Lecture 11- small & large intestine

Question 1

What are the three subdivisions of the small intestine ?

Answer 1

duodenum
jejunum
ileum

Question 2

What is the ileocaecal sphincter?

Answer 2

transition between the small and large intestine

Question 3

How much nutrient absorption occurs in the small intestine?

Answer 3

90%

Question 4

What is present in the mucosa in small intestine?

Answer 4

simple columnar epithelium and microvilli

Question 5

What is present in the submucosa in small intestine?

Answer 5

intestinal glands

Question 6

What are plicae?

Answer 6

transverse folds of the intestinal lining

Question 7

What are villi?

Answer 7

fingerlike projections of the mucosa

Question 8

What are intestinal glands in the small intestine lined by?

Answer 8

li enteroendocrine cells
goblet cells
stem cells

Question 9

What is the purpose of mucosal folds in the jejunum?

Answer 9

circular folds which increase the surface area, and aid in mixing ingesta

Question 10

Villi in small intestine

Answer 10

mucosa forms multitude of projections that protrude into the lumen and are covered with epithelial cells

Question 11

Microvilli

Answer 11

lumenal plasma membrane of absorptive epithelial cells is studded with densely-packed microvilli

Question 12

Duodenum overview

Answer 12

closest to the stomach
25cm long
“mixing bowl”

Question 13

Duodenum secretions

Answer 13

submucosal glands secrete enterogasterones
brunner’s glands (duodenal glands)- alkaline mucous secretions for protection

Question 14

What is the function of the duodenum?

Answer 14

receives chyme from the stomach
neutralises acids before they can damage absorptive surfaces of small intestine

Question 15

Jejunum overview

Answer 15

middle section of small intestine
2.5m long
has few plicae
small villi

Question 16

What mostly takes place in the jejunum?

Answer 16

chemical digestion
nutrient absorption

Question 17

Ileum overview

Answer 17

final section of small intestine
3.5m long
ends at the ileocaecal valve ( a sphincter that controls the flow of material from ileum to large intestine

Question 18

What is the function of the ileum?

Answer 18

absorbs vit B12
absorbs bile salts

Question 19

What are intestinal villi covered in?

Answer 19

simple columnar epithelium
microvillli

Question 20

Intestinal glands of small intestine

Answer 20

mucous cells between columnar epithelium cells
eject mucins onto intestinal surface

Question 21

What are crypts of lieberkuhn

Answer 21

openings from intestinal glands:
to intestinal lumen
at bases of villi
are entrances for brush border enzymes

Question 22

What are brush border enzymes

Answer 22

integral membrane proteins
on surfaces of intestinal microvilli

Question 23

What is the function of brush border enzymes?

Answer 23

break down materials in contact with brush border

Question 24

What are duodenal glands also called?

Answer 24

brunner’s glands

Question 25

Brunner’s glands

Answer 25

secrete a lot of alkaline mucous for protection

Question 26

What is the function of intestinal secretions?

Answer 26

moisten chyme
assist in buffering acids
keep digestive enzymes and products of digestion in solution

Question 27

What intestinal movements occur in the small intestine?

Answer 27

weak peristaltic contractions move chyme slowly toward jejunum

Question 28

What reflexes occur?

Answer 28

gastro- enteric reflex
gastro-ileal reflex

Question 29

What does the gastro-enteric reflex do?

Answer 29

stimulates motility and secretion along the entire small intestine

Question 30

What does the gastro-ileal reflex do?

Answer 30

triggers relaxation of ileocaecal valve
allows materials to pass from small to large intestine

Question 31

Large intestine

Answer 31

between terminal ileum and anus

Question 32

What are the functions of the large intestine?

Answer 32

reabsorb water
compact materials into faeces
absorb vits k, biotin and B5
store fecal matter

Question 33

What are the 3 major segments of the large intestine?

Answer 33

caecum + appendix
colon
rectum

Question 34

What is the function of the caecum?

Answer 34

collection
storage
compaction of fecal matter

Question 35

What are the four segments of the colon?

Answer 35

ascending (retroperitoneal)
transverse (peritoneal)
descending (retroperitoneal)
sigmoid (peritoneal)

Question 36

What is the function of the rectum?

Answer 36

terminates faeces at the anal canal

Question 37

Rectum muscles

Answer 37

internal (smooth muscle):
external (skeletal muscle):
anal sphincters

Question 38

Histology of large intestine

Answer 38

absence of villi
goblet cells present
deep intestinal glands

Question 39

What motility occurs in the large intestine?

Answer 39

haustral contractions- slow segmental movements every 30 mins
mass movements- long slow movements, 3/4 times a day- move contents to rectum

Question 40

What triggers the rectum to defecate?

Answer 40

distension

Question 41

How is the defecation reflex initiated?

Answer 41

stretching of rectal wall following mass movements from sigmoid colon

Question 42

Defecation reflexes

Answer 42

long and short reflexes
initial involuntary contraction of external anal sphincter
followed by voluntary relaxing of sphincter if necessary

Question 43

How much water approx enters the digestive tract daily?

Answer 43

2200ml