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.

3.1 THE MALE REPRODUCTIVE SYSTEM

The male reproductive system is located in the pelvis region

(Figure 3.1a). It includes a pair of testes alongwith

accessory ducts, glands and the external genitalia.

CHAPTER 3

HUMAN REPRODUCTION

3.1 The Male Reproductive

System

3.2 The Female Reproductive

System

3.3 Gametogenesis

3.4 Menstrual Cycle

3.5 Fertilisation and

Implantation

3.6 Pregnancy and

Embryonic Development

3.7 Parturition and Lactation

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The testes are situated outside the

abdominal cavity within a pouch

called scrotum. The scrotum helps

in maintaining the low temperature

of the testes (2–2.5

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 3.1b).

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 3.2 ). 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 3.2). 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 3.1b). 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 3.1a). 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.

Figure 3.1(a) Diagrammatic sectional view of male pelvis

showing reproductive system

Figure 3.1(b) Diagrammatic view of male reproductive system

(part of testis is open to show inner details)

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The penis is the male external genitalia (Figure 3.1a, 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 3.1a, 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.

3.2 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 3.3a). 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 3.3b). 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.

Figure 3.2 Diagrammatic sectional view of seminiferous tubule

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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 3.3b), 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

Figure 3.3 (b) Diagrammatic sectional view of the female reproductive system

Figure 3.3 (a) Diagrammatic sectional view of female pelvis showing

reproductive system

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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 3.3b) 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 3.3a). 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.

Figure 3.4 A diagrammatic sectional view of Mammary gland

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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 3.4). 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.

3.3 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 3.5). 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

Figure 3.5 Diagrammatic sectional view of a

seminiferous tubule (enlarged)

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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 3.6). 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 3.7). 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 3.8b). The

Figure 3.6 Structure of a sperm

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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 3.7).

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 3.8).

Figure 3.7 Diagrammatic Section view of ovary

Figure 3.8 Schematic representation of (a) Spermatogenesis; (b) Oogenesis

(a) (b)

3.4 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

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Figure 3.9 Diagrammatic presentation of various events during a menstrual cycle

of each menstrual cycle. The major events of the menstrual cycle are

shown in Figure 3.9. 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 3.9). The secretion of

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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 14

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 3.9). 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.

3.5 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 the

fallopian tube (Figure 3.11b). The ovum released by the ovary is also

transported to the ampullary region

where fertilisation takes place.

Fertilisation can only occur if the

ovum and sperms are transported

simultaneously to the ampullary

region. This is the reason why not all

copulations lead to fertilisation and

pregnancy.

The process of fusion of a sperm

with an ovum is called fertilisation.

During fertilisation, a sperm comes in

contact with the zona pellucida layer

of the ovum (Figure 3.10) and induces

changes in the membrane that block

the entry of additional sperms. Thus,

it ensures that only one sperm can

fertilise an ovum. The secretions of the

acrosome help the sperm enter into the

cytoplasm of the ovum through the

zona pellucida and the plasma

Figure 3.10 Ovum surrounded by few sperms

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

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Figure 3.11 Transport of ovum, fertilisation and passage of growing embryo through fallopian tube

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 3.11) and forms

2, 4, 8, 16 daughter cells called

blastomeres. The embryo with 8 to 16

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blastomeres is called a morula (Figure 3.11e). The morula continues to

divide and transforms into blastocyst (Figure 3.11g) 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 3.11h). This is called implantation

and it leads to pregnancy.

3.6 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 3.12).

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

Figure 3.12 The human foetus within the uterus

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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.

3.7 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.

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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 junction of the isthmus and

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)

(d) Male and female gametes are _____________ (diploid/haploid)

(e) Zygote is _____________ (diploid/haploid)

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(f) The process of release of ovum from a mature follicle is called

_____________

(g) Ovulation is induced by a hormone called _____________

(h) The fusion of male and female gametes is called _____________

(i) Fertilisation takes place in _____________

(j) Zygote divides to form _____________which is implanted in uterus.

(k) The structure which provides vascular connection between foetus

and uterus is called _____________

2. Draw a labelled diagram of male reproductive system.

3. Draw a labelled diagram of female reproductive system.

4. Write two major functions each of testis and ovary.

5. Describe the structure of a seminiferous tubule.

6. What is spermatogenesis? Briefly describe the process of spermatogenesis.

7. Name the hormones involved in regulation of spermatogenesis.

8. Define spermiogenesis and spermiation.

9. Draw a labelled diagram of sperm.

10. What are the major components of seminal plasma?

11. What are the major functions of male accessory ducts and glands?

12. What is oogenesis? Give a brief account of oogenesis.

13. Draw a labelled diagram of a section through ovary.

14. Draw a labelled diagram of a Graafian follicle?

15. Name the functions of the following:

(a) Corpus luteum (b) Endometrium

(e) Fimbriae

16. 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)

(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)

17. What is menstrual cycle? Which hormones regulate menstrual cycle?

18. What is parturition? Which hormones are involved in induction of parturition?

19. In our society the women are often blamed for giving birth to daughters.

Can you explain why this is not correct?

20. 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?

21. How many eggs do you think were released by the ovary of a female dog

which gave birth to 6 puppies?

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