The female germ cells: oocytes
The eggs (oocytes) of the woman as primordial germ cells arise during embryonic development. Several hundred thousand primordial germ cells develop initially to progenitor cells (primary oocytes), while the number of these cells decreases until the onset of puberty at about 40,000. Each one of these cells then matured during the female cycle capable of being fertilized egg is a single set of chromosomes during ovulation and is released from the ovaries into the fallopian tubes, where fertilization takes place. In the fertile phase of life a woman who takes 30 to 35 years, up to 400 fertilizable oocytes are formed. It is mostly due to pregnancy and hormonal contraceptives like the pill but actually less.
A single human egg has a diameter of about 0.1 millimeters and can be barely seen with the naked eye. The egg is the largest cell in the body.
The male germ cells: sperm
The sperm of the man are from puberty to old age formed in the seminiferous tubules (spermatogenesis). They arise from special cells, called spermatogonia, which can multiply more and more. The spermatogonial progenitor cells to develop into first with a single set of chromosomes, the spermatids. These mature during a development phase lasting about 70 days then approached to the fertilizable sperm. An ejaculation from two to six milliliters of seminal fluid contains up to 600 million sperm, however, a certain part of it, for example by deformation or limited movement unable to fertilize an egg. The quality of sperm decreases with age and can be studied using a semen analysis.
The oval head of a sperm cell contains the genetic material and has a diameter of about three to five microns. He is thus about 25 times smaller than an egg. Along with neck, middle piece and tail, used to measure locomotion, a sperm length after about 60 microns.
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