7 - Exocrine Tissues Flashcards
Where is the parotid gland?
Wraps around the mandibular ramus (angle of the jawbone)
Anterior to the mastoid process, level with head of the mandible
What type of acini are found most commonly in the parotid gland?
Serous acini
The striated ducts in the parotid glands are made up of what type of epithelium?
How are these cells different from the way this type of epithelium usually appears?
Simple columnar epithelium
Nuclei are closer to the apical surface (normally closer to the basement membrane)
What types of acini are found in:
a) parotid glands
b) submandibular glands
c) sublingual glands
a) almost all serous acini
b) serous and mucous acini
c) almost all mucous acini
Where is the submandibular gland?
Lies behind the body of the mandible. In two parts, superficial and deep (separated by mylohyoid muscle)
How is salivary secretion regulated?
Only by neural control - no hormones
Parasympathetic - serous secretion rich in enzymes (large volume)
Sympathetic - mucous secretion
Describe the hepatic blood supply.
- Hepatic artery - supplies liver with oxygenated blood from the aorta
- Hepatic vein - returns deoxygenated blood from the liver to the inferior vena cava
- Hepatic portal vein - connects capillary bed in stomach/intestine to the sinusoids in the liver
HA –> GI capillaries –> HPV –> liver sinusoids –> HV
What percentage of the hepatic blood supply comes from the portal vein?
70-75%
Remainder from the hepatic artery
In a liver sinusoid, a triad of vessels comes together, what are these vessels?
Where do the vessels drain into?
Triad - hepatic artery, portal vein, bile canaliculus
artery and portal vein drain into central vein –> hepatic vein
Bile canaliculus drains in opposite direction into the bile duct
What is a sinusoidal vessel?
Where in the body are these found?
- Irregularly shaped blood vessel with large gaps between the cells (intercellular gaps)
- Cells can get through into the blood
- Incomplete basement membrane
Liver, spleen, bone marrow, lymph nodes
How many sinusoid segments (acini) make up a liver lobule? How are they arranged?
6
Hexagonal arrangement - portal triads around the edges draining into the central vein
Hepatocytes usually have …. or …. nuclei because the cells need to make lots of ………..
2 or 3, proteins
What do pit cells do in the liver?
Form of natural killer (NK) cell
Kills tumour cells that enter the sinusoids
What do stellate cells do in the liver?
Pick up and store vitamin A (retinoic acid) in cytoplasmic vacuoles
In hepatocytes, specialisations are on the ……………… surface of the cells, facing the sinusoids
Basolateral
Normally on apical surface in most cells
What is the space of Disse?
Space between the hepatocytes and the epithelial cells of the sinusoid
What are Kupffer cells? What do they do?
Specialised macrophages that patrol the sinusoids
Recycle old red blood cells and ingest pathogens. Can take over RBC removal from the spleen (splenectomy)
What happens to stellate cells in liver cirrhosis?
Lose vitamin A storage capability
Differentiate into myofibroblasts
What does the liver store?
- Iron
- Lipid soluble vitamins (A, B12, D, K)
- Glycogen
- Copper
What are the liver’s anabolic functions?
Makes more than 60% of body proteins
- Plasma proteins (e.g. albumin)
- Enzymes (e.g. catalase)
- Lipid carrier proteins (HDL, LDL)
- Amino acid synthesis
- Haemopoiesis in the fetus
What are the liver’s catabolic functions?
Destruction of:
- Drugs
- Hormones (e.g. steroids, insulin etc)
- Haemoglobin (bilirubin)
- Poisons/toxins
After splenectomy, also removal of RBCs
Besides its storage and metabolic functions, what else does the liver do?
- Bile production
- Filtering of cellular debris
- Hormone production (e.g. angiotensinogen)
- Modifies hormones (e.g. thyroxine to T3)
What is the largest exocrine gland in the body? What is its constitutive secretion?
The liver
Bile (bile salts)
What does bile do?
Stored in the gall bladder and is slowly released into the duodenum
Emulsifies fats and assists in vitamin K absorption from the small intestine
What is the largest endocrine gland in the body? What is its constitutive secretion? What is its regulated secretion?
The liver
Constitutive - albumin
Regulated - IGF-1
Both the liver and pancreas have endocrine and exocrine secretions, what makes their secretion different?
In the liver, the same cell does both endocrine and exocrine functions (hepatocyte).
In the pancreas, different cells perform endocrine and exocrine functions.
