Stale urine smells like ammonia because

The average $pH$ of human urine is

Choose the correct pair regarding urine formation.

Which of the following diagrams is correct with regard to the proximal $(P)$ and distal $(D)$ tubule of the Nephron?

Identify the true statements and choose the correct option accordingly.
$I.$ Blood vessel leading to the glomerulus is called efferent arteriole.
$II.$ Vasa-recta,peritubular capillaries and glomerulus,all have blood.
$III.$ Cortical nephrons have highly reduced vasa-recta.
$IV.$ Vasa-recta runs parallel to the Henle's loop in the juxta-medullary nephron.

Explain briefly,micturition and disorders of the excretory system.