QS Study

Histological Structure and development of Urinary Bladder

The urinary bladder is a muscular reservoir of urine which lies in the anterior part of the pelvic cavity. Its primary function is as a reservoir for urine. It is an organ that serves to accumulate urine to be voided through urination after the urine is filtered through the kidneys.

Histologically, the urinary bladder is lined with transitional epithelium and does not produce mucus.

Histological structure

The wall of urinary bladder presents from outside inwards – Serous, muscular, submucous and mucous coats.

Serous coat: It is derived from the peritoneum and is incomplete. It covers the superior surface and in male upper part of the base of the bladder. It is an outermost protective covering layer made up of dense irregular connective tissue.

Muscular coat: It is called the detrusor muscle. It has 3 layers – Outer longitudinal, middle circular and inner longitudinal. The outer layer is continuous with that of the prostate. Around the internal urethral orifice, it forms the sphincter vesicae. Few muscle fibers around the internal ureteric orifice form an internal urethral sphincter which controls the outflow of urine from the bladder.

Submucous coat: It consists of loose areolar tissue and is present all over the bladder except the trigone where mucosa is adherent to the underlying muscle.

Muscosa: It is lined by transitional epithelium which is devoid of muscularity mucosa and mucous glands. The mucosa is heavily folded – this helps to accommodate for large volume changes. The mucous membrane is rich in alkaline phosphatase.

Fig: Histological Structure of Urinary Bladder

Development

(A) The mucous membrane is developed from the following sources:

  1. Trigone is derived from mesoderm by the incorporation of the caudal part of the two mesonephric ducts.
  2. The rest of the mucous membrane is developed from the endoderm of the vesicourethral part of the cloaca.

(B) Musculature and other structures are derived from the splanchnic layer of the lateral plate mesoderm which surrounds the cloaca.

(C) The mucous membrane of trigonum vesicae is originated from the mesoderm of the comprised lower ends of the mesonephric ducts.

(D) Mucous membrane in the remaining part of the bladder is originated from the endoderm of the vesicourethral part of the cloaca.