Gametogenesis involves the formation of male and female reproductive cells, i. e., sperms and ova under the influence of hormones. Spermatogenesis is the process of formation of sperms and that of ova is called oogenesis.
Spermatogenesis and Oogenesis
Mammalian sperm vs Mammalian Ovum
 The sperms are microscopic and motile cells. A mature spermatozoan is about 60 um long, flagellated, motile cell. It consists of head, neck, middle piece and a long narrow tail. The shape of spematozoan helps to surge  forward relentlessly in the vast female genital tract until it reaches its target,  the ovum, situated at the outer end of fallotubian tube.  Sperms remain alive and retain their ability to fertilize the ovum from 24 to 48 hours after being entered in the female reproductive tract.

The ovum in humans is alecithal, i.e.  it is almost devoid of yolk and has bulky cytoplasm  and a centrally located nucleus. It measures approximately 100 μm in diameter and remains surrounded by a secreted transparent , non cellular layer called zona pellucida. An in vestment of radially elongated follicle cells is present outside this layer which is known as corona radiate. Between the cell membrane or vitelline membrane and the zona pellucida, a distinct space , said to be perivitelline space, is present.
Mammalian Sperms
1. Sperm is flagellated and motile.
2. A sperm is formed of four parts: Head, neck, middle piece and tail.
3. Small amount of cytoplasm is present
4. Nucleus condensed with no nucleoplasm.
5. Centrioles is present.
6. Mitochondrion is compactly arranged and form a spiral called nebenkern.
7. Surrounded by only plasma membrane.

Mammalian ovum
1. Ovum is spherical and non motile.
2. Ovum is alecithal and has an excentric nucleus.
3. Large amount of cytoplasm is present.
4. Nucleus is bloated with nucleoplasm and is called germinal vesicle.
5. Centrioles is absent.
6. Mitochondria scattered in the cytoplasm.
7.Surrounded by a number of egg envelopes.

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