THE NEPHRON

Each kidney contains approximately 1 million nephrons, one of which is shown diagrammatically. Each nephron consists of a spherical filtering component, called the renal corpuscle, and a tubule extending from the renal corpuscle. Let us begin with the renal corpuscle, which is responsible for the initial step in urine formation: the separation of a protein-free filtrate from plasma.

Relationships of component parts of a long-looped nephron, which has been “uncoiled” for clarity (relative lengths of the different segments are not drawn to scale). The combination of glomerulus and Bowman’s capsule is the renal corpuscle.