1.  What are the characteristics of kidneys?

1.1 Kidney composition

The kidneys are bean-shaped and about 10 cm x 5 cm in size.

A kidney is made up of richly vascularized filtration units, the nephrons, which are composed of a renal capsule (blood glomerulus enveloped in Bowman's capsule). This is extended by a long, contoured tube, comprising four portions with different functions:

• proximal tube;

• the U-shaped loop of Henlé ;

• distal tube;

• Bellini's collecting tube, which evacuates urine.

An adult human kidney contains around 1 million nephrons.