What is the common duct shared by the reproductive and excretory systems in the human male?

What is the $Tunica \text{ } albuginea$ a covering of?

The seminal plasma in humans is rich in which of the following?

From the seminiferous tubules, the spermatozoa pass into:

$A$: The scrotum acts as a temperature regulator for the testes.
$R$: The wall of the scrotum is supported by dartos muscles,which help in the positioning of the testes.

What are the location and secretion of the $Leydig$ cells,respectively?