Mid- Sem Test 1: A1 Flashcards
Section A
What is a hepatic lobule
Lobules are a functional unit of the liver, consisting of a portal triad at the lobule corners, one-cell-thick plate-like layers of hepatocytes and a central vein. The hepatocytes radiate from the central vein to the edge of the lobule.
What is the portal area of the liver
It is another functional unit/complex of the liver which consists of branches of the hepatic portal vein, hepatic artery, bile duct and nerve. It is located at the corner of each hexagonal lobule.
What are the 4 basic cell types of the liver
- The hepatocytes
- Stellate fat-storing cell
- Kupffer cells
- Liver endothelial cell
What are hepatocyte cells
They are liver cells that synthesise protein, cholesterol, bile salts, fibrinogen, phospholipids and glycoproteins
What are liver endothelial cells
They are scavenger cells that secrete cytokines and transport WBC’s thereby increasing immune tolerance
What are Kupffer cells
They are the macrophages of the liver. They secrete mediators for the immune response system
and protect the liver from bacteria and foreign material via phagocytosis.
what are stellate cells
Stores Vitamin-A and fat, promotes proliferation of chemical response to stress
Give 5 examples of important functions that the liver performs:
- Production of bile
- Production of cholesterol, carbohydrates and proteins
- Clearance of bilirubin in RBC haemolysis
- Detoxification of drugs
- Regulate blood clotting
What is the role of the liver in protein metabolism?
THREE ROLES
- Deamination: removal of amine group from molecule of amino acid, and conversion of non-nitrogenous part of those molecules to glucose/lipids
- Removal of ammonia (by-product of deamination) through urea formation
- Plasma protein synthesis - Albumin and clotting factors
- Amino acid interconversions and synthesis of other compounds from amino acids
What is the protein metabolism disorder that results from Ammonia being unable to be removed from the liver?
Ammonia detoxification disorder leads to
- > failure of urea formation
- > hyperammonemia (increased conc ammonia: buildup in blood)
- > hepatic encephalopathy
- > hepatic coma
- > death
What is the role of the liver in carbohydrate metabolism?
Maintaining a normal blood glucose concentration
How is a normal blood glucose concentration maintained?
It is maintained due to the <b>glucose buffer function</b> which is the process of removing excess glucose from blood, storing it as glycogen and when blood conc of glucose decreases, fast return into blood as glucose.
Define glycogenesis
Formation of glycogen by converting excess glucose in blood and through the liver sequestered as large polymer glycogen, its storage form.
Define glycogenolysis
Breakdown of glycogen in the liver to glucose
When does the liver go through glycogenolysis
When blood concentrations of glucose get low, the liver activates other pathways to depolymerise glycogen and export it back into the blood for transport to other tissues
Define gluconeogenesis
Synthesising glucose out of amino acids and non-hexose carbohydrates
What are insulin and glucagon’s roles in glucose metabolism?
Insulin and glucagon are hormones secreted by the pancreas. Insulin is secreted in response to high glucose levels, and affects surrounding body cells to increase their glucose uptake so as to lower glucose concentration in the blood
Glucagon is secreted in response to low glucose levels and affects surrounding body cells but mainly the liver. It induces liver cells to carry out glycogenolysis as well as gluconeogenesis.
What are the two stages of secretion in bile formation?
- First portion is secreted from hepatocytes and contains bile acids, cholesterol, organic constituents
- Additional secretion is from secretory epithelial cells lining the ducts, and is a watery solution of sodium and bicarbonate.
What is bile composed of?
Water, electrolytes, bile acids, cholesterol, phospholipids and bilirubin
Where are bile acids synthesised and from what?
Synthesised in the liver from cholesterol
What is the role of bile?
- Emulsify and break down fats (bile salts do this specifically)
- Waste disposal - bilirubin, excess cholesterol, heavy metals, drugs/toxins
- Gastric acid neutralisation by bicarbonate
What hormones are involved in bile secretion and what are their roles?
CCK
-> stimulates bile secretion due to presence of fats in duodenum - <i>breaks down fat</i>
Secretin
-> stimulates bicarb and water secretions from bile duct and pancreas due to presence of acids in duodenum - <i>maintain pH</i>
Acetylcholine
What are the two forms of bilirubin?
Unconjugated bilirubin: indirect and not water soluble
Conjugated bilirubin: direct and water soluble
