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GI Midterm > Histology of SI and LI > Flashcards

Histology of SI and LI Flashcards

1
Q

Small Intestine

  • parts
  • function
  • characteristics
A

Duodenum, jejunum, ileum

Principal site for digestion of food & absorption of digestion products

Pilcae circulares (arrows):

  • transverse folds with a submucosal core
    • cannot lay flat if distended
    • visible in jejunum, less so in ileum
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2
Q

Intestinal Villi

  • definition
  • cells
A

Mucosal folds that project into lumen & cover surface of SI

  • increase absorptive surface area

Enterocytes: simple columnar cells that produce enzymes for digestion & absorption

Goblet Cells: provide mucus coat to shield from abrasion & bacterial invasion

Core of loose CT with a lacteal

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3
Q

Pilica circulares

- where is it seen

A

foldings of entire mucosa & some submucosa

  • absent in duodenum, visible in jejunum, less prominent in ileum
  • covered in intestinal villi
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4
Q

Villi

A

fingerlike folds of mucosa projecting into lumen

  • covered with microvilli
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5
Q

Enterocyte Microvilli

A

” Striated border”

  • provide amplification of luminal surface
  • Glycocalyx coat assists in nutrient uptake
  • actin microfilament core anchors to other proteins & myosin 1 via terminal web
    • permits contraction of microvilli
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6
Q

Mucosa (SI)

- cell type

A

simple columnar epithelium with tubular intestinal glands

-lamina propria and muscularis mucosae

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7
Q

Submucosa (SI)

- cell type

A

dense irregular CT

neurovasculature, lymphatics, glands may be present

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8
Q

Muscularis (SI)

- cell type

A

inner circular & outer longitudinal layers

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9
Q

Serosa (SI)

- cell type

A

loose CT covered by visceral peritoneum

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10
Q

Innervation of the SI and LI

A

Motility controlled by the ANS

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11
Q

Intrinsic Nervous System

A

aka enteric nervous system

  • submucosal plexus of Meissner & myenteric plexus of Auerbach
    • sympathetic visceral sensory fibers
      - parasympathetic (terminal) ganglia
      - preganglionic & postganglionic parasympathetics
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12
Q

Extrinsic Nervous System

A

Preganglionic parasympathetic (vagus and pelvic nerves)

Postganglionic sympathetics

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13
Q

Intestinal Glands

  • cells ( 4)
  • cell type
A

Simple tubular glands lined by simple columnar epithelium

1) Enteroendocrine cells
2) Paneth Cells
3) Intestinal Stem cells
4) M (microfold) cells

  • covers intestinal villi
  • open onto luminal surface of the intestine at the base of the villi
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14
Q

Enteroendocrine Cell

  • location
  • function
  • hormones
A
  • found throughout the intestinal glands
  • secrete peptide hormones to control gut motility, regulate secretion of enzymes, HCl, bile & other components for digestion
  • gastrin, secretin, gastric inhibitory polypeptide (GIP), motilin, & cholecystokinin
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15
Q

Paneth Cells

  • characteristic
  • location
  • function
A

-pyramidal-shaped cells

  • base of intestinal glands
  • found in normal colon in small numbers ( if a lot=> pathological conditions)

function:

  • innate immunity by secreting antimicrobial substances
  • lysozymes, alpha-defensins, other glycoproteins
  • regulate normal bacterial flora via antibacterial action and phagocytosis
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16
Q

Intestinal Stem Cells (ISCs)

  • location
  • function
  • cell types
A
  • reside in a niche at crypt base ( near Paneth cells)
  • repoplate epithelia lining
  • daughter cells move out of crypts
  • > differentiate into goblet cells, enterocytes, and enteroendocrine cells
17
Q

M (Microfold) Cells

  • characteristics
  • cells
  • function
A

specialized cells that overlie Peyer’s patches at other large lymphatic nodules

  • has microfold & thin glycocalyx
  • has deep pocket-like recess, connected to extracellular space, houses dendritic cells, macrophages, and T & B cells
  • apical surface expresses receptors that bind specific macromolecules & gram-negative bacteria
    • internalized & transferred to immune cells
    • function as highly specialized ANTIGEN- TRANSPORTING CELLS
18
Q

Gastroduodenal Junction consist of which two organs?

A

Stomach (pyloris) and Duodenum (SI)

19
Q

Gastroduodenal Junction: Pyloris (stomach)

A

thick wall due to presence of pyloric sphincter muscle

pyloric glands at base of each gastric pit

20
Q

Gastroduodenal Junction : Duodenum (SI)

A

abundant Brunner’s glands in submucosa, DEEP to the muscularis mucosae

secretory mucosa with villi

21
Q

Duodenum

  • characteristics
  • hallmark
  • function
A
  • initial segment of SI
  • leaf-like villi
  • tubular intestinal glands in mucosa

HALLMARK: brunner’s glands in submucosa
- tubuloacinar mucous glands

Function

  • produce alkaline secretion
  • neutralize acidic chyme
  • collect bile and pancreatic secretion via hepatopancreatic ampulla
22
Q

Jejunum

  • Hallmarks
  • location
A

HALLMARK: long finger-like villi

  • tubular intestinal glands
  • villus core contain a well-developed lacteal

HALLMARK: no submucosal glands

  • lymphoid nodules/follicles in lamina propria
  • tubular intestinal glands in mucosa
23
Q

Ileum

  • characteristics
  • hallmark
A

finger-like villi ( shorter than jejunum)

tubular intestinal glands in mucosa

HALLMARK: peyer’s patches
- mucosal lymphoid nodules specific to ileum

paneth cells found at base of intestinal glands

24
Q

Ileoceccal Junction

A
  • food is propelled from ileum into cecum through ileoceccal valve
  • abrupt transition from villi of SI-> to glandular epithelium of LI
  • Valve has thickened extension of muscularis mucosae
    • critical function is to limit reflux of colonic contents into ileum
  • muscularis (externa) is also somewhat thickened
25
Q

Large Intestine

  • function
  • characteristics
  • Hallmark
A

function: absorbe water, sodium, vitamins & minerals, will uptake sedatives, anesthetics, steroids

Characteristics: opening of tubular intestinal glands (crypts of Lieberkuhn) are hallmark of mucosa

HALLMARK: intestinal glands, goblet cells, NO INTESTINAL VILLI

26
Q

Mucosa (LI)

  • cell type
  • cells
  • location
A

glandular, simple columnar epithelium
- colonocytes, goblet cells, stem cells, enteroendocrine cells

location

  • lamina propria & muscularis mucosae are present
  • GALT is extensive and may penetrate submucosa
27
Q

Submucosa (LI)

- cell type

A

dense irregular CT

vascularized

28
Q

Muscularis (LI)

- characteristics

A
  • inner layer is typical

- outer longitudinal layer organized into taeniae coli, will form haustra of LI

29
Q

Serosa

A

lining that covers INTRAperitoneal portions of colon

30
Q

Colon

  • characteristics
  • cell type
  • hallmark
A
  • simple columnar epithelium
  • short microvilli
  • dilated intercellular spaces with interdigitating leaflets of cell membrane ( active water transport)

HALLMARK: numerous goblet cells

31
Q

Veriform Appendix

  • characteristics
  • layers
A
  • diverticulum of the cecum with layers similar to those of LI

Mucosa

  • simple columnar epithelium
  • goblet cells
  • lymphoid follicles and lymphocytes with lamina propria
  • extend into submucosa

Submucosa

  • adipocytes
  • dense irregular CT
  • inner circular layer is well developed, but outer longitudinal layer is not
  • covered with serosa
32
Q

Hirschprung’s Disease

  • characteristics
  • statistics
  • presentation
  • diagnosis
  • treatment
A
  • Aganlionosis in distal colon
  • Mutation in RET gene (for migration & differentiation of NCC)
  • failure of NCC development in both plexuses of a bowel segment

1:5000 neonates

Presentation: constipation, poor feeding, progressive abdominal distention

Diagnosis: delayed BM < 48hrs after birth ; rectal biopsy, barium enema

Treatment: surgical removal of affected colon segment, pull through of ganglionic colon segments

33
Q

Inflammatory Bowel Disease

  • symptoms
  • types of IBD (2)
A
  • include ulverative colitis & Crohn’s Disease
    symptoms: diarrhea, pain, periodic relapses

1) Ulcerative colitis- affect mucosa of large intestin
2) Crohn’s Disease- affect any segment of intestinal tract

34
Q

Crohn’s Disease

A

chronic inflammatory process involving terminal ileum and large intestine

  • inflammatory cells produce cytokines that cause damage to intestinal mucosa
  • infiltration of neutrophils into cyrpts of Liberkuhn-> destruction of intestinal glands due to crypt abscesses-> progressive atrophy, ulceration of mucosa
35
Q

Rectum

  • parts
  • glands
A

Parts

1) Rectum proper (upper part): typical mucosa with tubular intestinal glands, transverse rectal folds
2) Anal Canal ( lower part)
- anal columns: mucosal folds
- anal sinuses: depressions between columns
- anal glands: extend into submucosa & muscularis externa

Circumanal glands: large apocrine glands surrounding anal orifice

36
Q

Anal Canal

  • Zones (3)
    • cell types
  • what happens at level of anus?
A

1) Colorectal Zone: simple columnar epithelium identical to rectum ( upper 1/3)
2) Anal transitional zone (ATZ): simple columnar epithelium
- > stratified squamous epithelium of perianal skin (middle 1/3)
3) Squamous zone: stratified squamous epithelium continuous with perineal skin (lower 1/3)

At level of anus, inner circular layer thickens to form the internal anal sphincter

37
Q

Mucosa of the Recto-anal junction

- cell types

A

1) non-keratinized stratified squamous

2) Simple columnar with tubular intestinal glands

GI Midterm (10 decks)

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