Final: Lecture 23 Flashcards
0
Q
Plicae
A
•These are folds of the mucosa, each with a submucosal core
1
Q
The three orders of folding are?
A
- Microvilli, Crypt-villus system, and Plicae
* Increase surface area in the small intestine
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
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
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)
5
Q
Cells of the Crypts of Lieberkuhn:
A
- Goblet cells
- Enterocytes
- Paneth cells
- Enteroendocrine cells
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
7
Q
Paneth cells
A
- Basal crypt cells
- Prominent eosinophilic granules
- Produce lysozyme to control intestinal flora
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
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
10
Q
Duodenum
A
- Villi with wide spatulate or “leaflike” distal shape
- Deep crypts of Lieberkuhn
- Brunner’s glands with excretory ducts in submucosa
11
Q
Jejunum
A
- Villi longer and narrow
- Crypts of Lieberkuhn present
- No glands in submucosa
12
Q
Ileum
A
- Villi longer and narrow
- Crypts of Lieberkuhn present
- No glands in submucosa
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
14
Q
Exposed bands of longitudinal muscle in the large intestines are ______.
A
•Taeniae coli
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
The primary immunoglobulin produced by GALT is ___.
* 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
Lining in the stomach and small intestine is replaced every ___ days in humans
•5
26
Rapid cell turnover
* 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
Anal Canal
* Epithelium returns to stratified squamous
| * Skeletal muscle returns as external anal sphincter
