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GI > GI Histo > Flashcards

GI Histo Flashcards

1
Q

What is the ratio of pylorus pits:glands?

A

3:1

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2
Q

What is the ratio of fundus/body pits:glands?

A

1:3

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3
Q

What is the ratio of cardia pits:glands?

A

1:1

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4
Q

What are surface mucous cells?

A
  • cells with granules containing glycoproteins (mucins) that combine with water on the surface to form a protective and insoluble gel
  • produce HCO3- that diffuses into surface mucous gel (protects cells below surface from stomach acid)
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5
Q

What are neck mucous cells?

A

Produce a soluble mucous at the top of the glandular portion of the lumen of the gastric gland

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6
Q

What are the 6 cells in of the gastric gland?

A

surface mucous cells, neck mucous cells, stem cells, parietal cells, chief cells, DNES cells (enteroendocrine)

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7
Q

What do parietal cells produce?

A

HCl, HCO3-, and IF

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8
Q

What is IF?

A

A glycoprotein that complexes with vit B12 in stomach an duodenum. Essential for B12 absorption from the ileum.

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9
Q

How does B12 lead to pernicious anemia?

A

B12 is important for RBC development.

W/o B12 a person can develop pernicious anemia.

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10
Q

What are key features of an inactive parietal cell?

A

cytoplasm is filled with tubules and vesicles (membrane reserve)

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11
Q

What are key features of an active parietal cell?

A
  • prominent intracellular canaliculus
  • secretion of acid occurs along internalized surface
  • mitochondria provide energy needed
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12
Q

What stimulates acid secretion from parietal cells?

A

Ach, histamine, and gastrin

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13
Q

In response to stimulation/food, how does pH change in the:

  • stomach lumen?
  • blood?
  • lumen?
A

1) HCl secreted into lumen of stomach (lower pH) via canaliculi of the parietal cells (K+/H+ exchange w/ ATPase)
2) Simultaneously, Cl- and K+ ions are activated so these ions flow into lumen.
3) HCO3- is transported into the interstitial fluid by antiport that carries Cl- into cell:

Thus: pH in BLOOD and URINE INCREASES because of HCO3-

(bicarb has protective fxn)

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14
Q

What do chief cells produce?

A

produce pepsinogen and gastric lipase (very basophilic)

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15
Q

How are chief cells stimulated?

A
  • found in basal half of glands

- stimulated by ACh (neural stim) and secretin

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16
Q

What does pepsinogen do?

A

proenzyme that is converted to pepsin in the presence of H+

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17
Q

What protection mechanism are in place in the stomach?

A
  • mucous cells produce mucous and bicarb (protective)
  • TJxns: prevent H+ ions from crossing from epithelial to parietal level toward capillary
  • prostaglandins increase blood flow and bicarb secretion
  • pepsinogen in inactive form
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18
Q

Where are the stem cells in the stomach/gastric glands?

A
  • base of gastric pits and upper neck of isthmus
  • give rise to mature epithelium over 4-5 days; replace cells lost as a result of association with the noxious environment of the gastric lumen
19
Q

What are destructive mechanisms in the stomach?

A
  • HCl and PEPSIN (active form)
  • stress, aspirin and NSAIDs inhibit prostaglandins
  • H. pylori: normally counteracted by protective mechs so not noticed
20
Q

What cells are used to communicate between upper regions of gut to rest of gut/organs?

A

DNES cells (enteroendocrine cells)

21
Q

What do DNES cells do?

A

NB: SECRETES HORMONES TOWERD LAMINA PROPRIA (not lumen);
cells are open (extend to lumen) or closed type

  • interact with other DNES cells and neurons and glands
  • influence motility and digestion
  • have a trophic role
  • found in multiple locations throughout GI tract
  • produce members of cholexcytokinin/gastrin family, members of secretin/glucagon family and other hormones
22
Q

What are key features of the stomach?

A

Pits and glands
simple columnar epith
pyloric sphinctor
3 muscle layers

23
Q

What are key features of the duodenum?

A

villi and crypts
simple columnar epith
brunner’s glands (submucosal; produce alkaline substance)
2 muscle layers

24
Q

Where are the cypts of lieberkuhn?

A

small intestine

invaginations that increase surface area

25
Q

What are and where are the plicae circularis?

A

Submucosal folds (permanent) of small intestine

26
Q

What are the 6 specialized cells of the small intestine?

A

enterocytes: absorb and digest

(4 that protect) goblet cells, paneth cells, immune cells, stem cells

DNES cells (communication)

27
Q

What cells are in the SI villus?

A

enterocytes (absorb), goblet cells, immune cells, DNES cells

28
Q

What are the cells of the SI crypt?

A

Paneth, stem, DNES, enterocytes

29
Q

WHat is in the SI lamina propria?

A

capillaries, lacteals, smooth muscle, lymphocytes and nerves

30
Q

What do enterocytes absorb?
Produce?
Process?

A

Absorb: lipids, sugars, AAs, vitamins, minerals, ions, water

Produce: TM enzymes associated with glycocalyx (pancreatic enzymes in glycocalyx)

Process: lipid processing

Also: Terminal digestion of proteins and carbs

31
Q

What is a lacteal?

A

blind-ending lymphatic vessel at the core of the villus

32
Q

What are the protective mechanisms in the SI?

A
  • goblet cells: protective layer of mucus
  • stem cells
  • paneth cells
  • immune cells
33
Q

What do paneth cells produce?

A

lysozyme (anti-bacterial enzyme that controls the gut flora, stored in granules and released into gut lumen)

Tumor Necrosis Factor-alpha (pro-inflammatory)

Defensins or cryptidins (antiomicrobial effect)

34
Q

GALT

A

Gut Associated Lymphoid Tissues

-T and B lymphocytes (lamina propria and intraepithelial), plasma cells, eosinophils, mast cells, macrophages

35
Q

What are Peyer’s Patches? Where found?

A

aggregate nodules of lymphatic tissues, usually in lower pts of instestine

36
Q

What are M Cells?

A

specialized epithelial cells found over lymphoid nodules in follicle associated epithelium

37
Q

What do M cells do?

A

Take up antigen and transport it to underlying cells

  • look like umbrellas with lymphocytes and macrophages below.
  • carry antigens across cells to come into contact with lymphocytes and macrophages
38
Q

What and where are the plicae semilunaris?

A

submucosal folds of large intestine: increase surface area

39
Q

What are the 5 cell types of large intestine?

A

absorptive cells
(3 cells for protection): goblet cells, immune cells, stem cells (base)
DNES cells

40
Q

What is the epithelium and key features of rectum?

A
  • lined with simple columnar epithelium

- crypts are more tortuous than colon

41
Q

What is the epithelial change in the anal canla?

A

-simple columnar changes to stratified squamous epithelium

42
Q

What muscles are in the internal and external sphincters of the anal canal?

A

internal: circl. smooth
external: skeletal

43
Q

Where is the myenteric plexus?

A

between muscularis layers (aka Auerbach)

SNS and PSNS

44
Q

What is Meissner’s plexus?

A

submucosal

  • neuronal CBs located at outer edge of submucosa, adjacent to muscularis externa
  • small unmyleinated nerve fibers
  • sensory nerves present
  • surrounded by lots of CT

GI (17 decks)

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