Question

Explain the structure of sperm.

Answer 1

Hint: As we know that Testes are the primary sex organs in male reproductive system which are located in an extra abdominal pouch of skin called scrotum. Testis possess several testicular lobules and each lobule has one to three seminiferous tubules that are the site major site of sperm production. Morphologically, sperm cells look like a tadpole larva.

Complete answer:
• We know that sperm is male gamete which is divisible into four parts which are head, neck, middle piece and the tail.
• Head possesses a nucleus with a haploid set of chromosomes and it is covered by a cap-like structure known as Acrosome. This Acrosome has enzymes called Sperm Lysins which dissolves the overlying layer of female gamete and helps in fertilisation of female gamete.
• Then comes the neck which has a pair of centrioles, proximally it helps in cleavage division and distally it gives off axial filaments.
• Next we have the middle piece which contains numerous spiral mitochondria/ Nebenkern which serves as an energy source for motility of sperm for the purpose of fertilisation. At the other end of the middle, ring centrioles/Annulus of unknown function is present.
• Lastly the tail part which is responsible for the wriggling movement of sperm.

Additional information:
Sperms are decapitated in Epididymis and reach the female gamete where it encounters three covering layers. The Acrosomal cap of sperm bursts and releases Sperm Lysin enzymes. The Hyaluronidase digest the ground substance layer of the female gamete and the corona penetrating enzyme digest the corona radiata layer. Acrosin enzymes digest the zona pellucida layer and a cone of reception is formed for the entry of sperm to fertilise the female gamete.

Note: Remember that $200 - 300$ millions sperms are released per ejaculation and for normal fertility approximately $60\% $of sperms should have normal shape and size while $40\% $ of sperms should have vigorous motility.