The female reproductive system consists of two
ovaries, two
fallopian tubes, the
uterus, the
cervix and the
vagina. During
ovulation, an egg is produced by either the right or
left ovary about 11 to 17 days before the woman's next menstrual period, or
approximately once a month. The egg is released from the ovary into a fallopian
tube and swept by tiny hairlike cells (cilia) and muscle action into the
uterus.
See a picture of the
female
reproductive system
.
The male reproductive system consists
of the penis, two
testicles, two
epididymides, two
vas deferentia, two
seminal vesicles, and the
prostate gland.
Sperm develop in the
testicle and finish maturing in the epididymis. When the man comes
(ejaculation), the sperm move out of the epididymides through the vas deferens
and into the tube (urethra) that runs through the penis. Semen (the thick
liquid associated with sperm) is produced in the seminal vesicles and prostate
gland and added to the sperm before ejaculation from the penis. Semen protects
the sperm from the acid environment in the vagina.
See a picture
of the male reproductive system
.
For pregnancy
to occur, sperm must travel up the vagina through the uterus and into the
fallopian tube to combine with an egg (fertilization) soon after ovulation. The
fertilized egg must then implant in the lining of the uterus.
Hormones and reproduction
In both men and women,
reproduction begins in the brain. A part of the brain (hypothalamus) produces a
substance called gonadotropin-releasing hormone (GnRH). GnRH causes the
pituitary gland to release two hormones into the
bloodstream:
luteinizing hormone (LH) and
follicle-stimulating hormone (FSH).
In
men, LH causes the release of the male hormone testosterone, while FSH causes
the testicles to produce sperm. In women, LH and FSH cause eggs to mature and
be released (ovulation). They also cause production of the female hormones
estrogen and
progesterone.
Many problems with
infertility are caused by too little or too much of these hormones, the pattern
of hormone levels over time, or problems in the
hypothalamus or
pituitary gland.