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NJDS Histology - Digestive Glands


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Question: What organ functions as both an exocrine and an endocrine gland?
Answer: Pancreas
Question: The exocrine portion of pancreas is responsible for..
Answer: The production and release of digestive enzymes
Question: Where do digestive hormones produced from?
Answer: In aggregates of cells called ISLETS OF LANGERHANS (Digestive hormones are eventually released into the bloodstream)
Question: Which digestive enzymes do exocrine component of pancreas produce?
Answer: 1.Lipase - breaks down fats 2.Carboxypeptidase - breaks down certain peptide bonds 3.Trypsin - hydrolyzes peptide bonds 4.Chymotrypsin - cleaves carboxyl links of certain amino acids 5.Amylase - breaks down starch and glycogen 6.Elastase - hydrolyzes elastin
Question: What are the 2 hormones that control pancreatic secretion?
Answer: 1.Secretin - produced by enteroendocrine cells of the small intestine. Causes buffer to be released by ductal cells, and insulin release 2.Cholecystokinin - produced by APUD cells of small intestine. Causes gall bladder contraction, slows gastric emptying time, stimulates pancreas enzyme secretion
Question: Describe the structure of exocrine portion of the pancreas
Answer: The exocrine portion of the pancreas is compound acinar gland, similar to the parotid gland. The acini are made up of acinar and centroacinar cells (intra-acinar extension of the intercalated ducts).
Question: When digestive enzymes are produced from acini, which pathway do they follow?
Answer: Acinar cell -> Centroacinar cell -> Intercalated ducts -> columnar interlobular ducts (there are no striated ducts in the pancreas) -> Two main ducts - Duct of Santorini (accessory) and Duct of Wirsung (main)
Question: The duct cells in pancreas produce..
Answer: Bicarbonate-rich buffer solution, which neutralizes the acidic gastric contents passing into the duodenum
Question: Endocrine component consists of..
Answer: The islets of Langerhans, which are distributed throughout the pancreas, but are more numerous in the tail of the gland.
Question: Describe the structure of the cells of the islets of Langerhans
Answer: The cells 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.
Question: How many types of cells comprise the islets of Langerhans and what are they?
Answer: Five types of cells.
1. Alpha(A)-cells
2. Beta(B)-cells
3. Delta(D)-cells
4. F(PP) cells
5. G cells
Question: What is the morphology and function of Alpha(A)-cells?
Answer: Large cells with dark cytoplasm that are mainly found on the periphery of the islet (20% of islet cells).
Secrete glucagon, which increases blood sugar.
Question: What are the mechanism and functions of glucagon?
Answer: Glucagon is released when blood glucose levels are low - acts on hepatocytes, which break down glycogen into glucose and release it into bloodstream. It also activates gluconeogenesis.
Question: What is the morphology and function of Beta(B)-cells?
Answer: (70% of islet cells) Smaller in cell and granule size than A-cells.
Secrete insulin, which decreases blood sugar.
Question: What are the mechanism and functions of insulin?
Answer: 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.
Question: What is the function of Delta(D)-cells?
Answer: (5% of islet cells)
Secrete somatostatin
Question: What are the functions of somatostatin?
Answer: Serves both a paracrine and endocrine function (inhibits hormone release in adjacent A and B cells of pancreas, and reduces smooth muscle contractions of the alimentary tract and gall bladder.
Question: What is the function of F(PP)cells?
Answer: (1% of islet cells)
Secrete pancreatic polypeptide (inhibits exocrine pancreatic secretions)
Question: What is the function of G cells?
Answer: (1% of islet cells)
Secrete gastrin, which stimulates production of HCL by parietal cells in stomach.
Question: What is the second largest organ of the body?
Answer: Liver
Question: What are the main functions of liver?
Answer: It serves to process and store the nutrients absorbed by the digestive tract, in addition to many other functions.
Question: The liver is surrounded by..
Answer: a thin capsule called Glisson's capsule, which extends into the organ subdividing it into lobes and lobules.
Question: How many kinds of lobules do liver contain and what are they?
Answer: 3 kinds
1. The liver (classic) lobule
2. The portal lobule
3. Hepatic acinus (lobule)
Question: The liver lobule consists of..
Answer: a poorly-demarcated collection of hepatocytes that form a hexagonal structure.
Question: What is the name of an area (point) where three liver lobules contact each other
Answer: Portal Area (TRIAD)
Question: Portal area is comprised of..
Answer: connective tissue, hepatic artery, portal vein, bile duct and (sometimes)lymphatics
Question: How many triads per one liver lobule?
Answer: 3-6 triads
Question: What is located at the center of the liver lobule?
Answer: Central vein (toward which there are converging plates of anastomosing hepatocytes, enclosing liver sinusoids)
Question: Describe portal lobule.
Answer: Another method of visulaizing liver function (in terms of bile drainage).
Question: The portal lobule is a 1.______ structure with the 2._______ at the center and the 3._______ at the tip of each angle.
2.portal triad
3.central vein
Question: Describe hepatic acinus.
Answer: a diamond-shaped area that is supplied by a terminal branch of the distributing veins encompassing portions of two adjacent liver lobules.
Question: How many zones are in hepatic acinus?
Answer: 3 zones
Zone I - closest to the distributing vein and the first to affect or be affected by the passing blood; these hepatocytes are actively synthesizing proteins
Zone II - middle zone (transition zone)
Zone III - encounters blood on its way to the central vein that has been heavily altered by zones I and II. Largely deoxygenated blood; the hepatocytes here play a role in detoxification.
Question: Liver receives blood from two sources. What are they?
Answer: Portal vein (80%) and hepatic artery (20%)
Question: What are the properties of blood that passes portal vein?
Answer: Oxygen-poor, nutrient-rich blood from pancreas, spleen and intestines.
Question: In the triads, the branches of the portal vein are called..
Answer: the portal venules
Question: Branches of portal vein that surround the periphery of the lobules are called..
Answer: the distributing veins
Question: What is the pathway of deoxygenated-blood exiting the liver starting from distributing veins?
Answer: Distributing veins -> inlet venules -> sinusoids -> central vein -> sublobular vein -> hepatic veins -> out of liver
Question: Hepatic arter branches to form the 1.______, some of which occupy the 2._______, and some of which empty directly into the 3.________.
1.interlobular arteries
2.portal area
Question: The sinusoids contain both..
Answer: arterial and venous blood
Question: Hepatocyte morphology and location.
Answer: 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.
Question: What is the space between adjacent hepatocytes called?
Answer: Bile canaliculus
Question: What are the functions of hepatocytes?
1.Storage - vitamins (A,D,B12)
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
Question: What are the functions of bile?
Answer: absorbs fats, eliminates most of the cholesterol produced by the liver, excretes the breakdown products of blood.
Question: What is space of Disse?
Answer: Space of Disse separates the endothelial cells of the sinusoids from the hepatocytes.
Question: Which components comprise space of Disse?
Answer: Hepatocyte microvilli, nonmyelinated nerve fibers, Ito cells(fat storage), and pit cells(type of NK cell).
Question: What phagocytic cell reside within the sinusoids?
Answer: Kupffer cells
Question: Bile is composed of..
Answer: cholesterol, lecithin, fatty acids, bilirubin glucuronide, bile salts, and water. Most of these components are absorbed in the intestine and transported via the blood to the bile canaliculi.
Question: What is bile canaliculi?
Answer: the initial part of the bile duct system. It consists of narrow channels between adjacent hepatocytes, into which protrude microvilli. The canaliculi reach their endpoint near the portal areas - bile therefore flows in the opposite direction of blood
Question: What are the cell types of the bile duct?
Answer: clear cuboidal or columnar cells.
Question: Numerous bile ducts eventually converge to form..
Answer: the right and left hepatic ducts (which lead bile to gall bladder)
Question: Gall bladder is a 1.______ organ that rests along the underside of the 2._______.
Question: What are the functions of gall bladder?
Answer: Functions in bile storage, concentration, and release. Also, communicates with the hepatic duct by way of the cystic duct, to form the common bile duct.
Question: What are the layers of gall bladder
Answer: Mucosa (highly folded, simple columnar epithelium), lamina propria (areolar connective tissue), muscularis externa, and serosa. No muscularis mucosa.
Question: What hormone causes gall bladder contraction?
Answer: cholecystokinin, which is released by the enteroendocrine cells of the small intestine from the stimulus of dietary fat present within its lumen.
Question: Bile empties into duodenum through..
Answer: ampulla of Vater (junction of common bile duct and pancreatic duct surrounded by sphincter of Oddi)

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