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Histo Exam 3 > Digestive System (Lower GI) > Flashcards

Digestive System (Lower GI) Flashcards

1
Q

so approximately how long is the small intestine?

A

> 6 meters long

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2
Q

what are the regions of the small bowel?

A

duodenum, jejunum, and ileum

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3
Q

what are the main general functions of small intestine?

A

hormone secretion, digestion, nutrient absorption

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4
Q

key features of duodenum, jejunum, and ileum?

A

duodenum: brunner’s gland’s in submucosa, broad/short villi, incomplete serosa - mostly adventitia
jejunum: long finger-like villi, well developed lacteals, numerous Paneth cells in crypts
ileum: short, finger-like villi, Peyer’s patches, Paneth cells

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5
Q

what tissue modifications increase surface area in the small intestine?

A

plicae circulares, villi, and microvilli - increase luminal surface area > 400-600x

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6
Q

what the heck are the valves of Kerckring?

A

another name for plicae circulares, permanent spiral folds of mucosa/submucosa

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7
Q

where would someone find valves of Kerckring?

A

found in duodenum distal half, jejunum, & proximal half of ileum

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8
Q

if you saw finger/leaf-like projections in the mucosa of the small intestine, what would you call it?

A

intestinal vili

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9
Q

the villus core of intestinal villi consists of what?

A

lamina propria with plasma cells, lymphocytes, fibroblasts, mast cells, smooth muscle cells, capillaries & a single lacteal

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10
Q

what are lacteals?

A

blind-end lymphatic channel - absorbs fat as chylomicrons

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11
Q

what are the capillary plexi that drain the intestinal villi

A

villus capillary plexus and pericryptal capillary plexus

these drain into submucosal venules

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12
Q

what are the 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

the crypts are composed of what types of cells?

A

goblet cells, columnar cells, enteroendocrine cells, regenerative cells, & Paneth cells

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14
Q

what would you find on the apical surface of enterocytes

A

microvilli

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15
Q

what do microvilli core contain?

A

actin filaments linked with fimbrin and villin

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16
Q

how is actin in the microvillus core anchored?

A

anchored to plasma membrane by myosin I & calmodulin

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17
Q

what is the role of actin “rootlets”

A

they are at the base of actin bundles and are cross-linked by intestinal forms of spectrin to adjacent rootlets.

ends of these rootlets attach to cytokeratin-containing intermediate filaments

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18
Q

what are terminal webs composed of

A

cytokeratin-containing intermediate filaments (attached to rootlets) and spectrin

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19
Q

what is the small intestine’s motility controlled by?

A

autonomic nervous system

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20
Q

where would you find Meissner’s plexus & Auerbach’s myenteric plexus?

A

Meissner’s plexus - submucosa

Auerbach’s myenteric plexus - between inner & outer smooth muscle layers of muscularis externa

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21
Q

what is the cell type for intestinal epithelium?

and what types of cells comprise this layer? (5 types)

A

intestinal epithelium are all Simple Columnar Epithelium:

goblet cells
absorptive cells (enterocytes)
paneth cells
antigen processing cells (M cells & dendritic cells)
enteroendocrine cells
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22
Q

Goblet cells are _______ (unicellular/multicellular) glands producing mucinogen which (is/is not) identical to that in the stomach

A

Goblet cells are unicellular glands producing mucinogen which is not identical to stomach mucous secretions

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23
Q

mucinogen in goblet cells accumulates in membrane-bound granules in the (apical/basal) region

A

apical region

think about where they will be expected to release these-into the lumen of the intestine

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24
Q

after mucinogen is released, it is converted to _______

A

mucous

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25
Q

“if you were a little person” traveling down the small intestine from duodenum to ileum, you would expect to see (more/fewer) goblet cells

A

more - goblet cells increase in number from the duodenum to ileum

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26
Q

enterocytes are another name for

A

surface absorptive cells

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27
Q

surface absorptive cells are (short/tall) (columnar/cuboidal) cells

A

surface absorptive cells are tall columnar cels

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28
Q

what structural characteristic about enterocytes is probably most important to their funtion

A

apical surface possesses microvilli covered by glycocalyx

remember microvilli increase surface area for absorption

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29
Q

per Dr. Turek, what binds really well to the glycocalyx and could contribute to the pathology in Gluten enteropathy?

A

plant lectin (e.g. wheat & rye)

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30
Q

back to enterocytes, what type of intercellular connections do they have?

A

well-developed zonulae occludens (tight junctions)
zonulae adherens
lateral plications

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31
Q

how often are enterocytes renewed? and where do these cells tend to be in the intestine?

A

renewed every 5-6 days

cells divide down in crypt and migrate up villus - slough@ villus tip

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32
Q

where and with what do enterocytes digest carbohydrates?

A

in the brush border of the cell membrane, enterocytes have lactase, maltase, and sucrase to digest carbs

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33
Q

if an enterocyte was to have a deficiency in lactase, what would be expected to happen?

A

deficiency in lactase = lactose intolerance = diarrhea

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34
Q

so proteins are initially digested where and with what?

A

they are initially digested by pepsin, trypsin, chymotrypsin, etc. in the lumen of the stomach

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35
Q

by the time they get to the small bowel, what are first enzymes to digest these partially digested proteins?

A

by the time they get to the intestines, enterokinase & aminopeptidase in microvilli degrade oligopeptides into di/tripeptides

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36
Q

what digests these di/tripeptides in enterocytes?

A

cytoplasmic peptidases degrade di/tripeptides to amino acids

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37
Q

what happens to fully digested proteins (amino acids) after they’ve been broken down by enterocytes?

A

amino acids diffuse or are transported across the basal plasma membrane into blood

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38
Q

where is lipid broken down in enterocytes and what is it broken down into?

A

lipids are broken down in the lumen of intestines to fatty acids and monoglycerides by pancreatic lipase & bile salts

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39
Q

what happens to the broken down lipids in the lumen? how do they get into the intestine?

A

FAs & monoglycerides form into micelles and diffuse across the microvilli

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40
Q

the micelles get linked to what proteins in microvilli?

A

they get linked to fatty acid binding protein (FABP)

^makes sense, right?

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41
Q

so this complex of micelle + FABP go where to form what

A

transported, esterified in smooth ER to form triglycerides

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42
Q

where do triglycerides go after formation to form apolipoprotein complexes (e.g. chylomicrons)?

A

they go to the Golgi

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43
Q

where do chylomicrons go after being formed?

A

they fuse with baso-lateral plasma membrane & move into intercellular space & then lacteals

44
Q

what are DNES and APUD cells again?

A

they are enteroendocrine cells (also found in stomach, half-moon shape)
secrete gastrin, cholecystokinin, gastric inhibitory peptide and other hormones

45
Q

What does the M in M cell stand for?

where are they found

A

M cells = microfold cells (cell surface has microfolds rather than microvilli)

they are found on epithelium over lymphoid nodules in ileum

46
Q

function of M cells

A

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

47
Q

what can the basolateral portion of M cells form?

what could someone find in these formations?

A

basolateral portion may form an intraepithelial pocket - B cell located in these pockets

48
Q

what are the antigens in M cells processed by?

A

antigens are processed in protease (cathepsin E) and are transcytosed to B cells

49
Q

what are dendritic cells closely associated with?

A

closely associated with lymphoid follicular epithelium in Peyer’s patches

50
Q

what can dendritic cells do to expose itself with the intestinal lumen?

A

may extend cell processes across basal lamina & between enterocyte tight junctions so that a small portion is exposed to the intestinal lumen

51
Q

how would you identify a Paneth cell?

A

large eosinophilic apical secretory granules

occur @ bottom of crypts of Lieberkuhn

52
Q

what do Paneth cells produce?

A

produce lysozyme continuously

secrete defensins

produce tumor necrosis factor alpha

53
Q

what do lysozymes do?

A

cleaves peptidoglycan in bacteria cell walls

54
Q

what’s another name for secretins

A

cryptidins

55
Q

what are secretins secreted in response to?

A

in response to bacteria, bacterial antigens, food-related stimulation by acetylcholine

56
Q

what is the functional role of defensis

A

protecting regernative cells in crypt

57
Q

what is tumor necrosis factor alpha

A

proinflammatory cytokin

58
Q

where do you find regenerative cells

A

found in lower half of crypt

59
Q

what do regenerative cells regenerate into?

A

may differenitate into absorptive or goblet cell

60
Q

where would you find lamina propria in intestinal villi

A

occupies villi core & interstices between the cryptes of Lieberkuhnk

61
Q

where would you find lacteals?

A

lamina propria

62
Q

where would you find Brunner’s glands?

A

submucosa in duodenum

63
Q

brunner’s glands branch into what?

A

tubuloalveolar glands

64
Q

what kind of secretion do Brunner’s glands have?

why?

A

alkaline secretion of neutral and alkaline glycoproteins & bicarb ions & gastric inhibitory proteins

protects intestine from acidic chyme (receiving contents from stomach)

65
Q

what does gastric inhibitory peptide do?

A

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

66
Q

characteristic features of ileum

A

Peyers patches! contains aggregate lymphoid nodules (part of gut-associated lymphoid tissue (GALT))

67
Q

primary function of cecum & colon?

A

absorption of water & electrolytes

68
Q

do the cecum and colon have villi?

A

of course not, that’s a small intestine thing

69
Q

what types of cell epithelium would expect with what types of cells involved?

A

simple columnar epithelium - goblet, absorptive (enterocyte?), & some enteroendocrine cells

70
Q

how would you describe the lamina propria of large intestine?

A

its really similar to the lamina propria of small intestine

lymphoid nodules and closely packed crypts

71
Q

does the large intestine have Paneth cells?

A

of course not, that’s an ileum/jejunum thing

72
Q

what type of submucosal contents would you find in the cecum/colon?

A

fibroelastic connective tissue
Meissner’s plexus
NO glands

73
Q

what’re the characteristics of large bowel’s muscularis externa?

A

inner circular layer of smooth muscle

modified outer longitudinal layer of smooth m. (gathered in 3 longitudinal smooth muscle bands that form teniae coli)

74
Q

what are the sacculations that teniae coli can form are called

A

haustra

75
Q

what would you find between the smooth muscle layers of the large intestine?

A

Auerbach’s (myenteric) plexus between muscle layers

76
Q

the appendix is a short ______ arising from the ______

A

diverticulum, cecum

77
Q

does the appendix have a lumen? and how would you describe it?

A

yes - narrow, irregularly shaped lumen often containing debris

78
Q

walls of appendix have lots of?

A

lots of lymphoid nodules in mucosa & submucosa in middle-aged individuals

79
Q

proposed purpose of appendix in young people?

what about in general?

A

immune system function

higher risk for intestinal carcinomas later in life if removed early, reservoir of bacteria to repopulate gut after diarrheal disease

80
Q

appendix mucosa has what type of epithelium cells

A

simple columnar epithelium wiht goblet cells

81
Q

lamina propria of appendix mucosa has what type of lymph tissue and is capped by what?

A

lymphoid nodules capped by M cells

82
Q

does the appendix have villi?

A

nope

83
Q

what types of cells does the appendix have in its shallow crypts? (5)

A 
goblet 
surface columnar 
regenerative 
some Paneth cells
many enteroendocrine cells deep in crypts
84
Q

what is the rectum most similar to?

how is it different

A

it’s most similar to the colon

fewer & deeper crypts of Lieberkuhn

85
Q

the anal mucosa has longitudinal folds called ___ ______

and the regions between these are called _____ _______

A

longitudinal folds called anal columns

regions between these adjacent columns are called anal sinuses

86
Q

how does anal epithelium change?
rectum to anal canal
distal to anal valves
and at the anus

A

starts as simple columnar
changes to simple/stratified cuboidal/columnar
ditsal to anal valves: occasionally stratified squamous nonkeratinized
@ anus: stratified squamous keratinized

87
Q

gastritis is a gastric mucosal inflammation that is common in what age group of people?

A

middle-aged and older individuals

88
Q

gastritis is caused by?

A

unknown etiology - we don’t know

89
Q

does gastritis affect the superficial layer of mucosa or the entire thickness?

A

it can be either superficial or affect the entire thickness causing mucosal atrophy

90
Q

do you want to see flashcards on gastric/peptic ulcers?

A

if yes, go over the upper GI segment; Turek just copies and pastes stuff

91
Q

what can malabsorption disorders cause?

don’t overthink it

A

can lead to malnutrition, result in wasting disease

92
Q

what the heck is gluten enteropathy - nontropical sprue

A

rye & wheat glutens bind to intestinal villi reducing the surface area available for absorption

93
Q

how do you treat gluten enteropathy?

A

treat by eliminating wheat and rye products

94
Q

idiopathic steatorrhea is what?

A

when you have stools with high fat content

due to malabsorption of digested fats

95
Q

what is idiopathic steatorrhea caused by

A

unknown etiology

96
Q

malabsorption of what vitamin could lad to clotting insufficiency?

A

vitamin K

97
Q

malabsorption of what vitamin could lead to pernicious anemia?

A

B12

98
Q

what allows for the absorption of vitamin B12?

A

parietal cells release gastric intrinsic actor which allow for absorption of vitamin B12

99
Q

what is the 2nd highest cause of cancer death in the US

A

colorectal carcinoma

100
Q

what is colorectal carcinoma usually arising from?

A

adenomatous polyps - can be asymptomatic for years

101
Q

what age are people more likely to get colorectal carcinoma?

A

> 50 yrs, highest incidence in 60-70 y/o group

102
Q

how do you treat colorectal carcinoma?

A

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

103
Q

appendicitis is associated with what symptoms?

A

pain in RLQ of abdomen, fever, nausea, vomiting and high white blood count (high wbc)

104
Q

how do people die from appendicitis?

A

appendix ruptures > peritonitis/endotoxic shock > death

105
Q

rectal bleeding during defectation is caused by?

A

hemorrhoids -breakage of dilated thin-walled vessels of venous plexuses above or below anorectal line

106
Q

hirschsprung’s disease is also called?

A

megacolon

107
Q

what happens in hirschsprung’s disease?

A

mutation of endothelin B receptor/ligand, endothelin 3 and rearranged during transfection (?)

main point: prevents migration and differentiation of neural crest cells into neurons of enteric nervous system

Histo Exam 3 (6 decks)

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