Session 8 imaging and control of GI system

• Volvulus - Torsion of the bowel • Occurs commonly in sigmoid colon of constipated elderly patient
• Caecal Volvulus - Points towards LUQ

  
• Sigmoid Volvulus

  • Starts in the LIF
  • Coffee bean sign
  • Points towards the RUQ
  • Obstruction

  
• Colonic dilatation without obstruction in toxic megacolon.
• Rigler’s Sign - Presence of free air can result in both sides of the bowel wall becoming visible.

  
• Long Reflexes - Integrated within in the CNS and ANS
• Short Reflexes - Mediated by the enteric nervous system.
• entrance of chyme into duodenum gets the enteric nervous system going, secreting:

  • Secretin– slows gastric emptying & gastric acid production– Stimulates bicarbonate (HCO 3 ) production from pancreas to buffer acidic chyme
  • cholecystokinin (CCK) - Secreted in response to lipids and slows gastric motility and gastric acid secretion– Acts hormonally on the hypothalamus
  • Incretin hormones
  • GIP (gastric inhibitory peptide)
  • GLP-1 (glucagon-like peptide1)
  • Slow gastric acid and emptying
  • stimulate insulin release from pancreas
• Ghrelin hormone secreted by the stomach wall increases appetite.
• Leptin (produced by adipose tissue) and PYY (produced by small intestine) suppresses appetite.