply

Answer 5

ascending and first 2/3rds transverse portions

Question 6

what section does inferior mesenteric artery supply

Answer 6

final 1/3rd transverse colon, descending, sigmoid and rectum

Question 7

how is innervation distributed

Answer 7

parasympathetic via vagus nerve innervates ascending and most of transverse colon, pelvic nerves innovate distal colon

Question 8

where does sympathetic innervation arise from

Answer 8

lower thoracic and upper lumbar spinal cord - inhibitory function

Question 9

what does the ileocaecal valve separate

Answer 9

distal lumen from caecum

Question 10

features of ileocaecal valve

Answer 10

muscular, tonically active, constricted; only relaxes to allow passage of fluid chyme into large intestine; prevents microbiota from migrating into ileum

Question 11

what is the caecum

Answer 11

blind pouch distal to ileocaecal valve

Question 12

what is the appendix

Answer 12

thin, finger-like extension protruding from caecum, potentially acting as a safe refuge for gut bacteria

Question 13

how is appendicitis treated

Answer 13

surgical removal of appendix

Question 14

where does ascending colon start and finish

Answer 14

starts at ileocaecal valve and runs up right-hand side of body to hepatic flexure

Question 15

where does transverse colon start and finish

Answer 15

starts at hepatic flexure and runs across abdomen to splenic flexure

Question 16

where does descending colon start and finish

Answer 16

starts at splenic flexure and runs inferiorly to first bend of sigmoid colon

Question 17

where does the sigmoid colon start and finish

Answer 17

s-shaped that starts at descending colon and runs until the rectum

Question 18

what is the rectum and what is its function

Answer 18

dilated portion of colon that acts as storage site for faeces following mass movement in sigmoid colon

Question 19

difference in histological structure of rectum

Answer 19

transverse rectal folds in submucosa, no taeniae coli in musclaris externa

Question 20

in rectum, what do transverse rectal folds form

Answer 20

convenient shelves for faeces to occupy until convenient time to defaecate

Question 21

function of anal canal

Answer 21

control movement of things out of GI tract

Question 22

what surrounds anal canal

Answer 22

2 anal sphincters, internal and external

Question 23

features of internal anal sphincter

Answer 23

smooth muscle under central control

Question 24

features of external anal sphincter

Answer 24

striated muscle under voluntary control

Question 25

what nerves control external anal sphincter

Answer 25

somatic motor fibres in pudendal nerves

Question 26

4 unique features of large intestine

Answer 26

appendices epoploicae, longitudinal muscle, circular muscle, nodules of lymphoid tissue

Question 27

what are appendices epiploicae

Answer 27

fatty tags arising from serosa; perhaps protective function vs intra-abdominal infections

Question 28

features of 3 longitudinal muscle bands (taeniae coli) in large intestine

Answer 28

equally spaced, relatively thicker than typical longitudinal muscle layers, within muscularis externa, shorter than length of colon so colon forms regular pouches (hastra)

Question 29

features of circular muscle in large intestine

Answer 29

segmentally thickened; bundles of muscle from taeniae coli (3 longitudinal bands) penetrate circular muscle at irregular intervals to keep them together and anchor them

Question 30

where are nodules of lympod tissue located in large intestine

Answer 30

solitary nodules (Peyer’s patches in distal small intestine)

Question 31

what is Hirschsprung’s disease

Answer 31

loss of intramural ganglia

Question 32

where is myenteric plexus glanglia

Answer 32

concentrated beneath taeniae coli

Question 33

hormonal/paracrine control: aldosterone

Answer 33

promotes Na+ and water absoprtion

Question 34

what controls wall regulation

Answer 34

enteric hormonal system