Human Anatomy: The Urinary System

The Urinary System

• The outer layer of the bladder is composed of connective tissue, containing blood vessels, lymph vessels, and nerves, with the superior surface covered by parietal peritoneum.
• The bladder wall has three openings (orifices) that form a trigon.
• The upper two openings are the ureters, located on the posterior wall.
• The lower opening is the point of origin of the urethra.
• The internal urethral sphincter is a thick layer of involuntary smooth muscle fiber at the point of origin of the urethra.

Urethra

• The urethra is a tube lined with mucous membrane that extends from the neck of the urinary bladder to the exterior of the body.

Female Urethra

• The female urethra lies directly behind the symphysis pubis and anterior to the vagina.
• It extends downward and forward from the bladder for a distance of about 3-4cm and opens at the external urethral orifice just in front of the vagina.
• The external urethral orifice is guarded by the external urethral sphincter, which consists of voluntary striated muscle fiber.

Male Urethra

• The male urethra is about 19-20cm long.
• It passes through the prostate gland just after leaving the bladder.
• Within the prostate, it's joined by two ejaculatory ducts.
• The urethra extends down, forward, then up to enter the base of the penis, then travels through the center of the penis and ends as a urinary meatus at the tip of the penis.