Spermatozoa (Sperm)

Spermatozoa (sperm) are the mature male reproductive cells responsible for fertilizing the female egg (ovum) during sexual reproduction.

The head of the spermatozoon has a species-specific shape. The nucleus is oval and flattened, surrounded by a nuclear membrane.

The chromatin is compact. The anterior two-thirds of the nucleus is covered by the acrosome, a membrane-bound lysosome that contains hydrolytic enzymes such as acrosin, hyaluronidase, zonalysin, esterases, and acid hydrolases, which are essential for penetrating the cellular investments and the zona pellucida.

The tail composed of capitulum, middle piece, the principal piece and the terminal piece.

The capitulum fits into the implantation socket, a depression in the posterior nucleus.

Anterior portion of the tail consists of laminated columns-gives neck region flexibility.

Axonemal components of tail originate from the distal centriole consists of 9 pairs of microtubules arranged radically around 2 central filaments. Surrounding this 9+2+2 arrangement are 9 dense fibres that are unique to the flagellum of spermatozoa.

The mitochondrial sheath is arranged in a helical pattern around the outer dense fibre of the tail and contributes to the middle piece.

The middle piece terminates at the annulus, which marks the junction between the middle piece and the principal piece. The principal piece forms the majority of the tail and continues distally to connect with the terminal piece.

Biometry of Spermatozoa in Different Species

Biometry of spermatozoa in different species refers to the measurement and comparison of sperm size and structure across various animals.