Mid- Sem Test 1: A1

Question 1

What is a hepatic lobule

Answer 1

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.

Question 2

What is the portal area of the liver

Answer 2

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.

Question 3

What are the 4 basic cell types of the liver

Answer 3

1. The hepatocytes
2. Stellate fat-storing cell
3. Kupffer cells
4. Liver endothelial cell

Question 4

What are hepatocyte cells

Answer 4

They are liver cells that synthesise protein, cholesterol, bile salts, fibrinogen, phospholipids and glycoproteins

Question 5

What are liver endothelial cells

Answer 5

They are scavenger cells that secrete cytokines and transport WBC’s thereby increasing immune tolerance

Question 6

What are Kupffer cells

Answer 6

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.

Question 7

what are stellate cells

Answer 7

Stores Vitamin-A and fat, promotes proliferation of chemical response to stress

Question 8

Give 5 examples of important functions that the liver performs:

Answer 8

1. Production of bile
2. Production of cholesterol, carbohydrates and proteins
3. Clearance of bilirubin in RBC haemolysis
4. Detoxification of drugs
5. Regulate blood clotting

Question 9

What is the role of the liver in protein metabolism?

Answer 9

THREE ROLES

1. Deamination: removal of amine group from molecule of amino acid, and conversion of non-nitrogenous part of those molecules to glucose/lipids
2. Removal of ammonia (by-product of deamination) through urea formation
3. Plasma protein synthesis - Albumin and clotting factors
4. Amino acid interconversions and synthesis of other compounds from amino acids

Question 10

What is the protein metabolism disorder that results from Ammonia being unable to be removed from the liver?

Answer 10

Ammonia detoxification disorder leads to

• > failure of urea formation
• > hyperammonemia (increased conc ammonia: buildup in blood)
• > hepatic encephalopathy
• > hepatic coma
• > death

Question 11

What is the role of the liver in carbohydrate metabolism?

Answer 11

Maintaining a normal blood glucose concentration

Question 12

How is a normal blood glucose concentration maintained?

Answer 12

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.

Question 13

Define glycogenesis

Answer 13

Formation of glycogen by converting excess glucose in blood and through the liver sequestered as large polymer glycogen, its storage form.

Question 14

Define glycogenolysis

Answer 14

Breakdown of glycogen in the liver to glucose

Question 15

When does the liver go through glycogenolysis

Answer 15

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

Question 16

Define gluconeogenesis

Answer 16

Synthesising glucose out of amino acids and non-hexose carbohydrates

Question 17

What are insulin and glucagon’s roles in glucose metabolism?

Answer 17

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.

Question 18

What are the two stages of secretion in bile formation?

Answer 18

1. First portion is secreted from hepatocytes and contains bile acids, cholesterol, organic constituents
2. Additional secretion is from secretory epithelial cells lining the ducts, and is a watery solution of sodium and bicarbonate.

Question 19

What is bile composed of?

Answer 19

Water, electrolytes, bile acids, cholesterol, phospholipids and bilirubin

Question 20

Where are bile acids synthesised and from what?

Answer 20

Synthesised in the liver from cholesterol

Question 21

What is the role of bile?

Answer 21

1. Emulsify and break down fats (bile salts do this specifically)
2. Waste disposal - bilirubin, excess cholesterol, heavy metals, drugs/toxins
3. Gastric acid neutralisation by bicarbonate

Question 22

What hormones are involved in bile secretion and what are their roles?

Answer 22

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

Question 23

What are the two forms of bilirubin?

Answer 23

Unconjugated bilirubin: indirect and not water soluble

Conjugated bilirubin: direct and water soluble