Which of the following structure is lacking from the placenta
Arteries
Veins
Smooth muscles
Nerves
$A$ : The secretions of male accessory glands constitute the seminal plasma which is rich in fructose, calcium and certain enzymes.
$R$ : Fructose serves as a source of energy for the sperms.
The hormones of the sperm are called
The primordial germ cells make their appearance from wall of
In mammals, corpus luteum is found in which organ?
Archenteron is lined with