Male anatomy

The bladder

The bladder is a muscular bag that stores urine. Urine is made by the kidneys, travels down two thin tubes called ureters, and collects in the bladder. When the bladder is full, the muscle of the bladder contracts to push the urine out.

The prostate

The prostate is a small organ, about the size of a walnut, sitting just under the bladder. The tube that carries urine out of the body (the urethra) runs straight through the middle of the prostate.

This is why the prostate matters so much in urology:

• If the prostate enlarges with age (this is called BPH, or benign prostatic hyperplasia), it can press on the urethra and slow down the urine flow.
• If cancer develops in the prostate, treatment has to take into account that the urethra and the bladder neck are very close.

The prostate also produces some of the fluid in semen.

The seminal vesicles

The seminal vesicles are two small pouches behind the prostate. They produce most of the fluid in semen. They join the prostate from above and drain through the prostate.

The testicles and the vas deferens

The testicles sit in the scrotum and have two main jobs:

• Producing sperm.
• Producing testosterone, the main male hormone.

Sperm travel up from each testicle through a thin tube called the vas deferens, which goes up into the body and joins the back of the prostate. There the sperm mix with the fluid from the prostate and the seminal vesicles to form semen, which then travels out through the urethra during ejaculation.

Why this anatomy matters in surgery

The prostate sits in a deep, hard-to-reach part of the pelvis. Several important structures sit very close to it:

• The bladder sits on top of the prostate.
• The urethra runs through it.
• The nerves for erections lie on either side of the prostate.
• The rectum sits just behind it.

This is why operations on the prostate (for cancer or for an enlarged prostate) need to be very precise. Robotic surgery and laser surgery have both been developed in part to help reach this deep area more safely.