September 04, 2011
Mommy, how are babies made?
The adventure of human reproduction is one of interest to most people at
some point in his or her life. To answer
this question, follow a fascinating journey of Jack and Jill, a sperm and an egg
respectively, as they face the exciting, yet challenging obstacles from development
to fertilization. Learn how the male and
female sex organs, both external and internal, participate in Jack and Jill’s
expedition. The what, why, and how
humans procreate; the biology and psychology behind the tada, it’s a boy (or
girl).
Just by looking, it is not difficult to see that men and women are
born with very different body parts, known as secondary sex characteristics. Developed to entice the opposite sex for the
purposes of reproduction, with an internal sex drive that, according to Sigmund
Freud (1856 – 1939) is the primary source of human motivation (Freud, as cited
by Rathus, et. al, 2005, p. 17). Upon closer inspection, these external body
parts, the male penis and scrotum, and the female vulva and breasts, are very
complex; all are extremely sensitive to sexual stimulation. With stimulation the penis becomes engorged
with blood and erection occurs; whereas the female sex organ and its many
external parts (i.e. the labia majora and labia minora) hide the erect
clitoris. Both the erect penis and
clitoris are motivating factors in the initial journey to fertilization.
What is not seen are referred to as the internal sex organs; where
both the sperm and the egg (Jack and Jill) are developed and nourished with
testosterone and estrogen. According to
Rathus, et. al. (2005), Jack and thousands of other sperm are manufactured in
the testes. Jack matures in approximately
72 days and will contain 23 of the 46 chromosomes needed to produce either a girl
or a boy (i.e. an X or Y sex chromosome will be within the chromosomal chain of
each sperm) at fertilization. Whereas,
Jill and all the ova (egg cells) a woman will ever have remain dormant within the
ovaries from birth. After menarche a woman
goes through menses approximately every 28 days as estrogen levels rise; at
which time Jill and up to 20 other ova begin to ripen or mature. As Rathus et. al. (2005) indicates, when
estrogen levels peak, normally one ovum, Jill, reaches maturity and is released
from the ovary. As with Jack, Jill
contains 23 chromosomes to complete the standard 46 and will always contain a
female (X) sex chromosome. Fertilization
occurs when Jack enters Jill to complete the chain of 46 chromosomes to produce
either a female or a male embryo.
When a man and a woman
experience sexual stimulation, as mentioned earlier, and wish to experience
sexual gratification, the man will insert his erect penis through the vestibule
or opening to the woman’s vagina. With
additional stimulation, sperm travel from the testicles through the vas
deferens over the bladder and are deposited into the ejaculatory ducts
(2005). There, semen from the seminal
vesicles is mixed with the sperm and other nutrients to produce motility. The ejaculate propels Jack beyond the
ejaculatory ducts through the penis into the vagina; at or during this
stimulation process sexual gratification, known as orgasm may occur for both the
man and woman. Upon ejaculation, Jack
and thousands of other sperm travel beyond the cervix of a woman into the
uterus and fallopian tubes, filling the female reproductive system in search of
Jill (2005). Jill, mere inches from the
ovary must be fertilized within one to two days after full maturation,
continues her journey through the fallopian tube in search of Jack. Progesterone and estrogen released from the
corpus luteum (glands within the ovaries) cause the lining of the uterus to
thicken in preparation of fertilization.
As Jack and the other sperm use their scent receptors (much like the
nose), they can locate Jill (Wilkinson, 2003, as cited by Rathus, et. al.,
2005, p. 118). Upon reaching one another
fertilization may occur; as one they travel to the uterus where the growing
embryo implants on the thickened lining and remains throughout development.
From the maturation of internal organs to the development of
secondary sex characteristics, Jack and Jill are destined to mature and seek
out the other. With internal sex drives,
both male and female are biologically stimulated to proliferate; that is to reproduce. Many mechanisms are required for the creation
of sperm and ovum; testes and ovaries house, nurture, and produce the
testosterone, estrogen, and progesterone needed for both external and internal
organs, sperm, and ovum development. Chromosomal
chains from each sperm and ovum combine to produce a complete fertilized male
or female embryo. The combination of
sperm, semen, and other fluids produce an ejaculate that will fill the
reproductive system of the woman. The
release of estrogen promotes maturation of several ovum, with one released to
fulfill the fertilization process; if fertilization occurs the embryo may
implant on the thickened uterus wall and development can occur. Although Jack, the sperm, and Jill, the egg
are produced for procreative purposes, most of the time they are destined to
never meet, but when they do beautiful creations are made.
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