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2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation

As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.

2.1 THE MALE REPRODUCTIVE SYSTEM

The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.

The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5o C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 2.1b).

Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 2.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 2.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.

The penis is the male external genitalia (Figure 2.1a, b). It is made up
of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold
of skin called foreskin.
The male accessory glands (Figure 2.1a, b) include paired seminal
vesicles, a prostate and paired bulbourethral glands. Secretions of these
glands constitute the seminal plasma which is rich in fructose, calcium
and certain enzymes. The secretions of bulbourethral glands also helps
in the lubrication of the penis.

2.2 THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries alongwith a pair
of oviducts, uterus, cervix, vagina and the external genitalia located in
pelvic region (Figure 2.3a). These parts of the system alongwith a pair of the
mammary glands are integrated structurally and functionally to support
the processes of ovulation, fertilisation, pregnancy, birth and child care.
Ovaries are the primary female sex organs that produce the female
gamete (ovum) and several steroid hormones (ovarian hormones).
The ovaries are located one on each side of the lower abdomen
(Figure 2.3b). Each ovary is about 2 to 4 cm in length and is connected to
the pelvic wall and uterus by ligaments. Each ovary is covered by a thin
epithelium which encloses the ovarian stroma. The stroma is divided into
two zones – a peripheral cortex and an inner medulla.

The oviducts (fallopian tubes), uterus and vagina constitute the female
accessory ducts. Each fallopian tube is about 10-12 cm long and extends
from the periphery of each ovary to the uterus (Figure 2.3b), the part closer
to the ovary is the funnel-shaped infundibulum. The edges of the
infundibulum possess finger-like projections called fimbriae, which help in
collection of the ovum after ovulation. The infundibulum leads to a wider

part of the oviduct called ampulla. The last part of the oviduct, isthmus has
a narrow lumen and it joins the uterus.
The uterus is single and it is also called womb. The shape of the uterus
is like an inverted pear. It is supported by ligaments attached to the pelvic
wall. The uterus opens into vagina through a narrow cervix. The cavity of
the cervix is called cervical canal (Figure 2.3b) which alongwith vagina
forms the birth canal. The wall of the uterus has three layers of tissue. The
external thin membranous perimetrium, middle thick layer of smooth
muscle, myometrium and inner glandular layer called endometrium that
lines the uterine cavity. The endometrium undergoes cyclical changes during
menstrual cycle while the myometrium exhibits strong contraction during
delivery of the baby.
The female external genitalia include mons pubis, labia majora, labia
minora, hymen and clitoris (Figure 2.3a). Mons pubis is a cushion of fatty
tissue covered by skin and pubic hair. The labia majora are fleshy folds of
tissue, which extend down from the mons pubis and surround the vaginal
opening. The labia minora are paired folds of tissue under the labia majora.
The opening of the vagina is often covered partially by a membrane called
hymen. The clitoris is a tiny finger-like structure which lies at the upper
junction of the two labia minora above the urethral opening. The hymen is
often torn during the first coitus (intercourse). However, it can also be broken
by a sudden fall or jolt, insertion of a vaginal tampon, active participation
in some sports like horseback riding, cycling, etc. In some women the hymen
persists even after coitus. In fact, the presence or absence of hymen is not
a reliable indicator of virginity or sexual experience.

A functional mammary gland is characteristic of all female mammals.
The mammary glands are paired structures (breasts) that contain
glandular tissue and variable amount of fat. The glandular tissue of each
breast is divided into 15-20 mammary lobes containing clusters of cells
called alveoli (Figure 2.4). The cells of alveoli secrete milk, which is stored
in the cavities (lumens) of alveoli. The alveoli open into mammary tubules.
The tubules of each lobe join to form a mammary duct. Several mammary
ducts join to form a wider mammary ampulla which is connected to
lactiferous duct through which milk is sucked out.

GAMETOGENESIS
The primary sex organs – the testis in the males and the ovaries in the
females –produce gametes, i.e, sperms and ovum, respectively, by the
process called gametogenesis. In testis, the immature male germ cells
(spermatogonia) produce sperms by spermatogenesis that begins at
puberty. The spermatogonia (sing. spermatogonium) present on the
inside wall of seminiferous tubules multiply by mitotic division and
increase in numbers. Each spermatogonium is diploid and contains 46
chromosomes. Some of the spermatogonia called primary
spermatocytes periodically undergo meiosis. A primary spermatocyte
completes the first meiotic division (reduction division) leading to
formation of two equal, haploid cells called
secondary spermatocytes, which have
only 23 chromosomes each. The secondary
spermatocytes undergo the second meiotic
division to produce four equal, haploid
spermatids (Figure 2.5). What would be the
number of chromosome in the spermatids?
The spermatids are transformed into
spermatozoa (sperms) by the process
called spermiogenesis. After
spermiogenesis, sperm heads become
embedded in the Sertoli cells, and are finally
released from the seminiferous tubules by
the process called spermiation.
Spermatogenesis starts at the age of
puberty due to significant increase in the
secretion of gonadotropin releasing hormone
(GnRH). This, if you recall, is a hypothalamic hormone. The increased
levels of GnRH then acts at the anterior pituitary gland and stimulates
secretion of two gonadotropins – luteinising hormone (LH) and follicle
stimulating hormone (FSH). LH acts at the Leydig cells and stimulates
synthesis and secretion of androgens. Androgens, in turn, stimulate the
process of spermatogenesis. FSH acts on the Sertoli cells and stimulates

secretion of some factors which help in the
process of spermiogenesis.
Let us examine the structure of a sperm. It
is a microscopic structure composed of a head,
neck, a middle piece and a tail (Figure 2.6).
A plasma membrane envelops the whole body
of sperm. The sperm head contains an elongated
haploid nucleus, the anterior portion of which
is covered by a cap-like structure, acrosome.
The acrosome is filled with enzymes that help
fertilisation of the ovum. The middle piece
possesses numerous mitochondria, which
produce energy for the movement of tail that
facilitate sperm motility essential for fertilisation.
The human male ejaculates about 200 to 300
million sperms during a coitus of which, for
normal fertility, at least 60 per cent sperms
must have normal shape and size and at least
40 per cent of them must show vigorous
motility

Sperms released from the seminiferous
tubules, are transported by the accessory
ducts. Secretions of epididymis, vas deferens, seminal vesicle and
prostate are essential for maturation and motility of sperms. The seminal
plasma along with the sperms constitute the semen. The functions of
male sex accessory ducts and glands are maintained by the testicular
hormones (androgens).
The process of formation of a mature female gamete is called oogenesis
which is markedly different from spermatogenesis. Oogenesis is initiated
during the embryonic development stage when a couple of million gamete
mother cells (oogonia) are formed within each fetal ovary; no more oogonia
are formed and added after birth. These cells start division and enter into
prophase-I of the meiotic division and get temporarily arrested at that stage,
called primary oocytes. Each primary oocyte then gets surrounded by a
layer of granulosa cells and is called the primary follicle (Figure 2.7). A
large number of these follicles degenerate during the phase from birth to
puberty. Therefore, at puberty only 60,000-80,000 primary follicles are
left in each ovary. The primary follicles get surrounded by more layers of
granulosa cells and a new theca and are called secondary follicles.
The secondary follicle soon transforms into a tertiary follicle which is
characterised by a fluid filled cavity called antrum. The theca layer is
organised into an inner theca interna and an outer theca externa. It is
important to draw your attention that it is at this stage that the primary
oocyte within the tertiary follicle grows in size and completes its first meiotic
division. It is an unequal division resulting in the formation of a large
haploid secondary oocyte and a tiny first polar body (Figure 2.8b). The

secondary oocyte retains bulk of the
nutrient rich cytoplasm of the primary
oocyte. Can you think of any advantage
for this? Does the first polar body born
out of first meiotic division divide further
or degenerate? At present we are not
very certain about this. The tertiary
follicle further changes into the mature
follicle or Graafian follicle (Figure 2.7).
The secondary oocyte forms a new
membrane called zona pellucida
surrounding it. The Graafian follicle now
ruptures to release the secondary oocyte
(ovum) from the ovary by the
process called ovulation. Can you
identify major differences between
spermatogenesis and oogenesis? A diagrammatic representation of
spermatogenesis and oogenesis is given below (Figure 2.8).

2.4 MENSTRUAL CYCLE
The reproductive cycle in the female primates (e.g. monkeys, apes and
human beings) is called menstrual cycle. The first menstruation begins
at puberty and is called menarche. In human females, menstruation
is repeated at an average interval of about 28/29 days, and the cycle of
events starting from one menstruation till the next one is called the
menstrual cycle. One ovum is released (ovulation) during the middle

of each menstrual cycle. The major events of the menstrual cycle are
shown in Figure 2.9. The cycle starts with the menstrual phase, when
menstrual flow occurs and it lasts for 3-5 days. The menstrual flow
results due to breakdown of endometrial lining of the uterus and its
blood vessels which forms liquid that comes out through vagina.
Menstruation only occurs if the released ovum is not fertilised. Lack of
menstruation may be indicative of pregnancy. However, it may also be
caused due to some other underlying causes like stress, poor health etc.
The menstrual phase is followed by the follicular phase. During
this phase, the primary follicles in the ovary grow to become a
fully mature Graafian follicle and simultaneously the endometrium
of uterus regenerates through proliferation. These changes in the
ovary and the uterus are induced by changes in the levels of
pituitary and ovarian hormones (Figure 2.9). The secretion of

gonadotropins (LH and FSH) increases gradually during the follicular
phase, and stimulates follicular development as well as secretion of
estrogens by the growing follicles. Both LH and FSH attain a peak level
in the middle of cycle (about 14th day). Rapid secretion of LH leading to
its maximum level during the mid-cycle called LH surge induces rupture
of Graafian follicle and thereby the release of ovum (ovulation). The
ovulation (ovulatory phase) is followed by the luteal phase during which
the remaining parts of the Graafian follicle transform as the corpus
luteum (Figure 2.9). The corpus luteum secretes large amounts of
progesterone which is essential for maintenance of the endometrium.
Such an endometrium is necessary for implantation of the fertilised
ovum and other events of pregnancy. During pregnancy all events of
the menstrual cycle stop and there is no menstruation. In the absence
of fertilisation, the corpus luteum degenerates. This causes disintegration
of the endometrium leading to menstruation, marking a new cycle. In
human beings, menstrual cycles ceases around 50 years of age; that is
termed as menopause. Cyclic menstruation is an indicator of normal
reproductive phase and extends between menarche and menopause.

Menstrual Hygiene

Maintenance of
hygiene and sanitation
during menstruation is
very important. Take
bath and clean yourself
regulary. Use sanitary
napkins or clean
homemade pads.
Change sanitary
napkins or homemade
pads after every 4–5 hrs
as per the requirement.
Dispose of the used
sanitary napkins
properly wrapping it
with a used paper. Do
not throw the used
napkins in the
drainpipe of toilets or
in the open area. After
handling the napkin
wash hands with soap.
Menstrual Hygiene

2.5 FERTILISATION AND IMPLANTATION

During copulation (coitus) semen is released by the penis into the vagina(insemination). The motile sperms swim rapidly, pass through the cervix,enter into the uterus and finally reach the ampullary region of thefallopian tube (Figure 2.11b). The ovum released by the ovary is alsotransported to the ampullary regionwhere fertilisation takes place.Fertilisation can only occur if theovum and sperms are transportedsimultaneously to the ampullaryregion. This is the reason why not allcopulations lead to fertilisation andpregnancy.The process of fusion of a spermwith an ovum is called fertilisation.During fertilisation, a sperm comes incontact with the zona pellucida layerof the ovum (Figure 2.10) and induceschanges in the membrane that blockthe entry of additional sperms. Thus,it ensures that only one sperm canfertilise an ovum. The secretions of theacrosome help the sperm enter into thecytoplasm of the ovum through thezona pellucida and the plasma

membrane. This induces the completion of the meiotic division of the
secondary oocyte. The second meiotic division is also unequal and results
in the formation of a second polar body and a haploid ovum (ootid). Soon
the haploid nucleus of the sperms and that of the ovum fuse together to
form a diploid zygote. How many chromosomes will be there in the zygote?
One has to remember that the sex of the baby has been decided at this
stage itself. Let us see how? As you know the chromosome pattern in the
human female is XX and that in the male is XY. Therefore, all the haploid
gametes (ova) produced by the female have the sex chromosome X whereas
in the male gametes (sperms) the sex chromosome could be either X or Y,
hence, 50 per cent of sperms carry the X chromosome while the other 50 per
cent carry the Y. After fusion of the male and female gametes the zygote
would carry either XX or XY depending on whether the sperm carrying X
or Y fertilised the ovum. The zygote carrying XX would develop into a female
baby and XY would form a male (you will learn more about the chromosomal
patterns in Chapter 5). That is why, scientifically it is correct to say that the
sex of the baby is determined by the father and not by the mother!
The mitotic division starts as the zygote moves through the isthmus
of the oviduct called cleavage towards the uterus (Figure 2.11) and forms
2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8 to 16

membrane. This induces the completion of the meiotic division of the
secondary oocyte. The second meiotic division is also unequal and results
in the formation of a second polar body and a haploid ovum (ootid). Soon
the haploid nucleus of the sperms and that of the ovum fuse together to
form a diploid zygote. How many chromosomes will be there in the zygote?
One has to remember that the sex of the baby has been decided at this
stage itself. Let us see how? As you know the chromosome pattern in the
human female is XX and that in the male is XY. Therefore, all the haploid
gametes (ova) produced by the female have the sex chromosome X whereas
in the male gametes (sperms) the sex chromosome could be either X or Y,
hence, 50 per cent of sperms carry the X chromosome while the other 50 per
cent carry the Y. After fusion of the male and female gametes the zygote
would carry either XX or XY depending on whether the sperm carrying X
or Y fertilised the ovum. The zygote carrying XX would develop into a female
baby and XY would form a male (you will learn more about the chromosomal
patterns in Chapter 5). That is why, scientifically it is correct to say that the
sex of the baby is determined by the father and not by the mother!
The mitotic division starts as the zygote moves through the isthmus
of the oviduct called cleavage towards the uterus (Figure 2.11) and forms
2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8 to 16

blastomeres is called a morula (Figure 2.11e). The morula continues to
divide and transforms into blastocyst (Figure 2.11g) as it moves further
into the uterus. The blastomeres in the blastocyst are arranged into an
outer layer called trophoblast and an inner group of cells attached to
trophoblast called the inner cell mass. The trophoblast layer then gets
attached to the endometrium and the inner cell mass gets differentiated
as the embryo. After attachment, the uterine cells divide rapidly and covers
the blastocyst. As a result, the blastocyst becomes embedded in the
endometrium of the uterus (Figure 2.11 step H). This is called implantation
and it leads to pregnancy.

2.6 PREGNANCY AND EMBRYONIC DEVELOPMENT
After implantation, finger-like projections appear on the trophoblast called
chorionic villi which are surrounded by the uterine tissue and maternal
blood. The chorionic villi and uterine tissue become interdigitated with
each other and jointly form a structural and functional unit between
developing embryo (foetus) and maternal body called placenta (Figure 2.12).
The placenta facilitate the supply of oxygen and nutrients to the
embryo and also removal of carbon dioxide and excretory/waste materials
produced by the embryo. The placenta is connected to the embryo through
an umbilical cord which helps in the transport of substances to and from
the embryo. Placenta also acts as an endocrine tissue and produces
several hormones like human chorionic gonadotropin (hCG), human
placental lactogen (hPL), estrogens, progestogens, etc. In the later
phase of pregnancy, a hormone called relaxin is also secreted by
the ovary. Let us remember
that hCG, hPL and relaxin
are produced in women
only during pregnancy. In
addition, during pregnancy
the levels of other hormones
like estrogens, progestogens,
cortisol, prolactin, thyroxine,
etc., are increased several-
folds in the maternal blood.
Increased production of these
hormones is essential for
supporting the fetal growth,
metabolic changes in the
mother and maintenance of
pregnancy.
Immediately after
implantation, the inner cell
mass (embryo) differentiates

into an outer layer called ectoderm and an inner layer called endoderm. A
mesoderm soon appears between the ectoderm and the endoderm. These
three layers give rise to all tissues (organs) in adults. It needs to be mentioned
here that the inner cell mass contains certain cells called stem cells which
have the potency to give rise to all the tissues and organs.
What are the major features of embryonic development at various
months of pregnancy? The human pregnancy lasts 9 months. Do you
know for how many months pregnancy last in dogs, elephants, cats?
Find out. In human beings, after one month of pregnancy, the embryo’s
heart is formed. The first sign of growing foetus may be noticed by listening
to the heart sound carefully through the stethoscope. By the end of the
second month of pregnancy, the foetus develops limbs and digits. By the
end of 12 weeks (first trimester), most of the major organ systems are
formed, for example, the limbs and external genital organs are well-
developed. The first movements of the foetus and appearance of hair on
the head are usually observed during the fifth month. By the end of about
24 weeks (end of second trimester), the body is covered with fine hair,
eye-lids separate, and eyelashes are formed. By the end of nine months
of pregnancy, the foetus is fully developed and is ready for delivery.

2.7 PARTURITION AND LACTATION
The average duration of human pregnancy is about 9 months
which is called the gestation period. Vigorous contraction of the uterus at
the end of pregnancy causes expulsion/delivery of the foetus. This process
of delivery of the foetus (childbirth) is called parturition. Parturition is
induced by a complex neuroendocrine mechanism. The signals for
parturition originate from the fully developed foetus and the placenta
which induce mild uterine contractions called foetal ejection reflex. This
triggers release of oxytocin from the maternal pituitary. Oxytocin acts on
the uterine muscle and causes stronger uterine contractions, which in
turn stimulates further secretion of oxytocin. The stimulatory reflex between
the uterine contraction and oxytocin secretion continues resulting in
stronger and stronger contractions. This leads to expulsion of the baby
out of the uterus through the birth canal – parturition. Soon after the
infant is delivered, the placenta is also expelled out of the uterus. What do
you think the doctors inject to induce delivery?
The mammary glands of the female undergo differentiation during
pregnancy and starts producing milk towards the end of pregnancy by
the process called lactation. This helps the mother in feeding the new-
born. The milk produced during the initial few days of lactation is called
colostrum which contains several antibodies absolutely essential to
develop resistance for the new-born babies. Breast-feeding during the
initial period of infant growth is recommended by doctors for bringing up
a healthy baby.

SUMMARY
Humans are sexually reproducing and viviparous. The male
reproductive system is composed of a pair of testes, the male sex
accessory ducts and the accessory glands and external genitalia. Each
testis has about 250 compartments called testicular lobules, and each
lobule contains one to three highly coiled seminiferous tubules. Each
seminiferous tubule is lined inside by spermatogonia and Sertoli cells.
The spermatogonia undergo meiotic divisions leading to sperm formation,
while Sertoli cells provide nutrition to the dividing germ cells. The Leydig
cells outside the seminiferous tubules, synthesise and secrete testicular
hormones called androgens. The male external genitalia is called penis.
The female reproductive system consists of a pair of ovaries, a pair
of oviducts, a uterus, a vagina, external genitalia, and a pair of
mammary glands. The ovaries produce the female gamete (ovum) and
some steroid hormones (ovarian hormones). Ovarian follicles in different
stages of development are embedded in the stroma. The oviducts, uterus
and vagina are female accessory ducts. The uterus has three layers
namely perimetrium, myometrium and endometrium. The female
external genitalia includes mons pubis, labia majora, labia minora,
hymen and clitoris. The mammary glands are one of the female
secondary sexual characteristics.
Spermatogenesis results in the formation of sperms that are
transported by the male sex accessory ducts. A normal human sperm
is composed of a head, neck, a middle piece and tail. The process of
formation of mature female gametes is called oogenesis. The
reproductive cycle of female primates is called menstrual cycle.
Menstrual cycle starts only after attaining sexual maturation (puberty).
During ovulation only one ovum is released per menstrual cycle. The
cyclical changes in the ovary and the uterus during menstrual cycle
are induced by changes in the levels of pituitary and ovarian hormones.
After coitus, sperms are transported to the ampulla, where the sperm
fertilises the ovum leading to formation of a diploid zygote. The presence
of X or Y chromosome in the sperm determines the sex of the embryo.
The zygote undergoes repeated mitotic division to form a blastocyst,
which is implanted in the uterus resulting in pregnancy. After nine
months of pregnancy, the fully developed foetus is ready for delivery.
The process of childbirth is called parturition which is induced by a
complex neuroendocrine mechanism involving cortisol, estrogens and
oxytocin. Mammary glands differentiate during pregnancy and secrete
milk after child-birth. The new-born baby is fed milk by the mother
(lactation) during the initial few months of growth.

EXERCISES

1. Fill in the blanks:
   (a) Humans reproduce _ (asexually/sexually)
   (b) Humans are _ (oviparous, viviparous, ovoviviparous)
   (c) Fertilisation is _ in humans (external/internal)
   (d) Male and female gametes are _ (diploid/haploid)
   (e) Zygote is _ (diploid/haploid)
2. (f) The process of release of ovum from a mature follicle is called
3. (g) Ovulation is induced by a hormone called _
4. (h) The fusion of male and female gametes is called _
5. (i) Fertilisation takes place in _
6. (j) Zygote divides to form _______which is implanted in uterus. (k) The structure which provides vascular connection between foetus and uterus is called _______
7. Draw a labelled diagram of male reproductive system.
8. Draw a labelled diagram of female reproductive system.
9. Write two major functions each of testis and ovary.
10. Describe the structure of a seminiferous tubule.
11. What is spermatogenesis? Briefly describe the process of spermatogenesis.
12. Name the hormones involved in regulation of spermatogenesis.
13. Define spermiogenesis and spermiation.
14. Draw a labelled diagram of sperm.
15. What are the major components of seminal plasma?
16. What are the major functions of male accessory ducts and glands?
17. What is oogenesis? Give a brief account of oogenesis.
18. Draw a labelled diagram of a section through ovary.
19. Draw a labelled diagram of a Graafian follicle?
20. Name the functions of the following:
    (a) Corpus luteum (b) Endometrium
    (c) Acrosome (d) Sperm tail
    (e) Fimbriae
21. Identify True/False statements. Correct each false statement to make
    it true.
    (a) Androgens are produced by Sertoli cells. (True/False)
    (b) Spermatozoa get nutrition from Sertoli cells. (True/False)
    (c) Leydig cells are found in ovary. (True/False)
    (d) Leydig cells synthesise androgens. (True/False)
    (e) Oogenesis takes place in corpus luteum. (True/False)
    (f) Menstrual cycle ceases during pregnancy. (True/False)
    (g) Presence or absence of hymen is not a reliable indicator of virginity
    or sexual experience. (True/False)
22. What is menstrual cycle? Which hormones regulate menstrual cycle?
23. What is parturition? Which hormones are involved in induction of parturition?
24. In our society the women are often blamed for giving birth to daughters.
    Can you explain why this is not correct?
25. How many eggs are released by a human ovary in a month? How many
    eggs do you think would have been released if the mother gave birth to
    identical twins? Would your answer change if the twins born were
    fraternal?
26. How many eggs do you think were released by the ovary of a female dog
    which gave birth to 6 puppies?