Week 21

• What are the functions of the gut?

  • Motility (of substances through tract)
  • Absorption
  • Storage
  • Digestion
  • Secretion
• How is the enteric nervous system arranged?

  • Nerves around submucosa
  • Parasympathetic
  • Regulates fluid & hormonal release from gut tubes into lumen of gut
  • Myenteric plexus regulates motility and muscle action through gut
  • Both plexus receive input from luminal receptors, hormones and autonomic nervous system
• What does a gut endocrine cell look like?

  Columnar epithelium

  Pyramidal appearance ( wide secretory base & narrow sensory apex exposed to gut lumen)

  Microvilli

  Many ER & secretory granules to release hormones

  
• What other hormones are linked to satiety ?

  CCK, Peptide YY & glucagon-like peptide 1

  CCK lowers gastric emptying to give a sensation of fullness
• How is glucagon-like peptide 1 (GLP-1) used as a weight-loss aid?

  Secreted from gut cells & neurones

  Released following ingestion

  Promotes insulin secretion

  Inhibits gastric emptying, acid secretion & motility

  Stimulates satiety
• What is a gastric bypass?

  • Cut top of stomach & small intestine & bind together to bypass duodenum
  • Less absorption due to shorter distance
  • Invasive & irreversible
  • Restrictive/malabsorptive
• What is orlistat?

  Inhibits pancreatic & gastric lipases so fat is not absorbed
• What is semaglutide?

  Diabetes medication

  Binds to & activates GLP-1 receptor

  Makes you feel full
• What is bariatric surgery?

  Long-term 'cure'

  Restrictive (reduced stomach size & dietary intake) e.g, gastric band (minimally invasive & adjustable)- certain part of stomach stretches to make you feel full

  Malabsorptive (bypassing stomach & small intestine so can't absorb fat anymore)
• What does the endocrine pancreas do?

  Regulate sugar uptake/release

  Islets of Langerhans:

  • Alpha cells- secrete glucagon
  • Beta cells- secrete insulin
  • D cells- Secrete somatostatin

  (cells are most abundant in pancreas tail)
• When is glucagon secreted?

  Low blood sugar

  Breaks down glycogen -> glucose in liver
• When is insulin secreted?

  Blood glucose high

  Storage of glucose in liver skeletal muscle & fat cells triggered
• When is somatostatin secreted?

  Low pH

  Supresses release of hormones from alpha & beta cells

  inhibits gut motility & exocrine secretion
• What is an overweight BMI?

  Over 25

  Obesity= 30