Digestive Glands Flashcards
What are the digestive glands?
Pancreas
Liver and biliary tree
What are the origin of the digestive glands?
From endoderm as an outgrowth of the foregut during 4th week of development
What are the anatomical parts of the pancreas?
Head- surrounded by the duodenum and pierced by the common bile duct
Body
Tail- anchored by the spleen
What are the characteristics of the pancreas?
Stroma made of thin capsule extending into tissue as septa to divide organ into lobules
Exocrine pancreas consisting of secretory acini and ductal system
Endocrine pancreas consisting of islets of Langerhans
What are the characteristics of the secretory acini of the exocrine pancreas?
Serous acini, spherical in shape
Composed of single cell type of secretory cells pyramidal shape called pancreatic acinar cells (PAC)
PAC have typical characteristics of protein secreting cells with basally placed RER and apical eosinophilic granules
PAC produce trypsinogen and chymotrypsinogen
What are the types of ducts that made the ductal system?
Intralobular ducts
Interlobular ducts-larger than intralobular, lined with simple columnar epithelium and drains into main duct
Main duct
What are the parts of the intralobular ducts?
Centro-acinar cells are the non secretory squamous ductal cells within serous acini, continuous with intercalated ducts
Intercalated ducts-short portions with low simple cuboidal epithelium, secrete HCO3 and H2O second way to neutralize gastric acid
Intralobular collecting ducts- larger than intercalated ducts, lined with simple cuboidal or low simple columnar epithelium
What are the characteristics of the islets of Langerhans?
Irregular cords
More numerous in tail
Rich in capillaries with fenestrated endothelium
What are the islets of Langerhans cells?
Alpha cells-20% of cells, located at the periphery, secrete glucagon to increase blood glucose
Beta cells-70% of cells, located in the central part, secrete insulin to decrease blood glucose
Delta cells-5 to 10% of cells secrete somatostatin which function is unclear but may inhibit release of insulin and glucagon
Other endocrine cells
What are the characteristics of the liver?
Largest gland on the body
Largest internal organ
Function both as an exocrine (bile production) and endocrine gland
What are the functions of the liver?
Bile production Synthesis of most plasma proteins Lipid,glucose and iron metabolism Storage of vitamin A Conversion of vitamins D and K Detoxification of drugs and toxins
What are the components of the liver?
Parenchyma-Plates of hepatocytes forming lobules
Stroma made of thin CT capsule surrounding liver (Glisson’s capsule) and a network of reticular fibers
Blood supply from 2 sources: hepatic artery and portal vein
Hepatic vein for outflow
What is the vasculature within liver?
Conducting branches formed by portal vein and hepatic arteries
Interlobular branches in spaces part of portal triad
Terminal branches drain blood to hepatic sinusoids
Hepatic sinusoids drain into central veins
Central veins drain into sublobular veins
Sublobular veins to collecting tributaries of hepatic veins
What are the characteristics of the hepatic sinusoids?
Large , discontinuous capillaries with fenestrated endothelial cells
Presence of gap between endothelial cells allow exchange of proteins
Separate plate of hepatocytes
What are the liver cells?
Hepatocytes
Kupffer cells
Fat storing cells (Ito cells)
What are the characteristics of hepatocytes ?
Main cell type within the liver (60%)
Relatively long shelf life (3months)
Have the ability to regenerate
What is the structure of the liver hepatocytes cells?
Have a large, spherical nucleus often polypoid
Abundant mitochondria present
Well developed RER and Golgi due to very active protein secretion
Abundant SER for detoxification function
Large number of glycogen particles
Lysosomes for iron storage
What are the characteristics of Kupffer cells?
Macrophages derived from blood monocytes
Reside within hepatic sinusoids
What are the characteristics of the fat storing cells or ito cells?
Found in the space of Disse
Derived from fibroblasts
Main function is storage of vitamin A and lipids
In pathological conditions caused liver cirrhosis by synthesizing collagen
What is the structure of a classic hepatic lobule?
Hexagonal prism with a central vein running thru center
Plate of hepatocytes radiate from central vein towards periphery
Space of Disse is the narrow space between plate of hepatocytes and basement membrane of hepatic sinusoid
Portal canals located at angle of prisms
What are the characteristics of the portal canal?
Contain the portal triad made of interlobular branch of portal vein, interlobular branch of hepatic artery and interlobular bile duct lined of simple cuboidal epithelium
Bring blood to lobule and collect bile from lobule
countercurrent between blood and bile: blood from periphery to center,bile from center to periphery
What are the characteristics of plate of hepatocytes?
One cell thick anastomosing sheets
Bile canaliculi run through plates draining into bile ductules
Space of Disse separate hepatocytes and endothelial cellsof sinusoids offer site of exchange between blood and liver cells
What are the characteristics of portal lobule?
Emphasizes the exocrine function and production of bile
Centered on portal triad
What are the characteristics of liver acinus?
Centered on terminal branches of portal vein/hepatic artery and on canal of Hering. Has 3 zones:
Zone 1 with more oxygen and nutrients gets intoxicated first
Zone 2-middle
Zone 3 with less oxygen dies first in reduced perfussion but gets intoxicated last
What are the characteristics of the biliary tree?
System of conduits of increasing diameter that bile flows thru
Smallest branch is the bile canaliculi within plate of hepatocytes
Bile canaliculi lining is formed by hepatocytes
Bile canaliculi drain into bile ductule or Canal of Hering
What are the characteristics of Gall bladder?
Pear shaped distensible sac attached to the visceral surface of the liver
Concentrate and store bile
What are the layers of the Gallbladder?
Mucosa has a simple columnar epithelium and lamina propria blending with submucosa,no muscularis mucosae
Submucosa made of CT
Muscularis externa made of bundles of smooth muscle and collagen
Serosa in the part projection into peritoneum
Adventitia in the rest
