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Histology > GI Tract Part 2 > Flashcards

GI Tract Part 2 Flashcards

1
Q

where are goblet cells located

A

interspersed among enterocytes

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2
Q

what do goblet cells synthesize and what is it stored in

A

mucinogen stored in membrane bound granules

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3
Q

what does mucinogen (mucus) do

A

lubricates and protects epithelium

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4
Q

where are actively dividing stem cells located

A

at base of crypts

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5
Q

where do actively dividing stem cells migrate as they mature

A

up villus, mature and are shed

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6
Q

how often is the entire epithelial lining replaced

A

every 3-5 days

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7
Q

where are paneth cells found

A

at the base of crypts

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8
Q

what do paneth cells contain and what do they produce

A

large eospinophilic granules that produce antibacterial proteins called defensins and enzymes including lysozyme

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9
Q

what do A cells secrete

A

glucagon

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10
Q

what do K cells secrete

A

GIP

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11
Q

where is MALT located

A

lamina propria and submucosa of small intestine

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12
Q

what are M cells

A

squamoid enterocytes modified for Ag sampling and uptake of macromolecules

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13
Q

what are Peyer’s patches

A

dome shaped areas grossly visible on surface of mucosa and project into lumen

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14
Q

what is the duodenum characterized by

A

Brunner’s glands in submucosa

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15
Q

what do Brunner’s glands contain

A

large numbers of highly convoluted branches, tubuloalveolar submucosal glands

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16
Q

what do brunner’s glands do

A

secrete mucus and zymogens

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17
Q

what is the main function of the duodenum

A

neutralize gastric acid and pepsin

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18
Q

what assists the duodenum in its function

A

pancreas and gallbladder

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19
Q

what do the pancreatic duct and bile duct empty into

A

duodenum at major duodenal papulla

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20
Q

what does chyme from the stomach stimulate the release of

A

secretin and CCK from APUD cells

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21
Q

what do secretin and CCK promote

A

section of exocrine pancreas

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22
Q

describe the ph of pancreatic secretions and why

A

highly alkaline due to bicarbonate

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23
Q

what does CCK stimulate

A

contraction of bladder and release of bile acids

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24
Q

what do bile acids do

A

act as emulsifying agents for digestion of lipids to form micelles

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25
Q

what do pancreatic secretions contain

A

proteolytic enzymes trypsin and chymotrypsin for digestion of proteins, and amylase and lipase

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26
Q

what are enzymes in pancreatic secretions secreted as

A

inactive precursors (zymogens) such as trypsinogen and chymotrypsinogen

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27
Q

why are enzymes secreted as inactive precursors

A

to prevent autolysis

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28
Q

what is trypsin activated by

A

enterokinase

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29
Q

what does trypsin activate

A

chymotrypsin

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30
Q

what are the two steps in the digestion process

A

luminal digestion and membrane digestion

31
Q

what does luminal digestion involve

A

mixing of chyme with pancreatic enzymes that results in molecular breakdown

32
Q

what does membrane digestion involve

A

enzymes of glycocalyx on plasma membrane of enterocytes

33
Q

what do enterocytes synthesize

A

enzymes and carrier proteins for absorption of carbohydrates and amino acids

34
Q

what enzymes do enterocytes synthesize

A

peptidases, peptide hydrolases, disaccharidases,

35
Q

what are proteins initially denatured by and hydrolyzed by

A

denatured by HCl from parietal cells and hydrolyzed by pepsin into polypeptide fragments

36
Q

what continutes to breakdown proteins

A

pancreatic enzymes which results in small peptide fragments (AAs) that are absorbed by enterocytes via active transport by carrier proteins

37
Q

what are the types of carbohydrates

A

poly-, oligo-, and disaccharides

38
Q

what hydrolyzes starch to disaccharides

A

salivary and pancreatic amylase

39
Q

what are disaccharides further broken down into

A

monosaccharides

40
Q

what are examples of disaccharides? monosaccharides?

A

disaccharides: sucrose, lactose, maltose, isomaltose
monosaccharides: glucose, galactose and fructose

41
Q

what are monosaccharides and AAs absorbed by

A

enterocytes lining villi, transported across epithelium, enter capillaries within lamina propria -> portal vein to liver for storage

42
Q

what are lipids and what are they emulsified by

A

triglycerides from diet, emulsified by bile acids

43
Q

what are lipids further broken down into

A

monoglycerides and fatty acids by pancreatic lipase to form extracellular micelles

44
Q

what are micelles absorbed by

A

enterocytes then re-synthesized into triglycerides within enterocytes and coated with proteins and phospholipids to form intracellular chylomicrons

45
Q

where are chylomicrons transported

A

across enterocytes to lacteals

46
Q

what are lacteals

A

blind ended lymph vessels within lamina propria of villi

47
Q

where are chylomicrons eventually carried to

A

thoracic duct and general circulation

48
Q

what does the large intestine include

A

cecum, appendix, ascending, transverse, descending and sigmoid colon, and rectum

49
Q

what does the large intestine lack

A

villi and plicae circulares

50
Q

what is the appendix

A

small, blind ended sac distal to ileo cecal junction

51
Q

what does the appendix contain

A

large amounts of submucosal MALT

52
Q

what is the primary function of the colon

A

water and electrolyte resporption
-also produces mucus for elimination of undigested food and waste

53
Q

what does the colon contain

A

large numbers of goblet cells in epithelium and colonic glands in submucosa

54
Q

what does the colon not have

A

brunner’s glands, villi, plicae circulares

55
Q

what is the mucosal epithelium in the colon similar to

A

small intestine but paneth cells are generally absent in adults

56
Q

what does the MALT not form in large intestine

A

Peyers patches

57
Q

are lacteals present in the lamina propria of the colon

A

NO

58
Q

where does epithelial replacement occur in the colon

A

from stem cells at the base of glandular crypts

59
Q

what type of bacteria is common in the colon

A

commensal bacteria

60
Q

describe the outer longitudinal muscle layer in muscularis externa of the colon

A

reduced or incomplete- forms 3 longitudinal strips called taenia coli

61
Q

what are taenia coli responsible for

A

formation of haustra

62
Q

what are polyps

A

adenomas
- any mass arising from the wall of the colon that protrudes into the lumen

63
Q

what is the most common sign of polyps

A

rectal bleeding

64
Q

what is colon cancer

A

adenocarcinoma

65
Q

what decreases colon cancer risk

A

increased fiber in diet which decreased transit time and increases GI motility

66
Q

describe the rectum

A

short dilated terminal portion of large intestine

67
Q

what does the rectum contain

A

transverse rectal folds and large numbers of mucus glands

68
Q

what is the transition of mucosa at anal canal

A

simple columnar epithelium to stratified squamous epithelium

69
Q

what does the anal canal contain

A

longitudinal folds called anal columns

70
Q

where are anal glands located

A

extend into submucosa and muscularis externa

71
Q

describe the type of glands anal glands are

A

branched, straight, tubular glands that secrete mucus

72
Q

what is the external anal sphincter made of? internal?

A

external: skeletal muscle
internal: smooth muscle

73
Q

what are occasional enlargement and irritation of submucosal veins called

A

hemorrhoids

74
Q

what is the anus

A

external opening, exit of GI tract

Histology (27 decks)

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