EXam 3 - gI histology III

Question 1

What major features provide a defense mechanism for segments of the GI tract?

Answer 1

• Tight junction barrier that prevents passage of material through epithelial cell layer
• Toll like receptor on a enteroctye surface
• br cell activating factor is produced and b cells in lamina propria mature intonplasma cells = antibodies
• antigen is teken up by microfold cells associated with Peyer Patch in intestinal mucosa
• antigens are transported to lymphocytes located in folds of M cells
• ANtigens are 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
• In the node T cells differentiate into (T_H1 and T_H2) interact with dendritic cell and translocate to the lamina propria
• T_H1 expresses proinflammatory tumor necrosis factor ligand and interferon-gamma. egulate T_H2 regulates proinflammitory cytokines by expressesing interleukin-10 to block T_H1

Question 2

What are functions of paneth Cells

Answer 2

• secrete
  
  • lysozyme
    
    • to increase permeability of bacteria by degradining peptidoglycan coat
  • Defensins
    
    • to increase membrane permeability of target organiss
  • tumor necrosis factor
    
    • alpha (proinflammatory cytokine)
  • May phagocytize some microogranisms and help regulate intestinal flora

Question 3

What are toll-like receptors?

Answer 3

• recptors found on surface of enterocytes
• type of patteren recognition receptor
• recongize structurally conserved molecules broadly shared by pathogens but distinguishable from host molecules (pathogen associated molecular patterns ) PAMPS

Question 4

What is the role of IgA in the immune defense of Gi tract?

Answer 4

• It is produced by galt as Secretory IgA or sIgA
  
  • Synthesized and secreted by plasma cells in the lamina propria of the gut. Picked up at basal surface of enterocytes and transported across the cell
• Linked to a protein called secretory component that inhibts degradation of sIGA by proteolytic enzymes in the GI lumen.
• Secretory IgA does not stimulate the complement system but function by coating microorganisms thus inhibiting microorganism binding to epithelium.

Question 5

What are M cells and what is their role in defense?

Answer 5

Sample particulate antigens and present it to antigen presnting cells underlying lamina propria

Question 6

What are GALT ?

Answer 6

• Bulk of the bodys immune defenses are sentered in GALT
• componets
  
  • transitory aggreation o flymphocytes, neurtophils, and esinophils
  • permanent structures
    
    • appendix
    • peyers patches
    • mesenteric lymph nodes

Question 7

What are Peyer patches?

Answer 7

• Dome shaped lymphoid structures under mucosal surface
• contain B and T cell dependt areas
• high endothelial venules (HEVs) which facilitate entrance of plymphocytes inyo lymphoid organs from blood stream
• The mucosal covering of dome of the Peyers atches include specialized M (micro folds cells)
• The antigen presenting cells (APCs) and macrophages phagocytize the antigen and present it to helper and cytotoxic T cells as well as B lymphocytes

Question 8

What is epithelium and musculature of the anal canal?

Answer 8

EPithelium of anus returns to stratified squamous epithelium

skeletal muscle returns as external anal sphincter