gastroenterology- small bowel

Question 1

function of small bowel?

Answer 1

absorb nutrients, salts and water

Question 2

What is function of mesentery?

Answer 2

anchors small and large bowel from abdonminal wall, allowing movement

and provides conduit for vessles and nerves

Question 3

What makes up small bowel and is exclusive to it?

Answer 3

villi

Question 4

characteristics of villi?

Answer 4

Question 5

what cells make up villi?

Answer 5

enteroctyes - absportive

secretory - scattered goblet and enteroendocrine cells

Question 6

what cells make up up crypts of lieberkuhn?

Answer 6

Paneth and stem cells

Question 7

What are characteristics and function of enterocytes?

Answer 7

tall columnar cells with micro villi and basal nucleus

specialsited for absoprtion and trasnport of substnaces

life span 1-6 days

LARGE SA

Question 8

what is another word for brush border?

Answer 8

microvilli

Question 9

what is the surface of microvilli covered in?

Answer 9

glycoclayx

Question 10

Which membrance is glycocalyx found?

What is its function?

Answer 10

apical

protection from digestional lumen

produces ‘unstirred layer’ - that regulates rate of absoprtion from intestinal lumen

Question 11

What is the unstirred layer?

Answer 11

layer of water and mucous

Question 12

What do goblet cells contain?

Answer 12

mucous containnig granules at apical end of cell

Question 13

What is the function of mucous of the goblet cell?

Answer 13

faclitates passage of material through bowel

Question 14

distribution of goblet cells?

Answer 14

as you go down bowel more goblet cells,

more in colon

not a lot in duodenum

Question 15

where are enternedocrine found?

Answer 15

scattered among enterocytes

in lower parts of crypts

Question 16

What is function of enteroendorine cells?.

Answer 16

hormone secreting - affect gut motility

Question 17

where are pnaeth cells?

Answer 17

bases of crypts

Question 18

what do paneth contain?

Answer 18

large acidophlic granules

Question 19

what do paneth granules contain?

Answer 19

lysozyme, protects stem cell

glyocopritnets and zinc

(zinc can be used as essential trace metal for no of enzs)

Question 20

what are other functions of paneth cells?

Answer 20

engulf bacteria and protoza

regulating intestinal flora

Question 21

What is purpose of stem cells in GI tract?

Answer 21

continaully replenish surface of epithelium

migrate to top of villus replace cells at top of villus

can divide to many cell types - pluripotent

Question 22

why do enterocytes and goblet cells have short life span?

only 36 hours

Answer 22

can be affected bt toxic substances in diet and lesions are short lived - important as they are first line of defense against GI pathongens

Question 23

How are entercytes replenished?

Answer 23

escalator like transit

if impaired by e.g radiation severe intestinal dysfunction

Question 24

is there a sudden transition between duodenum,jejunum,ileum?

Answer 24

NO

Question 25

How is duodenum distingushed?

Answer 25

they have brunners glands submucosal coiled tubular mucous glands secrete alkaline fluid, open into base of crypts

Question 26

what is purpose of alkaline secretions of brunner's gland?

Answer 26

neutralizes acidic chyme from stomach optimise pH for action of pancreatic enzymes

Question 27

difference between jejunum and ileum?

Answer 27

jejunum - thick waller than illem as it has **more plicae circualres** differnet attachment to aorta - jejunum above and left, ilem below and right jeje- few arcades and long terminals, iluem - more arcades and shorter terminals iluem only has peyers patch

Question 28

functions of small intestine motility?

Answer 28

Question 29

what are 3 movement parts of motility?

Answer 29

segmentations peristalis migrating motor complex

Question 30

What is segmentation?

Answer 30

mixing stationary contraction of circular muscless more freq in duodenum pix pancratic enzyme and bine to mix chyme

Question 31

what is peristalisi?

Answer 31

sequestial contraction of adjacment rings of smooth muscles propels chyme towards colon

Question 32

what is migrating motor complex?

Answer 32

cycles of smooth muscles contraction sweeping through cut prevents migration of coloinc bacteria in ileum

Question 33

how do pancreatic enzymes and bile enter duodenum?

Answer 33

from common bile duct and main pancreatic duct

Question 34

where else are enzymes produced apart from pancrase?

Answer 34

duodenal epitherlium

Question 35

where does digestion of carbs being + by which enzyme?

Answer 35

mouth salivary a amylase - destroyed in stomach by low pH

Question 36

Where does pancreatic a amylase have it effects?

Answer 36

secreted into duodenum in response to meal continues digestion in small bowel

Question 37

what does a amylase need to work optimunally?

Answer 37

Cl- and neutral/slightly alkaline pH

Question 38

where exactly in small bowel does it have it effect?

Answer 38

1. mainly lumen and adsorbs brush border then after the products digestion of amylase products occurs at bursh border

Question 39

How is glucose and galactose absorpted?

Answer 39

by secondary active tranposrt SGLT-1 apical membrane

Question 40

How is fructose absoprted?

Answer 40

facilitated diffusion, GLUT-5 apical membrane

Question 41

what does GLUT 2 do?

Answer 41

facilitates exit at basolateral membrane into intersistial space

Question 42

where does digestion of protien begins?

Answer 42

stomach by pepsin but it is inactivated in alakine of duodenum

Question 43

how are the proteases activated?

Answer 43

enterokinase (enz located on duodenal brush border) activates trypsin from trypsinogen trypsin acitavtes other protients

Question 44

How does digestion of different AA length work?

Answer 44

AAn progessively hydrolysed at brush border to AA some AAn are direclty absobred via action of H+ and PepT1 digested to AAs by peptidases in enterocytes

Question 45

what is first step of lipid digestion?

Answer 45

secretion of bile salts and pancreatic lipases

Question 46

what is 2nd step of digestion of lipids?

Answer 46

emulisification, increase surface area for digestion

Question 47

what is 3rd step of lipases

Answer 47

enyzmatic hydrolosysis of ester linkages colipase complexes with lipase - prevent bile salts displacing lipase from fat droplet

Question 48

what is the last step of lipid digestion?

Answer 48

solublity of lipoytic products in bile salt MICELLES

Question 49

What happens to FA after mielles?

Answer 49

leave it and enter enterocytes FA and MG resynthesized intro triglyverides by **monogltceride acylation (major) or phosphatidic acid pathway (minor)** **F**orms chylomicrons- liportien, mainly TGs in golgi appartus and released by exosytsosi into lacteal, lymph capillary transports away from bowel

Question 50

how is ilewum sperated from colon?

Answer 50

by ileocaecal valve

Question 51

What is function of ileocaecal valve?

Answer 51

relax and contract control passage of material into colon prevents backflow of bacteria into ileum