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Cell Biololgy and Histology BAM > Final: Lecture 23 > Flashcards

Final: Lecture 23 Flashcards

0
Q

Plicae

A

•These are folds of the mucosa, each with a submucosal core

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1
Q

The three orders of folding are?

A
  • Microvilli, Crypt-villus system, and Plicae

* Increase surface area in the small intestine

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2
Q

Crypt-villus system

A
  • Each villus contains core of lamina propria
  • Extend down between villi below bases of the villi
  • Walls composed of simple columnar epithelium with goblet cells
  • Crypts and villi constitute glands of small intestine
  • Each villus contains a capillary plexus, blind-ending lymphatic reffered to as lacteal
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3
Q

Microvilli

A
  • Covered with glycoprotein and glycocalyx (contains array of brush-boarder enzymes
  • Maltase, sucrase, isomaltase, lactase, lipase, peptidases,
  • Produced by small intestine epithelial cells
  • Bundles of actin filaments within microvillus is covered by a formin cap
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4
Q

Microvilli supported by core of actin microfilaments:

A
  • Actin filaments are tied to terminal web intermediate filaments (cytokeratins) via spectrin fibrils
  • Bound to plasma membrane covering villus via membrane-linking proteins (myosin I and calmodulin)
  • Bound to each other via actin cross-linking proteins (villin and fimbrin)
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5
Q

Cells of the Crypts of Lieberkuhn:

A
  • Goblet cells
  • Enterocytes
  • Paneth cells
  • Enteroendocrine cells
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6
Q

Enterocytes

A
  • Columnar epithelial cells with the following characteristics:
  • basal nucleus, perinuclear Golgi, apical brush border
  • Produce disaccharidases
  • Involved in absorption of proteins, carbohydrates, lipids
  • Enzymes present on apical brush border are important in carb digestion
  • Produce enteropeptidase which is necessary for the activation of pancreatic zymogens and proenzymes
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7
Q

Paneth cells

A
  • Basal crypt cells
  • Prominent eosinophilic granules
  • Produce lysozyme to control intestinal flora
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8
Q

Enteroendocrine cells

A
  • Stain with chromium
  • Agryrophillic (respond to silver stains)
  • Produce peptide hormones and serotonin
  • May produce paracrine or autocrine secretions
  • Analogous to unicellular goblet cells
  • Formed from endodermal stem cells in all regions of the GI tract
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9
Q

Glands of Brunner

A
  • Found in submucosa of duodenum
  • Responsible for formation of bicarbonate and mucus
  • Supplements bicarbonate from pancreas, necessary to neutralize gastric acid
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10
Q

Duodenum

A
  • Villi with wide spatulate or “leaflike” distal shape
  • Deep crypts of Lieberkuhn
  • Brunner’s glands with excretory ducts in submucosa
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11
Q

Jejunum

A
  • Villi longer and narrow
  • Crypts of Lieberkuhn present
  • No glands in submucosa
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12
Q

Ileum

A
  • Villi longer and narrow
  • Crypts of Lieberkuhn present
  • No glands in submucosa
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13
Q

Large intestine

A
  • Simple columnar epithelium, crypts but no villi
  • Functions: secretion of mucus for lubrication, *goblet cell is the prominent cell, absorption of fluid, formation of fecal mass, continuation of digestion initiated in small intestine
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14
Q

Exposed bands of longitudinal muscle in the large intestines are ______.

A

•Taeniae coli

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15
Q

An appendix epiploica is an aggregate of _______ surrounded by the serosa.

A

•Adipocytes

16
Q

Paneth cells

A
  • Characteristics: basophilic basal cyto, supranuclear Golgi complex, large, intensely acidophilic apical secretory granules
  • Secrete: lysozyme to increase permeability of bacteria by degrading peptidoglycan coat*
  • Defensins to increase membrane permeability of target organisms
  • Tumor necrosis factor-alpha (proinflammatory cytokine)
  • May phagocytize some microorganisms and help regulate intestinal flora
17
Q

Mucosal Layer

A
  • Coats intestinal epithelial luminal surface
  • Secreted by goblet cells
  • Made up of two layers: other containing microorganisms, inner contains antimicrobial proteins (from Paneth, enterocytes, and goblet cells) that resist microbial penetration
18
Q

Toll-like receptors

A
  • Found on surface of enterocytes
  • Secreted by goblet cells
  • Outer layer contain microorganisms
  • Inner layer contains antimicrobial proteins that resist microbial penetration
19
Q

Immune Surveillance System (path 1)

A
  • Antigen binds to toll-like receptor on enterocyte surface
  • B cell-activating factor produced
  • B cells lamina propria mature into plasma cells–>antibodies
20
Q

Immune Surveillance System (part 2)

A
  • Antigen is taken up by M (microfold) cells ass. with Peyer patch in the intestinal mucosa
  • Antigens transported to lymphocytes located in pockets in folds of M cells
  • Bound to Ig receptors on surface of lymphocytes
  • Lymphocytes transfer Ig-bound antigen to dendritic cells in lamina propria
  • Dendritic cells interact with T cells in lamina propria to activate immune response
21
Q

GALT

A
  • Components: transitory aggregations of lymphocytes, neutrophils, eosinophils
  • Permanent structures: appendix, Peyer’s patches, mesenteric lymph nodes
22
Q

Bulk of the body’s immune defenses centered in _______.

A

•GALT

23
Q

Peyer’s Patches

A
  • Dome-shaped lymphoid structures under the mucosal surface
  • Contain B and T cell dependent areas
  • Possess high endothelial venuels (HEVs), which facilitate entrance of lymphocytes into lymphoid organs from bloodstream
  • Mucosal covering of the dome includes specialized M (microfold) cells: sample particulate antigen and present it to antigen-presenting cells in the underlying lamina propria
  • Antigen-presenting cells (APCs) and macrophages phagocytize the antigen and present it to helper cytotoxic T cells as well as B lymphocytes
24
Q

The primary immunoglobulin produced by GALT is ___.

A
  • IgA
  • Synthesized and secreted by plasma cells in lamina propria of the gut
  • Picked up at the basal surface of enterocytes and transported across the cell
  • While in the cell, IgA is linked to a protein called secretory component that inhibits degradation by proteolytic enzymes in GI lumen
  • Secretory IgA, unlike IgG, doesn’t stimulate the complement system, but functions by coating microorganisms, thus inhibiting them binding to epithelium
25
Q

Lining in the stomach and small intestine is replaced every ___ days in humans

A

•5

26
Q

Rapid cell turnover

A
  • In esophagus and anus: new cells formed in basal layer of stratified epithelium and migrate through sub-basal levels to be sloughed off into lumen
  • In small intestine: new cells formed in crypts from undifferentiated cells
  • Large Intestine: no villi, so proliferative compartment found in base of crypts
  • Stomach: stem cells are found in the neck of gastric glands, differentiate into surface and neck mucus cells enteroendocrine, parietal, and chief cells
27
Q

Anal Canal

A
  • Epithelium returns to stratified squamous

* Skeletal muscle returns as external anal sphincter

Cell Biololgy and Histology BAM (11 decks)

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