Small Intestine And Digestion

Question 1

Bicarbonate necessary for:

Answer 1

Neutralising acid->
Digestive enzymes, micelle formation, protecting duodenal mucosa
Dependent in Cl- exchange

Question 2

Control of the pancreas

Answer 2

Vagus nerve-> conditioned stimuli or food in stomach
Secretin->released in response to acid in the duodenum->stimulates HCO3- production
Cholecystokinin-> released in response to fat and protein presence in duodenum-> stimulates enzyme rich secretion.
Inhibited by somatostatin

Question 3

Carbohydrate digestion

Answer 3

Begins in mouth-> amylase
Small intestine-> pancreatic amylase->1,4 glycosidic linkages.
Brush border-> di and tri peptides
Absorbed with sodium.

Question 4

Protein digestion

Answer 4

Begins in stomach-> pepsin->stopped by alkaline pancreatic secretion
Endopeptides-> cleave interior peptide bonds
Exopeptides-> cleave exterior peptide bonds
Tripsin-> converts precursors to enzymes
Brush border->oligopeptidase->oligopeptides to amino acids for absorption. Aminopeptidases-> oligopeptides to di and tri peptides

Question 5

Fat digestion

Answer 5

Pancreatic lipase.
Bile salts emulsify fats, negative tails repel each other.
Now water soluble so can be digested by pancreatic lipase-> monoglycerides and free fatty acids.
Absorbed by using bile salts to form a micelle
Resynthesised to form triglycerides-> combine with protein, phospholipids, cholesterol-> chylomicron
Transported in lymphatics

Question 6

Pancreatic exocrine cells

Answer 6

Acinar->enzymes
Centroacinar->HCO3-
Duct cells->HOC3-/Cl- exchanger.