STRUCTURE OF SPERMATOZOAN

Structure of sperm is divided into 3 parts -     

(1) Head                 

(2) Middle piece            

(3) Tail

1.       HEAD

1. It is the anteriormost part of the spermatozoan. It is often conical but its shape varies considerably.
2. It may be long and slender, spheroidal, rod-shaped or lance-shaped, spoon-shaped or short and flat, thin and crescentric, cork-screw-shaped or hooked.
3. The head is formed of acrosome and nucleus. Outer membrane of nucleus is thick and is called basal plate.
4. Pores are absent in nucleus membrane. Haploid chromosome are present in the nucleus.
5. Nucleolus and RNA are absent.
6. Argenine histone or protamine proteins are present (Histon protein absent).
7. The anterior most part of the head is occupied by the acrosome.
8. The acrosome is formed by golgi body and it is bounded by unit membrane.
9. Following enzymes are present in the acrosome -
10. Acid hydrolases, Acid phosphatase, Hyleuronidase, Acrosomine, Acrocin etc.
11. Plasma membrane of sperms have acidic protein, it is called antifertilizin. Antifertilizin act as a specific receptors to the fertilizing of egg envelop.

2.      Middle piece

1. Middle piece connect to the small neck of sperm. In neck of sperm 2 centrioles are present.
2. Proximal centriole form the mitotic spindle after the fertilization process. This centriole arranged longitudinaly to the main axis. Distal centriole form the axis of sperm.
3. Axial filament of sperm structure as 9 + 2 manner. 2 central fibres and 9 peripheral fibres present.
4. Posterior part of middle piece may has a ring centriole of annulus or jensen's ring. This ring centriole prevent the mitochondria toward the tail reason. 9 + 2 manner does not have.

3.      Tail

1. It is a longest part of sperm. In the tail the axial filament is covered by a sheat, which is made up of 9 singlet fibres.
2. This sheat is absent around the terminal end of the tail.
3. Stored food materials absent in the sperm, ribosome endoplasmic reticulum, nucleolus and RNA is absent in the sperm.

Structure of Mammalian Sperm