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GI Tract III
UBSDM 2015 Histology
Question | Answer |
---|---|
Liver | Produces Yellow/Green Bile containing bile salts, bile pigments, and cholesterol to emulsify fats. Detoxifies drugs, toxins, antibiotics, steroids, bilirubin. Largest gland in the body. Can regenerate. |
Gall Bladder | Stores 30-50ml of bile and concentrates it by removing water |
Pancreas | Secretes (co)enzymes for digestion. Proenzymes are activated by trypsin which is activated by enterokinase in brush border of S.intestine. CCK is released by enteroendocrine cells when fatty acids are present. |
Cholecystokinin (CCK) | Signals the Gall bladder to contract and release bile salts to emulsify fats making the fats susceptible to hydrolysis by pancreatic lipase. Also triggers exocytosis of enzymes from pancreatic acinar cells. |
Hepatocyte | Liver cell that form the parenchyma(working tissue). Resembles epithelial tissue. Large, close together. Has its own blood supply. |
Hepatocyte – Characteristics | Consistent with H&E prep. High concentration of SER, RER, Golgi, mitochondria, lipids, glycogen, lysosomes. One or two Nuclei and acidophilic cytoplasm. |
Liver – Capillary Bed | Sinusoids are lined by a discontinuous layer of endothelial cells with no basal lamina and macrophages (Kupffer Cells). Allows blood to contact the hepatocytes and quick dissemination of liver excretions. Continuous with veins that drain the liver. |
Liver – Veins | central, sublobular and heapatic veins which drain in that order into the inferior vena cava. |
Liver – Bile Duct System | bile canaliculi are formed by the membranes of adjacent liver cells, bile ducts and hepatic ducts. Through this system of conduits, bile reaches the duodenum or gall bladder during times of quiescent digestion. |
Kupffer Cells (Liver Macrophages) | Long Cytoplasm processes extending into sinusoids. Sometime nucleus is too. Remove dead liver cells and clean blood. |
Liver Lobule | Central Vein surrounded by cords of cells and sinusoids that extend from central vein to C.T. in periphery of lobule and portal areas. |
Liver - Hepatocyte Cords | Arranged into branching lines of cells called cords (they look like a bicycle chain). Separated by clear spaces – the sinusoids - that parallel the cords. The cords and spaces radiate away from a central vein like the spokes of a wheel |
Space of Disse | Lymph channel between hepatocytes and sinusoids. Drains the lymph to a true lymphatic vessel in the portal area. |
Liver - Bile Canaliculus | Chanel for bile formed by hepatocytes. Very small, ~diameter of mitochondria. Sealed by tight junctions to prevent bile leakage. |
Liver - Portal Area | Contains a Bile duct lined by simple cuboidal epithelium, branch of hepatic artery, and branch of portal vein. Forming a Portal Triad. Lymphatics are present but hard to see. |
Liver – Limiting Plate | portal areas surrounded by a plate of hepatocytes with high regenerative capacity. |
Liver – Space of Moll | a space that separates the limiting plate from the portal area |
Liver – Functional Lobule (or Rapport) | AKA Liver Acinus. Includes 2+ liver lobules around a portal tract and between central veins. |
Zones of Lobules of Rapport | Zone 1 – richest blood supply. Last to die & 1st to regenerate. Zone 2, gets less. Zone 3 gets least. The structure of the cells in is subtly different in each cell. |
Gall Bladder – Structure | The wall consists of- simple columnar absorptive epithelium 2. lamina propria of loose C.T 3. muscularis of smooth muscle that forces bile into the cystic duct 4. serosa or adventitia depending on whether the wall faces the liver or peritoneal cavity |
Pancreas | Divided into lobules by CT Septae. No radiating chains of cells. Red and blue colors in H&E. Islets of Langerhans do not stain well. |
Pancreas – Acinus | Short round tube with exocrine acinar cells. Centroacinar Cells lie at the middle. (Looks like a Balloon with a straw inserted) |
Pancreas – INTRAlobular (intercalated) Duct | Small and often unseen. Low cuboidal epithelium. Poorly staining cytoplasm. Lie back to back with acini with no CT. May have capillary bed |
Pancreas – INTERlobular Ducts | As large or larger than acinus. Taller (columnar) cells. Supported by CT. |
Pancreas – Excretory Duct | Larger than interlobular. Taller Lining Cells. Supported by CT. Has Small mucous glands. |
Pancreas v. Parotid Gland | Islets of Langerhans in Pancreas. Centroacinar Cells in Pancreas. Striated Ducts in Parotid Gland |
Gall Bladder v. Small Intestine | Small intestine has 7 layers. Gall Bladder has 4 layers. Small Intestine has many specialized cells. |