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138 Cards in this Set
- Front
- Back
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4 tunics that characterize the general structure of the GI tract:
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1. Mucosa
2. Submucosa 3. Muscularis externa 4. Adventitia |
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3 things that make up the mucosa:
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-Epithelium
-lamina propria -Muscularis mucosa |
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What type of epithelium forms the mucosal lining of the esophagus?
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Nonkeratinized stratified squamous
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What is the function of the nonkeratinized stratified squamous epithelial lining of the esophagus?
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To protect against abrasions caused by food sliding down.
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Which layer of the esophagus becomes more prominent as you get closer to the stomach?
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Muscularis mucosa
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What do submucosal glands in the esophagus do?
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Produce mucous to help food slide down
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What is the arrangment of the muscle layers in the muscularis externa?
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Inner = longitudinal
Outer = circular |
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How does the muscularis externa change as you get closer to the stomach?
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It gets thicker
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Where are skeletal muscle fibers present in the esophagus?
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In the upper and middle 1/3
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How does the epithelium change as you transition from esophagus to stomach?
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Esophag: stratified squamous
Stomach: simple COLUMNAR |
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What happens in Barrett's esophagus?
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Acid refluxes causes the stratified squamous cells to transition to simple columnar.
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How would you treat a patient with Barrett's esophagus?
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With a proton pump inhibitor, laser ablation, or esophagectomy.
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What is the concern with a Barrett's esophagus type of mucosa?
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It is a precancerous lesion
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What is Scleroderma?
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A systemic disease of unknown cause that primarily affects women.
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What happens to the GI tract in scleroderma?
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The muscularis mucosa atrophies.
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What symptoms might you expect in a patient whose systemic sclerosis has affected the alimentary tract?
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Dysphagia, esophageal hypomotility, atony, and dilation. Acid reflux.
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What are the 4 anatomical regions of the stomach?
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-Cardia
-Fundus -Body -Pylorus |
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Which regions are histologically similar?
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Cardia and Fundus
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What is the characteristic feature of the mucosa in the cardia/fundus?
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It is HIGHLY FOLDED to form GASTRIC PITS
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What other characteristic feature is seen in the mucosa of the cardia/fundus?
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Gastric GLANDS
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Where are the openings of gastric glands?
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At the bottoms of the gastric pits
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What makes up tunic #1 of the stomach wall?
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Mucosa - epithelium, lamina propria, and muscularis mucosa.
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How many layers of muscle are in the muscularis externa? Why?
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3 - because the stomach is a saccular organ
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What are the 3 layers in the stomach's muscularis externa?
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1. Inner oblique
2. Middle circular 3. Outer longitudinal |
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Is it easy to distinguish these layers?
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No
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What are special foldings of the mucosa + submucosa called? When are they present?
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Rugae - only present when the stomach is empty.
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Where in the stomach are these rugae seen?
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Fundus
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What is the shape of gastric glands in the CARDIA?
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Coiled
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What is the shape of gastric glands in the FUNDUS?
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Straight
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What is the shape of gastric glands in the PYLORUS?
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Coiled
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What type of epithelial cells are seen in the Fundus region? What are they called?
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Still simple columnar, but called SURFACE LINING CELLS
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What are the surface lining cells NOT in the stomach?
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Goblet cells
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What are the surface cells at the base of gastric pits called?
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Neck mucous cells
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What are the large round eosinophilic cells with central nuclei found within gastric glands called?
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Parietal cells
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What are the cells with a basophilic cytoplasm and basally located nuclei?
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Chief cells
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Where are chief cells distributed more within gastric glands?
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Toward the base
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What are the 5 total cells present in the CARDIAC gastric mucosa?
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-Surface lining cells
-Neck mucous cells -Stem cells -Enteroendocrine cells -Parietal cells |
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What cells are present in the FUNDUS region?
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All that are in the cardiac region PLUS chief cells
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What cells are present in the pyloric region?
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All that are in the cardiac region
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How can you distinguish a neck mucous cell?
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It will be located in a gland at the base of a gastric cleft, and look like a goblet cell
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How can you distinguish a Parietal cell?
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It will be eosinophilic and have a round central nucleus
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How can you distinguish a chief cell?
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It will have basophilic cytoplasm and a basal-located nucleus.
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How can you distinguish a neuroendocrine cell?
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It looks like a purple splotch of nucleus surrounded by clear cytoplasm
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How can you distinguish stem cells?
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They will be mitotic
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What is the product of surface lining cells and neck mucous cells? What is its function?
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Mucous; it lubricates the epithelium and protects it from autodigestion
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What is the product of Parietal cells?
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HCL and IF
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What is hte product of chief cells?
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Pepsinogen
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What is the product of enteroendocrine cells? Function?
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Hormones for regulating digestion, peristalsis and bloodflow.
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What is the function of Stem cells?
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To replace other cell types except enteroendocrine cells.
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What is the ratio of gastric pit length to gastric gland length in the Cardiac, Fundic, and Pyloric regions?
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Cardiac: 1:1
Fundic: 1:3 Pyloric: 3:1 |
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So the characteristic feature of the pyrloric region is that its gastric pits are ____ and its gastric glands are _____:
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Pits = deep
Glands = short |
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What does the fundus have that the pylorus does not?
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Chief cells - NOT in the pylorus.
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What is the prominent feature of the pylorus?
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Its inner circular muscle layer THICKENS to form the pyloric SPHINCTER.
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What type of epithelium does the stomach have?
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Simple columnar
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What type of epithelium does the duodenum have?
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Simple columnar
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What do we call the epithelial cells in the stomach?
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Surface lining cells
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What do we call the epithelial cells in the duodenum?
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Goblet cells and Absorptive cells!
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Where the stomach is characterized by PITS, the small intestine is characterized by:
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villi!
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What is the ratio of length for gastric pits vs glands in the stomach near the pyloric sphincter?
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3:1 - long pits, short glands
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Distinguishing feature of the duodenum that makes it different from any other part of the SI, or the stomach:
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Brunner's glands in the submucosa
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4 ultrastructural features of enterocytes that contribute to their function:
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-Microvilli
-Intercellular junctional complexes -Numerous mitochondria -Glycocalyx |
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What is the function of the secretory product of submucosal glands of brunner?
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To neutralize acidic chyme!
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Why does the small intestine have a large surface area?
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To facilitate its functions of digestion and absorption.
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What projects into the lumen of the small intestine?
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Intestinal villi
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What are intestinal villi composed of?
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Finger-like projections of lamina propria and its overlying epithelium, with underlying muscularis mucosa too.
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What type of epithelium covers a villus?
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Simple columnar
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What is the principle cell type within the epithelium of the villi?
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Enterocytes
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What is the function of enterocytes?
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To absorb nutrients and produce digestive enzymes.
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What specialization of the apical membrane is present on enterocytes?
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Brush border formed by microvilli
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What is the function of the brush border?
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To increase the surface area for absorption
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Does the submucosa extend into the core of a villus?
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NO
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Are goblet cells present within the mucosal epithelium?
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YES
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What do goblet cells produce? What is their secretion's function?
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Mucin to lubricate and protect the epithelium.
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What makes these cells readily apparent?
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Carbohydrate, which stains brightly with PAS staining.
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What are the spaces between villi called?
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Intestinal Crypts of Lieberkuhn
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Where is the muscularis mucosa with reference to the crypts?
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It lies at their base.
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What cells are found at the base of crypts?
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Paneth cells
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What allows you to distinguish Paneth cells?
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They are eosinophilic and have secretory granules in their apical cytoplasm.
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How do Paneth cells behave that is different from the other cells in the mucosa?
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They don't migrate to the villus epithelium, but are long lived and stay at the crypt.
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What do Paneth cells secrete?
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-Defensins
-Lysozyme |
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What is the function of the Paneth cell secretions?
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To protect the organism from bacteria and viruses.
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list the 6 cell types prsent in the mucosa of the small intestine:
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-Enterocytes
-Goblet cells -Paneth cells -Enteroendocrine cells -Stem cells -T cells |
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Where are enteroendocrine cells' secretory granules stored? Why?
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At their BASAL side; Because they secrete into the bloodstream, whereas Paneth cells secrete into the lumen.
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What do enteroendocrine cells secrete again?
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Locally acting hormones that regulate GI motility and secretion.
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If enteroendocrine cells have their granules at the basal side, where is their nucleus displaced?
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Toward the apical side.
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Where do T-cells cluster?
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In the submucosa and lamina propria
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How could you positively identify enteroendocrine cells in a section of gut?
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By immunocytostaining.
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Are stem cells found in crypts? How do you know?
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Yes - because they are mitotic figures.
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What do we call diffuse, unencapsulated lymphoid tissue in the GI tract mucosa?
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GALT - Gut associated lymphatic tissue.
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What very important structures lie at the center of a villus?
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Lacteals and capillaries
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Where are stem cells located?
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In the crypts of lieberkuhn
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What would you look for on an esophagogastroduodenoscopy (EGD) if a patient had acid reflux and was tired?
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Polyps or ulcers that could cause internal bleeding.
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What changes can be seen in a patient with Sprue?
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Loss of villi and hyperplasia of the crypts - so it all looks solid instead of nice dips and peaks of villi/clefts.
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What symptoms would you expect in an adult with Celiac disease (sprue)?
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-Weight loss
-Diarrhea -Lassitude -Anemia |
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What will children with celiac disease complain of?
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Chronic abdominal pain (but then don't they all?)
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What will infants exhibit?
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Failure to thrive
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What treatment would you recommend for celiac disease?
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Gluten free diet
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What would you order to follow up for a patient diagnosed with sprue?
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Follow-up biopsy
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What should the followup biopsy show?
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Normal villous architecture after some months of gluten-free diet.
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How many layers of muscle are in the muscularis externa of the small intestine? What is their orientation?
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Two:
-Inner circular -Outer longitudinal |
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What are the functions of the muscularis externa in the small intestine?
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Mixing and propulsion
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What important structure is located between the muscle layers in the small intestine?
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Auerbach's plexus
-Myenteric plexus |
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How can you identify the ganglia of the myenteric plexus?
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-Clusters of large basophilic cells
-LARGE cell bodies -Large nuclei -Prominent nucleoli |
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What division of the ANS innervates the myenteric plexus?
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The Parasympathetic division; CN 10 - innervates the fore/midgut
S2-S4 innervate the Hindgut |
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What is the additional tissue on the left of the slide of duodenum?
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Pancreas
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what are the large folds that have submucosa at their core and villi projecting from their surfaces in the jejunum?
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PLICAE CIRCULARES
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What lies deep to the plicae circulares within jejunum?
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Muscularis externa
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Do these plicae circulares obliterate when the jejunum is extended?
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no
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What is the function of plicae circulares?
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To slow the passage of intestinal contents and increase the surface area for absorption.
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What is located at the base of villi in the jejunum?
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Still Crypts of Lieberkuhn
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What cells are located at the base of the crypts in the jejunum?
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Still Paneth cells
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How do you know they're paneth cells?
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Their apical cytoplasm is filled with red secretory granules.
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What important structure is present within the submucosa of the jejunum slide?
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Submucosal plexus (Meissner's)
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How can you tell whether you're looking at the Myenteric or Submucosal nerve plexus?
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By looking to see if it's surrounded by muscle or submucosa stuff.
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What won't be in that submucosal stuff?
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Brunner's glands - they're ONLY in the duodenum.
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What is cresyl violet used to stain for?
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Nissl substance - of neurological structures.
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What is nissl substance?
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Rough ER
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What disease results when neural crest cells fail to migrate into the developing small intestine?
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Hirschprung's disease
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What would happen to regions affected by lack of nerve structures?
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Reduced diameter and no peristalsis
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What happens to downstream areas even if they do have neurological structures?
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The flow through upstream "constricted" areas is blocked, so nothing gets to the downstream areas.
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What is the general result of Hirschprung's disease?
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Blockage of the colon - failure to pass meconium.
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3 main features of the ileum:
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-Presence of villi
-Abundance of GALT -no brunner's glands |
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What are collections of HUUUUGE lymphoid aggregates called?
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Peyer's patches
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What selection is representative of the large intestine?
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Cecum and appendix
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Are there villi in the large intestine?
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NO
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What type of epithelium lines the large intestine?
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Simple columnar
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What are 2 nutrients absorbed by the enterocytes of the large intestine?
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-Water
-Electrolytes |
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Are there crypts of lieberkuhn's in the large intestine?
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I think so, yes
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What cells are ABUNDANT in the simple columnar epithelium of the large intestine? Why?
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Goblet cells - to secrete mucus to facilitate the passage of feces thru the large intestine.
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What covers the outside of the large intestine?
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The serosa (adventitia)
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What is prominent within the large intestine submucosa and lamina propria?
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GALT
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What is the arrangement of the layers of the muscularis externa in the large intestine?
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Outer = longitudinal
Inner = circular |
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Why does it look like the simple columnar epithelial cells of the appendix are underneath another layer?
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Because there's JUNK in the lumen (crap)
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What type of epithelium lines the anal canal?
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Stratified squamous
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What is present in the anal skin?
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Sweat glands, sebaceous glands, and hair follicles.
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What is the general term for varicose dilations of the rectal venous plexus?
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Hemorrhoids
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What causes hemorrhoids?
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Portal obstruction
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What is the rectum good for?
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Delivering meds like Diazepam for seizures.
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