Accessory Organ Histology Flashcards
What two major endocrine secretions do pancreatic inslet (of langerhans) cells release?
1) Glucagon:
- secreted by A-cells
- increases glycogenolysis and lipolysis
- elevates blood glucose levels
2) insulin:
- secretary by B-cells
- increases glucose uptake into cells
- lowers blood glucose levels
What products do pancreatic serous acini secrete?
1) proteases
- get activated by trypsin and work to digest proteins
2) a-amylase
- converts starches and glycogen into monosaccharides
3) lipases:
- digest lipids into subunits of glycerol, FAs and monogylcerides
4) nucleases:
- digests DNA and RNA into nucleotides
What are the primary function of intercalated ducts?
Drain pancreatic acini and also secrete bicarbonate ions
Are lined by simple squamous/low-cuboidal epithelium
Contain centroacinar cells which are the primary cells that secrete the bicarbonate fluid
- are proximal to the lumen and pale-staining
What stimulates serous cells of the exocrine acini into releasing their products?
CCK
Parasympathetic activity
What stimulates the intercalated duct cells/centroacinar cells into secreting bicarbonate?
Secretin
Parasympathetic activity
NOTE: centroacinar cells are activity wise the same as intercalated duct cells
Why are centroacinar cells so important?
They secrete bicarbonate which helps to make sure no damage is done by stomach acid and to make sure no remnant zymogens remain in the pancreas
- (would cause self-Autophagy if left there = pancreatitis)
also prevents premature activation of proteases/zymogens and nucleases
Why does pancreatic tumors become metastatic so often?
The pancreatic tissues are highly vascularized and islet cells have such a high endocrine function
- there is little resistance from metastasis and a wide number of blood vessels to enter
also most pancreatic cancers are asymptomatic until they become near grade 4, making them exceptionally dangerous
most common site is head of pancreas and in ductal cells
What are the major functions of the liver?
1) first pass metabolism
- drugs and absorbed macronutrients
2) bile synthesis and secretion
3) stores the following:
- glycogen
- triglycerides
- vitamins DEAK and B12
- iron and copper
4) produces hormones and plasma proteins
What is a hepatic lobule?
The functional unit of the liver
Is a hexagonal shape with 3-6 portal triads within them. Portal triads are venules/arterioles and bile ducts with lymphatic vessels
Also contains hepatocyte plates
What are hepatocyte plates?
Congregates of hepatocytes within hepatic lobules
- are supported by a delicate stroma and reticulum fibers
Also contain vascular sinusoids between plates which allows venous and arterial blood to mix before reaching the central vein
- also the sinusoids have thin epithelium (called peri sinusoidal space of disse) to allow for endocrine products to empty into the blood easier
What are bile canaliculi?
The formation of two apical membranes of two hepatocyte plates
- carries bile to the bile ductules found in the portal triads
Multiple canaliculi form anastomoses and ultimately form bile canals of herring
- these canals empty into bile ductules in the portal triads
What are the functions of hepatocytes?
- most diverse cell type of the body and are made up of large cuboidal/polyhedral cells with microvilli*
- have a large round centrally located binuclei is with eosinophilic (pink) cytoplasm
1) endocrine secretion
- albumin
- transferrin
- fibrinogen
- apolipoproteins
2) perform Gluconeogenesis
3) deamination
- converts free excess AAs into urea to be excreted
4) detoxification and conjugation of toxins
5) stores:
- glycogen
- triglycerides
- vitamins DEAK and B12
- copper and iron
note dont often produce scar tissues, that’s fibroblasts
How are hepatocytes split into subsections?
Ones that do extensive protein synthesis = lots of RER granules
Ones that store glycogen = lots of glycogen granules
Ones that have no granules = lots of detoxification
What is a classic lobule?
Structure of hepatic lobule that has a central vein with 3-6 portal triads draining into it
- hexagonal shaped lobule
Primary function = drains blood and emphasizes endocrine functions
What is a Portal lobule
Contains 3 central veins with 1 portal triad in between.
- triangle shaped lobule
Emphasizes exocrine function and the flow of bile
What is a hepatic acini?
Contains two portal triads and a lot of hepatocytes
- rhomboid shaped lobule
Emphasizes oxygen and nutrient distribution to hepatocytes
Contains 3 zones based on how close that are to the triads.
- zone 1 = closest to the portal triads and has the highest level of oxygen and nutrients (highest levels of function as well)
- zone 2 = 2nd closest to the portal triads and has highest level of oxygen and nutrients
- zone 3 = furthest from the portal triads and has lowest level of oxygen and nutrients
(Lowest levels of function as well)
Cirrhosis of the liver
Development of dense CT beyond the hilum of the liver causes proliferation of fibroblasts and hepatic stellate cells
Disrupts arrangement of lobules and functions of hepatocytes and sinusoids
- can cause secondary blood disorders/clotting disorders and hypoalbuminemia
almost always irreversible
Fatty liver disease
Accumulation of large lipid droplets within hepatocytes (steatosis). Produces progressive inflammation of the liver and hepatitis
Most common causes are alcohol and obesity
usually reversible
Jaundice
Occurs when too much bilirubin is present in the system
- liver cant produce bilirubin gluconuronide which is nontoxic
Causes yellowing of skin and eyes
Difference between cholesterol and pigment gallstones
Cholesterol = yellow-white color
Pigment = brown-black color
Stellate macrophages (Kupffer cells)
Located in the sinusoids of the hepatic lobules
Function is to remove effete erythrocytes and freeing heme and iron for either reuse or storage as ferritin complexes
- also act as APC’s and remove bacteria/pathogens from the portal system blood
Hepatic stellate cells (ito cells)
Found in the perisinusoidal space
Function to store vitamin DEAK (but especially vitamin A and retinol)
- plays essential role in retinol homeostasis and liver regeneration
are the cells that become fibroblasts and lead to fibrosis of the liver as needed
different vessels in the liver and their fucntions
Central vein
- located dead center in lobules
- collects processed/filtered blood from hepatocytes and empty’s it into the inferior vena cava
Portal venule
- found portal triads
- carries O2-poor/ unprocessed nutrient rich blood from GI tract into liver
Portal arteriole
- found in portal triad
- carries O2 rich/ processed nutrient rich blood from GI tract into liver
Bile ductule
- found in portal triad
- carries bile from gallbladder out into circulatory system
Bile flow pathway
Gallbladder -> bile canaliculi -> bile canals of hering-> bile ductules in hepatic triads -> hepatic ducts -> common bile duct -> main pancreatic duct at hepatopancreatic ampulla -> duodenum via major duodenal papilla
