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Human Reproduction
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Human Reproduction
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Gametes
The function of the reproductive organs is to produce gametes, that is, sperm cells in men and egg cells in women. The size of the human egg cell, compared to other species’ eggs is huge, about 80–100 micrometers. It is not capable of active movement. Unlike egg
cells, sperm cells are relatively small in size and
very motile. Despite the size difference, both cells contain the same amount of DNA. During sexual intercourse, the female and male gametes can
meet and fertilisation may take place.
Cell membrane
During fertilisation, it unites with
the cell membrane of the sperm cell.
Zona pellucida
It is made up of proteins. Its function is, partly, to prevent the sperm of other species from fertilising the egg.
Corona radiata
It protects and provides the egg with the necessary nutrients.
Egg cell
During a woman’s reproductive life cycle, around 500 egg cells mature. After reaching sexual maturity, one egg cell matures in the female body every month (on average), due to the effect of sex hormones. The mature egg cell is released from the ovary into the abdominal cavity, from where it travels towards the uterus through the fallopian tube. If the egg cell is not fertilised within 48 hours, it dies.
Cytoplasm
Egg cells contain a lot more cytoplasm than
sperm cells. Most of the substances necessary
for the fusion of the egg and the sperm
originate in the cytoplasm of the egg cell.
Nucleus
A haploid nucleus that contains the genetic material. During fertilisation, it unites with the haploid sperm cell, which results in the formation
of a diploid nucleus.
Sperm cell
Sperm cells are produced by the testicles. These contain a single cell of chromosomes, that is, they are haploid. Mature human sperm cells are about 50–60 micrometers long, very motile, and consist of a head, a neck and a tail. In the body of an average adult male, 70–150 million sperm cells are produced every day.
Neck
It connects the head and the tail.
Tail
A flagellum; its lashing movements propel
the sperm cell.
Midpiece
Contains mitochondria which coils around it.
Its role is to ensure the movement of the cell.
Head
It consists of the nucleus and the acrosome.
The acrosome contains enzymes which digest
the outer membrane of the egg during fertilisation.
