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*Histology > GI 3-4 > Flashcards

GI 3-4 Flashcards

1
Q

Small Intestine

A

Longest component of alimentary canal; 3 portions duodenum, jejunum, ileum; serves to digest food, absorb nutrients, secrete enzymes, control microbial growth and regulate GI function

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2
Q

Structure of SI

A

mucosa, submucosa, muscularis externa, and serosa/adventitia; UNIQUE: PLICA CIRCULARES; Mucosa contains villi

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3
Q

Duodenum

A

shortest and widest part of SI; Brunner’s glands, least goblet cells

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4
Q

Jejunum

A

begins at DJ junciton and gradually changes its character to become ileum; tallest villi, prominent lacteals

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5
Q

Ileum

A

lower 3/5 of SI ending at Ileocecal junction; most goblet cells; Peyer’s patches and shorter villi

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6
Q

What system regulates GI function?

A

endocrine secretion by enteroendocrine cells

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7
Q

Where are plicae most numerous?

A

Distal duodenum and proximal jejunum

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8
Q

What is the role of plicae?

A

Increase surface area

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9
Q

What is the most unique feature of mucosa of the SI?

A

Villi: all mucosa (no submucosa); loose CT of lamina propria; role is to increase SA more; found on columnar cells of surface epithelium; atrophty is found in coeliac diasease

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10
Q

Gluten enteropathy/Coeliac disease

A

found in patients with hypersensitivity to gluten and caused by total or subtotal atrophy of the villi in the SI. Results in malabsorption syndrome characterized by weight loss, steatorrhea.

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11
Q

Surface epithelium of SI

A

simple columar: does not change between villi and intervilli; includes enerocytes which absorb nutrients, produce digestive enzymes, break down lipids, and transcytose IgA to protect mucosa.

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12
Q

Enterocytes

A

Tall columnar cells with numerous microvilli on apical surface forming brush border to increase SA. They are bound by tight and anchoring junctions to create a barrier between intestinal lumen and epithelial intercellular component.

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13
Q

What is digested in the glycocalyx of enterocytes

A

proteins and carbs

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14
Q

What happens to lipids in the SI and where does this occur>

A

broken down to monogylcerides for transport occurs in the lumen of intestine and are rebuilt into trglycerides in the smooth ER. Fat droplets then fo to the golgi to get a protein coat, becoming CHYLOMICRA which can be released into extracellular for uptake by lymph

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15
Q

IgA role in SI

A

Found in lamina propria, moved to intestinal lumen after synthesis and secretion by plasma cells. They protect mucosa by controlling microbial growth.

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16
Q

Goblet Cells (of SI)

A

unicellular mucous glands intersperesed amoung enterocytes that INCREASE IN NUMBER IN THE TERMINAL ILEUM. 1* role is to produce mucus. Narrow base, wide apex, frothy cytoplasm, mucinogen granules. Pale staining.

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17
Q

M-Cells

A

limited distribution, found in epithelium OVERLYING LYMPHOID FOLLICLES. Antigen transporters: alert invaders of lumen to the lympoid follicles. Endocytosed using carrier vesicles and delivered to basolateral membrane to be discharged into intercellular space near T-lymphocytes.

18
Q

Enteroendocrine cells

A

same structure and function as in stomach: Mostly concentrated at base of gland. Secrete product into lamina propria. Secrete gastrointestinal hormones to regulate functioning of alimentary canal. (including gastrin, ghrelin.) Rest on basement membrane and form microvilli that reach lumen of gland. Filled with membrane bound secretory granules in basilar part of cell.

19
Q

Intraepithelial Lymphocytes

A

unusual T-lymphocytes; dervied from progenitor cells in crypts of lieberkuhn (blood derived) and help mucosal immunity

20
Q

Mucosal Glands

A

Crypts of Lieberkuhn; simple invaginations. Extend through muscularis mucosa. The 2 unique cells here are paneth and progenitor cells

21
Q

Panteth cells

A

bottom of crypt of Lieberkuhn; regulate bacterial growth; numerous large eosinophilic granules in apical part containing AB enzyme lysozyme, Alpha defensins, etc; basilar ER

22
Q

Progenitor Cells

A

mainly found in cypts of L; undifferentiated cells that replace any epithelium except lymphocytes; indentifiable as mitotic cells

23
Q

Lamina Propria of the SI

A

loose CT with lymphoid follicles

24
Q

Lyphoid Follicles

A

scattered throughout lamina propria; GALT; Largely identifiable as peyers patches in the ileum and consist of m-cells

25
Q

Small Intestine LYMPHOMA

A

most common of SI, arises from B- or T- lymphocytes in lamina propria in proximal SI, wall becomes thickened and inflitrated with lymphocytes

26
Q

Blood supply to SI

A

capillary loops from arterioles of submucosal vascular plexus and return to venules of same plexus; solubel nutrients like AA and carbs are transported by blood vessels (NOT FAT)

27
Q

Lymphatics of SI

A

Each villus has a central blind-ended capillary called LACTEAL. These drain into larger vessels in submucosa. Transports the chylomicra (fat) ingested by enterocytes

28
Q

Muscularis Mucosae or SI

A

several layers of smooth muscle

29
Q

Submucosa of SI

A

Dense CT, vascular and nerve (Meissner’s) plexi; glands: BRUNNERS OF DUODENUM

30
Q

Brunner’s Glands

A

only found in DUODENUM, mucus-producing branched tubular glands of alkaline secretion that protects the intestine by neutralizing acidic chye from stomach

31
Q

Muscularis Externa of SI

A

inner circular and outer longitudinal layer; Auerbach’s plexi between muscle layers

32
Q

Most of the duodenum is covered with ___ while the jejunum and ileum are covered with ____.

A

adventitia, serosa

33
Q

Large Intestine

A

Cecum, colon, rectum, and anal canal; serves to reabsorb water and electrolytes while eliminating undigested food and waste; same comp as alimentary canal; NO VILLI

34
Q

Mucosal Epithelium of LI

A

no villi, no paneth cells, yes progenitor cells, columnar absorber cells (enterocytes) predominate, goblet cells are MORE ABUNDANT than SI and outnumber enterocytes in rectum

35
Q

Goblet Cells of the LI

A

MORE ABUNDANT than SI and outnumber enterocytes in rectum; procude extensive amounts of mucus to facilitate the elimination of solid waste

36
Q

Adenocarcinoma

A

most common and malignant tumor of the LI usually in colon or rectum. Usually arise in patients with adenomatus polyps or UC. Tx- resection.

37
Q

Submucosa of LI

A

same structure as alimentary canal

38
Q

Muscularis Externa of LI

A

2 layers of smooth muscle: inner O and outer l; change is that the outer longitudinal layer forms 3 thickened bands called teniae coli

39
Q

Serosa of LI

A

contain omental appendices (fatty deposits)

40
Q

Colon

A

largest portion of LI, well expressed teniae coli

41
Q

Veriform appendix

A

useless, has aggregated lymphatic follicles, no teniae coli

42
Q

Rectum

A

similar mucosa to distal colon, prominent transverse rectal folds, no teniae coli

*Histology (11 decks)

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