Session 6

Question 1

What are some of the properties of chyme from the stomach?

Answer 1

Acidic
Hypertonic
Partially digested

Question 2

What are the properties of chyme when it leaves the duodenum?

Answer 2

Neutral

Isotonic

Question 3

How is the acidity of Chyme corrected?

Answer 3

HCO3- is secreted from the pancreas, liver and duodenal mucosa

Question 4

How is the hypertonicity of Chyme corrected?

Answer 4

Osmotic movement of water across the duodenal wall

Question 5

What completes digestion of Chyme?

Answer 5

Enzymes from the Pancreas, Liver and duodenal mucosa

Question 6

What does the exocrine glands of the Pancreas secrete?

Answer 6

Alkaline juices

Enzymes (Proteases - trypsin, elastase, Amylases, Lipases)

Question 7

What are the 2 types of cells in the exocrine Pancreas?

Answer 7

Acinar cells - Specialised cells that secrete enzymes

Duct cells - Secrete alkaline juices

Question 8

Why are enzymes made in the Acinar cells packaged?

Answer 8

Packaged into condensing vacuoles by the Golgi body so they can cross the cell membrane. They form Zymogen granules that are secreted by exocytosis

Question 9

What may be a sign of damage to the Pancreas?

Answer 9

Pancreatic enzymes in the blood eg Amylase

Question 10

What stimulates Acinar secretion?

Answer 10

Cholecystokinin (Which has a similar structure to Gastrin so same receptors can also be stimulated slightly by Gastrin)

Question 11

How does the Vagus nerve stimulate the Pancreas?

Answer 11

Releases Ach which causes enzymes to activate before chyme reaches the Duodenum

Question 12

What stimulates release of HCO3-?

Answer 12

Secretin released from jejunal cells in response to low pH (Not usually a low pH so not much stimulus)

Question 13

What facilitates the action of Secretin?

Answer 13

Cholecystokinin

Question 14

What are some of the functions of the Liver?

Answer 14

Energy metabolism
Detoxification
Bile production (Bile acids, alkaline juices and bile pigments)
Synthesises plasma proteins

Question 15

What is flow of blood in the Liver?

Answer 15

Blood from the Hepatic portal vein (from gut) enters sinusoid lined hepatocytes and drains into the central vein

Question 16

What is the flow of bile in the Liver?

Answer 16

Secreted into canaliculi lined with hepatocytes and flows in the opposite direction (towards the gut) into branches of the bile duct

Question 17

What are the 2 components of bile?

Answer 17

Bile acid dependent

Bile acid independent

Question 18

Where is the bile acid dependent component of bile secreted from? (And what does it contain)

Answer 18

Secreted into canaliculi by hepatocytes

Contains bile acids (Allows fat absorption) and pigments

Question 19

Where is the bile acid independent component of bile secreted from? (And what does it contain)

Answer 19

Secreted by duct cells.
Alkaline juices (like that from pancreatic duct cells)

Question 20

How are bile acids made soluble?

Answer 20

Conjugated to Amino acids so can travel in bile as micelles (Need bile acids, phospholipids and cholesterol to make a stable core)

Question 21

What are bile acids needed for?

Answer 21

Fat digestion and absorption

Question 22

How is lipid digestion complicated?

Answer 22

The hydrophobic nature of fats causes them to form large globules as stomach acid breaks down the natural emulsions
There is a low surface area for enzymes to act

Question 23

How do bile acids aid fat digestion?

Answer 23

Emulsify fats into smaller globules

Increased surface area for lipases to cleave fatty acids & glycerol

Question 24

What happens when the micelles reach the cell?

Answer 24

The core enters into the cell where it is recombined into fats again using Glycerol. (Put into chylomicrons by epithelial cells to be exported to lymphatics)

Question 25

What happens to bile acids after the fatty acids are absorbed?

Answer 25

They are released into the lumen of the GI tract where they continue to the terminal ileum. Here specialised epithelium place them back into the blood to go back to the liver (Hepatic portal vein). Here the hepatic sinudsoids actively take up the bile acids and re secrete them into the canaliculi

Question 26

Bile acids are secreted before the next meal, where are they stored?

Answer 26

In the Gall bladder

Question 27

How are Gall stones formed?

Answer 27

Volume stored is reduced by concentration (Osmolarity doesn't decrease, slowly increases) Transport of salt and water across the gall bladder epithelium Concentration process increases the risk of precipitation Usually fine unless they move or are too big to let bile pass

Question 28

What causes Cholecystokinin to be secreted by the Duodenum?

Answer 28

A response to gastric emptying

Question 29

What does secretion of Cholecystokinin from the Duodenum cause?

Answer 29

Contraction of the Gall bladder to eject concentrated bile acids and Pancreatic enzymes Alkali release from the Pancreas and liver

Question 30

What is Steatorrhoea?

Answer 30

Fat in faeces Occurs if bile acids/pancreatic enzymes are not secreted in adequate amounts. Faeces will be pale, floating and foul smelling

Question 31

What is pre hepatic jaundice?

Answer 31

When the liver cannot excrete bilirubin quick enough

Question 32

What is hepatic jaundice?

Answer 32

There is damage to the hepatocytes so they cannot conjugate the bilirubin for excretion