Microanatomy of GI Glands Flashcards
What are the 4 accessory organs of the GIT
1- Liver
2- Pancreas
3- Gallbladder
4- Salivary glands
List lobes of liver
- largest gland in body
- 4 lobes : right , left, quadrate, caudate
Describe the micro anatomy of the liver ( epithelium , blood supply )
- mainly epithelial tissue , little CT
- 2 major blood vessels : hepatic artery and hepatic portal vein
Key features of hepatic artery
- supplies 30% of blood passing through liver
- Rich in oxygen ,
Key features of Hepatic portal vein
- supplies 70% of blood passing through liver
- take what’s absorbed by GIT and takes to liver for processing
low in oxygen - high in nutrients
What is the Portal Hepatis
the hilum of the liver where the vessels enter and divide into branches
- includes : nerves, hepatic vein , common hepatic duct , lymphatic vessels, hepatic artery and hepatic portal vein
How is the liver drained and what type of blood is leaving
- by the hepatic vein that empties into IVC
- highly nutrient blood
What is the common hepatic duct
takes bile produced in liver to gallbladder
What are the functions of the liver ( 5)
1- exocrine gland function - bile synthesis
2- endocrine gland function - plasma protein synthesis
3- process nutrients absorbed in GIT and store till needed
4- degrades toxins
5- destroys won-out RBC, pathogens
What are the two ways to describe liver morphology
1- Classic Lobule ( 3 lobes )
2- Liver Acinus
What is the Classic Lobule model based on
histology of liver
Main Features of Classic Lobule Model
- Polygonal lobes
- irregular rows of hepatocytes ( liver cells)
- hepatocytes arranged around central vein , radiating outward
- Peripheral portal areas ( in corner )
- Vascular sinusoids
What is in portal areas
Hepatic portal vein
Bile duct
Lymphatic vessels
What are vascular sinusoids and function
- where blood will drain
- nutrients and toxins in blood will pass through sinusoids into hepatocytes for processing
- will drain blood into central vein of lobule which drains into hepatic vein
Label Lobule
Label
Label Portal Area
What is the Liver Acinus Model based on
based on liver function
Main features of Liver Acinus Model
- Spread over 2 lobules inbetween central veins of lobes
- Hepatocytes and sinusoids within them
- peripheral Portal areas in classic lobule
- central vein in middle in classic lobule
- Acinus is seperated in zones , hepatocytes in each zone have different metabolic activity depending on distance from portal area
What does the Liver Acinus Model help explain
- oxygen gradient : hepatocytes farer from blood supply will be supplied with blood with lover o2 levels
- distribution of drug metabolism enzymes : hepatocytes farthest from portal area have most enzymes
- zones of histological damage due to ischaemia or toxicicity
Describe Zone 1
- closest to blood suply
- farthest from terminal hepatic venule ( central vein in classic module )
- recieve oxygen and nutrient rich blood
- actively synthesis glycogen and plasma proteins
Describe Zone 2
- intermediate hepatocytes
- recieve second class blood
Describe Zone 3
- furthest from portal area
- recieve blood lowest in oxygen and nutrients
- Closest to terminal hepatic venule
- site of alcohol and drug detoxification
- most susceptible to hypoxia and toxic damage since they get the least oxygen and nutrients and the most toxins
What can cause damage to zone 3
if there is low perfusion cells could die
How thick are rows of hepatocytes and why
one cell thick so they can easily exchange with blood suplly flowing through sinusoids
What is the role of the central vein
taakes deoxygentaed blood from sinusoids and drains into IVC
How is bile produced and travels
- Bile is produces by hepatocytes
- travels through small intercellular channels called bile canaliculi
- drain into bile duct at portal area
- Bile and blood DO NOT MIX
Describe Bile Canalculi position and formation
- intercellular channels sealed by tight junstions and formed by hepatocytes plasma membrane
Describe Sinusoid microanatomy
- lined with fenestrated epithelium for exchange
Describe Hepatocyte Sinusoid boundry
Space of disse: where plasma filters to make contact with microvili of hepatocyte
- in between microvilli and sinusoid epithelium
What are Kupffer cells
- macrophages that break old RBC
- located on inner walls of sinusoids
- derived from circulating monocytes
- phacoytose any foreign matter
Where are Bile canalculi located
inbetween/ in hepatocytes
Is the pancreas divided
- divided into lobules by CT septa
- has portions that are both endocrine and exocrine
Explain the exocrine portion of the pancreas
- composed of serous acini ( secretory unit ) and branching duct system
- produce enzymes for food digestion
- produce in inactive form to avoid self-digestion and transported to duodenum
Explain the endocrine portion of pancreas
- composed of islets of langerhand ( specialized epithelial cells ) and blood capillaries within them
- produce hormones : insulin , glucagopn, somatostatin , pancreatic polypeptide
What are serous acini
- secretory units that produce digestive enzymes which are secreted into small ducts that drain into main duct that goes to duodenum
How do islets of langerhans present in micrograph
- pale staining cells
Describe microanatomy of islet
- compact mass of epithelial cells
- 4 cell types : alpha cells ( glucagon ) beta cells ( insulin ) delta cells (somatostatin) f-cells ( pancreatic polypeptide )
- 4 cells can’t be visualized with normal staining
Role of salivary glands
produce secretions from mostly acinar type units
Label part of pancreas
Label
