L28 Active: Gastrointestinal Physiology

Question 1

Name the organ responsible for digestion and absorption

Answer 1

Small intestine

Question 2

Need to go back to encore

Question 3

How do the liver and gall bladder work together?

Answer 3

Liver secretes bile (containing bile salts to emulsify fat and aid enzymatic hydrolysis)

Gall bladder stores, concentrates and ejects (CCK hormone from SI, released when chyme enters the small intestine)

Question 4

Which of the two main plexuses of the GI tract is largely responsible for controlling the secretions from the enteric mucosa?

Answer 4

Submucosal plexus because of its location beneath the mucosal layer - where the secretion would take place

Question 5

What are the pacemaker cells of the GI tract called and where are they located?

Answer 5

Cells of Cajal (ICC) in the stomach, SI and LI

Question 6

Which tissue layer of the gastrointestinal walls are the ICC cells likely to be situated in to initiate slow wave action and control motility?

Answer 6

The myenteric plexus as this lies between the circular and longitudinal muscle layers

Question 7

What are the branches of the ANS involved in the control and regulation of the GI tract?

Answer 7

SNS, PNS, ENS

Question 8

Recall which cells are responsible for secreting which substances in the stomach (finish)

Answer 8

Protective: Epithelial - HCO3-, Mucous
Hydrolytic: Parietal cells - HCI, Chief cells - pepsinogen
Endocrine
Paracrime
Neuro/ enteroendocrine:

Question 9

Explain the mechanism of gastric acid secretion by parietal cells

Answer 9

H2CO3 dissociates into hydrogen ions and HCO3-.
H+ are secreted across the apical membrane via H+/K+ ATPase. Potassium is recycled into the lumen via potassium channels. Chloride ions follow via the apical chloride channel. Net secretion of HCL into the lumen and absorption of bicarbonate ions into the blood

Question 10

What component of the basolateral membrane is common to all the absorptive cells?

Answer 10

Sodium potassium ATPase is present in all of thme

Question 11

Explain how the Na+/K+ ATPase is utilised for the transport across the apical membrane in these cells?

Answer 11

Low IC sodium utilised as the driving force for sodium entry on apical membrane (sometimes coupled to other factors e.g. sugar or amino acids)

Question 12

The products of protein and carbohydrate hydrolysis use facilitated diffusion across the basolateral membrane of the enterocytes into the blood. Why can’t products of lipid hydrolysis simply diffuse into blood capillaries? What structure are they absorbed into?

Answer 12

Too large to enter through the walls of the fenestrated capillaries. Taken into lacteal of the lymphatic system within villus

Question 13

Recall the cell types of the islets of langerhans and their secretory products (finish)

Answer 13

Beta cells - insulin
Alpha cells - glucagon
Delta cells - somatostatin

Question 14

What is the most potent stimulator of insulin secretion?

Answer 14

High blood glucose concentration

Question 15

Lecture needs to go back to. She’s not finished it