Human reproduction starts usually by a sexual intercourse. The
female’s ovum is fertilized by the male’s sperm. After the gestation period of nearly 9 months the child birth occurs.
Testes, male reproductive organs, produce sperm (male reproductive cell, gamete).
These survive at around 37 deg C a little less than the body temperature of
38.4 deg C. The semen is received by vagina and uterus of the female through
The ovaries of the female reproductive system produce ova (reproductive
cell or gamete) at regular intervals. These go through the fallopian tube and
enter the uterus. A spermatozoon (sperm cell) penetrates the large ovum coat (surface)
and merge with the egg and fertilize it (with the help of hydrolytic enzymes).
This merged zygote cell is implanted along uterus. (Unfertilized eggs are
flushed out of female system through menstruation.)
The ovum cells contain sufficient nutrients for the zygote. The biological process of embryogenesis (formation
embryo) begins. The zygote undergoes mitotic divisions and cellular
In Mitosis process the chromosomes in the cell nucleus are
separated into two identical sets of chromosomes. Next cytokinesis process divides
cytoplasm, and organelles into two. Now, karyokinesis process divides the
nucleus into two equal diploid cells.
Later the process of morphogenesis (formation of shape) starts.
Foetus receives the nutrition and oxygenated blood from the female. Normally, the foetus (fetus) is developed
sufficiently in 266 days period (pregnancy period). The fetus is propelled to outside by the
dilations of cervix and contractions of uterus. Thus a new infant takes birth
and starts breathing on his/her own.
Sperm and ovum are haploids with single sets of chromosomes. They contain 23 pairs of chromosomes.
The chromosomes contain chromatin (complex macromolecules) which consist of proteins,
DNA and RNA. These chromosomes join to form a diploid cell with 46 chromosomes.
Chromosomes are paired and undergo meiosis. There 22 pairs of autosomes and one
pair of sex chromosomes. Genetic traits are inherited though the sex
chromosomes. Some inheritance comes via the autosomes.
The chromosomes decide
the gender of the infant. Females have two of the same kind of sex chromosomes (X X)
in the pair. Males have two distinct chromosomes (X and Y) in the pair. Foetus may form with X from mother and X or Y from father. In the former case, a female child is born. The
presence of gene called in the Y chromosome helps initiation of virilisation, i.e.,
development of foetus toward maleness.
Oestrogens or estrogens are hormones which regulate functions
of reproductive system in males. In young women they are present in higher
quantities. They do a number of functions like development of sexual
characteristics and are important during menstrual cycle and oestrous cycle.
The protein hormone called relaxin helps motility of sperm in semen. In women it relaxes ligaments and helps the changes that occur during pregnancy.
The fertilization is also done by artificial insemination
too, in these modern times. Fresh or frozen sperm from a sperm bank is
introduced into a female’s cervix (by needleless injection ) or uterus
(intrauterine insemination through a thin tube). Multiple inseminations may be
required for achieving pregnancy.