The human reproductive system is a collection of organs for the production of offspring.
The production of a new individual is based upon the union of the male gamete (spermatozoon) with the female gamete (ovum). This process is called fertilization. At this time, a double set of chromosomes is reconstituted.
If the zygote (fertilized egg) has two X chromosomes, the individual will be female (XX).
If the zygote has one X and one Y chromosome, the individual will be male.
Sex hormones belong to a chemical group called steroids. The sex hormones of the female progesterone. The sex hormones of the male are called androgens.
Each male has a pair of testes located within the scrotum.
For the production of mature sperm (spermatozoa), the testes must be at a temperature that is a few degrees lower than that of the body cavity.
Androgens are also produced by cells of the testes.
Each female has a pair of ovaries, located in the pelvic cavity. The uterus is a single pear-shaped organ located within the pelvic cavity of the female. The inner lining of the uterus is known as the endometrium.
One female gamete (ovum) is released per menstrual cycle (about 28 days).
At midperiod, the mature ovum is expelled from the follicle onto the surface of the ovary. The free ovum is picked up by the uterine tube.
After the ovum has been expelled from the follicle, the resulting cavity is filled with a yellowish material known as the corpus luteum. The corpus luteum secretes primarily progesterone, a hormone that helps prepare the uterus for pregnancy.
Most development of the embryo/ fetus is intrauterine (within the uterus). During the first 8 weeks of development, the developing individual is called an embryo.
During the remainder of the intrauterine period, the developing individual is known as the fetus.
The uterus is a single pear-shaped organ located within the pelvic cavity of the female. The inner lining of the uterus is known as the endometrium.
The amniotic sac surrounds the embryo. The embryo floats free, surrounded by amniotic fluid.
The embryo has an umbilical cord that originates in the center of its anterior abdomen. The umbilical cord is attached to the wall of the uterus by a special structure known as the placenta.
The cervix, the inferior end of the uterus, is inserted into the top of the vagina. Through the center of the cervix is the cervical canal.
The release of amniotic fluid is followed by the passage of the fetus through the birth canal. During this passage, the newborn makes two partial rotations to accommodate the diameters of the relaxed bony pelvis.
In the birthing process, there are several reflexes occurring at appropriate times. The head of the newborn presents itself in the perineum. If the central tendon of the perineum has not relaxed sufficiently, an episiotomy may be performed. Episiotomy involves cutting the posterior margin of the vagina to prevent tearing.