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54 Cards in this Set
- Front
- Back
Name 6 functions of the intestine
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Digestion
neutralization of chyme Absorption Limit microbial growth synthesis/secretion regulation of GI function |
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Name 3 surface features of the intestine
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Crypts of Lieberkuhn
Villi Plicae Circulares |
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Describe the cell layers involved in the plicae circulares
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mucosa and submucosa
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Location of the plicae circulares
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small intestine, prominent in the distal duodenum and jejunum, cease to exist distally
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Describe the cell layers involved in the villi
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JUST the mucosa
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Describe the location of the villi
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small intestine; prominent the in duodenum and jejunum, decrease in size and number distally
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Describe the shape of villi
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Wider proximally, tend to get more conical distally
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What are Crypts of Leiberkuhn?
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mucous glands
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Location of Crypts of Lieberkuhn
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throughout the intestine
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Describe how to differentiate between a crypt of a villus in a cross section?
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Crypts will contain lumen on the inside and lamina propria on the outside. Villi will contain lamina propria on the inside and lumen on the outside
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Describe the mucosal epithelium of the intestine
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simple columnar
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Name the 4 types of cells distributed within the intestinal surface epithelium
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Intestinal absorptive cells, goblet cells, enteroendocrine cells, intraepithelial lymphocytes
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Name a type of cell that is specifically located in assocation with lymphoid follicles
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M-cells
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What is the principal cell of the intestinal surface epithelium?
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Intestinal absorptive cell
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Describe the intestinal absorptive cell
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simple columnar, brush border, centrally located ovoid nucleus
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What is the primary function of intestinal absorptive cells?
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absorption
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Glycocalyx
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glycoprotein coat covering the microvilli
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Other than function for absorption, what do the intestinal absorptive cells do?
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synthesize digestive enzymes
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What is the function of the glycocalyx?
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contains enzymes that function in the final stages of digestion
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Describe how nutrients are absorbed within the intestine
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Glycocalyx contains enzymes to break down carbohydrates and proteins. These are then transported across the microvilli into the absorptive cell, then transported across the basolateral membrane into the lamina propria
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Describe the fate of lipids in the intestine
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broken down in the lumen, diffuse into absorptive cells, resynthesized into triglycerides, get a protein coat and become chylomicra, then released into the extracellular space
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Other than synthesis of enzymes and absorption, what are absorptive cells capable of?
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Transcytosis of IgA from the lamina propria to the intestinal lumen
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Where is IgA synthesized and secreted?
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in the plasma cells of the lamina propria
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How is IgA transported from the lamina propria to the lumen of the intestine?
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Binds to basolateral surface of intestinal absorptive cells, endocytosed via clathrin-coated vesicles, travels through endosomal reactions, released at the cell surface
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What is the function of IgA in the intestinal lumen?
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regulate microbial growth
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What are goblet cells?
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goblet-shaped mucous secreting cells
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Describe the organelle structure of the goblet cell
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Triangular nucleus, apical secretory vesicles, RER at the base
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Describe the pattern of goblet cell frequency in the intestine
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Increase in number proximally to distally
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Describe the location of enteroendocrine cells in the intestine
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Located within the surface of the intestine as well as in the crypts of lieberkuhn
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Describe the derivation of intraepithelial lymphocytes
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blood-derived
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Function of intraepithelial lymphocytes in the intestine
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Provide mucosal immunity
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Describe the frequency of intraepithelial lymphocytes
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present during infection, also increased in some disease states such as Celiac disease
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Where are M-cells located?
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in the epithelium overlying the lymphoid follicle
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What is the function of the M-cell?
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to facilitate an immune response by transporting antigens across the epithelium
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Describe the structure of the M-cell
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Contains a deep invagination at the basal membrane that contains macrophages, dendritic cells, and lymphocytes. Apical surface is covered by lamellae
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How do M-cells function in the antigen-presenting process?
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M-cells take up antigens from the intestinal lumen via endosomes at the surface, transfer to the basolateral pocket, then to antigen-presenting cells beneath M-cells
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How do antigen-presenting cells act once they receive an antigen from the M-cell?
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The endocytose the antigen and present it to lymphocytes
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What are M-cells derived from?
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progenitor cells in the crypts of lieberkuhn
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Characterize the Crypts of Lieberkuhn
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simple straight mucosal glands
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What is the function of the crypts of lieberkuhn?
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production of epithelial cells (the invagination forms a protective niche from the harsh lumen)
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Name the 3 types of cells located within the crypts of lieberkuhn
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Undifferentiated progenitor cells
Paneth cells Typical intestinal cells |
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How can progenitor cells be differentiated from intestinal absorptive cells?
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cells undergoing mitosis are progenitor cells
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Why would typical intestinal cells be located within the crypts of lieberkuhn?
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Because the crypts create all surface epithelial cells, so they would naturally have immature cells of all surface epithelial cells
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Where are Paneth cells located?
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at the base of the crypt of lieberkuhn
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Describe the structure of Paneth cells
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columnar, large aprical highly refractile granules
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What do Paneth cell granules contain?
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antibacterial proteins
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What is the function of the Paneth cell?
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regulate microbial growth
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Where in the intestine are Paneth cells located
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in the small intestine (NOT in the large intestine)
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Describe the lamina propria of the intestine
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loose connective tissue, highly cellular
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What is the function of the lamina propria in the intestine?
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immunological defense (contains plasma cells and lymphocytes and macrophages)
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What layer of the intestine are lymphoid follicles typically found?
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mainly in the lamina propria, but also can be located in the submucosa
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Describe the pattern of frequency of lymphoid follicles within the intestine
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increase proximally to distally with large masses of them located within the appendix
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What are Peyer's Patches?
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visible as white spots, aggregates of lymphoid follicles within the intestine on the antimesenteric side of the ileum
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Describe the mucosa covering the lymphoid follicles
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bulges into the lumen, lacks villi, contain M cells
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