Parts of the Renal System

The Kidneys

Your kidneys are located on either side of your spinal cord in your lower back, slightly above your waistline. Kidneys are bean-shaped and about 4 to 5 inches long and 2 to 3 inches wide. 


Units of the kidney are called nephrons, which are the filtration units of the renal system. Each kidney has an immense filtering capacity with its 800,000 to 1,000,000 nephrons. The blood enters the filtering part of the nephron, called the glomerulus. The glomerulus filters blood, allowing fluid and small particles, such as electrolytes, to enter the tubule part of the nephron.

Your kidneys’ tubules are divided into sections known as the proximal tubule, the loop of Henle, the distal tubule, and the collecting duct. Proximal means “nearest” and distal means “away from,” indicating the position of the tubules relative to the glomerulus. These tubules adjust the filtrate’s water and electrolyte concentrations before it flows into your ureters.


There are two ureters, one originating from each kidney. They are long, thin tubes about 10 inches long, and they transport the urine from the combined nephrons to the urinary bladder.

Urinary bladder

The urinary bladder is essentially a bag that inflates to store urine before it is removed from your body when you go to the bathroom.


Urine is carried from the urinary bladder and out of your body through a tube called the urethra. In women, the urethra opens just above the vagina. In men, the urethra runs the length of the penis.