The first successful human organ transplant was a

kidney transplant performed in 1953. Because the
donor and recipient were identical twins, rejection was
not a problem. Thousands of kidney transplants have
been performed since then, and the development of
immunosuppressive medications has permitted many
people to live normal lives with donated kidneys.
Although a person usually has two kidneys, one kidney

is sufficient to carry out the complex work required to

maintain homeostasis of the body fluids.

The urinary systemconsists of two kidneys, two

ureters, the urinary bladder, and the urethra (Fig.

18–1). The formation of urine is the function of the

kidneys, and the rest of the system is responsible for

eliminating the urine.

Body cells produce waste products such as urea,

420 The Urinary System

Diaphragm

Right kidney

Psoas major muscle

lliacus muscle

Right ureter

Urinary bladder

Urethra

Symphysis pubis

Trigone of bladder

Opening of ureter

Sacrum

Pelvis

Lumbar vertebra

Left common iliac

artery and vein

Left ureter

Left kidney

Left renal artery and vein

Superior mesenteric artery

Left adrenal gland

Inferior vena cava

Aorta

Ribs

Figure 18–1. The urinary system shown in anterior view.

QUESTION:Why is blood pressure relatively high in the kidneys? What do you see that

would suggest this?