FUNCTIONAL ANATOMY OF URINARY BLADDER AND URETHRA

Micturition is a process by which urine is voided from the urinary bladder. It is a reflex process. However, in grown up children and adults, it can be controlled voluntarily to some extent. The functional anatomy and nerve supply of urinary bladder are essential for the process of micturition.

FUNCTIONAL ANATOMY OF URINARY BLADDER AND URETHRA

URINARY BLADDER

Urinary bladder is a triangular hollow organ located in lower abdomen. It consists of a body and neck. Wall of the bladder is formed by smooth muscle. It consists of three ill-defined layers of muscle fibers called detrusor muscle, viz. the inner longitudinal layer, middle circular layer and outer longitudinal layer. Inner surface of urinary bladder is lined by mucus membrane. In empty bladder, the mucosa falls into many folds called rugae. At the posterior surface of the bladder wall, there is a triangular area called trigone. At the upper angles of this trigone, two ureters enter the bladder. Lower part of the bladder is narrow and forms the neck. It opens into urethra via internal urethral sphincter.

URETHRA

Male urethra has both urinary function and reproductive function. It carries urine and semen. Female urethra has only urinary function and it carries only urine. So, male urethra is structurally different from female urethra.

Male Urethra

Male urethra is about 20 cm long. After origin from bladder it traverses the prostate gland, which lies below the bladder and then runs through the penis Throughout its length, the urethra has mucus glands

called glands of Littre.

Male urethra is divided into three parts:

1. Prostatic urethra

2. Membranous urethra

3. Spongy urethra.

1. Prostatic urethra

Prostatic urethra is 3 cm long and it runs through prostate gland. The prostatic fluid is emptied into this

part of urethra through prostatic sinuses. Sperms from vas deferens and the fluid from seminal vesicles are also emptied into prostatic urethra via ejaculatory ducts. Part of the urethra after taking origin from neck of bladder before entering the prostate gland is known as preprostatic urethra. Its length is about 0.5 to 1.5 cm. This part of urethra is considered as part of prostatic urethra.

2. Membranous urethra

Membranous urethra is about 1 to 2 cm long. It runs from base of the prostate gland through urogenital

diaphragm up to the bulb of urethra.

3. Spongy urethra

Spongy urethra is also known as cavernous urethra and its length is about 15 cm. Spongy urethra is surrounded by corpus spongiosum of penis. It is divided into a proximal bulbar urethra and a distal penil urethra. Penile urethra is narrow with a length of about 6 cm. It ends with external urethral meatus or orifice, which is located at the end of penis. The bilateral bulbourethral glands open into spongy

urethra. Bulbourethral glands are also called Cowper glands.

Female Urethra

Female urethra is narrower and shorter than male urethra. It is about 3.5 to 4 cm long. After origin from

bladder it traverses through urogenital diaphragm and runs along anterior wall of vagina. Then it terminates at external orifice of urethra, which is located between clitoris and vaginal opening.

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