Urinary Bladder Trigone Anatomy

 Write a short note on the Trigone of the Urinary Bladder.
Answer:

Trigone of the Urinary Bladder:

• It is a smooth triangular area of the internal urinary bladder just above the internal urethral orifice.
• It is formed by lines joining two ureteric orifices and an internal urethral orifice.
• It is bounded above by an intraurethral crest and on either side by a ureters-urethral ridge.

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Urinary bladder Features:

• It develops from mesoderm
• The mucous membrane in this region is smooth
• Presents a small elevation (uvula vesicae) above the internal urethral orifice
• It is very sensitive to expansion and once stretched to a certain degree one feels like urinating

Enumerate the Histological Features of the Urinary Bladder.
Answer:

In a histological section, the wall of the bladder presents 3 coats; From inward to outside, these are:

1. Mucosa
2. Muscular coat, and
3. Adventitia

1. Mucosa:
   • Lined by transitional epithelium (6–8 cells) thick.
   • Lamina propria is made up of loose connective tissue containing blood vessels, lymphatics, and nerves.
2. Muscular coat:
   • It is thick and made up of 3 ill-defined layers of smooth muscle fibers, viz.
   • Inner longitudinal
   • Middle circular and
   • Outer longitudinal.
3. Serosa/adventitia: It is a well-defined layer of mesothelium or fibro-elastic tissue.

Write a brief note on the development of the urinary bladder and enumerate common congenital anomalies associated with it.
Answer:

Urinary Bladder Development:

The urinary bladder develops in the 4–7 weeks of IUL, from the upper part of the vesicourethral canal. The small part near the apex is derived from allantois.

Points to note:

• The epithelium of the whole of the bladder is endodermal in origin (derived from the vesicourethral canal) except that of trigone, which is mesodermal in origin (derived from absorbed mesonephric ducts).
• The muscle coat (detrusor muscle) of the bladder develops from splanchnopleuric mesoderm.

Congenital anomalies:

• Ectopia vesicae: In this condition, the lower part of the anterior abdominal wall and anterior wall of bladder is absent, and posterior wall of bladder is exposed to the exterior.
• Urachal sinus, urachal fistula, and urachal cyst: The urachus may remain patent only in the upper part (urachal sinus) or along the entire extent (urachal fistula) or only a small part in the middle (urachal cyst).