Nephron The basic functional unit of the kidney is the nephron. Each kidney contains approximately one million nephrons. Kidney function can be understood in relation to the structure of the nephron. The portion of the filtrate that is needed by the body is returned to the circulatory system and the material that is not required and may be potentially harmful is retained in the urine. The blood supply to the nephron is unique .
Vessels supplying the nephron are afferent arterioles.
The afferent arteriole brakes up into a tuft of capillary loops called the glomerulus. The remaining blood is conducted away from the nephron by the efferent arterioles. Instead of a venule, there is another arteriole that collects the blood from the capillary. This second arteriole makes it possible to exert a greater level of control over the glomarular blood pressure . Due to this second arteriole system there is a second set of capillaries.