The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
(a) Label parts 1, 2, 3 and 4.
(b) State the reason for the high hydrostatic pressure in the glomerulus.
(c) Name the blood vessel which contains the least amount of urea in this diagrams.
(d) Name the two main stages of urine formation.
(e) Name the part of the nephron which lies in the renal medulla.