The female reproductive system produces eggs, transports them, and supports pregnancy. The ovaries produce eggs and hormones like estrogen and progesterone that regulate the menstrual cycle. If an egg is fertilized, it implants in the uterus where the embryo develops. Menopause occurs when egg production and the menstrual cycle cease. The male reproductive system produces sperm through spermatogenesis and hormones that support fertility. Both systems work together through the hypothalamic-pituitary-gonadal axis to regulate the reproductive cycles.

1. UNIT - 10 THE REPRODUCTIVE SYSTEMS
FEMALE REPRODUCTIVE SYSTEM
The female reproductive system provides several functions. The ovaries produce the egg cells, called the ova
or oocytes. The oocytes are then transported to the fallopian tube where fertilization by a sperm may occur.
The fertilized egg then moves to the uterus, where the uterine lining has thickened in response to the normal
hormones of the reproductive cycle. Once in the uterus, the fertilized egg can implant into thickened uterine
lining and continue to develop. If implantation does not take place, the uterine lining is shed as menstrual
flow. In addition, the female reproductive system produces female sex hormones that maintain the
reproductive cycle.
During menopause, the female reproductive system gradually stops making the female hormones necessary
for the reproductive cycle to work. At this point, menstrual cycles can become irregular and eventually stop.
One year after menstrual cycles stop, the woman is considered to be menopausal.
The Reproductive System
 Female reproductive system-
Menstrual cycle,
function and hormones of ovary, oogenesis,
fertilization, implantation,
Functions of breast
• Male reproductive system-
Spermatogenesis,
hormones and its functions,
Semen
Application and implication in providing nursing care

2. Menstrual Cycle
Menstruation occurs on a monthly cycle throughout female reproductive life. Menarche (the first menstrual
cycle) normally occurs between the ages of 11 and 15 and the menopause between the ages of 45 and 55. The
normal duration of a single cycle is 21-35 days.
The Hypothalamic-Pituitary-Gonadal (HPG) Axis
The hypothalamus, anterior pituitary gland and gonads (ovaries) work together to regulate the menstrual cycle.
Gonadotropin releasing hormone (GnRH) from the hypothalamus stimulates luteinising hormone (LH) and
follicular stimulating hormone (FSH) release from the anterior pituitary gland. LH and FSH are gonadotropins
that act primarily on the ovaries in the female reproductive tract:
• FSH binds to granulosa cells to stimulate follicle growth, permit the conversion of androgens (from theca
cells) to oestrogens and stimulate inhibin secretion
• LH acts on theca cells to stimulate production and secretion of androgens.
The menstrual cycle is controlled by feedback systems:
• Moderate oestrogen levels exert negative feedback on the HPG axis
• High oestrogen levels (in the absence of progesterone) positively feedback on the HPG axis
• Oestrogen in the presence of progesterone exerts negative feedback on the HPG axis
• Inhibin selectively inhibits FSH at the anterior pituitary
The Ovarian Cycle
Follicular Phase
The follicular phase marks the beginning of a new cycle as follicles (oocytes surrounded by stromal cells)
begin to mature and prepare to release an oocyte.
At the start of a new cycle (menses) there is little ovarian hormone production and the follicle begins to
develop independently of gonadotropins or ovarian steroids. Due to the low steroid and inhibin levels, there

3. is little negative feedback at the HPG axis, resulting in an increase in FSH and LH levels. These stimulate
follicle growth and oestrogen production.
Only one dominant follicle can continue to maturity and complete each menstrual cycle. As oestrogen levels
rise, negative feedback reduces FSH levels, and only one follicle can survive, with the other follicles forming
polar bodies.
Follicular oestrogen eventually becomes high enough to initiate positive feedback at the HPG axis, increasing
levels of GnRH and gonadotropins. However, the effect is only reflected in LH levels (the LH surge) due to
the increased follicular inhibin, selectively inhibiting FSH production at the anterior pituitary. Granulosa cells
become luteinised and express receptors for LH.
Ovulation:
In response to the LH surge, the follicle ruptures and the mature oocyte is assisted to the fallopian tube by
fimbria. Here it remains viable for fertilisation for around 24 hours.
Following ovulation, the follicle remains luteinised, secreting oestrogen and now also progesterone, reverting
back to negative feedback on the HPG axis. This, together with inhibin (inhibits FSH) stalls the cycle in
anticipation of fertilisation.
Luteal Phase:
The corpus luteum is the tissue in the ovary that forms at the site of a ruptured follicle following ovulation. It
produces oestrogens, progesterone and inhibin to maintain conditions for fertilisation and implantation.
At the end of the cycle, in the absence of fertilisation, the corpus luteum spontaneously regresses after 14 days.
There is a significant fall in hormones, relieving negative feedback, resetting the HPG axis ready to begin the
cycle again.
If fertilisation occurs, the syncytiotrophoblast (Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'-
"of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly
vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation
between the embryo and the mother. It is a multinucleate, terminally differentiated syncytium, extending to
13 cm.) of the embryo produces human chorionic gonadotropin (HcG), exerting a luteinising effect,
maintaining the corpus luteum. It is supported by placental HcG and it produces hormones to support the

4. pregnancy. At around 4 months of gestation, the placenta is capable of production of sufficient steroid
hormone to control the HPG axis.
The Uterine Cycle
Proliferative Phase
Following menses, the proliferative phase runs alongside the follicular phase, preparing the reproductive tract
for fertilisation and implantation. Oestrogen initiates fallopian tube formation, thickening of the endometrium,
increased growth and motility of the myometrium and production of thin alkaline cervical mucus (to facilitate
sperm transport).
Secretory Phase
The secretory phase runs alongside the luteal phase. Progesterone stimulates further thickening of the
endometrium into a glandular secretory form, thickening of the myometrium, reduction of motility of the
myometrium, thick acidic cervical mucus production (a hostile environment to prevent polyspermy), changes
in mammary tissue and other metabolic changes.
Menses

5. Menses marks the beginning of a new menstrual cycle. It occurs in the absence of fertilisation once the corpus
luteum has broken down and the internal lining of the uterus is shed. Menstrual bleeding usually lasts between
2-7 days with 10-80ml blood loss.
FUNCTION AND HORMONES OF OVARY
The ovaries produce and release eggs (oocytes) into the female reproductive tract at the mid-point of each
menstrual cycle. They also produce the female hormones oestrogen and progesterone.
The ovaries have two main reproductive functions in the body. They produce oocytes (eggs) for fertilisation
and they produce the reproductive hormones, oestrogen and progesterone. The function of the ovaries is
controlled by gonadotrophin-releasing hormone released from nerve cells in the hypothalamus which send
their messages to the pituitary gland to produce luteinising hormone and follicle stimulating hormone. These
are carried in the bloodstream to control the menstrual cycle.
The ovaries release an egg (oocyte) at the midway point of each menstrual cycle. Usually, only a single oocyte
from one ovary is released during each menstrual cycle, with each ovary taking an alternate turn in releasing
an egg. A female baby is born with all the eggs that she will ever have. This is estimated to be around two
million, but by the time a girl reaches puberty, this number has decreased to about 400,000 eggs stored in her
ovaries. From puberty to the menopause, only about 400-500 eggs will reach maturity, be released from the

6. ovary (in a process called ovulation) and be capable of being fertilised in the fallopian tubes/uterine
tube/oviduct of the female reproductive tract.
HORMONES OF OVARY
The major hormones secreted by the ovaries are oestrogen and progesterone, both important hormones in the
menstrual cycle. Oestrogen production dominates in the first half of the menstrual cycle before ovulation, and
progesterone production dominates during the second half of the menstrual cycle when the corpus luteum has
formed. Both hormones are important in preparing the lining of the womb for pregnancy and the implantation
of a fertilised egg, or embryo.
If conception occurs during any one menstrual cycle, the corpus luteum does not lose its ability to function
and continues to secrete oestrogen and progesterone, allowing the embryo to implant in the lining of the womb
and form a placenta. At this point, development of the foetus begins.
OOGENESIS
Oogenesis is the type of gametogenesis through which ova, also called the female gametes are formed and the
produced female gamete is known as an ovum. In general terms, the female gametes are referred to as eggs,
but the word egg can involve various stages of development, therefore, the significance of an egg varies based
on the type of organisms.
For example, Once, after the birds lay eggs, the entire development of an egg until the transformation of the
egg into the chick occurs within the eggs. Whereas, in the placental mammals, once the egg is fully developed
and fertilized, it begins to divide and we no more call it as an egg. We need to recall that every ovum has to
be haploid and consist of a single copy of every chromosome.
Oogenesis is the differentiation of the ovum. Spermatogenesis and oogenesis are two different forms of
gametogenesis. Gametogenesis in the male is known spermatogenesis and in the female is known oogenesis,
which results in the formation of ova in the female. Oogenesis completely differs from spermatogenesis in
several ways.
Oogenesis is the process of formation of female gametes. This process begins inside the fetus before birth.
The steps in oogenesis up to the production of primary oocytes occur before birth. Primary oocytes do not
divide further. They either become secondary oocytes or degenerate.

7. Oogenesis occurs in the outermost layers of the ovaries. Oogenesis starts with a germ cell called oogonium
and undergoes mitosis to increase in number. The process of oogenesis takes place in the following three
stages:
• Pre-natal
• Antral
• Pre-ovulatory
Process of Oogenesis
The process of oogenesis is completed in the following three stages:
Pre-natal Stage
The primary oocyte grows while being arrested in meiosis-I. The follicular cells proliferate and form a
stratified cuboidal epithelium. Such cells are known as granulosa cells. These cells secrete glycoproteins to
form zona pellucida around the primary oocyte.
Antral Stage
The fluid-filled area, present between granulosa cells, combines to form a central fluid-filled space called the
antrum. These are known as secondary follicles. In every month cycle, these secondary follicles develop under
the influence of follicle-stimulating hormone and luteinizing hormone.
Pre-Ovulatory Stage
This stage is induced by LH surge, and meiosis-I completes here. Two haploid cells of unequal sizes are
formed within the follicle. One of the daughter cells that receive less cytoplasm forms a polar body. This cell
does not participate in ovum formation. The other daughter cell is known as the secondary oocyte. The two
daughter cells undergo meiosis-ll. The polar body replicates to form two polar bodies, while the secondary
oocyte arrests in the metaphase stage of meiosis-Il.

8. Ovulation
Development of oocyte takes place in ovaries. Every oocyte is neighboured by follicle cells to form a follicle.
As the menstrual cycle starts, primary oocytes initiate to grow bigger, and follicle cells rise in number, causing
the follicle to grow larger too.
Normally, some nurturing oocytes degenerate and leave just one follicle to mature. Here, fraternal twins may
be born, which are distinct genetically.
When a follicle attains maturity, the primary oocyte finishes its primary meiotic division and becomes
secondary oocyte. Soon after, the follicle breaks and secondary oocyte is liberated in the fallopian tube even
when the second meiotic division has not happened. This release of a secondary oocyte from ovaries is known
as ovulation.

9. FERTILIZATION AND IMPLANTATION
Fertilization is the natural life process, which is carried out by the fusion of both male and female gametes,
which results in the formation of a zygote. In humans, the process of fertilization takes place in the fallopian
tube.
During this process, semen comprising thousands of sperms are inseminated into the female vagina during
coitus. The sperms move towards the uterus and reach the opening of the fallopian tube. only a few sperms
will succeed in reaching the opening of the fallopian tube.
The secondary oocyte releases from the matured Grafian follicle of the ovary and enters into the fallopian
tube, where it is fertilized within 24 hours, after which it is released from the ovary.
Though surrounded by several sperms, the oocyte is fertilized by a single sperm. During meiosis-II, the sperm
enters the secondary oocyte and completes the meiosis. After this, the secondary oocyte is known as the egg.

10. Both sperm and egg can show their vitality only to a limited period. Sperm is alive for 48-72 hours in a female
reproductive system, whereas the egg can be fertilized for 24 hours before it is released.
Steps of Fertilization in Humans
The fertilization process in humans takes place in several stages involving both the chemical and physical
events. The different stages of fertilization in humans are mentioned below:
Acrosomal Reaction
The sperms incapacitation undergo acrosomal reactions and release certain chemicals known as sperm lysins
present in the acrosome.
Due to the acrosomal reactions, the plasma membrane of the secondary oocyte and the sperm are fused
together so that the contents of the sperms can enter. When the plasma membrane of the sperm binds with that
of the secondary oocyte, the plasma membrane of the oocyte depolarizes. This prevents polyspermy.
Calcium ions play a significant role in the acrosomal reaction. The main factors essential for acrosomal
reactions are optimum pH, temperature and calcium and magnesium concentration.
Cortical Reaction
Soon after the fusion of the plasma membranes, the oocyte shows cortical reactions. Cortical granules found
under the plasma membrane of the oocyte, which fuses with the plasma membrane and releases cortical
enzymes between the zona pellucida and plasma membrane. The zona pellucida is hardened by the cortical
enzymes that prevent polyspermy.
Sperm Entry
A projection known as the cone of reception is formed by the secondary oocyte at the point of sperm contact.
This cone of reception receives the sperm.
Karyogamy
After the entry of the sperm, the suspended second meiotic division is completed by the secondary oocyte.
This gives rise to a haploid ovum and a second polar body.

11. The head of the sperm containing the nucleus detaches from the entire sperm and is known as male pronucleus.
The tail and the second polar body degenerates. The nucleus of the ovum is known as female pronuclei.
The male and female pronuclei fuse and their nuclear membranes degenerate. The fusion of the chromosomes
of male and female gametes is called karyogamy. The ovum is now fertilized and is known as a zygote.
Activation of Eggs
The entry of sperm triggers the metabolism in the zygote. Consequently, protein synthesis and cellular
respiration increase.
Implantation
Once fertilization happens, the cell starts to divide and multiply within 24 hours in the fallopian tube. This
detached multi-celled structure is called a zygote. Later, after 3-4 days it travels to the uterus and now we call
it as an embryo.
The embryo develops and undergoes various stages and gets attached to the endometrial layer of the uterus.
This process of attachment is known as implantation.
FUNCTIONS OF BREAST
The breast is an organ whose structure reflects its special function: the production of milk for lactation (breast
feeding). The epithelial component of the tissue consists of lobules, where milk is made, which connect to
ducts that lead out to the nipple.
• Female hormones - namely, estrogen, progesterone and prolactin - play a key role in breast development and
function.
• Estrogen stretches milk ducts and helps them create side branches to carry more milk.
• Prolactin promotes the production of progesterone and prepares glands for milk production.
• Progesterone increases the number and size of lobules in preparation for breastfeeding. This hormone also
enlarges blood vessels and breast cells after ovulation. You may experience swollen, tender breasts.

12. MALE REPRODUCTIVE SYSTEM - SPERMATOGENESIS, HORMONES AND ITS FUNCTIONS,
SEMEN
Male Reproductive System

13. The male reproductive system is mostly located outside of the body. These external organs include the penis,
scrotum and testicles. Internal organs include the vas deferens, prostate and urethra. The male reproductive
system is responsible for sexual function, as well as urination.
The entire male reproductive system is dependent on hormones. These are chemicals that stimulate or regulate
the activity of your cells or organs. The primary hormones involved in the functioning of the male reproductive
system are follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone.
FSH and LH are produced by the pituitary gland. It's located at the base of your brain and it's responsible for
many functions in your body. FSH is necessary for sperm production (spermatogenesis). LH stimulates the
production of testosterone, which is necessary to continue the process of spermatogenesis. Testosterone is also
important in the development of male characteristics, including muscle mass and strength, fat distribution,
bone mass and sex drive.
Spermatogenesis
Spermatogenesis is a process of developing male gametes, known as sperm within the male reproductive
organs, the testes. In this process, each sperm containing a single copy of each chromosome. In order to create
the haploid gamete, a cell undergoes the process of meiosis in which the genome is replicated and divided
twice to produce four haploid gametes.
This process generally occurs in the seminiferous tubules of the testes following different stages. It is followed
by maturation in the epididymis where they are secreted in the form of semen along with glandular secretions.
This process begins during puberty and ends only when the individual dies. The complete process of
spermatogenesis in males are carried out by the actions of Leydig cells, hypothalamus, and pituitary gland.
The quantity of these sperms gradually reduces with the age and finally leads to infertility.
The process of Spermatogenesis occurs to create mature male gametes, which then fertilize female gametes
to create a zygote, a single-celled organism. This results in cell division and multiplication to create a fetus.

14. For a healthy offspring, the number of chromosomes must be maintained properly across the body as failure
can lead to some abnormalities.
The Process of Spermatogenesis

15. Stage 1: The Diploid spermatogonia is situated in the seminiferous tubules which include twice the total
number of chromosomes. This replicates mitotically in interphase before the method of meiosis 1 to create 46
pairs of sister chromatids.
Stage 2: In this, the chromatids allow the exchange of genetic information through the synapsis process. It is
done before dividing into haploid spermatocytes through meiosis.
Stage 3: In this division, the new two daughter cells will further divide into 4 spermatids, having unique
chromosomes that are approximately half in number to the original spermatogonium.
Stage 4: In this stage, the cells move from the lumen of the testes to the epididymis. They get mature and
developed into four sperm cells with the growth of microtubules on the centrioles to develop an axoneme. The
remaining centrioles elongate and develop into sperm tail.
Factors Affecting Spermatogenesis
This process seems to be very sensitive and can easily be affected by minute changes in the hormone level.
For example- testosterone is developed through the hypothalamus, Leydig cells, and pituitary gland. This
process is very sensitive to changes in temperature, deficiency in the diet, alcoholism, exposure to drugs and
the presence of disease can affect the rate of sperm formation adversely.
HORMONES AND ITS FUNCTION
Male Hormones
The onset of puberty is controlled by two major hormones: FSH initiates spermatogenesis and LH signals the
release of testosterone.
Puberty is a period of several years in which rapid physical growth and psychological changes occur,
culminating in sexual maturity. The average onset of puberty is age 11 or 12 for boys. Some of the most
significant parts of pubertal development involve distinctive physiological changes in individuals' height,
weight, body composition, and circulatory and respiratory systems. These changes are largely influenced by
hormonal activity. Hormones play an organizational role, priming the body to behave in a certain way once
puberty begins, and an activational role, referring to changes in hormones during adolescence that trigger
behavioral and physical changes.

16. At the onset of puberty, the hypothalamus begins secreting high pulses of GnRH, or gonadotropin-releasing
hormone. In response, the pituitary gland releases follicle stimulating hormone (FSH) and luteinizing hormone
(LH) into the male system for the first time. FSH enters the testes, stimulating the Sertoli cells, which help to
nourish the sperm cells that the testes produce, to begin facilitating spermatogenesis. LH also enters the testes,
stimulating the interstitial cells, called Leydig cells, to make and release testosterone into the testes and the
blood.
Testosterone, the hormone responsible for the secondary sexual characteristics that develop in the male during
adolescence, stimulates spermatogenesis, or the process of sperm production in the testes. Secondary sex
characteristics include a deepening of the voice, the growth of facial, axillary, and pubic hair, and the
beginnings of the sex drive.
A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus
and anterior pituitary to inhibit the release of GnRH, FSH, and LH. The Sertoli cells produce the hormone
inhibin, which is released into the blood when the sperm count is too high. This inhibits the release of GnRH
and FSH, which will cause spermatogenesis to slow down. If the sperm count reaches 20 million/ml, the
Sertoli cells cease the release of inhibin, allowing the sperm count to increase.
SEMEN
Semen is the cloudy white bodily fluid that is emitted from the urethra and out of the penis during ejaculation.
It consists of mobile sperm cells (called spermatozoa) and a nutrient-rich fluid called seminal fluid. The
purpose of the seminal fluid is to both transport the sperm cells and enhance their fertilization abilities.

17. Cowper's Glands
The first portion of seminal fluid (about 5%) consists of secretions from the Cowper's glands. These pea-sized
glands produce what is called the pre-ejaculate fluid, the small amount of fluid that is released before
ejaculation. This fluid lubricates the urethra and neutralizes any acidity, allowing the sperm to travel easily.
Prostate Gland
Around 15% to 30% of semen is produced by the prostate gland, a walnut- sized gland located at the base of
the bladder surrounding a man's urethra. The prostate gland is the primary source of acid phosphatase, citric
acid,
inositol, calcium, zinc, and magnesium.
All of these unique components play a role. For example, zinc is believed to be an antibacterial factor.
Interestingly, some experts believe that this may contribute to the reason why urinary tract infections are not
as common in men compared to women.

18. The prostate gland also releases enzymes that work to liquefy semen about 15 to 30 minutes after ejaculation.
This liquefying process allows the sperm to be slowly released.
The sperm cells can then enter the cervix and travel upstream in the female reproductive system in an orderly
fashion, with the ultimate goal of finding an egg to fertilize.
Seminal Vesicles (Seminal Glands)
Around 65% to 75% of seminal fluid is produced by the seminal vesicles, which are located above the prostate
gland at the base of the bladder. They contribute components like fructose (a sugar) and prostaglandins.
Fructose nourishes the sperm cells, providing them with energy. Prostaglandins help trigger the contraction
of vaginal muscles in order to propel the sperm up the vaginal canal and through the cervix.
Clotting factors are also present in the fluid secreted by the seminal vesicles. This makes the semen clump
together, forming a jelly-like consistency right after ejaculation.
The purpose of the clotting process is to hold the sperm in place until it can be slowly released during the
liquefying process (controlled by enzymes secreted by the prostate gland).
Semen often has a chlorine-like smell and tastes slightly sweet due to its high content of fructose. That being
said, the taste of semen tends to change slightly from person to person.
Normal semen may have an off-white or slightly yellow tint.