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

LARGE INTESTINE

• The large intestine is very short and ends at the cloaca.
• This section includes paired caeca, colon and rectum and the rectum being the terminal part.
• The bursa of fabricius is located immediately above the cloaca of young birds, but disappears when the birds have reached approximately one year old.

Caeca

• Paired caeca or blind pouches are about 16-18 centimeters long in the adult.

Structure of the caeca

• Outer serous membrane
• Outer longitudinal muscle
• Circular muscle
• Inner longitudinal muscle forming the muscularis mucosae of the mucous membrane

Cecal function

• Microbial digestion of cellulose.
• Reflux of urine into the ceca exposes the cecal microflora to urea and uric acid, which are then degraded; the nitrogen is not recycled for use by the host.
• Microbial synthesis of B compex vitamins 

Cloaca

• It is a tubular cavity opening to the exterior of the body provides a common passage to the digestive and urogenital tracts.
• It divides into three chambers as follows:
• The copradaeum - a continuation of the colon-rectum
• The urodaeum - middle part into which the ureters and genital ducts open
• The proctodaeum - opens to the exterior of the vent. Birds less than one year old have a dorsal opening leading into the blind, rounded sac - the bursa of fabricius.