NEET PG Medical – 2015 – Question – 76
Trigone of urinary bladder develops from:
a) Mesoderm
b) Ectoderm
c) Endoderm of urachus
d) None of the above
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Correct Answer – A
- With differential growth of the dorsal bladder wall, the ureters come to open through the lateral angles of the bladder, and the mesonephric ducts open close together in what will be the urethra.
- That part of the dorsal bladder wall marked off by the openings of these four ducts forms the trigone of the bladder.
- Thus, lining of the bladder over the trigone is mesodermal in origin;
- The smooth muscle of the bladder wall is derived from the splanchnopleuric mesoderm.
- The apex of the bladder is continuous with the allantois, which now becomes obliterated and forms a fibrous core, the urachus.
- The urachus persists throughout life as a ligament that runs from the apex of the bladder to the umbilicus and is called the median umbilical ligament
o Linining epithelium of bladder mucosa is transitional epithelium.
When empty mucosa is thrown into rugae except in trigone, where mucosa is smooth and firmly adherent.
o just beneath the mucosa of trigone there is layer of smooth muscle, Trtgonal muscle of Bell which replaces the submucous coat in trigone area
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