Chapter 1: Gametes Flashcards
Male gametes
Sperms
Female gametes
Ova
What are gametes?
Reproductive cells.
How are the sperms formed?
From primordial germ cells by a process called speematogenesis.
How are ova formed?
They are formed from primordial germ cells by a process called oogenesis.
What is the site of formation of sperms?
Testis
Where is the site of formation of ova
In the ovary
What is the time of formation of sperms?
It starts at puberty and continues in old age.
What is the time of formation of ova?
It starts in intrauterine life, then arrested to be continued from puberty to menopause through ovarian cycles.
Ovulation occurs t the 14th day of the ovarian cycle.
Morphology of mature sperms.
A human sperm is 55 microns long and consists of:
1. Head
2. Neck
3. Middle piece
4. Tail
Head
4 microns long and contains:
1. Condensed nucleus which carries hereditary material of the father (22 autosomal and X or Y sex chromosomes) mostly covered by acrosomal cap that has enzymes that facilitate penetration of the coverings of the ova (fertilization).
2. Minimal cytoplasm.
3. Cell membrane.
Neck
Narrow part between head and middle piece.
Middle piece
6 micron long and composed of mitochondrial sheath, which is the source of energy for sperm motility.
Tail
- 45 microns long.
- Composed of axial filament with cell membrane around most of it.
- The tail directs the movement of the sperm towards the ovum, then helps fertilization.
Ovum
The diameter of mature ovum is about 120 microns.
