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digestion and metabolism - Wk 3 > small intestine - monday > Flashcards

small intestine - monday Flashcards

1
Q

what does the intestine do

A

continues digestion and absorption of food and fluids

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2
Q

what makes up the small intestine

A
  • duodenum
  • jejunum
  • ileum
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3
Q

what are the 4 general histological layers of the GI tract

A
  • mucosa
  • submucosa
  • muscularis externa
  • serosa/adventitia
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4
Q

what type of epithelium is in the SI

A

simple columnar epithelium

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5
Q

what are plicae circulares

A

fold of mucosa and submucosa encircling lumen, grossly viewable

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6
Q

unlike rugae of the stomach, plicae circulares are ____ folds

A

permanent

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7
Q

what are villi

A

fingerlike projections of mucosal layer only into lumen of gut

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8
Q

what type of epithelium are villi lined by

A

simple columnar

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9
Q

what are the 3 cell types that villi consist of

A
  1. enterocytes
  2. goblet cells
  3. enteroendocrine
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10
Q

what are enterocytes

absorptive cells

A

on the apical surface of villi and contain thousands of microvilli which form a brush border

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11
Q

what do microvilli contain

A
  • actin core
  • enzymes - lactase, maltase, sucrase
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12
Q

what are the enzymes in microvilli involved in

A

the terminal digestion of carbs and proteins

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13
Q

what triggers the movement of microvilli

A

submucosal (meissner’s) plexus

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14
Q

what are the two functions of the brush border

A
  • increase surface area for absorption
  • increase surface area for enzymes that perform final stages of extracellular digestion, preparing them for transport across the cell membrane
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15
Q

what is the purpose of maximizing surface area

A

digestion and absorption require mixing of ingesta with bile and enzymes, retention of chyme, with exposure to adequate SA

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16
Q

what are lacteals

A

blind-ended lymphatic vessel

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17
Q

what are goblet cells

A

produce mucus to protect the lumen from abrasion and bacterial invasion

18
Q

what are enteroendocrine cells

A

cells that secrete their contents basally

19
Q

what is within the core of each villus (in the lamina propria)

4 things

A
  1. capillar plexus
  2. lacteal
  3. thin strands of muscularis mucosae
  4. lymphocytes, eosinophils, macrophages, etc
20
Q

where are crypts located

A

between villi - invaginations of the mucosa

21
Q

what are the 5 things that are in crypts

A
  1. simple tubular glands
    2. stem cells
  2. enteroendocrine cells
    4. paneth cells
  3. sometimes goblet cells
22
Q

what are paneth cells

A

protect lining of gut from microorganims such as bacteria & parasites

in SI only

23
Q

what do paneth cells secrete

A

lysozymes and defensins

24
Q

what animals are paneth cells absent in

only some animals

A

dogs, cats, pigs, and racoons

25
Q

where are paneth cells located

A

base of crypt

26
Q

where do secretions from paneth cells enter

A

lumen directly - do NOT enter the bloodstream

27
Q

what cells are responsible for the rapid turnover of the intestinal epithelium

A

stem cells

28
Q

what is the first part of the SI

A

duodenum

29
Q

what is the unique feature of the duodenum

A

brunner’s glands in submucosa

30
Q

what do brunner’s glands produce

A

mucus and bicarbonate to offset acidic chyme expelled from stomach

31
Q

what does the duodenum contain

A
  • brunner’s glands
  • villi: short, broad, leaf-like with scattered enteroendocrine cells
  • retroperitoneal
  • houses bile and pancreatic ducts
  • paneth cells at base of crypts
32
Q

what types of nervous systems does the enterogastric reflex involve

A

CNS and ENS, endo/paracrine signals

33
Q

what is the enterogastrin reflex

A
  • afferent fibers of the vagus nerve receive stimuli in duodeum
  • these stimuli block vagus-induced stomach empyting
34
Q

what is released from enteroendocrine cells in the duodeum

enterogastric reflex

A

CCK and secretin gets secreted into the bloodstream

35
Q

what do CCK and secretin suppress

enterogastric reflex

A

gastric empyting

36
Q

what is the second part of the SI

A

jejunum

37
Q

what are the characteristics of the jejunum

A
  • longest villi
  • abundant paneth cells in crypts
  • no glands in submucosa
38
Q

what is the third part of the SI

A

ileum

39
Q

what are the characteristics of the ileum

A
  • shorter villi
  • paneth cells
  • peyer’s patches in submucosa
40
Q

what are peyer’s patches

A

specialized lymphatic nodules

41
Q

what are M cells

microfold cells

A

specialized epithelial cells that contain small microfolds on their lateral edges

42
Q

what do M cells do

A
  • trap antigens from the lumen of the gut via endocytosis
  • antigens released beneath M cells and taken up by APC (DC) in underlying dome
  • antigens presented to T cells to initate immune response

digestion and metabolism - Wk 3 (5 decks)

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