Gastric motility and pancreatic function

Question 1

What are pacemaker cells in the enteric nervous system?

Answer 1

• ~3/min

- Longitudinal muscle

Question 2

What are slow waves in the enteric nervous system?

Answer 2

• Not enough to cause AP
  
  • More AP the stronger
  • Spontaneous polarisation/ depolarisation
  • Gap junctions in longitudinal muscle
  • Rhythm= BER (Basic electrical rhythm)

Question 3

Describe innervation/ inhibition in the enteric nervous sytem

Answer 3

• Gastrin: increases contraction
  
  • Stomach detentions causes fast/ slow reflexes which increases contraction
  • Fat/ amino acid/ hypertoxicity in the duodenum causes inhibition

Question 4

Explain the mechanisms involved in the neutralisation of gastric acid in the duodenum

Answer 4

• Bicarbonate
- Released by Brunner’s gland duct cells (submucosal)
• Innervation/ inhibition
- Secretin released by S cells (also pancreas and liver) causes innervation
- Long (vagal) and short (ENS) reflexes
- Neutralisation of acid inhibits

Question 5

Explain the role of gastric motility in digestion and describe the mechanisms controlling gastric emptying

Answer 5

• Stomach body
	- No mixing
	- Moving down
	• Stomach antrum 
	- Mixing
	- Some chyme proceeds through pyloric sphincter and the rest goes back up before falling back to antrum
	• Peristalsis

Question 6

What are the pancreatic enzymes?

Answer 6

• Pancreatic enzymes

- α-amylase: starch to maltose to glucose
- Phospholipase: phospholipids to fatty acids 
- Lipase: Triglycerols to glycerol and fatty acids (cleaves peptide bonds)
- Proteases: Proteins to amino acids
- Nucleases: hydrolyses DNA/RNA
    - collagen digestion

Question 7

What is the exocrine function of the pancreas?

Answer 7

• Secretion of bicarbonates by duct cell

- Secretion of digestive enzymes by acinar cell

Question 8

What is the endocrine function of the pancreas?

Answer 8

• Glucagon and insulin production (islets of Langerhans)

- Somatostatin secretion: controls insulin and glucagon secretion

Question 9

Describe the actions of secretin and cholecystokinin (CCK) on pancreatic and bile secretion and the stimuli that will cause their release

Answer 9

• Secretin (secreted from S cells)
- Bicarbonate secretion
- Released in response to acid in duodenum
- Inhibited by acid neutralisation
• Cholecystokinin (CCK)
- Increases bile production
- Released in response to fat/ amino acids in the duodenum

Question 10

Describe the control of pancreatic enzyme secretion and the role of zymogens

Answer 10

• Zymogens
- Stops pancreatic autodigestion
- Trypsinogen is converted to trypsin by enterokinase
- Trypsin activates all other zymogens
• Control over pancreatic enzyme secretion
Zymogen secretion stimulated by CCK

Question 11

Describe the anatomy and histology of the pancreas

Answer 11

• Head: at duodenum
  
  • Body
  • Tail: towards spleen

Question 12

Describe the structure of the endocrine pancreas (inside)

Answer 12

Acinar made up of lobules-> intercalated duct-> intralobular duct-> interlobular duct -> main pancreatic bile duct-> Common bile duct-> Oddie’s sphincter-> duodenum