Lecture 25 Flashcards
What structures (include the type of cell these are found on) are important in preventing paracellular transport in the GI tract? what are these structures formed by?
Tight junctions between the epithelial cells of the GI tract
these junctions are formed by occluding junctions that contain claudin and occludin transmembrane proteins
In the GI tract, what do paneth cells, enterocytes, and goblet cells all have in common?
they all resist microbial penetration in some fashion
State what the mucosal layer is secreted by and the distribution of the microorganisms is protects against.
The mucosal layer that is secreted by goblet cells
Its outer layer contains microorganisms and its inner layer contains paneth cells, enterocytes, and goblet cells that resist microbial penetration
What functions do paneth cells use to protect against pathogens? (2 functions)
Paneth cells secrete lysozyme to degrade the peptidoglycan coat of potential pathogens
They also secrete defensins to increase the membrane permeability of target organisms
What does tumor necrosis factor do in order to defend the GI tract?
Tumor necrosis factor alpha can elicit an inflammatory response as a defense mechanism
List the functions of Paneth cells (3, sort of 4 of them)
Secrete lysozyme to increase permeability of bacteria by degrading peptidoglycan coat
Secrete defensins to increase membrane permeability of target organisms
Secrete tumor necrosis factor alpha (proinflammatory cytokine)
May phagocytize some microorganisms and help regulate intestinal flora
What are toll-like receptors and what is their function?
They are a type of pattern recognition receptor that are found on the surface of enterocytes
They recognize structurally conserved molecules broadly shared by pathogens but distinguishable from host molecules (pathogen associated molecular patterns [PAMPs])
What is the primary immunoglobulin and where is it produced?
IgA is the primary immunoglobulin that is produced by GALT (gut associated lymphatic tissue)
Compare the 2 types of IgA and their functions
Secretory IgA: unlike IgG, does not stimulate the complement system, but functions to coat microorganisms, thus inhibiting microorganism binding to the epithelium
sIgA: while in the cell, is linked to a protein called secretory component that inhibits degradation of the sIgA by proteolytic enzymes in the GI lumen
What are M cells and what is their role in defense? how do they accomplish this role?
M (microfold) cells, which are associated with peyer’s patches in the intestinal mucosa, take up antigens and transport them to lymphocytes
M cells sample particulate antigens and present it to antigen-presenting cells in the underlying lamina propria
State the full name of GALT and their function
GALT = gut associated lymphoid tissue
They secrete IgA (which includes both secretory IgA and sIgA)
Describe Peyer’s patches (include the types of cells they contain). Also state the method in which antigens are presented to the cell types that are found in Peyer’s patches.
Peyer’s patches: dome shaped lymphoid structures under the mucosal surface that contain B and T-cell dependent areas
The antigen-presenting cells (APC’s) and macrophages phagocytize the antigen and present it to helper an cytotoxic T cells as well as B lymphocytes
In terms of Peyer’s patches, describe HEV’s and also state where M cells lie in these patches.
High endothelial venules (HEV’s), facilitate the entrance of lymphocytes into lymphoid organs from the bloodstream
The mucosal covering of the dome on Peyer’s patches is where M cells lie
Compare the epithelium and musculature of the anal canal to other regions of the digestive tract.
The epithelium of the anus returns to stratified squamous epithelium (as opposed to the simple columnar tissue that comprises the majority of the rest of the GI tract)
The external anal sphincter is composed of skeletal muscle (as opposed to the smooth muscle that composes the rest of the GI tract)
