Spermatozoa(sperm) is composed of a head and a tail. The head comprises the condensed nucleus of the cell with only a thin cytoplasmic and cell membrane layer around its surface. On the outside of the anterior two thirds of the head is a thick cap called the acrosome that is formed mainly from the Golgi apparatus. This contains a number of enzymes including hyaluronidase (it can digest proteoglycan filaments of tissues) and powerful proteolytic enzymes (it can digest proteins). These enzymes play important roles in allowing the sperm to enter ovum and fertilization to happen.
The tail of the sperm, called the flagellum has three major components: (1) a central skeleton constructed of 11 microtubules, collectively called the axoneme (2) A thin cell membrane covering the axoneme and (3) A collection of mitochondria surrounding the axoneme in the proximal portion of the tail (called the body of tail).
Back and forth movement provided motility for the sperm. The movement results from a rhythmical longitudinal sliding motion between the anterior and posterior tubules that make up the axoneme. The energy for this process is supplied in the form of ATP synthesized by mitochondria in body of tail.
Normal sperm move in fluid medium at a velocity of 1 to 4 mm/min.
References:
- Textbook of medical physiology, 11th edition , Arthur C. Guyton and John E. Hall.