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GIGU Exam 1 > Histology Of The SI And LI > Flashcards

Histology Of The SI And LI Flashcards

1
Q

The SI is the principal site for what?

A

Digestion of food and absorption of digestion products

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2
Q

What are pilcae circulares?

A

Transverse folds with a submucosal core located in the SI
Cannot lay flat if distended
Visible in jejunum but less so in ileum

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3
Q

What are intestinal villi?

A

Mucosal folds that project into the lumen and cover the surface of the SI
Covered with a simple columnar epithelium of enterocytes and goblet cells
Core of loose CT with microvasculature and a lacteal (absorbs lipids and sends to lymphatics)

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4
Q

What do enterocytes produce?

A

Enzymes for digestion and absorption

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5
Q

Goblets cells provide what?

A

Mucus coating to shield from abrasion and bacterial invasion

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6
Q

What are microvilli?

A

Cover intestinal villi to increase absorptive surface area

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7
Q

Describe the mucosa of the SI

A

Simple columnar epithelium with tubular intestinal glands

Lamina propria and muscularis mucosa

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8
Q

Describe the submucosa of the SI

A

Dense irregular CT, neurovasculature, lymphatics and glands may be present

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9
Q

Describe the muscularis of the SI

A

Inner circular and outer longitudinal layers

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10
Q

What is the outer layer of the SI?

A

Serosa - loose CT covered by visceral peritoneum

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11
Q

Describe the gastroduodenal junction

A

Pyloris (stomach)
-Thick wall due to the presence of the pyloric sphincter muscle and pyloric glands at the base of each gastric pit
Duodenum (SI)
-Abundant duodenal glands in submucosa, deep to the muscularis mucosa
-Secretory mucosa with villi

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12
Q

Describe the LI

A

Absorbs water, Na, vitamins and minerals
Will uptake sedatives, anesthetics and steroids
Openings of tubular intestinal glands are hallmark of the mucosa

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13
Q

What are the hallmarks for the LI?*

A

Intestinal glands, goblet cells but no intestinal villi

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14
Q

Describe the mucosa of the LI

A

Glandular, simple columnar epithelium
Colonocytes, goblet cells, stem cells and enteroendocrine cells
Lamina propria and muscularis mucosa present
GALT is extensive and may penetrate submucosa

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15
Q

Describe the submucosa of the LI

A

Dense irregular CT and vascularized

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16
Q

Describe the muscularis of the LI

A

Inner layer is typical

Outer longitudinal layer organized into taeniae coli which will form haustra of the LI

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17
Q

Intraperitoneal portions of the colon are covered by what?

A

Serosa

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18
Q

What are intestinal glands (crypts of Lieberkuhn)?

A

Simple, tubular glands lined by simple columnar epithelium
Continuous with simple columnar epithelium that covers intestinal wall
Open onto the luminal surface of the intestine at the base of the villi
Includes Paneth cells, M cell, stem cells and enteroendocrine cells

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19
Q

What are Paneth cells?

A

Pyramidal shaped cells at the base of the intestinal glands

Large, eosinophilic secretory granules in their apical cytoplasm

20
Q

What are the functions of Paneth cells?

A

Functions in innate immunity by secreting antimicrobial substances (lysozyme and alpha-defensins)
Regulate normal bacteria flora via antibacterial action and phagocytosis

21
Q

What are M (microfold) cells?

A

Epithelial cells specialized for transepithelial transport of particles and microorganism
Located in the ileal mucosa, overlying Peyer patches
Pocket formed by deeply invaginated membrane containing lymphocytes and macrophages

22
Q

How do M cells function as highly specialized antigen transporting cells?

A

Apical surface expresses receptors that bind specific macromolecules and gram-negative bacteria (e.g. E. coli)
Internalized and transferred to immune cells

23
Q

What are intestinal stem cells (ISCs)?

A

Reside in a niche at crypt base near Paneth cells
Repopulate epithelial lining
Daughter cells move out of the crypts and differentiate into goblet cells, enterocytes and enteroendocrine cells

24
Q

Describe the innervation of the SI and LI

A

Motility controlled by the ANS
Enteric (intrinsic) NS consists of the submucosal plexus of Meissner and myenteric plexus of Auerbach
-Sympathetic visceral sensory fibers
-Parasympathetic (terminal) ganglia
-Preganglionic and postganglionic parasympathetics
Regulated by extrinsics —> preganglionic parasympathetics (vagus and pelvic nerves) and postganglionic sympathetics

25
Q

What is Hirschsprung’s disease?

A

Aganglionosis in the distal colon
Mutations of the RET gene required for migration and differentiation of NCC
Failure of NCC development in both plexuses of a bowel segment

26
Q

What are the three categories of Hirschsprung disease?

A

Short segment disease, long segment disease, and total colonic aganglionosis

27
Q

What is short segment disease?

A

Aganglionosis confined to rectosigmoid colon

85% of cases

28
Q

What is long segment disease?

A

Aganglionosis extends past rectosigmoid colon to the splenic flexure
10% of cases

29
Q

What is total colonic aganglionosis?

A

Affects entire colon

5% of cases

30
Q

What is the presentation of Hirschsprung’s disease?

A

Constipation, poor feeding, and progressive abdominal distention

31
Q

How is Hirschsprung’s disease diagnosed?

A

Delayed BM <48 hours after birth, rectal biopsy or barium enema

32
Q

What is the treatment for Hirschsprung’s disease?

A

Surgical removal of the affected colon segment, pull through of ganglionic colon segments

33
Q

What is the rectum proper?

A

Upper part
Typical mucosa with tubular intestinal glands
Transverse rectal folds

34
Q

What is the anal canal?

A

Lower part of rectum
Anal columns with mucosal folds
Anal sinuses - depressions between columns
Anal glands extend into the submucosa and muscularis externa

35
Q

What are circumanal glands?

A

Large apocrine glands surrounding the anal orifice

36
Q

What are the three different zones of the anal canal?

A

Colorectal zone, anal transition zone (ATZ), squamous zone

37
Q

What is the colorectal zone?

A

Simple columnar epithelium identical to the rectum (upper 1/3)

38
Q

What is the anal transition zone (ATZ)?

A

Simple columnar epithelium —> stratified squamous epithelium of perianal skin (middle 1/3)

39
Q

What is the squamous zone?

A

Stratified squamous epithelium continuous with perineal skin (lower 1/3)

40
Q

At the level of the anus, the inner circular layer thickens to form what?

A

The internal anal sphincter

41
Q

Describe the mucosa of the duodenum

A

Simple columnar epithelia with scattered goblet cells

42
Q

Describe the submucosa of the duodenum

A

Contains duodenal glands: tubuloacinar mucous glands that produce an alkaline secretion which neutralizes acidic chyme*

43
Q

Describe the mucosa of the jejunum

A

Simple columnar epithelia with scattered goblet cells
Long finger like villi; villus core contains a well developed lacteal
Tubular intestinal glands
Lymphoid nodules/follicles in the lamina propria

44
Q

Describe the submucosa of the jejunum

A

No submucosal glands present

45
Q

Describe the mucosa of the ileum

A

Simple columnar epithelium with scattered goblet cells
Villi typically shorter than jejunum
Peyer’s patches: lymphoid nodules (MALT)
Paneth cells found at base of intestinal glands

46
Q

Describe the submucosa of the ileum

A

No submucosal glands

GIGU Exam 1 (19 decks)

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