Digestion

Question 0

Chief cells

Answer 0

In stomach, secrete pepsinogen which is converted to pepsin by HCl which breaks down proteins into peptides
Secrete gastric lipase which splits triglycerides into fatty acids and monoglycerides

Question 1

Parietal cells

Answer 1

In stomach - secrete HCl which kills microbes in food, denatures proteins and converts pepsinogen into the proteolytic enzyme pepsin
Secrete intrinsic factor which is needed for absorption of vit B12 in the terminal ileum which is used for RBC formation

Question 2

G cells

Answer 2

In stomach, secrete gastrin which stimulates parietal cells to secrete HCl and chief cells to secrete pepsinogen, contracts lower oesophageal sphincter, increases stomach motility and relaxes pyloric sphincter

Question 3

Pancreas

Answer 3

Secretes NaHCO3 which gives pancreatic juice an alkaline pH, this buffers the acidic gastric juice, stops the action of pepsin and creates proper hp for action of digestive enzymes in small intestine
Secretes digestive enzymes like pancreatic lipase that digests triglycerides

Question 4

Liver

Answer 4

Produces bile that emulsifies fats so pancreatic lipase can more rapidly digest them, also aids in absorption of lipids following digestion

Question 5

Gall bladder

Answer 5

Stores and concentrates bile, and releases it into the small intestine

Question 6

Small intestine

Answer 6

Secretes intestinal juice that combines with pancreatic juice to create a liquid medium that aids absorption
Absorptive cells synthesise brush border enzymes that break down disaccharides into monosaccharides that can be absorbed

Question 7

Large intestine

Answer 7

Haustral churning, peristalsis and mass peristalsis drive contents of colon into rectum
Bacteria convert protein to amino acids, and produce some B vitamins and vitamin K
Absorbs water, ions and vitamins

Question 8

How are carbohydrates digested?

Answer 8

Amylase hydrolysis polysaccharides to disaccharides in the mouth
Pancreatic amylase completes this to monosaccharides in small intestine
Monosaccharides absorbed into epithelial cells of small intestine via facilitated diffusion by Na and energy dependent secondary active transport, exit cell at basal membrane by passive facilitated diffusion and enter blood by simple diffusion

Question 9

How are proteins digested?

Answer 9

Chief cells of stomach secrete pepsin which hydrolyses protein to peptide fragments in the stomach
Pancreas secretes trypsin, chymotrypsin, carboxypeptides, which further break these fragments down in the duodenum
Many small peptides are converted into amino acids by the aminopeptidases in the brush borders of the small intestine
Amino acids are absorbed into epithelial cells by Na and energy element secondary active transport via a symporter
Then broken down by intracellular peptidases and absorbed into blood

Question 10

How are fats digested?

Answer 10

Pancreatic lipase is secreted into the small intestine where it hydrolyses triglycerides to fatty acids and monoglycerides
The liver produces bile salts which are stored in the gall bladder and released into the small intestine via the cystic duct and common bike duct which emulsify the fats
Carried to epithelial cells within water soluble micelles and diffuse through lipid bilayer of luminal membrane
Resynthesized into triglycerides inside epithelial ells which aggregate and are coated in lipoprotein from the ER to form chylomicons
These leave the basal membrane via exocytosis and enter the lymphatic vessels via lacteals