Sperm: Structure ||Class 12 Biology

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     A mature spermatozoa or a sperm cell is a microscopic, tadpole-shaped structure of about 2-5 micrometer in diameter and 50 micrometer long. A plasma membrane encloses the whole body of sperm.
     Sperm consists of head, neck, middle piece and tail.

      1. Head: It is flat, oval and composed of a large haploid nucleus and a small cap-like structure called acrosome. It lies at the tip of the nucleus and is formed from the Golgi complex. It contains hydrolytic enzymes and is used to contact and penetrate the egg (ova) during fertilization.

      2. Neck: Neck is the smallest part, it is short structure that contains two centrioles- one parallel to the base of the nucleus and called proximal centriole and other distal centriole perpendicular to the previous one. The proximal centriole enters into the egg during fertilization and starts the first cleavage division of the egg which has no centriole. The distal centriole gives rise to the axial filament which forms the tail.

      3. Middle piece: It is cylindrical in shape and known as the power house of the sperm as it possesses numerous mitochondria to produce energy for the movement of the tail that facilitates sperm motility, essential for fertilization.

      4. Tail: It is a very long (longest part), slender and tapering structure formed of cytoplasm. A fine thread called the axial filament arises from the posterior centrioles and traverses the middle piece and the tail.

Structure of Sperm



Location: India

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