lect 34 & 35- Lower GI

Question 1

what does the small intestine consists of

Answer 1

duodenum
jejunum
ileum

Question 2

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

Answer 2

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

Question 3

define lacteal

Answer 3

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

Question 4

what are the main histological characteristics of the duodenum

Answer 4

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

Question 5

define crypts of lieberkuhn

Answer 5

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

Question 6

what absorption are enterocytes involved in

Answer 6

absorption of proteins, carbs and lipids

Question 7

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

Answer 7

carbohydrate digestion

Question 8

what do enterocytes produce and what is it necessary for

Answer 8

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

Question 9

what are characteristics of paneth cells

Answer 9

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

Question 10

what do you stain enteroendocrine cells with

Answer 10

chromium (chromaffin)

Question 11

what do enteroendocrine cells produce

Answer 11

peptide hormones and serotonin

may produce paracrine or autocrine secretions

Question 12

what are enteroendocrine cells analogous to

Answer 12

unicellular goblet cells

Question 13

what are enteroendocrine cells formed from

Answer 13

endodermal stem cells in all regions of the GI tract

Question 14

where are brunner glands found and what are they responsible for

Answer 14

found in submucosa of duodenum

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

Question 15

what are histological characteristics of jejunum

Answer 15

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

Question 16

what are histological characteristics of the ileum

Answer 16

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

Question 17

what type of epithelium is in the large intestine

Answer 17

simple columnar epithelium

crypts but no villi

Question 18

what is the main functions of large intestine

Answer 18

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

Question 19

what is the prominent cell of the large intestine

Answer 19

goblet cell

Question 20

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

Answer 20

absorption of water, sodium, vitamins and minerals

Question 21

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

Answer 21

aggregate into 3 spaced bands called taeniae coli

Question 22

define appendix epiploica

Answer 22

aggregate of adipocytes surrounded by serosa

Question 23

how are epithelial cells of the GI tract held together

Answer 23

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

Question 24

what do paneth cells secrete

Answer 24

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

Question 25

what is TNF-alpha produced in response to

Answer 25

diverse infectious agents and tissue injury

Question 26

what are the 2 layers of the mucosal layer

Answer 26

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

Question 27

where are toll-like receptors found

Answer 27

on surface of enterocytes

Question 28

what do toll-like receptors do

Answer 28

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

Question 29

what immunglobulin is most involved in the immune response system

Answer 29

IgA

Question 30

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

Answer 30

GALT

Question 31

what are the components of GALT

Answer 31

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

Question 32

where are peyer's patches located

Answer 32

under mucosal surface

Question 33

what do HEVs facilitate

Answer 33

entrance of lymphocytes into lymphoid organs from the blood stream

Question 34

what do specialized M (micro fold) cells do

Answer 34

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

Question 35

what is IgA secreted and synthesized by

Answer 35

plasma cells in lamina propria of the gut

Question 36

what is IgA linked to in the cell

Answer 36

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

Question 37

how does secretory IgA function

Answer 37

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

Question 38

where are new cells formed in the esophagus and anus

Answer 38

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

Question 39

where are new cells formed in the small intestine

Answer 39

in the crypts from undifferentiated cells

Question 40

where is the proliferative compartment found in the large intestine

Answer 40

base of the crypts (because there are no villi)

Question 41

where are stem cells found in the stomach

Answer 41

neck of the gastric gland

Question 42

what do the stem cells in the stomach differentiate into

Answer 42

surface and neck mucus cells enteroendocrine cells parietal cells chief cells

Question 43

what does amylase do

Answer 43

hydrolyzes starch to form sugars. starch is hydrolyzed to disaccharides

Question 44

where does the break down of disaccharides to monosaccharides occur

Answer 44

brush border of small intestine

Question 45

what are monosaccharides absorbed by and what transporter is involved

Answer 45

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

Question 46

where does digestion of proteins occur

Answer 46

stomach

Question 47

what are proteins hydrolyzed to

Answer 47

peptides

Question 48

what type of environment is required for pepsin to work

Answer 48

acidic environment

Question 49

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

Answer 49

trypsin, chymotrypsin, elastase, carboxypeptidase

Question 50

what is the activation of pancreatic proteolytic enzymes initiated by

Answer 50

enteropeptidase (enterokinase) secreted by duodenal enterocytes

Question 51

where does digestion of lipids begin

Answer 51

small intestine

Question 52

what do lipids enter the small intestine as

Answer 52

triglyceride droplets

Question 53

what does pancreatic lipid esterase do

Answer 53

splits cholesterol esters into cholesterol and fatty acids

Question 54

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

Answer 54

fatty acid binding proteins (FABPs) in apical membrane

Question 55

where are chylomicrons enclosed

Answer 55

within membranes in golgi apparatus

Question 56

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

Answer 56

transported to the liver via the hepatic portal system

Question 57

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

Answer 57

upper intestinal mucosa (duodenum) | secreted in response to gastric contents

Question 58

what does cholecystokinin do

Answer 58

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

Question 59

what is the site of secretion of gastrin

Answer 59

pyloric-antral portion of stomach

Question 60

what are the effects of gastrin

Answer 60

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

Question 61

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

Answer 61

epithelial cells of duodenum and stimulated by acid contents of stomach

Question 62

what are the targets and effects of secretin

Answer 62

enhances release of insulin by pancreatic beta cells | stimulates bicarbonate secretion by pancreas