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Histology - Exam 3 > Digestive System - Lower > Flashcards

Digestive System - Lower Flashcards

1
Q

description of small intestine

A
  • > 6 meters long

- 3 regions: duodenum, jejunum, ileum

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2
Q

functions of small intestine

A
  • hormone secretion
  • digestion
  • nutrient absorption
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3
Q

description of duodenum

A
  • Brunner’s glands in submucosa
  • short and broad villi
  • incomplete serosa
  • mostly adventitia
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4
Q

description of jejunum

A
  • long, finger-like villi
  • well developed lacteals
  • numerous Paneth cells in crypts
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5
Q

desription of ileum

A
  • short, finger-like villi
  • Peyer’s patches
  • Paneth cells
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6
Q

tissue modifications to increase SA in small intestine

A
  • plicae circulares
  • villi
  • microvilli
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7
Q

how much do tissue modifications increase SA in small intestine?

A

400-600x

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8
Q

plicae circulares

A

vales of Kerckring

  • permanent spiral folds of the mucosa and submucosa
  • found in duodenum distal half, jejunum, and proximal half of ileum
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9
Q

intestinal villi

A

finger/leaf-like projections of mucosa

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10
Q

composition of villus core

A

lamina propria with:

  • plasma cells
  • lymphocytes
  • fibroblasts
  • mast cells
  • smooth muscle cells
  • capillaries
  • a single lacteal
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11
Q

lacteal

A

blind-end lymphatic channel

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12
Q

crypts of Lieberkuhn

A

-simple tubular glands that extend from the middle of the villus to base of epithelium near muscularis mucosae

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13
Q

composition of crypts of Lieberkuhn

A
  • goblet cells
  • columnar cells
  • enteroendocrine cells
  • regenerative cells
  • Paneth cells
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14
Q

where are microvilli located?

A

apical surface of enterocytes (striated border)

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15
Q

composition of microvillus core

A

-actin filaments linked w/ fimbrin and villin

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16
Q

how does actin of the microvillus core attach to the plasma membrane?

A

anchored to membrane by myosin I and calmodulin

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17
Q

what is at the base of the actin bundle and how do these link?

A

rootlet - crosslinked by an intestinal form of spectrin to adjacent rootlets

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18
Q

what does the end of the rootlet attach to?

A

cytokeratin-containing intermediate filaments

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19
Q

composition of terminal web of microvillus

A

spectrin + cytokeratin-containing intermediate filaments

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20
Q

how is small intestine motility controlled?

A

ANS - submucosal Meissner’s plexus and Auerbach’s myenteric plexus (b/w inner and outer smooth muscle layers of muscularis externa)

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21
Q

intestinal epithelium

A

simple columnar

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22
Q

cells of intestinal epithelium

A
  • goblet cells
  • absorptive cells (enterocytes)
  • paneth cells
  • antigen processing cells (M cells and dendritic cells)
  • enteroendocrine cells
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23
Q

goblet cells

A

unicellular glands that produce mucinogen (not same as stomach) which accumulates in membrane-bounded granules in apical region

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24
Q

what does mucinogen become?

A

after being released, it becomes mucous

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25
Q

distribution of goblet cells in small intestine

A

increase in number from duodenum to ileum

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26
Q

surface absorptive cells (enterocytes)

A
  • tall columnar cells
  • microvilli on apical surface covered by glycocalyx
  • well-developed zonulae occludens, zonulae adherens, and lateral plications
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27
Q

how often are enterocytes renewed and how does this happen?

A

every 5-6 days - cells divide down in crypt and migrate up villus; slough off at villus tip

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28
Q

what enzymes digest carbohydrates?

A

lactase, maltase, sucrase in brush border cell membrane

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29
Q

what does deficiency in lactase result in?

A

lactose intolerance -> diarrhea

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30
Q

initial digestion of proteins

A

by enzymes in lumen - pepsin, trypsin, chymotrypsin

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31
Q

digestion of proteins in microvilli

A

enterokinase and aminopeptidase - degrade oligopeptides into di- and tripeptides and aa’s

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32
Q

digestion of proteins in cytoplasm

A

cytoplasmic peptidase - degrade di-, tripeptides to aa’s

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33
Q

what happens to aa’s in enterocytes?

A

aa’s diffuse or are transported across the basal plasma membrane into blood

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34
Q

digestion of lipids in lumen

A

pancreatic lipase - breakdown to FA’s and monoglycerides and micelles formed

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35
Q

what are micelles bound to?

A

diffuse into microvilli and attach to FABP - fatty acid binding protein

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36
Q

what happens to micelles once bound to FABP?

A

transported to sER and esterified to form triglycerides

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37
Q

where are triglycerides transported to from sER?

A

golgi to form apolipoprotein complex - chylomicron (35 nm diameter)

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38
Q

where happens to chylomicrons after formation in golgi?

A

fuse with basolateral plasma membrane -> intercellular space -> lacteals

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39
Q

DNES/APUD cells - what do they produce and secrete?

A
  • gastrin
  • cholecystokinin
  • gastric inhibitory peptide
  • other hormones
40
Q

M cells

A

microfold cells - has surface microfolds instead of microvilli

41
Q

where are M cells found?

A

in epithelium over lymphoid nodules in ileum

42
Q

what may form in the basolateral portion of M cells?

A

an intraepithelial pocket that contains lymphocytes (B cells)

43
Q

function of M cells

A

antigen uptake, processing, and transport to lymphocytes and macrophages in the lamina propria

44
Q

how are antigens processed in M cells?

A

in protease (cathepsin E) containing vesiles and trnascytosed to B cells

45
Q

where are dendritic cells?

A

associated with lymphoid follicular epithelium in Peyer’s patches

46
Q

dendritic cell description

A

may extend cell processes across basal lamina and b/w tight junctions so that a small portion is exposed to the intestinal lumen

47
Q

paneth cells

A
  • contain large eosinophilic apical secretory granules

- occur at bottom of crypts of Lieberkuhn

48
Q

what do paneth cells produce?

A
  • lysozyme continuously - cleaves peptidoglycan in bacteria cell wall
  • TNF-a - proinflammatory cytokine
49
Q

life span of paneth cells

A

20 days

50
Q

what do paneth cells secrete?

A

microbicidal defensins in response to bacteria, bacterial antigens, or food-related stimulation by ACh to protect regenerative cells in crypt

51
Q

defensins

A

antimicrobial peptides also called cryptidins

52
Q

where are regenerative/intermediate cells found?

A

lower half of crypt

53
Q

what can regenerative/intermediate cells become?

A

absorptive or goblet cells

54
Q

where is the lamina propria located?

A

villi cores and interstices b/w the crypts of Lieberkuhn

55
Q

small intestine lamina propria composition

A

loose CT with:

  • lymphoid cells
  • fibroblasts
  • mast cells
  • smooth muscle cells
  • nerve endings
  • lymphoid nodules
  • lacteals
56
Q

where are Brunner’s glands found?

A

submucosa of duodenum

57
Q

description of Brunner’s glands

A

-branched tubuloalveolar glands

58
Q

Brunner’s gland secretion?

A

alkaline secretion of neutral and alkaline glycoproteins, HCO3-, and GIP

59
Q

GIP

A

gastric inhibitory peptide = urogastrone

-polypeptide hormone that enhances epithelial cell division and inhibits gastric HCl production

60
Q

describe lymphatics in ileum

A

contain aggregate lymphoid nodules - part of the gut-associated lymphoid tissue (GALT)

61
Q

primary function of cecum and colon

A

absorption of water and electrolytes

62
Q

villi of cecum and colon

A

no villi or specialized mucosal folds

63
Q

epithelium of cecum and colon

A

simple columnar epithelium with:

  • goblet cells
  • absorptive cells
  • some enteroendocrine cells
64
Q

lamina propria of cecum and colon

A

similar to small intestine - lymphoid nodules and closely packed crypts

65
Q

submucosa of cecum and colon

A
  • fibroelastic CT
  • Meissner’s plexus
  • NO glands
66
Q

muscularis externa of cecum and colon

A

inner circular and modified outer longitudinal layer of smooth muscle - outer layer gathered in 3 longitudinal smooth muscle bands = teniae coli

67
Q

what do teniae coli form in the walls of the colon and cecum?

A

sacculations = haustra coli

68
Q

what is found b/w muscle layers in the cecum and colon?

A

Auerbach’s (myenteric) plexus

69
Q

appendix

A

short diverticulum arising from cecum

70
Q

lumen of appendix

A

narrow, irregularly shaped - often contains debris

71
Q

what do walls of appendix contain?

A

large aggregates of lymphoid nodules in the mucosa and submucosa - in middle-aged people

72
Q

function of appendix

A
  • function in immune system in young people

- reservoir of bacteria to repopulate gut after diarrheal disease

73
Q

what are people with appendectomies at higher risk of later in life?

A

intestinal carcinomas

74
Q

appendix mucosa

A
  • simple columnar epithelium w/ goblet cells
  • lamina propria has lymphoid nodules capped by M cells
  • no villi
  • shallow crypts
  • goblet cells
  • surface columnar cells
  • regenerative cells
  • some paneth cells
  • many enteroendocrine cells deep in crypts
75
Q

rectum

A

similar to colon - contains fewer and deeper crypts of Lieberkuhn

76
Q

anal mucosa

A
  • longitudinal folds called anal columns

- regions b/w adjacent columns = anal sinuses

77
Q

anal epithelium

A

-simple columnar that changes to simple/stratified cuboidal/columnar occasionally then to stratified squamous nonkeratinized distal to anal valves, then to stratified squamous keratinized (epidermis) at the anus

78
Q

gastritis

A

gastric mucosal inflammation common in middle-aged and older individuals w/ unknown etiology - may be superficial or affect the entire thickness -> mucosal atrophy

79
Q

malabsorption disorders

A

can lead to malnutrition and result in wasting diseases

80
Q

gluten enteropathy - nontropical sprue

A

due to destructive effects of certain glutens (rye and wheat) on the intestinal villi - reduce SA available for absorption

81
Q

how is gluten enteropathy treated?

A

eliminating wheat and rye products

82
Q

idiopathic steatorrhea

A

malabsorption of digested fats of unknown etiology - results in stools w/ high fat content

83
Q

malabsorption of vitamin K

A

clotting insufficiency

84
Q

malabsorption of vitamin B12

A

can cause pernicious anemia - results from inadequate production of gastric intrinsic factor by the parietal cells

85
Q

2nd highest cause of cancer death in US

A

colorectal carcinoma

86
Q

what does colorectal carcinoma usually arise from?

A

adenomatous polyps - may be asymptomatic for years

87
Q

colorectal carcinoma may be diet related how?

A

high fat and refined carb diet that is low in fiber

88
Q

age group that most often presents with colorectal carcinoma

A

individuals > 50 y/o w/ highest incidence in 60-70 y/o

89
Q

how do you treat colorectal carcinoma?

A

colon resection - highest survival rates in patients whose tumors do not extend beyond muscularis mucosae

90
Q

appendicitis

A

associated with pain and/or discomfort in the lower right abdominal region - fever, nausea, vomiting + elevated WBC count

91
Q

what can happen if appendix ruptures?

A

death from peritonitis and endotoxic shock

92
Q

hemorrhoids

A

rectal bleeding during defecation

93
Q

what causes hemorrhoids?

A

breakage of dilated, thin-walled vessels of venous plexuses above (internal hemorrhoids) or below (external hemorrhoids) the anorectal line

94
Q

age group that hemorrhoids are common in

A

> 50 y/o

95
Q

hirschsprung’s disease

A

prevents migrattion and differentiation of neural crest cells into neurons of enteric nervous system

96
Q

cause of hirschsprung’s disease

A

mutations in 1 of 4 genes:

  • endothelin B receptor or ligand
  • endothelin 3
  • rearranged during transfection RET
97
Q

megacolon

A

enlarged colon due to lack of ganglia - causes back up b/c part that is not innervated cannot continue peristalsis

Histology - Exam 3 (12 decks)

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