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histology (E1 Woods) > lect 34 & 35- Lower GI > Flashcards

lect 34 & 35- Lower GI Flashcards

1
Q

what does the small intestine consists of

A

duodenum
jejunum
ileum

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2
Q

what are the layers of the intestinal wall of the small intestine (inside to outside)

A

mucosa with lamina propria and muscular is mucosa
submucosa
muscularis layers
serosa

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3
Q

define lacteal

A

single blind-ending central lymphatic vessel that is present at the core of a villus

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4
Q

what are the main histological characteristics of the duodenum

A

villi with spatulate or leaflike distal shape
deep crypts of lieberkuhn
brunner’s glands with ex. ducts in submucosa

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5
Q

define crypts of lieberkuhn

A

simple tubular glands within the intestinal mucosa that open between adjacent villi and extend to muscular is mucosa

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6
Q

what absorption are enterocytes involved in

A

absorption of proteins, carbs and lipids

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7
Q

what are the enzymes on the apical brush border of enterocytes important for

A

carbohydrate digestion

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8
Q

what do enterocytes produce and what is it necessary for

A

enteropeptidase (enterokinase) which is necessary for the activation of pancreatic zymogens and proenzymes

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9
Q

what are characteristics of paneth cells

A

basal crypt cells
prominent eosinophilic granules
produce lysozyme to control intestinal flora

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10
Q

what do you stain enteroendocrine cells with

A

chromium (chromaffin)

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11
Q

what do enteroendocrine cells produce

A

peptide hormones and serotonin

may produce paracrine or autocrine secretions

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12
Q

what are enteroendocrine cells analogous to

A

unicellular goblet cells

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13
Q

what are enteroendocrine cells formed from

A

endodermal stem cells in all regions of the GI tract

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14
Q

where are brunner glands found and what are they responsible for

A

found in submucosa of duodenum

responsible for formation of bicarbonate and mucus (necessary to neutralize gastric acid)

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15
Q

what are histological characteristics of jejunum

A

villi longer and narrow
crypts of lieberkuhn present
no glands in submucosa

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16
Q

what are histological characteristics of the ileum

A

villi longer and narrow
crypts of lieberkuhn present
no glands in submucosa

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17
Q

what type of epithelium is in the large intestine

A

simple columnar epithelium

crypts but no villi

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18
Q

what is the main functions of large intestine

A

secretion of mucus
absorption of fluid
formation of fecal mass
continuation of digestion initiated in small intestine

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19
Q

what is the prominent cell of the large intestine

A

goblet cell

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20
Q

what is the main function of the mucosa of the large intestine

A

absorption of water, sodium, vitamins and minerals

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21
Q

how do the fascicles of the outer longitudinal layer in the large intestine aggregate

A

aggregate into 3 spaced bands called taeniae coli

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22
Q

define appendix epiploica

A

aggregate of adipocytes surrounded by serosa

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23
Q

how are epithelial cells of the GI tract held together

A

by occluding junctions containing transmembrane proteins (claudins and occluding) which function to prevent paracellular transport

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24
Q

what do paneth cells secrete

A

lyozyme (increases perm. of bacteria by degrading peptidoglycan coat)
defensins: increase membrane perm. of target organism
TNF-alpha

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25
Q

what is TNF-alpha produced in response to

A

diverse infectious agents and tissue injury

26
Q

what are the 2 layers of the mucosal layer

A

outer: contains microorganisms
inner: contains antimicrobial proteins that resist microbial penetration

27
Q

where are toll-like receptors found

A

on surface of enterocytes

28
Q

what do toll-like receptors do

A

recognize structurally conserved molecules broadly shared by pathogens but distinguishable from host molecule patterns (PAMPs)

29
Q

what immunglobulin is most involved in the immune response system

A

IgA

30
Q

where is the bulk of the body’s immune defenses centered

A

GALT

31
Q

what are the components of GALT

A

transitory aggregations of lymphocytes, neutrophils and eosinophils
permanent structures: appendix, peyer’s patch, mesenteric lymph nodes

32
Q

where are peyer’s patches located

A

under mucosal surface

33
Q

what do HEVs facilitate

A

entrance of lymphocytes into lymphoid organs from the blood stream

34
Q

what do specialized M (micro fold) cells do

A

sample particulate antigen and present it to antigen-presenting cells in the underlying lamina propria

35
Q

what is IgA secreted and synthesized by

A

plasma cells in lamina propria of the gut

36
Q

what is IgA linked to in the cell

A

secretory component that inhibits degradation of the sIgA by proteolytic enzymes in the GI lumen

37
Q

how does secretory IgA function

A

functions by coating microorganisms, thus inhibiting microorganism binding to the epithelium

38
Q

where are new cells formed in the esophagus and anus

A

in basal layer of stratified epithelium and migrate through sub-basal levels to be sloughed off into the lumen

39
Q

where are new cells formed in the small intestine

A

in the crypts from undifferentiated cells

40
Q

where is the proliferative compartment found in the large intestine

A

base of the crypts (because there are no villi)

41
Q

where are stem cells found in the stomach

A

neck of the gastric gland

42
Q

what do the stem cells in the stomach differentiate into

A

surface and neck mucus cells
enteroendocrine cells
parietal cells
chief cells

43
Q

what does amylase do

A

hydrolyzes starch to form sugars. starch is hydrolyzed to disaccharides

44
Q

where does the break down of disaccharides to monosaccharides occur

A

brush border of small intestine

45
Q

what are monosaccharides absorbed by and what transporter is involved

A

enterocytes

Na+-dependent sugar glucose transporter-1 (SGLT-1)

46
Q

where does digestion of proteins occur

A

stomach

47
Q

what are proteins hydrolyzed to

A

peptides

48
Q

what type of environment is required for pepsin to work

A

acidic environment

49
Q

what enzymes secreted by the pancreas are involved in the polypeptide breakdown to peptides in the small intestine

A

trypsin, chymotrypsin, elastase, carboxypeptidase

50
Q

what is the activation of pancreatic proteolytic enzymes initiated by

A

enteropeptidase (enterokinase) secreted by duodenal enterocytes

51
Q

where does digestion of lipids begin

A

small intestine

52
Q

what do lipids enter the small intestine as

A

triglyceride droplets

53
Q

what does pancreatic lipid esterase do

A

splits cholesterol esters into cholesterol and fatty acids

54
Q

what proteins are required for micelles to be passively absorbed across enterocyte apical plasma membrane

A

fatty acid binding proteins (FABPs) in apical membrane

55
Q

where are chylomicrons enclosed

A

within membranes in golgi apparatus

56
Q

how are proteins and carbohydrates entered into the blood vessels in the villi

A

transported to the liver via the hepatic portal system

57
Q

what is the site of secretion of cholecystokinin and what are they secreted in response to

A

upper intestinal mucosa (duodenum)

secreted in response to gastric contents

58
Q

what does cholecystokinin do

A

acts on pyloric sphincter to slow down emptying of stomach
stimulates bile release from gallbladder and secretion of pancreatic enzymes
competitive inhibitor of gastrins

59
Q

what is the site of secretion of gastrin

A

pyloric-antral portion of stomach

60
Q

what are the effects of gastrin

A

stimulates HCL production by gastric parietal cells, gastric motility, and release of insulin by pancreatic beta cells
promotes growth of gastric mucosa

61
Q

what is the site of the secretion of secretin and what is it stimulated by

A

epithelial cells of duodenum and stimulated by acid contents of stomach

62
Q

what are the targets and effects of secretin

A

enhances release of insulin by pancreatic beta cells

stimulates bicarbonate secretion by pancreas

histology (E1 Woods) (22 decks)

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