Physio- Liver Physio And Pancrea In Digestion

Question 1

Describe the structure of the liver lobules.

Answer 1

1. Hexagon structure consisting of plates of hepatocytes and a central vein.
2. Contain a portal space consisting of portal vein, bile duct and hepatic artery (Portal tract)

Question 2

Describe the blood supply of the liver.

Answer 2

— hepatic artery - oxygenated blood
— portal vein - venous blood
— hepatic vein - deoxygenated blood

Question 3

State the functions of the liver.

Answer 3

Secretion of bile
Metabolism of carbohydrates and lipids.
Detoxication of food
Storage of blood
Synthesis of plasma protein and clotting factors

Question 4

Describe the composition of bile.

Answer 4

Water
Bile pigments
Bile salts
cholesterol
Lecithin
Ions

Question 5

Explain the role of bile in the digestion of fats.

Answer 5

1. Bile assist pancreatic lipase in the digestion of fats.
2. Bile salts make fats water soluble
3. Bile salts assist in the emulsification of fat.

Question 6

Explain how bile makes fat water soluble.

Answer 6

A) The hydrophobic region interacts with the lipid globule
B) The hydrophilic region interacts with the watery chyme, making fat now soluble to be digested by lipase.

Question 7

Explain the role of micelle in fat absorption.

Answer 7

Fatty acid and glycerols can not be absorbed into the intestinal lumen , therefore, the micelle acts as a shuttle, transporting them to the lumen and moving back and forth.

Question 8

State the functions of gallbladder

Answer 8

1. Storage of bile
2. Concentration of bile.

Question 9

Describe the regulation of bile secretion by the liver and its release into the duodenum.

Answer 9

1. Bile acids are absorbed from the duodenum into the blood.
2. CCK and secretin are secreted by the exocrine cells in the duodenum.
3. Stimulation of the vagus nerve also stimulates bile release.

Question 10

Describe the metabolism of bilirubin.

Answer 10

Bilirubin is converted into urobilinogen by the intestinal microflora. It is metabolized in three ways:

A) it is converted into urobilin then sterobilin and passed out into feces.
B) it can absorbed into portal circulation, leave liver and recycled into bile
C) it can be absorbed into systemic circulation, leave kidney and excreted as urine.

Question 11

List the types of jaundice.

Answer 11

Prehaptic
Haptic
Extrahaptic

Question 12

Describe Prehaptic jaundice.

Answer 12

1. Caused by excess hemolysis on red blood cells.
2. Heme metabolizes and form excess amounts of free bilirubin
3. Due to free bilirubin being insoluble to water, it is not passed in urine therefore urine color is not changed.

Question 13

Describe hepatic jaundice.

Answer 13

1. Caused by liver disease causing an injury to the hepatocytes.
2. Both free and conjugated bilirubin from the hepatocytes leak into blood plasma.

Question 14

Describe Extrahepatic jaundice.

Answer 14

1. Caused by the obstruction of the common bile duct by gallstones or tumor.
2. Bilirubin is conjugated by the hepatocytes but not passed into the duodenum.
3. The conjugated bilirubin is accumulated in the liver and passed into the bloodstream.
4. Due to CB being water soluble it is passed into the urine and changes its color.
5. Due to CB not being passed into the duodenum, feces is pale.

Question 15

Describe bicarbonate secretion in the pancreatic ducts.

Answer 15

Process is the same of HCL section in the GI.

Question 16

Compare and contrast the ionic composition of pancreatic juice and blood plasma at variable secretion rates.

Answer 16

— an increase in secretion rate, pancreatic juice contains more bicarbonate, less concentration of Cl- and is more alkaline. This is to due to the exchange of bicarbonate and Cl- ions.

— a decrease in secretion rate, pancreatic juice contains less biocarbonate, less Cl- and less alkaline.

Question 17

List the pancreatic digestive enzymes.

Answer 17

Trypsin
Chymotrypsin
Elastase
Carboxylpeptidase
Aminopeptidase

Question 18

State the difference between endopeptidases and exopeptidases.

Answer 18

Endopeptidases digest peptide bonds into two smaller peptide bonds

Exopeptidases digest peptide bonds into two amino acids and a peptide bond.

Question 19

State a carbohydrate digesting enzyme and its functions.

Answer 19

Amalyse.
Breaks down starch into disaccharides, trisaccharides, oligosaccharides.

Question 20

List the triglyceride digesting enzymes and its functions.

Answer 20

Lipase - converts to fatty acids + monoglycerids
Cholesterol ester hydrolase- converts to cholesterol + fatty acids
Phospholase A2 - converts to lysolecithin + fatty acids.

Question 21

State the three phases of pancreatic secretion.

Answer 21

The phases of gastric secretion.

Question 22

Explain the cephalic phase of the pancreatic secretion.

Answer 22

1. Thought of food, smell and sight stimulates the vagal nuclei in the brain and receptors in the mouth.
2. These receptors send a signal to the gland to secrete pancreatic enzymes.

Note: neural mechanism is important in this secretion.

Question 23

Explain the gastric phase of the pancreatic secretion.

Answer 23

1. The digestion of food and into the stomach stimulates a mechanical and chemical stimulation of gastric mucosa.
2. The neural mechanism is the stimulation of the vagus nerve in response to stretch of stomach
3. Hormonal stimulation is the stimulation of the g- cells to secrete gastrin which in response increase the release pancreatic enzymes (acinus).

Question 24

Explain the intestinal phase of the pancreatic secretion.

Answer 24

When the gastric content is propelled into the duodenum, a mechanical and chemical stimulation occurs.

1. The neural mechanism is the vagus stimulation due to the stretching of the duodenum.
2. The hormonal mechanism is the stimulation of the release of CCK and secretin.
3. Vagus stimulation and CCK increase secretion of pancreatic enzymes. Secretin increase bicarbonates.