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70 Cards in this Set
- Front
- Back
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What kind of cells line the stomach?
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Surface lining cells = simple columnar epithelium
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What kind of cells line the small intestine?
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Absorptive cells (enterocytes) and goblet cells = simple columnar epithelium
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What are the ultrastructural features of enterocytes in the small intestine? Functions?
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- Microvilli - increase surface area
- Intercellular junctional complexes - prevent lumenal contents from accessing intercellular spaces - Mitochondria - high metabolic activity - Glycocalyx - protects plasma membrane from auto-digestion, binds secreted proteins, ions and water for localized proteolysis |
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What are the arrows pointing out in the duodenum?
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Submucosal glands of Brunner
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What is the characteristic histological feature of the duodenum?
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Presence of submucosal glands of Brunner
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What is the function of the secretory product of Brunner's glands?
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Alkaline mucous neutralizes acidic chyme from stomach
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What are the arrows pointing out in this section of the duodenum?
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Basophilic cells in the submucosa and lamina propria = Lymphocytes
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What term is used to describe the diffuse, unencapsulated lymphoid tissue in the mucosa of the GI tract?
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GALT: Gut-Associated Lymphatic Tissue
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What projects into the lumen of the small intestine (black arrows)?
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Intestinal Villi
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What are the spaces marked by the red arrow? What are they between (black arrows)
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Red arrow = Crypts of Lieberkuhn
Found in between Villi (black arrows) |
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What are the three layers of the mucosa?
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- Epithelium
- Lamina Propria - Muscularis Mucosa |
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What is labeled with A?
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Muscularis Mucosa
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What is labeled with B?
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Epithelium (simple columnar)
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What is labeled with C?
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Lamina Propria
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What tissue lies at the base of the Crypts of Lieberkuhn (red arrow)?
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Muscularis Mucosa
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What type of epithelium covers a villus?
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Simple Columnar Epithelium
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What is the principle cell type within the epithelium? What is its function?
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Enterocyte - absorption of nutrients, production of digestive enzymes
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What specialization of the apical plasma membrane is present on enterocytes? What is its function?
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Brush border formed by microvilli increases the surface area for absorption
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Does the submucosa extent into the core of a villus?
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No
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Are goblet cells present in the mucosal epithelium? Where?
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Yes
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What is the function of Goblet cells?
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Secrete mucin to lubricate and protect the epithelium
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What is the cell containing a pink glob at the base of a Crypt of Lieberkuhn?
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Paneth Cells
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What is the function of Paneth Cells?
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Secrete lysozyme and defensins to protect the organism against bacteria and viruses
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What is this cell type pointed out by the arrows?
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Enteroendocrine Cells
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What do Enteroendocrine Cells contain?
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- Contain secretory granules in basal cytoplasm
- Clear cytoplasm |
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What is the difference in polarity of the secretory granules in an enteroendocrine cell and a Paneth cell? Reason for this difference?
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- Enteroendocrine cells - secretory granules are basally located because they secrete into the bloodstream
- Paneth cells - secretory granules in are apically located because they secrete into the lumen of the gut |
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How could you positively identify enteroendocrine cells in a section of gut?
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Immunostaining
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What do the arrows point out?
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Stem cells (contain mitotic figures)
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What are the components of the Muscularis Externa?
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- Inner circular layer of smooth muscle
- Outer longitudinal layer of smooth muscle |
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What is the function of the muscularis externa in the small intestine?
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Contracts to mix chyme with digestive enzymes and propels chyme (peristalsis)
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What is the cluster of large basophilic cells with large nuclei and prominent nucleoli?
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Myenteric (Auerbach's) Plexus in between the layers of the muscularis externa
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Which division of the autonomic nervous system innervates the myenteric plexus?
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Parasympathetic division (CN X for foregut and midgut derivatives, S2-S4 for hindgut derivatives)
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What are the large folds in the tissue (this happens to be jejunum)? What is it made of?
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Plicae Circulares (valves of Kerckring)
- Folds have submucosa as their core - Villi project from the surface - Muscularis externa lies deep to the folds |
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What happens to the Plicae Circulares during intestinal distention?
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They do not obliterate with intestinal distention (unlike the rugae in the stomach)
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What is the function of the Plicae Circulares?
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- Slow the passage of intestinal contents
- Increase the surface area for absorption |
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How do you distinguish the myenteric from the submucosal plexuses?
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Based on the surrounding tissues
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What do the neurons of the myenteric and submucosal plexuses arise from?
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Embryonic neural crest
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What happens if there is failure of neural crest migration into the gut?
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Congenital aganglionosis = Hirschprung's disease - congenital megacolon
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What part of the GI tract is affected by Hirschprung's disease?
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Usually the rectum and sigmoid colon
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What are the symptoms in an infant with Hirschprung's disease?
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- Failure to pass meconium
- Bilious vomiting - Irritability - Refusal to feed |
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How do you diagnose Hirschprung's disease?
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Biopsy of the affected bowel segment, it will show few or no ganglia and abnormal proliferation of nerve fibers in the mucosa
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What can cause acquired Hirschprung's disease?
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Bacterial infection possibly
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Which histological, histochemical, or immunological stains might be used in the differential diagnosis of Hirschprung's disease?
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H&E plus acetylcholinesterase
- Ganglion cells (or a lack of them) are visible in H&E - Acetylcholinesterase indicates the proliferation of nerve fibers in the mucosa Microtubule associated tau protein detected immunohistochemically - Tau normally appears in cell bodies and nerve fibers, staining is absent in aganglionic segments of colon |
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Based ont he function of the myenteric and submucosal neurons, what would you expect to find on a lower abdomen x-ray of an affected patient following a barium enema?
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- Affected region is reduced in diameter
- There is no peristalsis here, so it blocks inflow from more proximal portions, leading to distention (enlargement) of the unaffected colon |
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What are the characteristics of the ileum?
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- Presence of villi
- Absence of submucosal glands (of Brunner) - Abundance of GALT - Abundant lymphocytes in lamina propria, some in aggregates |
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What is A?
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Serosa of the Ileum
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What is B?
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Muscularis Externa of the ileum
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What is C?
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Submucosa of the ileum
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What is D?
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Mucosa of the Ileum
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What is arrowed?
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Paneth Cells
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What is arrowed?
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Mitotic Figures (Stem Cells)
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What cells are circled?
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Eosinophils
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What cells are circled?
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Lymphocytes
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What cells are circled?
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Plasma Cells
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What is arrowed?
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Peyer's Patch:
- Collection of lymphoid aggregates in the gut - Part of the organism's defense against pathogens which might penetrate the epithelium |
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What is A?
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Serosa of colon
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What is B?
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Muscularis Externa of colon
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What is C?
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Submucosa of colon
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What is D?
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Mucosa of colon
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What type of epithelium lines the lumen of the colon?
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Simple columnar epithelium
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Name two nutrients that are absorbed by enterocytes in the epithelium of the large intestine.
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Water and electrolytes
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What do the bright blue blobs represent after this slide has been treated with the Periodic Acid Schiff (PAS) reaction and Alcian blue stains?
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Goblet Cells
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Why are Goblet cells abundant in this epithelium of the colon?
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Goblet cells secrete mucous which facilitates the passage of feces through the large intestine
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What is there a large amount of in the appendix? Where specifically?
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Lots of GALT in the lamina propria and submucosa
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What does the arrow point out in this slide of the appendix?
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Lymph nodule
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What kind of epithelium is found in the anus?
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Stratifed squamous
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What is this structure in the anus?
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Hair follicle
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What is the bright red structure in the anus?
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Rectal Venous Plexus
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What surrounds the internal portion of the rectal venous plexus?
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Loose connective tissue
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Why are the veins of the internal rectal plexus affected more by portal obstruction? What happens to them?
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- They are less supported by surrounding structures and less able to resist increased blood pressure
- They enlarge to cause varicose dilations = hemorrhoids |
