Question

Which part of sperm enters an egg of a human?
A. Complete sperm
B. Only head
C. Head and middle piece
D. Tail

Answer 1

The sperm is a haploid cell that consists of the male gamete. The sperm cell produced by the testis has a head, neck, middle piece, and a tail portion. The head consists of the haploid nucleus and the acrosome which possesses several enzymes.

Complete answer: The sperm is the male reproductive cell, which possesses the haploid gamete which when fused with the ovum fertilized to form an embryo. The sperm is produced in the male reproductive organs of the organism and is always smaller when compared to the ovum. The sperm is a motile cell that has 4 regions., the head, the neck, the middle piece, and the tail. Each performing specific functions to aid in fertilization. The head of the sperm consists of the haploid nucleus and several small structures called the acrosome. The acrosome contains enzymes that enable the sperm to penetrate the ovum. When a sperm encounters an egg, openings develop in the sperm acrosome, exposing enzymes, that digest a path through the zona pellucida surrounding the secondary oocyte. As soon as one sperm enters the secondary oocyte, changes occur that prevent the entrance of other sperm. As the fertilizing sperm enters, it usually loses its flagellum. Sperm entry stimulates the secondary oocyte to complete its second meiotic division. The head of the haploid sperm then swells to form the male pronucleus and fuses with the female pronucleus to form the diploid nucleus of the zygote.
Therefore, the correct option is B.

Note: As the sperm penetrates the zona pellucida, the ovum releases abundant zinc ions, which can be visually seen under a microscope as a spark discharge. These zinc ions effectively prevent any other sperm from penetrating the ovum by warding off sperm cells or making them enzymes of the acrosome incapable of functioning effectively.