Anatomy & Physiology
What is Sex?
When this question is raised the first thought that
comes to our minds is the sexual act, so commonly called
as sex everywhere. In fact, the word sex has such a
vast meaning. It is being male or female. Therefore,
my sexuality would be the way I talk, the way I think,
the way I behave being a male or a female person. We
see that the word sex is nothing other than our entire
make up as male or female.
We have been created by a God who loves us and who
has made us in His own image, male and female, in order
to love and to be loved. In this love, like God Himself,
we are designed to bring forth new life. Every child
therefore, is a gift of love to its parents.
Human sexuality is all about growing up to be a man
or a woman with the power to love and to give life.
Man finds in woman and woman in man the companion designed
by God. Thus, they help each other to achieve the purpose
of their creation.
Puberty is a transition from childhood to adulthood.
As boys and girls grow up, though sexually different,
they mix about easily with each other and show no consciousness
about the differences in their sexes till the time of
puberty. At puberty, there are certain specific physical,
emotional and personality changes taking place in them.
These changes are caused by certain chemicals in the
body called hormones. These changes usually start between
11 and 13 years of age. At first, girls mature faster
into womanhood, but later the boys overtake the girls
and grow faster and stronger than the girls.
Development In Girls
As girls grow into puberty, under the influence of
the female hormone, Oestrogen,
they develop the physical characteristics of women.
Their hips broaden and their breasts begin to develop,
not just with the purpose of giving them a good form,
but to prepare them to nourish their new born infant
one day. Besides, they also acquire womanly personal
qualities like receptivity, affection and tenderness.
Development In Boys
As boys grow into puberty, they also acquire the built
and the physical characteristics of manhood, under the
influence of the male hormone, Testosterone. Their shoulders
broaden, and their voice grows deeper. But even more
they develop masculine personal qualities like daring,
initiative and farsightedness. Such qualities, however,
are not exclusive to either sex and can to a certain
degree be seen in both men and women. For example a
woman may also show daring, initiative, farsightedness,
etc. to a certain extent and a man may also show affection,
tenderness, etc. at certain situations and moments.
In fact, because of these differences in both male
and female, both the sexes seem to be inclined towards
or get fascinated to the complimentary qualities of
the other, leading to a sexual attraction. When sexual
attraction leads to a desire of complete oneness with
just one person of the opposite sex, wanting to blend
and share their entire lives through thick and thin
as a matter of decision, it leads to the ultimate purpose
of sexual attraction, that is marriage, in order to
love, to be be loved and to give life.
THE REPRODUCTIVE SYSTEM
Let us now consider the reproductive organs of the
two sexes beautifully designed for the purpose of pro-creation.
THE FEMALE REPRODUCTIVE SYSTEM
Vulva: It is made up of the following
three structures that surround the entrance to the vagina,
each of which has its own function:
Labia Majora (major lips): They are
two large folds of skin, the inner surface of which
lie in contact with each other and close the vaginal
entrance. The outer sides are covered with coarse hair.
Labia Minora (minor lips): They are
two delicate flaps of soft skin, one on either side
of the vaginal opening. These vary considerably in size
and ordinarily their inner surfaces touch each other.
At the upper end, they split into two folds to encircle
the clitoris. The minor lips are very vascular and become
turgid during sexual excitement.
Clitoris (the female equivalent of the penis
in the male): It consists of erectile tissue
which gets filled with blood during sexual excitement
and is extremely sensitive to touch, as it is richly
supplied with nerves. It is the most erotically sensitive
part of the vulva. Normally, only its tip (glans) and
its covering (prepuce) are visible.
Vestibule: It is the cleft between
the minor lips. Into it open the urethra, the vagina
and the Bartholin's glands.
Urethra: It is the urinary passage.
Hymen: It is a delicate annular fold
of membrane which surrounds the vaginal opening. The
fold is wider at the lower position, hence it tends
to have a crescentic shape. The first sexual act nearly
always causes it to tear, with only a slight loss of
blood, since it is relatively avascular.
Bartholin's Glands: They are two pea-sized
glands, one on either side of the vagina, their secretion
moistens the vaginal entrance to help the penis penetrate
the vagina without discomfort.
Mons Pubis (Mons Veneris): The eminence
formed by the pad of fat which lies over the pubic bone
in the female.
Uterus: The uterus of an adult woman
(who has not yet borne children) is 3½ inches
in length, 2½ inches across at the upper end
and 1½ inches at the lower end. It is pear shaped.
The lining of the uterine cavity, is called the endometrium
(uterine lining). At the lower end it opens into the
vagina through the cervical canal.
Cervix: The neck of the uterus is
called the cervix. The passage through the cervix is
called the cervical canal. The mucus membrane lining
the cervical canal extends inwards to form complex pouches
called crypts. These crypts secrete an alkaline mucus,
that starts flowing about 4-5 days before the actual
day of ovulation.
Vagina: It is an elastic muscular
canal, 3 inches long, extending from the cervix (mouth
of the uterus) to the vulva. It is lined by mucous membrane
which has folds that give it a wrinkled appearance.
It is the female organ of sexual intercourse. It receives
the seminal fluid deposited by the penis during the
marital act and it serves as the birth canal, a passage
for the baby during birth. At the opening of the vagina
is a thin membrane called hymen.
Fallopian Tubes: The upper end of
the uterus on either side, is connected to the fallopian
tubes (uterine tubes). Each tube is 4 inches in length.
It is a muscular hollow tube which allows the ovum (egg)
to pass from the ovary to the uterine cavity (space
inside the uterus). The outer end is funnel shaped with
a number of finger like processes called fimbriae. In
the sterilisation procedure called tubectomy, resection
of a segment of both the fallopian tubes is done.
Ovary: These are two in number and
are the female sex glands. Each one is 4 cms long and
2 cms wide and less than 1 cm thick. It is connected
to the uterus with the help of a ligament and lies suspended
close to the outer end of the funnel shaped part of
the fallopian tube. The ovaries have the following two
1. To produce ova (female sex cells)
A new born baby girl has 2 million primary oocytes
in the ovaries. By puberty 400,000 remain. The single
ovum lies enclosed in a thin layer of cells called follicle.
The ovum is the female reproductive cell containing
23 chromosomes. It is the largest cell in the female
At puberty, a message from the Pituitary gland in the
brain causes few egg cells or ova to ripen which then
secretes oestrogen. Not just the ovum but the entire
follicle begins to mature and grow in size. It is not
true that only one follicle matures at a time. In fact,
you will find that a few follicles begin to mature at
the same time, but only one among them reaches to full
maturity. Therefore, if we look at the inside of an
ovary we'll be able to see the three growing stages
of the follicles. They are the Primary, Maturing and
Primary Follicles: This
is the stage of all follicles at infancy. It contains
the ovum in its earliest stages (called oocyte), surrounded
by a layer of small flat cells.
Maturing Follicles: At this stage
the ovum (still called oocyte because it is immature)
becomes larger and the surrounding cells enlarge and
multiply forming some more layers. Fluid-filled spaces
appear inside the wall of the follicle, thus pushing
the ovum to one side.
Mature Follicle: This follicle is
the largest, with a large amount of fluid. The follicle
is pushed near the wall of the ovary due to the pressure
created by the fluid within, just waiting to release
the ovum. Only one ovum is released from either the
left ovary or the right ovary in a cycle.
The release of an ovum from the mature follicle is
called ovulation. Let's learn what occurs in the process
As the mature follicle is pushed near the wall of the
ovary, the lining of the ovary overlying the follicle
gets thin and it appears as if there is a bulge on the
ovary at that end. After a short while, the ovum detaches
itself from the side of the follicle and escapes through
the burst opened follicle, then through a temporary
opening made at that part of the ovary. It is a gradual,
slow process taking several seconds or minutes. Once
ovulation takes place, the other follicles that were
maturing simultaneously stop developing and soon degenerate.
As the moment of ovulation approaches, the outer end
of the tube, moves towards the ovary and its finger
like processes, cap it. Once the ovum is released it
is pulled into the tube by movements of the fringes
and the muscular contractions of the tube. The egg moves
further into the tube through the contractions created
by the tube. Within a span of 12 - 24 hours, the ovum
dies out if it is not fertilised. The capping function
of the outer end of the tube is necessary so that the
ovum is not lost. Infection of the tubes and its inability
to cap the ovary is a cause of infertility in some women.
2. To produce the two female hormones, Oestrogen
Oestrogen is secreted by the growing follicles and
is responsible for mucus secretion by the cervical glands
and the development of the endometrium. Once ovulation
takes place, the follicle undergoes changes, and forms
the yellow body or the corpus luteum, which secretes
the hormone progesterone. This progesterone further
affects the lining of the uterus, developing it and
After ovulation, the layer of cells that form the wall
of the follicle form the yellow body (Corpus Luteum).
The formation of the yellow body takes 5 days, during
this time it is already functioning, it continues to
produce oestrogen and begins to secrete a new hormone
progesterone. Progesterone immediately thickens the
mucus and rapidly causes it to disappear. It further
acts on the uterine lining. The lining now thickens
and towards the completion of this thick lining, tiny
lakes of blood appear just under the thickened lining.
The yellow body shows maximum activity for the next
3-4 days after which, degenerative changes begin to
be seen 4-5 days before the next menstrual period begins.
At this time because the yellow body begins to degenerate,
there is a drop in the level of the two hormones which
it produces. Once the level drops completely, the uterine
lining begins to breakdown because their hormonal supports
are withdrawn. The lining is shed in pieces. Thus the
discharge consists not only of blood but also of the
lining, mucus and other cells. The bleeding is called
menstruation or menses (Latin word meaning month) and
the number of days it lasts is called the menstrual
period. As soon as the yellow body dies out, other primary
follicles begin to mature and the oestrogen that they
release during this process begins to repair the uterine
lining which means even before menstruation is over,
the repair work is in progress and about 3 days after
menstruation the lining is completely restored with
thickness of 1 mm
Signs and Symptoms before and during Ovulation
in order of importance:
Mucus changes: On an average
of 6 days before ovulation, the mucus begins to flow
from the cervix under oestrogen stimulation. At the
start it is thick, opaque, sticky and non-stretchy.
As the oestrogen level rises further, the mucus becomes
cloudy, then clear, watery, slippery and stretchy, like
raw egg white, which produces a sensation of slipperiness
& wetness. After ovulation, as the progesterone
level rises the mucus again becomes thick, opaque and
sticky which may last for a day or two, followed by
Temperature rise: There is a rise
in basal body temperature following ovulation. The rise
is usually by about 0.4º F. (The range is 0.2º
F - 1º F) The temperature remains at a higher level
till the end of the cycle. Thus the temperature chart
shows a biphasic pattern.
Changes in the cervix: After menstruation
the cervix feels firm, closed and dry and its level
is low in the pelvis. As the time of ovulation approaches
the cervix gets progressively softer, its level higher
by about an inch, its mouth open and feels wet due to
the presence of mucus. After ovulation, the cervix again
becomes firm, closed, low and dry.
Pain: A small percentage of women
experience pain around the time of ovulation. It is
felt in the lower abdomen on either one of the sides,
where the ovary lies, but never on both sides. Women
describe it as a dull heaviness, or a cramp-like pain
that comes and goes, waxes and wanes in intensity.
Slight bleeding: This is a small
intermenstrual flow of blood from the uterine lining
called "spotting". It is more often seen in
long cycles than in average ones. It appears by itself
or with the mucus giving it a reddish or brown tinge.
Vulval swelling: At the time of ovulation,
women often notice a slight swelling/congestion of the
MALE REPRODUCTIVE SYSTEM
Testis: It is the male sex gland,
which are two in number, each about 1½ inches
long in the adult male. The testes have two functions
To produce sperms: Sperms are the
male sex cells. These are the smallest cells in the
body of a male. Sperm production in a male begins at
puberty and continues right up to old age. Lets look
at the single sperm. A sperm has 23 chromosomes. A sperm
has three parts viz. head, neck and tail. The head consists
of the nucleus, which contains the chromosomes. The
X sperm has a rounded head, that is responsible for
a baby girl, and the Y sperm has an oval head and is
responsible for a baby boy. The neck of the sperm supplies
the energy to the sperm and the long tail of the sperm
helps the sperm to move ahead. The sperms swim in the
thick whitish fluid called semen. After the sperms are
produced in the testes they move on to the Epididymis,
which is a highly coiled tube. Here the sperms remain
for some days till they mature.
To secrete the male sex hormone (testosterone):
Testosterone is released in a very high quantity
at the time of puberty into the blood stream and this
is the cause of the secondary sexual characters like
the beard, moustache, hair on the chest and pubic area,
broadened chest, etc. It is responsible for the growth
and maintenance of the male secondary sexual characters.
The testis is placed in a thin, wrinkled bag of skin
called scrotum. The temperature inside the scrotum is
about 2° lower than the rest of the body, as this
is necessary for sperm production.
Vas Deferens: The long tube that connects
the testis to the sperm sac (seminal vesicle) is called
the sperm duct (Vas Deferens). The sperms travel from
the testis to the sperm sac through Vas Deferens. In
the sterilization of a male, a procedure called vasectomy,
it is the Vas Deferens that are cut and ligated to prevent
the sperms from passing through the penis.
Seminal Vesicles: These are two in
number, situated at the base of the bladder. The sperms
travel through the sperm duct and enter the sperm sac
(seminal vesicle). The sperm sacs are meant for mature
sperm storage and produce a lubricating substance that
facilitates the passage of the sperms.
Prostate Gland: The secretion of the
prostate gland nourishes the sperms, gives it mobility
and contributes to the liquid portion of the seminal
Cowper's Gland: They lie one on either
side of the Urethra below the prostate. It's duct opens
into the urethra. These glands (the equivalent of Bartholins
glands in the female), under sexual excitation secrete
an alkaline fluid meant to lubricate and neutralize
the acidity of the urethra for safe passage of the sperms.
Penis: It is a cylindrical organ,
3-4 inches in length in the adult male, yet differing
in size from one man to another. Most of all the function
is important and not the size. It consists mainly of
erectile (spongy) tissue. It is covered by a loose skin
that is continuous with the scrotum. The part of skin
that covers the tip of the penis is called the prepuce
or foreskin. The foreskin (prepuce) is cut or folded
upwards at the time of circumcision. This prevents the
smegma (a secretion) from being accumulated and helps
in hygiene. It is also noted that the chances of cancer
of the penis are greatly reduced in those who are circumcised
very early in life.
The penis has two functions
To pass urine through the narrow tube passing through
the penis which is connected to the urinary bladder
and ends at the tip of the penis. This tube is called
To pass and deposit the semen in the vagina during
the marital act. For both the above functions, the urethra
acts as the common passage. However, both do not take
place at the same time i.e. urination and ejaculation
(expulsion of semen) due to a sphincter at the base
of the bladder.
At the end of the marital act, the muscular
contractions of the sperm sacs, prostate gland and the
sperm ducts expel semen into the vagina through the
penis. Now when ejaculation is about to take place,
a circular muscle at the base of the bladder tightens
and prevents the semen from mixing with the urine. Under
sexual excitement, the erectile tissue of the penis
gets filled with blood, it becomes firm and it increases
in length. This condition is called erection, which
is necessary to perform the marital act. Males whose
penis is unable to function in the manner explained
above at the time of the marital act, experience impotency.
After erection of the penis and the penetration of
it in the vagina, ejaculation takes place and the semen
is deposited in the vagina. At each ejaculation about
300 to 500 million sperms are released.
How does the sperm travel?
After being produced in the testis the sperms are passed
into the epididymis. From here, the mature sperms pass
through the sperm duct (Vas Deferens) and enter the
sperm sac (Seminal Vesicle) getting a bit of the liquid
portion from this, it moves towards the prostrate gland.
Mature sperms have little movement till they mix with
the fluid from the prostrate gland to form the semen.
From here it passes on to the urethra through which
it passes out of the male's body. Erection and ejaculation,
when made to occur deliberately by forcing oneself with
provoked sexual excitement is called masturbation. This
is a serious sin. It is a self loving act. It affects
the individual's personality, making a person timid,
guilty and loose his self-confidence etc. Also, a frequent
practice of this can lead to spontaneous erection at
even a very slight sexual excitement and it may be out
of the person's control. This can be embarrassing if
it occurs at any time of the day. Sometimes, quite rarely,
when sperms are emitted at night, during the person's
sleep, without his knowledge, this phenomenon is called
night emission or wet dreams. This is a natural phenomenon
through which excess of sperms produced in the body
are given out as the law of nature permits.