2We all know that this is the main component of male infertility if everything is normal and becomes the main source of infertility if everything is abnormal. So it totally depends on the knowledge of normal anatomy and molecular physiology of normal spermatozoa. In infertile male there is high incidence of numerical chromosomal aberration and abnormal sperm morphology.
WHAT WE WANT TO SEE IN NORMAL SPERMATOZOON?
This is very special cell that do not grow or divide.
Spermatozoon has usually head with paternal hereditary material DNA and big tail for motility (Fig. 1.1).
The specific difference from somatic cell is absent of large cytoplasm but endowed with large nucleus.
The posterior portion of the sperm head is covered by the post nuclear cap, which is a single membrane. The equatorial segment consist of an overlap of the acrosome and the post nuclear cap.
The nucleus, constitutes 65 % of the head, is composed of DNA conjugated with protein.
Sperm nucleus can have incomplete condensation with apparent vacuoles. The genetic information carried by the spermatozoon is encoded and stored in the DNA molecules, which is made up of many nucleotides. The hereditary characteristic transmitted by the sperm nucleus include sex determination.
SPERM HEAD
Normal head is oval in shape 3 to 5 micrometer length and width is 2–3 micrometer (µm) (Fig. 1.2).
Head aberrations are as follows:
- Shape and size
- Large, small, tapering
- Pyrifrom
- Amorphous
- Vacuolated
- Double head.
Head is divided in two unequal parts
- Acrosomal region
- Postacrosome region
Head is usually flattened, ovoid and consists of nucleus only.
Acrosome is cap like and covers anterior 2/3 of head which arise from the golgi apparatus of the spermatid as it differentiate into spermatozoon (Fig. 1.3).
Hyaluronidase and proacrosin are in acrosome necessary for fertilization.
During fertilization of the egg, the enzyme rich contents of the acrosome are released at the time of acrosome reaction. During fusion of the outer acrosomal membrane with the Plasma membrane at multiple sites, the acrosomal enzymes are released.
The organization of DNA into loop domains is the only type of structural organization resolved so far and that is present in both somatic and sperm cells. DNA is coiled into nucleosomes, then further coiled into a 30 nm solenoid like fiber and then organized into DNA loop domains.
The mid piece possesses a cytoplasmic portion and a lipid reach mitochondrial sheath that consist of several spiral mitochondria, surrounding the axial filament in a helical fashion.
The mid piece provides the sperm with the energy necessary for motility (Fig. 1.4).
The central axis core of eleven fibrils is surrounded by an additional outer ring of nine coarser fibrils. Individual mitochondrium is wrapped around these fibrils in a spiral manner to form the mitochondria sheath, which contains the enzyme involved in the oxidative metabolism of the sperm.
The mitochondrial sheath of the mid piece is relatively short, being slightly longer than the combined length of the head and neck. The principal piece (main piece) is the longest part of the tail, and provide most of the propellant machinery (Fig. 1.5).
The coarse nine fibrils of the outer ring diminish in thickness and finally disappear leaving only the inner fibrils in the axial core for much of the length of the principal piece (Fig. 1.6).