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COM-GI > Histology of SI and LI > Flashcards

Histology of SI and LI Flashcards

1
Q

Layers of the S.I.

A

Mucosa
Submucosa
Muscularis externa
Serosa

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2
Q

4 “degrees” of folding in the SI

A

Plicae circulares
Villi on plicae
Crypts of Lieberkuhn at base
Microvilli on surface of enterocyte

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3
Q

Plicae circulares are most prominent where?

A

Jejunum

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4
Q

Where are intestinal glands located?

A

W/in the crypts of Lieberkuhn

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5
Q

4 main cell types in intestinal glands

A

Enterocytes
Goblet cells
Paneth cells
Enteroendocrine cells

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6
Q

The microvilli on the enterocytes collectively make a _____

A

Brush border (glycocalyx)

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7
Q

What is the mixing motion called in the S.I.?

Describe it

A

Segmentation

Contraction of the walls at random locations to push the chyme around and mix it up

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8
Q

What controls the segmentation process in the S.I.?

A

The ANS

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9
Q

Describe peristalsis

A

One part contracts while the next relaxes, etc. Moves in a wave-like motion

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10
Q

Explain the microcirculation in the S.I.

A

Blood moves in via arterioles, then goes into 2 capillary networks: villus plexus and pericryptal plexus

Then out through the mesentery and into the portal system

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11
Q

What are each of the 2 capillary networks in the S.I.?

A

Villus plexus - supplies villus and upper part of crypt w/ blood

Pericryptal plexus - supplies lower part of crypt w/ blood

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12
Q

Describe lymph flow in the S.I.

A

Nutrients pulled into lacteals at the ends of villi via chylomicrons, then out to lymphoid follicle to portal system to thoracic duct to systemic circulation

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13
Q

Two types of innervation for motility, etc. of S.I.

A

Intrinsic - from mucosa and muscle wall (enteric NS only)

Extrinsic - from CNS via vagus n. or greater splanchnic n. –> enteric NS

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14
Q

Glands and walls of duodenum

A

Leaf-like villi
Few goblet cells
Brunner’s glands - mucus for lubricating food (submucosa)

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15
Q

Glands and walls of jejunum

A

Lots of plicae

More goblet cells

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16
Q

Glands and walls of Ileum

A

Finger-like, short villi
Lots of goblet cells
Peyer’s Patches (immune)
M cells - antigen transport

17
Q

Cell types w/in Crypts of Lieberkuhn (5)

A 
Enterocytes
Goblet cells
Paneth cells
Stem cells
Enteroendocrine cells
18
Q

Describe enterocytes of S.I.

A

Absorption

Brush border of microvilli

Microvilli have lactase, maltase, sucrase for carb digestion

Carbs transported in by carrier proteins

19
Q

Lactose intolerance

A

No lactase enzyme in microvilli of enterocytes

Bacteria break it down instead –> gas, acids, etc.

20
Q

Function of goblet cells

What does that do?

A

Secrete mucus

Protects epithelium from mechanical abrasion and bacteria

21
Q

What is the largest endocrine gland in the body?

A

GI tract

22
Q

Role of enteroendocrine cells

A

Secrete peptide hormones - gastrin, secretin, CCK

23
Q

Role of each hormone secreted by enteroendocrine cells

A

Gastrin - inc. motility, HCl, insulin

Secretin - pancreatic bicarb. and insulin

CCK - bile and pancreatic enzyme release, contract pyloric sphincter to slow motility

24
Q

Role of Paneth cells

A

Contain antimicrobial proteins that degrade bacterial wall and limit contact w/ enterocytes

25
Q

Where would one find the secretion of Paneth cells?

A

Antimicrobial proteins - in mucus blanket over enterocytes

26
Q

7 things that protect the S.I.

A 
Mucus blanket (goblet cells)
Tight jxns btwn enterocytes
Peyer's patches
IgA - neutralize antigens
Antimicrobial proteins
Acidity of gastric juice - kills pathogens
Peristalsis - prevents colonization
27
Q

IBD / Crohn’s disease

A 
Neutrophils infiltrate crypts
Glands destroyed
Submucosa/muscularis inflammation
Lymphocytes accumulate = granulomas
Occlusion of lumen via fibrosis
Fistulas at times
28
Q

Fecal Microbiota Transplant

When would it be required?

Example of a bad bacteria

A

Replace bad bacteria w/ good bacteria from feces donor

Good bacteria destroyed via antibiotics

C. difficile (horrible diarrhea, sometimes fatal)

29
Q

Main function of the L.I.

A

Absorb ions and water

30
Q

Outer muscle layer in the L.I.

Form what?

A

Taenia coli

Haustra

31
Q

What does the L.I. NOT have that the S.I. does?

A

Villi, Paneth cells, plicae circulares

DO have plicae semilunares

32
Q

How are ions absorbed in the L.I.?

A

Na+ and Cl- absorbed via membrane channels

33
Q

Does the L.I. have goblet cells?

A

YES, lot’s of them

34
Q

How does aldosterone affect the L.I.?

What is its overall function?

A

Increases Na+ channels for ion uptake, thus increasing water absorption

Increase blood pressure by increasing water absorption, etc.

35
Q

Describe the walls of the appendix

A

Lots of lymphatic tissue

No villi, less crypts

Fatty tissue in submucosa

No taenia coli

36
Q

Possible role of appendix

A

Reservoir for good bacteria

37
Q

What does the pectinate line divide?

Above and below?

A

Regions of the rectum

Above - endoderm - innervated like viscera

Below - ectoderm - innervated like skin (but w/ voluntary control)

38
Q

Which type of rectal hemorrhoids are painful?

Why?

A

Lower

No pain fibers in upper - innervated like viscera above the pectinate line

39
Q

Familial adenomatous polyposis

Genetic cause?

A

Inherited condition where polyps develop on walls of colon

Due to defect in APC gene (hyperactive)

COM-GI (9 decks)

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