Draw a diagram of a mature human sperm. Label any three parts and write their functions.

STRUCTURE OF A MATURE SPERM

A mature sperm cell is made up of a head, a neck, a middle piece and a tail. It is covered by a plasma membrane. The head region consists of an elongated nucleus and little cytoplasm.

Acrosome – a cap-like structure present over the nucleus contains hydrolytic enzymes (called sperm lysins) which are capable of dissolving the membranes covering the ovum. These enzymes help the sperm cell to enter and fertilize the ovum. The acrosome is derived from Golgi apparatus. Sperm lysins include:

•Hyaluronidase – dissolve hyaluronic acid

•zona lysin – dissolves zona pellucida

•corona penetrating enzyme – dissolves corona radiata

Neck – the short neck contains 2 distinct granules having a significant role. The proximal centriole is required for the first cleavage division of zygote formed after fertilisation. The distal centriole gives rise to the axial filament of the tail and helps to maintain it.

Mitochondria – the middle piece of the sperm contains numerous mitochondria, which are spirally arranged around the axial filament. As it is known as the powerhouse of the cell, it produces energy and facilitates the sperm motility. The energy produced helps the sperm to swim and reach the site of fertilization.