VPB 121: Veterinary Physiology - II (2+1)

CHOLESTEROL

They belong to the group of steroid present in animal fat. About 10% of the bile is the cholesterol, secreted by hepatic cells. There are two principle sources of  cholesterol in the bile.

• Synthesised by the hepatic cells
• By absorption from the intestine through portal circulation to the liver 

Gall stones and their formation

• Two  kinds of gall stones are  formed
  • Cholesterol and bile pigments
  • Cholesterol,bile pigments and CaCO₃ with other fatty substances.
• The cholesterol is  insoluble in the water. Bile salts, fatty acids and lecithine present in the bile provide hydrophobic property to cholesterol and keep it as solution in bile . When the bile becomes concentrated, these hydrophobic substances also get concentrated. 
• Under abnormal conditions, cholesterol may be precipitated which results in the formation of gall stones in the bladder. 
• The following are the conditions that cause cholesterol precipitation:
  • Excessive absorption of water from the bile
  • Excessive absorption of hydrophobic  substances
  • Excess secretion  of  cholesterol in bile
  • Inflammation of the gall bladder  epithelium.
• Inflammation of gall bladder epithelium alters the absorption of  water, bile salts or other hydrophobic substances through gall bladder mucosa.
• Excessive absorption of water, bile salts or other hydrophobic substances, leads to  precipitation of cholesterol .
• Many  small cholesterol crystals act as a nidi or nucleus which favours further deposition of cholesterol crystals leads to occurrence of multiple  gall stones.