GIT physiology

Question 1

Transit mechanisms

Answer 1

Saliva - starts digestions
1st - voluntary swallowing
2nd - peristalsis (autonomically triggered)
3rd - stomach via oesophageal sphincter

Question 2

Cells and secretions - G cells

Answer 2

Gastrin

Question 3

Cells and secretions - Parietal cells

Answer 3

Pepsinogen

Question 4

Cells and secretions - Chief cells

Answer 4

H+

Question 5

Cells and secretions - enterochromaffin

Answer 5

Histamine

Question 6

Gastric juice formation

Answer 6

Gastrin -> CCK2 receptors on Enterochromaffin cells
EC cells release histamine -> parietal cells (ACh also activates parietal cells)
Cabonic anhydrase generates h+ & HCO3-.
HCO3- leaves, Cl- in. Cl- out, taking K+ out. K+ in, H+ out via H+/K+ ATPase.

Question 7

Increases acid production problems

Answer 7

GORD
Gastric bleeding
Ulceration

Question 8

Mucosa function

Answer 8

Protect againstacid & gastric enzymes
Secretory cells in pits (prostaglandin stimulation)
Function reduction - GI disorders, imbalance between damaging and protective agents

Question 9

Emesis (vomiting definition)

Answer 9

Sudden evacuation of stomach
Preceded by loss of appetite, nausea, vasoconstriction, sweating, dizziness
Layrnx/pharynx contraction
Stomach relaxes, duodenum forceful contraction.

Question 10

Emesis cause

Answer 10

Chemoreceptor trigger zone detects signals, and vomiting control centre coordinates them.
CTZ - D2 receptors ( metoclopramide, granisteron)

Question 11

Pancreas function

Answer 11

Endocrine - insulin & glucagon into blood

Exocrine - Digestive enzymes, Lowers duodenum pH

Question 12

Small intestine function

Answer 12

Major absorption area

Question 13

Large intestine function

Answer 13

Storage of undigested food
Absorb water and electrolytes
Fibre - hydrate bulk, allowing greater propulsion