Structure of sperm class 12th Biology


We are all known to the process of fertilization and know that gametes fuse together from that one is male and the other is the female gamete. The female gamete is the egg but what is the structure of the male gamete which is the sperm ? That is what we are going to talk about in this article. 

Related articles: Fertilization in humans

The sperm is the male gamete which carries DNA of the paternal (Father's) side. Sperm is also called spermatozoan. It is microscopic, long and haploid gamete. The length of the sperm is 0.055mm (60 μ). It stays in the female reproductive tract for 72 hours but it can only fertilize the egg in the first 12 hours

Structure of sperm:

Sperm consists of head, neck, middle piece and tail. Everyday the male testes forms 100 million sperms. The entire sperm is covered by a plasma membrane. 


Head:

The head is flat, oval and spoon shaped region which consists of a large nucleus and an acrosome. Acrosome is a cap like structure which secretes a hydrolytic enzyme "hyaluronidase" which helps the egg to penetrate during the process of fertilization. 

The head is formed of acrosome. The nucleus present in the head of the sperm contains chromosomes which are densely packed. The head is covered by a sheath of Galea

Neck:

The neck is a short region having two centrioles. The centriole present in the centre of the body which is called proximal centriole, it helps in the the formation of first cleavage of zygote. The centirole which is present away from the centre at the end of the neck is called distal centriole which forms an axial filament. The axial filament is the tail of the sperm

Middle piece:

The middle piece is cylindrical and consists of spirally coiled mitochondria, hence the middle piece also acts like a power house of sperms. It provides energy for the movement of sperms in female genital tract. 

Tail:

The tail of the sperm is long, slender and it becomes narrow as it comes towards the end (tapering) structure. It is formed of cytoplasm and is thread like. It arises from the distal centriole in the neck and extends from the middle piece. The tail is covered by fibrous sheath but the sheath is absent at the end of the tail. 

The tail is also known as flagella which helps in movement of the sperm in the female genital tract. It swims by vibrating the tail in the fluid medium. 

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