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75 Cards in this Set
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Pancreas
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an organ that functions as both an exocrine and an endocrine gland. The exocrine portion is responsible for the production and release of digestive enzymes. Digestive hormones are produced in aggregates of cells called islets of Langerhans and eventually released into the bloodstream.
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Exocrine component of the pancreas secrete what enzymes?
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carboxypeptidase
chymotrypsin trypsin amylase elastase lipase |
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lipases breaks down
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fats
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carboxypeptidases breaks down
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breaks down certain peptide bonds
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trypsin breaks down
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hydrolyzes peptide bonds
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chymotrypsin breaks down
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cleaves carboxyl links of certain amino acids
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amylase breaks down
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breaks down starch and glycogen
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elastase does what ?hyd...
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hydrolyzes elastin
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What 2 hormones control pancreatic secretions?
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1. cholecystokinin
2. secretin |
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Where is secretin produced?
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produced by enteroendocrine cells of the small intestine
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What does secretin do?
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Causes buffer to be released by ductal cells, and insulin release
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Where is cholecystokinin produced?
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produced by APUD cells of small intestine
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What does cholecystokinin do?
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Causes gall bladder contraction, slows gastric emptying time, stimulates pancreas enzyme secretion
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Where is Ach released?
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released from postganglionic parasympathetic fibers
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What is the exocrine portion of the pancreas?
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compound acinar gland
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What cells make up of the acinar gland of the pancreas?
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acinar and centroacinar cells
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Are there striated ducts in the pancreas?
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no
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The intercalated ducts merge into what?
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columnar interlobular ducts
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2 main ducts of the pancreas
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1. duct of Wirsung (main)
2. duct of Santorini (accessory) |
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What is the endocrine component of the pancreas?
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islets of Langerhans, which are distributed throughout the pancreas, but are more numerous in the tail of the gland.
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The structure of the endocrine portion of the pancreas
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the cells of the islets of Langerhans are round to polygonal in shape, and surrounded by a rich capillary network. A thin capsule of reticulin fibers separate each islet from the exocrine pancreatic parenchyma.
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5 cell types of the islets of Langerhans
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alpha(A)- cells
ß(B)- cells delta(D)- cells F (PP) cells G cells |
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alpha (A) cells
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large cells w/
dark cytoplasm mainly found on the periphery of the islet; consitute approximately 20% of islet cells, secrete glucagon Glucagon does what = |
(increases blood sugar)
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When is glucagon released?
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when blood glucose levels are low
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Glucagon acts on what?
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hepatocytes
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What does glucagon activate?
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glycogen to glucose
gluconeogenesis |
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Beta (B) cells
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comprise approximately 70% of islet cells; smaller in cell and granule size than a- cells; secrete insulin, which decreases blood sugar
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insulin
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insulin binds to insulin receptors on cells (especially skeletal muscle, liver, and adipose), which allows glucose to be taken into cell. It also encourages glucose utilization by cells, increases protein synthesis and formation and storage of neutral lipids
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delta(D)- cells
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account for 5% of islet cells; secrete somatostatin, which serves both a paracrine and endocrine function (inhibits hormone release in adjacent a and ß cells of pancreas, and reduces smooth muscle contractions of the alimentary tract and gall bladder)
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somatostatin
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inhibits hormone release in adjacent a and ß cells of pancreas, and reduces smooth muscle contractions of the alimentary tract and gall bladder
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F (PP) cells
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account for 1% of islet cells; secrete pancreatic polypeptide (inhibits exocrine pancreatic secretions)
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pancreatic polypeptide
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inhibits exocrine pancreatic secretions
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G cells
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account for 1% of islet cells; secrete gastrin, which stimulates production of HCl by parietal cells in stomach
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gastrin
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stimulates production of HCl by parietal cells in stomach
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Liver
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the second largest organ of the body, it serves to process and store the nutrients absorbed by the digestive tract, in addition to many other functions
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Structure of the liver
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the liver is surrounded by a thin capsule __________ capsule which extends into the organ subdividing it into lobes and lobules
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Glisson's capsule
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portal area (triad)
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At the point where three liver lobules contact each other, which contains
CT branches of the hepatic artery, portal vein, bile duct sometimes also lymphatics. |
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classic liver lobule consists of what?
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consists of a poorly-demarcated collection of hepatocytes that form a hexagonal structure
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How many triads are associated with each liver lobe?
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3 - 6 triads
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What is at the center of the liver lobule?
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central vein, toward which there are converging plates of
-anastomosing hepatocytes, -enclosing liver sinusoids. |
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Poral lobule
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The portal lobule major function is bile drainage.
The portal lobule is a triangular structure with the portal triad at the center and the central vein at the tip of each angle. |
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Hepatic acinus
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a diamond-shaped area that is supplied by a terminal branch of the distributing veins encompassing portions of two adjacent liver lobules.
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Zones of the hepatic acinus from the most proximal to the distributing veins
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Zone I
Zone II Zone III |
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Zone I of the Hepatic acinus
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closest to the distributing vein and the first to affect or be affected by the passing blood; these hepatocytes are actively synthesizing proteins
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Zone II of the Hepatic acinus
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middle zone
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Zone III of the Hepatic acinus
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encounters blood on its way to the central vein that has been heavily altered by zones I and IL Largely deoxygenated blood; the hepatocytes here play a role in detoxification.
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The liver's sources of blood supply
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1. portal vein
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portal vein of the liver
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80%; oxygen-poor, nutrient-rich blood from the pancreas, spleen, and intestines
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portal venules
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the branches of the portal vein in the triads
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distributing veins
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those branches that surround the periphery of the liver lobules
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describe the path of the blood supply to the liver from the portal vein
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-out of the distributing veins emerge the inlet venules, which lead to the sinusoids
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-the sinusoids lead to the central vein, which at the base of the lobule merges with the _______ vein
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Sublobular vein,
which eventually joins with other sublobular veins to form the __________ Vein |
hepatic veins
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hepatic artery
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20%; oxygen-rich -branches to form the interlobular arteries, some of which occupy the portal area, and some of which empty directly into the sinusoids
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What type of blood do sinusoids contain?
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arterial and venous blood
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hepatocyte
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polyhedral cells with 1-2 nuclei that form anastomosing plates that converge towards the central vein. They are exposed at several points to the walls of the sinusoids or to adjacent hepatocytes. They have several functions in the liver.
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bile canaliculus is the space between what?
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adjacent hepatocytes
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Functions of the hepatocyte
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1. Storage - vitamins (mostly A, D, B,2)
2. Transformation and detoxification - inactivation of drugs and toxins 3. Protein synthesis - mainly blood proteins (for coagulation, immune system, transport) 4. Metabolism - lipids, carbohydrates, proteins 5. Excretion - bilirubin (breakdown product of hemoglobin) 6. Bile production -- absorbs fats, eliminates most of the cholesterol produced by the liver, excretes the breakdown products of blood |
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The endothelial cells of the sinusoids are separated from the hepatocytes by what?
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space of Disse
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What cells are found in the space of Disse
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hepatocyte microvilli, nonmyelinated nerve fibers, Ito cells (fat storage), and pit cells (type of NK cell
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Ito cells store what =
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~fat storage cells
~Vit-A |
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What cells are found in the sinusoids?
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phagocytic Kupffer cells
Which differentiate from = |
Macrophages
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Components of bile
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composed of cholesterol, lecithin, fatty acids, bilirubin glucuronide, bile salts, and water
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Most of the components are absorbed in the intestine and transported via the blood to what?
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blood canaliculi
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Bile canaliculi
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the initial part of the bile duct system. They consist of narrow channels between adjacent hepatocytes, into which protrude microvilli.
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Where do the canaliculi reach their endpoints?
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near the portal areas
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bile ducts are composed of what?
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clear, cuboidal or cells
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movement of bile from bile canaliculi to liver
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1. bile canaliculi
2. bile ducts 3. portal triad 4. hepatic ducts (liver) |
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Gall Bladder
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hollow organ that rests along the underside of the liver and functions in bile storage, concentration, and release.
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How does the gall bladder communicate with the hepatic duct?
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via cystic duct
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the common bile duct
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hepatic duct and cystic duct
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Describe the mucosa of the gall bladder
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the mucosa of the gall bladder is highly folded and consists of a simple columnar epithelium, a lamina propria composed of areolar connective tissue, muscularis externa, and serosa. There is no muscularis mucosae
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In the gall bladder, what secretes mucous?
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tubuloacinar glands near the cystic duct
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What controls the contraction of the gall bladder?
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cholecystokinin which is released by the enteroendocrine cells of the small intestine and pancrease from the stimulus of dietary fat present within its lumen.
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cholecystokinin is released by what? secretion is stimulated by what?
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enteroendocrine cells of the small intestine and pancrease from the stimulus of dietary fat present within its lumen.
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ampulla of Vater describe
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junction of
common bile duct and pancreatic duct surrounded by sphincter of Oddi that empties into duodenum |
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