Describe the structure and function of …

The human excretory system comprises of the following structures: two bean-shaped kidneys, two ureters, one urinary bladder, and one urethra. 

Kidneys are the main organ of the human excretory system. The kidneys are paired organs and are located one on each side of the spine at the level of the liver. They are divided into three regions- the renal cortex which is the outer layer, the renal medulla which is the inner layer and the renal pelvis which is responsible for carrying the urine from the kidney to the ureter. The functional unit of a kidney is called the nephron.

There is one ureter that comes out of each kidney as an extension of the renal pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to the bladder.

The bladder receives urine from the ureters, one from each kidney. It is a sac-like structure that is lined with smooth muscle layer and is responsible for storage of urine till it is expelled from the body by micturition (urination).

The urethra is a tube that arises from the urinary bladder and expels urine by micturition. The urethra is shorter in females and longer in the males. In males, the urethra functions as a common path for sperms and urine. The opening of the urethra is guarded by a sphincter that is voluntary.