Spermatogenesis is the biochemical, morphological and functional process by which a spherical spermatid becomes the elongated spermatozoid. Phases: Golgi Phase, Head Phase, Achromosomal Phase and Maturational Phase.
In Golgi Phase, the new spermatides develop their Golgi apparatus inside the cytoplasm; from the granules developed juxtaposed with Golgi apparatus Achromosomal vesicles emerges.
The Head Phase involves a further achromosomal development. The acrosome attaches to the anterior pole of spermatide’s nucleus and forms the acrozomal head.
Nuclear changes start in the Acrozomal Phase.
Maturational Phase ends the spermatogenesis and the result is a mature spermatozoid. This phase involves the cytoplasmic phagocytosis of the residual material, near Sertoli cells. Mature spermatozoid has 60μm length; it is 1μm thick and contains one nucleus with the associated acrosome. Spermatozoid neck, the part which connects the head with the tale, has a pair of centriole and 9 segments, further it presents a 5-7μm long intermediary fragment equipped with a flagella axoneme surrounded by mitochondria and covered by a plasmatic external membrane. The tale of the spermatozoid reaches 45μm.
The duration of spermatogenesis
In humans, spermatogenesis takes about 74 days. Therefore there are 74 days necessary for sperm maturation inside a man’s testicles. This period doesn’t include the time necessary for spermatozoid maturation inside the epididymis or its transport. Normal sperm transits the epididymis in about 20 up to 30 days; therefore a man needs between 80 up to 100 days to produce the mature fertile ejaculated spermatozoid.
Spermatozoid Maturation inside the Epididymis
Spermatogenesis is not enough to produce gametes capable of fertilization. After the detachment of the seminiferous epithelium, the spermatozoid enter the rete testis, and transverse the deferent channels towards the epididymis. There is where the spermatozoid suffers a series of biochemical reactions which assume both the alteration of cell surface and intracellular molecules. Their interaction with the epididymal epithelium is also very important. It is known that the cells of the epididymal epithelium have the capacity of absorbing liquids which come from the lumen and of secreting spermatozoid specific components.
Inside the epididymis a spermatozoid goes through complex changes: acrosomic structural changes, inside the composition of its surface, furthermore, it loses its cytoplasm, and its motility becomes active.
At the biochemical level, a spermatozoid membrane plasmatic polypeptide and lipids go through changes which allow it to fuse with the oocyte. Spermatozoid’s motility is determined by cAMP cycle, it is increased by cAMP presence or other stimulants like coffee or calcium.
In the transport through the epididymis, sperm motility is influenced by intracellular pH.
The studies effectuated on spermatozoid oriented towards their motility can be extremely valuable in treating male infertility caused by low sperm motility.