Sperm Cells

Location

Sperm cells are specialized cells of the male reproductive system that form in the testes.

 Function:

The function of sperm cells is to deliver the paternal (father)  contribution of chromosomes to the ovum (egg).

How cell structure relates to function

Sperm cells have three distinct regions, the head, midpiece and tail.  The head consists of an acrosome and a nucleus.  The acrosome is a specialized lysosome containing enzymes that digest the protective outer layers of the ovum allowing the sperm to penetrate and fertilize the egg.  The nucleus contains the father’s contribution of chromosomes for the soon to be embryo.  All cytoplasm surrounding the nucleus is partitioned off during the maturation process to increase efficiency.  The midpiece is packed with mitochondria that break down glucose (present in semen) producing ATP to power the movement of the flagella.  The tail is a single flagellum composed of microtubules.  The flagellum is the source of locomotion.  Sperm can move about 3 mm per hour and must wave their flagellum more than 1000 times to move half an inch.

Differentiation Process

Sperm cells differentiate from precursor cells called spermatogonia.  The differentiation process begins when changes in gene expression induce the spermatogia to undergo meiosis, a special form of cell division that cuts the chromosome number in half.  After meiosis, changes in gene expression result in the formation of the acrosome, loss of excess cytoplasm, and formation of a flagellum.

Sperm Cells and the Cell Cycle

Fully differentiated sperm cells do not divide.  However, the spermatogonia divide daily.  A normal adult male produces between 50 and 150 million sperm cells each day.