1aHumans reproduce ________.
AnswerSexually.
00
Chapter Introduction
Read the whole reproductive sequence before studying each system in detail.
Human reproductive events occur after puberty and include formation of gametes (gametogenesis), transfer of sperm into the female genital tract (insemination), fusion of male and female gametes (fertilisation), zygote formation, cleavage, blastocyst formation and implantation, embryonic development during gestation, delivery of the baby by parturition and feeding of the newborn by lactation.
Core Idea
The chapter moves from gamete formation → fertilisation → development → birth → lactation.
Visualise the complete chapter
Whole-topic overview
What this diagram shows:
the complete conceptual flow of the chapter, so later topics can be
connected rather than memorised in isolation.
2.1
The Male Reproductive System
Structures involved in sperm formation, transport and insemination.
The male reproductive system is located in the pelvic region. It includes a pair of testes along with accessory ducts, accessory glands and external genitalia.
Testes and scrotum
The testes are situated outside the abdominal cavity in the scrotum. The scrotum maintains the temperature of the testes about 2–2.5°C lower than normal internal body temperature, which is necessary for spermatogenesis. In adults, each testis is oval, about 4–5 cm long and 2–3 cm wide. Each testis has about 250 testicular lobules, and each lobule contains one to three highly coiled seminiferous tubules.
Exam point: Scrotal position and its lower
temperature are linked with sperm formation.
Realistic anatomical view — male reproductive system
Overall pelvic relationship and sperm route
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Please check the file path and filename.
What this diagram shows: testes are outside the
main pelvic cavity; ducts connect sperm-producing regions to the
urethra; accessory glands contribute secretions to seminal plasma.
Seminiferous tubules, Sertoli cells and Leydig cells
Seminiferous tubules are the sites where sperm are produced. Their inner lining contains spermatogonia and Sertoli cells. Spermatogonia undergo meiotic divisions leading to sperm formation, while Sertoli cells provide nutrition to developing germ cells. Interstitial spaces outside the tubules contain blood vessels and Leydig cells, which synthesise and secrete androgens.
Realistic sectional view — seminiferous tubule
Cellular organisation
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Read the anatomy: developing germ cells lie within
the tubule; Sertoli cells support them; the lumen is the central
open space; Leydig cells occur outside the tubule in the
interstitial region.
Accessory ducts and glands
Accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. They store and transport sperm. Accessory glands include paired seminal vesicles, a prostate and paired bulbourethral glands. Their secretions form seminal plasma, rich in fructose, calcium and certain enzymes; bulbourethral secretions also aid lubrication.
Sequence: Seminiferous tubules → rete testis → vasa
efferentia → epididymis → vas deferens → ejaculatory duct → urethra.
Penis
The penis is the male external genitalia. Special tissue helps erection for insemination. The enlarged end is the glans penis, covered by foreskin. The urethra extends through the penis to the urethral meatus.
2.1 Important / exam points
- Scrotum keeps testes about 2–2.5°C below normal internal body temperature.
- Each testis has about 250 testicular lobules.
- Each lobule contains one to three highly coiled seminiferous tubules.
- Sertoli cells provide nutrition to developing germ cells.
- Leydig cells secrete androgens.
- Seminal plasma contains fructose, calcium and certain enzymes.
2.2
The Female Reproductive System
Structures that support ovulation, fertilisation, pregnancy, birth and child care.
The female reproductive system consists of a pair of ovaries, a pair of oviducts, the uterus, cervix, vagina, external genitalia and a pair of mammary glands.
Realistic anatomical view — female reproductive system
Overall pelvic organisation
Image could not be loadedPlease check the file path and filename.
What this diagram shows: each ovary connects
functionally with its oviduct; the uterus provides the internal
environment for implantation and pregnancy; the cervix connects
uterus and vagina.
Ovaries
Ovaries are the primary female sex organs. They produce the female gamete (ovum) and several steroid hormones. Each ovary is about 2–4 cm long and is connected to the pelvic wall and uterus by ligaments. The ovary is covered by thin epithelium and its stroma is divided into a peripheral cortex and inner medulla.
Ovary — sectional view
Follicles in different stages
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What this diagram shows: ovarian follicles are
embedded in the stroma; follicular development progresses from early
stages toward a mature Graafian follicle.
Oviduct
Each fallopian tube is about 10–12 cm long. The part nearer the ovary is the funnel-shaped infundibulum with finger-like fimbriae. It leads to the wider ampulla. The isthmus is the last, narrower part and joins the uterus. Fimbriae help in collection of the ovum after ovulation.
Uterus, cervix and vagina
The uterus is a single womb shaped like an inverted pear. The uterus opens into the vagina through the narrow cervix. The cervical canal together with the vagina forms the birth canal. The uterine wall has three layers: outer perimetrium, middle myometrium and inner endometrium. Endometrium undergoes cyclical changes during the menstrual cycle; myometrium contracts strongly during delivery.
Uterine wall — three layers
Cut-section interpretation
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Female external genitalia
The source lists mons pubis, labia majora, labia minora, hymen and clitoris. The source also states that presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
Important social-science point from the textbook:
hymen status cannot be used as a reliable indicator of virginity or
sexual experience.
Mammary glands
Each breast contains glandular tissue divided into 15–20 mammary lobes with alveoli. Alveoli secrete milk and have lumens where milk is stored. Alveoli open into mammary tubules; tubules join to form mammary ducts; several ducts form a mammary ampulla connected to a lactiferous duct that opens at the nipple.
Mammary gland — milk pathway
Internal organisation
Image could not be loadedPlease check the file path and filename.
2.2 Important / exam points
- Ovary: primary female sex organ producing ova and ovarian steroid hormones.
- Oviduct parts: infundibulum → ampulla → isthmus.
- Fimbriae help collect the ovum after ovulation.
- Uterine layers: perimetrium, myometrium, endometrium.
- Mammary gland pathway: alveoli → tubules → ducts → ampulla → lactiferous duct → nipple.
2.3
Gametogenesis
Formation of sperm in males and the mature female gamete through oogenesis.
The primary sex organs — testis in males and ovaries in females — produce gametes by gametogenesis. In the testis, sperm formation is called spermatogenesis; in the ovary, formation of the mature female gamete is called oogenesis.
Spermatogenesis
Spermatogonia present on the inside wall of seminiferous tubules multiply by mitotic division. They are diploid and contain 46 chromosomes. Primary spermatocytes undergo meiosis I to form two equal haploid secondary spermatocytes, each with 23 chromosomes. Secondary spermatocytes undergo meiosis II to form four equal haploid spermatids. Spermatids become spermatozoa by spermiogenesis, and mature sperm are released from the seminiferous tubules by spermiation.
Spermatogenesis — stage-by-stage
Division and differentiation sequence
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Hormonal regulation
Spermatogenesis begins at puberty with increased secretion of GnRH. GnRH stimulates the anterior pituitary to secrete LH and FSH. LH acts on Leydig cells and stimulates androgen synthesis and secretion; androgens in turn stimulate spermatogenesis. FSH acts on Sertoli cells and stimulates secretion of factors that support spermiogenesis.
Hormonal control of spermatogenesis
Source-based pathway
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Structure of sperm
A sperm is composed of head, neck, middle piece and tail. The plasma membrane surrounds the cell. The head contains an elongated haploid nucleus; its anterior region is covered by the cap-like acrosome. The acrosome contains enzymes that help fertilisation. The middle piece contains numerous mitochondria that produce energy for tail movement.
Source fact: about 200–300 million sperms may be
ejaculated; for normal fertility, at least 60% should have normal
shape and size and at least 40% should show vigorous motility.
Detailed scientific sperm diagram
Head → neck → middle piece → tail
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Oogenesis
Oogenesis begins during embryonic development. Oogonia form within the fetal ovary; after birth no more oogonia are formed or added. These cells enter prophase I and become primary oocytes. Each primary oocyte becomes surrounded by granulosa cells to form a primary follicle. Many follicles degenerate between birth and puberty, leaving about 60,000–80,000 primary follicles in each ovary at puberty. Primary follicles develop into secondary follicles, then tertiary follicles characterised by a fluid-filled antrum. The theca becomes organised into theca interna and theca externa. The primary oocyte completes its first meiotic division unequally to form a large haploid secondary oocyte and a tiny first polar body. The secondary oocyte forms a zona pellucida, the follicle becomes the mature Graafian follicle, and rupture releases the secondary oocyte by ovulation.
Oogenesis — follicular sequence
Developmental stages
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Graafian follicle — sectional study
Important labelled diagram
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2.3 Important / exam points
Spermatogenesis
- Begins at puberty.
- Spermatogonium: 46 chromosomes.
- Meiosis I → 2 secondary spermatocytes.
- Meiosis II → 4 spermatids.
- Spermiogenesis → spermatozoa.
- Spermiation → release.
Oogenesis
- Begins during embryonic development.
- Primary oocytes arrested in prophase I.
- Primary → secondary → tertiary → Graafian follicle.
- First meiotic division is unequal.
- Secondary oocyte retains most of the cytoplasm.
- Graafian follicle ruptures during ovulation.
2.4
Menstrual Cycle
Ovarian and uterine changes controlled by pituitary and ovarian hormones.
The reproductive cycle in female primates is called the menstrual cycle. In humans, the cycle repeats at an average interval of about 28/29 days. Menarche is the first menstruation at puberty; menopause is cessation of menstrual cycles around 50 years of age.
Menstrual phase
The cycle begins with menstrual flow and this lasts 3–5 days. The flow results from breakdown of the endometrial lining and its blood vessels, producing fluid that exits through the vagina. Menstruation occurs when the released ovum is not fertilised.
Follicular phase
Primary follicles grow toward a mature Graafian follicle, while the endometrium regenerates through proliferation. LH and FSH gradually increase and stimulate follicular development and estrogen secretion by growing follicles.
Ovulation
LH and FSH reach peak levels around the middle of the cycle, about the 14th day. Rapid secretion of LH produces the LH surge, which induces rupture of the Graafian follicle and release of the ovum.
Luteal phase
The remaining parts of the Graafian follicle form the corpus luteum, which secretes large amounts of progesterone. Progesterone is essential for maintenance of the endometrium, which is necessary for implantation and other events of pregnancy. If fertilisation does not occur, the corpus luteum degenerates and endometrium disintegrates, beginning a new cycle.
Menstrual cycle — coordinated visual
Ovary + hormones + uterus
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Important: menstruation, follicular development,
ovulation and luteal changes are coordinated with changing pituitary
and ovarian hormone levels.
2.4 Important / exam points
- Menarche = first menstruation at puberty.
- Average interval = about 28/29 days.
- Menstrual flow = 3–5 days.
- LH surge around mid-cycle induces ovulation.
- Corpus luteum secretes progesterone.
- Menstrual cycle stops during pregnancy.
- Menopause occurs around 50 years in the source.
2.5
Fertilisation and Implantation
From insemination and sperm transport to zygote, cleavage, blastocyst and implantation.
During coitus, semen is released into the vagina (insemination). Motile sperm pass through the cervix, enter the uterus and reach the ampullary region of the fallopian tube. The ovum is also transported to the ampullary region, where fertilisation takes place if sperm and ovum arrive there simultaneously.
Transport of sperm and ovum
Pathway to the ampullary region
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Fertilisation
A sperm comes in contact with the zona pellucida of the ovum and induces changes that block entry of additional sperms. Acrosome secretions help the sperm enter through the zona pellucida and plasma membrane. This triggers completion of the second meiotic division of the secondary oocyte, producing a second polar body and a haploid ovum (ootid). The haploid sperm nucleus and ovum nucleus then fuse to form a diploid zygote.
Fertilisation — sequential stages
From sperm–zona interaction to zygote
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Sex chromosome combination at fertilisation
The source explains that human females have XX and ova carry X; male sperms may carry X or Y. Therefore, a zygote may be XX or XY depending on whether an X-bearing or Y-bearing sperm fertilises the ovum. The source explicitly notes that this is why scientifically the sex of the baby is determined by the sperm contribution rather than the mother.
Cleavage and morula
The zygote undergoes mitotic division as it moves through the isthmus toward the uterus. Cleavage forms 2, 4, 8 and 16 blastomeres. An embryo with 8–16 blastomeres is called a morula.
Cleavage → morula → blastocyst → implantation
Developmental sequence
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2.5 Important / exam points
- Insemination = release of semen into the vagina.
- Fertilisation takes place in the ampullary region.
- Zona pellucida changes help block entry of additional sperm.
- Second meiotic division of secondary oocyte completes during fertilisation.
- Zygote is diploid.
- 8–16 blastomeres form the morula.
- Blastocyst has trophoblast and inner cell mass.
- Implantation of blastocyst into endometrium leads to pregnancy.
2.6
Pregnancy and Embryonic Development
Placenta, pregnancy hormones, germ layers and developmental milestones.
After implantation, finger-like projections called chorionic villi appear on the trophoblast. These are surrounded by uterine tissue and maternal blood. Chorionic villi and uterine tissue become interdigitated and jointly form the placenta, a structural and functional unit between the developing embryo/foetus and maternal body.
Placenta — maternal–foetal interface
Exchange and endocrine roles
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Functions in the source: placenta supplies oxygen
and nutrients, removes carbon dioxide and wastes, connects to the
embryo through the umbilical cord and acts as an endocrine tissue.
Placental hormones
The placenta produces hCG, hPL, estrogens and progestogens. In later pregnancy, relaxin is also secreted by the ovary. The source also notes increased maternal levels of estrogens, progestogens, cortisol, prolactin and thyroxine during pregnancy, supporting foetal growth, maternal metabolic changes and maintenance of pregnancy.
Embryonic germ layers
Immediately after implantation, the inner cell mass differentiates into an outer ectoderm and an inner endoderm, with mesoderm appearing between them. These three layers give rise to all tissues and organs in adults. The source also notes that the inner cell mass contains stem cells with the potency to give rise to tissues and organs.
Three embryonic germ layers
Basic developmental organisation
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Major developmental milestones
| Time | Source-described milestone |
|---|---|
| 1 month | Embryo’s heart is formed. |
| 2 months | Limbs and digits develop. |
| 12 weeks | Most major organ systems are formed; limbs and external genital organs are well developed. |
| 5 months | First foetal movements and appearance of hair on the head are usually observed. |
| About 24 weeks | Fine hair covers the body; eyelids separate and eyelashes form. |
| 9 months | Foetus is fully developed and ready for delivery. |
Foetal development timeline
Source-described milestones
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2.6 Important / exam points
- Chorionic villi + uterine tissue form the placenta.
- Umbilical cord connects placenta and embryo/foetus.
- Placenta supplies oxygen/nutrients and removes carbon dioxide/wastes.
- Placenta secretes hCG, hPL, estrogens and progestogens.
- Ectoderm, mesoderm and endoderm are the three embryonic layers.
- Human pregnancy lasts about nine months in the source.
2.7
Parturition and Lactation
Birth through neuroendocrine feedback, followed by milk production and newborn feeding.
The average duration of human pregnancy is about nine months, called the gestation period. Vigorous uterine contractions at the end of pregnancy cause expulsion of the foetus. This childbirth process is called parturition.
Parturition — neuroendocrine mechanism
Signals from the fully developed foetus and placenta induce mild uterine contractions called the foetal ejection reflex. This triggers oxytocin release from the maternal pituitary. Oxytocin acts on uterine muscle and strengthens contractions. Stronger contractions stimulate further oxytocin secretion, creating a positive feedback loop that continues until the baby is expelled through the birth canal. The placenta is expelled soon after delivery.
Parturition — positive feedback mechanism
Foetal ejection reflex and oxytocin
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Lactation and colostrum
Mammary glands differentiate during pregnancy and begin producing milk toward the end of pregnancy. This process is called lactation. Milk produced during the initial few days is called colostrum and contains several antibodies that are important for developing resistance in the newborn.
Lactation — mammary milk pathway
Connects with the mammary-gland structure learned in 2.2
Image could not be loadedPlease check the file path and filename.
2.7 Important / exam points
- Gestation period is about 9 months.
- Parturition is childbirth.
- Foetal signals initiate the foetal ejection reflex.
- Oxytocin strengthens uterine contractions through positive feedback.
- Placenta is expelled soon after delivery.
- Lactation is milk production after pregnancy begins to end-stage.
- Colostrum contains several antibodies important for newborn resistance.
R
Rapid Revision
One screen for the chapter’s most important sequences and facts.
Structures
- Male: testes, ducts, glands, penis.
- Female: ovaries, oviducts, uterus, cervix, vagina, external genitalia, mammary glands.
- Uterus: perimetrium, myometrium, endometrium.
- Mammary pathway: alveoli → tubules → ducts → ampulla → lactiferous duct → nipple.
Sequences
- Spermatogenesis: spermatogonium → primary spermatocyte → secondary spermatocytes → spermatids → spermatozoa.
- Oogenesis: oogonia → primary oocyte → follicles → Graafian follicle → secondary oocyte → ovulation.
- Zygote → 2, 4, 8, 16 blastomeres → morula → blastocyst → implantation.
Hormones
- GnRH → pituitary LH/FSH.
- LH → Leydig cells → androgens.
- FSH → Sertoli cells → support for spermiogenesis.
- LH surge → ovulation.
- Corpus luteum → progesterone.
- Placenta → hCG, hPL, estrogens, progestogens.
- Parturition → oxytocin positive feedback.
Key numbers from source
- Testis: ~4–5 cm long, 2–3 cm wide.
- ~250 testicular lobules per testis.
- 1–3 seminiferous tubules per lobule.
- Oviduct: ~10–12 cm.
- Menstrual cycle: about 28/29 days.
- Menstrual phase: 3–5 days.
- Pregnancy: about 9 months.
Q
NCERT-based Practice
Exercises represented from the supplied chapter.
Fill in the blanks
- Humans reproduce ________ (asexually/sexually).
- Humans are ________ (oviparous/viviparous/ovoviviparous).
- Fertilisation is ________ in humans (external/internal).
- Male and female gametes are ________ (diploid/haploid).
- Zygote is ________ (diploid/haploid).
- The process of release of ovum from a mature follicle is called ________.
- Ovulation is induced by a hormone called ________.
- The fusion of male and female gametes is called ________.
- Fertilisation takes place in ________.
- Zygote divides to form ________ which is implanted in uterus.
- The structure providing vascular connection between foetus and uterus is ________.
Diagram practice
- Draw a labelled male reproductive system.
- Draw a labelled female reproductive system.
- Draw a labelled seminiferous tubule.
- Draw a labelled sperm.
- Draw a section through ovary.
- Draw a labelled Graafian follicle.
Short answers
- Write two major functions each of testis and ovary.
- Describe the structure of a seminiferous tubule.
- What is spermatogenesis?
- Name the hormones involved in regulation of spermatogenesis.
- Define spermiogenesis and spermiation.
- What are the major components of seminal plasma?
- What is oogenesis?
Functions — practice
Write the functions of: corpus luteum, endometrium, acrosome, sperm tail, fimbriae.
True / False — source exercise set
- Androgens are produced by Sertoli cells.
- Spermatozoa get nutrition from Sertoli cells.
- Leydig cells are found in ovary.
- Leydig cells synthesise androgens.
- Oogenesis takes place in corpus luteum.
- Menstrual cycle ceases during pregnancy.
- Presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
Long-answer / conceptual questions
- What is the menstrual cycle? Which hormones regulate it?
- What is parturition? Which hormones are involved in its induction?
- Explain why women should not be blamed for the birth of daughters.
- How many eggs are released by a human ovary in a month? How would the answer change for identical and fraternal twins?
- How many eggs might have been released by a female dog giving birth to six puppies?
A
NCERT Exercise Answers
Chapter-based answers prepared directly from the supplied NCERT chapter. Use the answers after attempting the questions yourself.
How to use this section
First solve the exercise without looking below. Then compare your response with the chapter-based answer. Long answers are written in an exam-friendly form while keeping the source chapter's terminology and sequence.
21 Exercises Covered
Fill in the Blanks
Diagrams
Short Answers
True / False
Long Answers
Exercise 1 — Fill in the blanks
1bHumans are ________.
AnswerViviparous.
1cFertilisation is ________ in humans.
AnswerInternal.
1dMale and female gametes are ________.
AnswerHaploid.
1eZygote is ________.
AnswerDiploid.
1fRelease of ovum from a mature follicle is called
________.
AnswerOvulation.
1gOvulation is induced by a hormone called ________.
AnswerLH (luteinising hormone),
particularly the mid-cycle LH surge.
1hFusion of male and female gametes is called ________.
AnswerFertilisation.
1iFertilisation takes place in ________.
AnswerAmpullary region of the
fallopian tube.
1jZygote divides to form ________ which is implanted in
uterus.
AnswerBlastocyst.
1kThe structure providing vascular connection between foetus and
uterus is called ________.
AnswerPlacenta.
Exercise 2–3 — Labelled diagrams
2Draw a labelled male reproductive system.
In the diagram, label the testes, scrotum, epididymis, vas
deferens, seminal vesicles, prostate gland, bulbourethral glands,
urethra, penis, urinary bladder and related ducts shown in the
chapter.
3Draw a labelled female reproductive system.
Label the ovaries, oviduct/fallopian tube, infundibulum, fimbriae,
ampulla, isthmus, uterus, cervix, cervical canal and vagina.
Include the three uterine layers where a sectional view is asked.
Exercise 4–14 — Short answers and diagram answers
4Two major functions each of testis and ovary.
Testis
- Produces male gametes (sperms).
- Produces/secretes testicular hormones called androgens.
- Produces the female gamete (ovum).
- Produces steroid/ovarian hormones.
5Describe the structure of a seminiferous tubule.
Each testicular lobule contains one to three highly coiled
seminiferous tubules. Their inner lining contains male germ cells
(spermatogonia) and Sertoli cells. Germ cells undergo meiotic
divisions leading to sperm formation, while Sertoli cells provide
nutrition to the developing germ cells. Outside the tubules are
interstitial spaces containing blood vessels and Leydig cells.
6What is spermatogenesis? Briefly describe it.
Spermatogenesis is the process of formation of sperms from
spermatogonia in the seminiferous tubules. Spermatogonia multiply
mitotically; some become primary spermatocytes. A primary
spermatocyte undergoes meiosis I to form two haploid secondary
spermatocytes. These undergo meiosis II to form four haploid
spermatids. Spermatids are transformed into spermatozoa by
spermiogenesis, and the spermatozoa are released from the
seminiferous tubules by spermiation.
7Name the hormones involved in regulation of
spermatogenesis.
GnRH from the hypothalamus acts on the anterior pituitary, which
stimulates secretion of LH and FSH. LH acts on Leydig cells to
stimulate androgen secretion. FSH acts on Sertoli cells and
stimulates factors supporting spermiogenesis.
8Define spermiogenesis and spermiation.
Spermiogenesis: transformation of spermatids into
spermatozoa (sperms).
Spermiation: release of spermatozoa from the seminiferous tubules after spermiogenesis.
Spermiation: release of spermatozoa from the seminiferous tubules after spermiogenesis.
9Draw a labelled diagram of sperm.
Label
head, acrosome, haploid nucleus, neck, middle piece,
mitochondria, tail
and the surrounding plasma membrane.
10Major components of seminal plasma.
The secretions of the accessory glands form seminal plasma. The
source specifically describes it as rich in
fructose, calcium and certain enzymes.
11Major functions of male accessory ducts and glands.
Accessory ducts: store and transport sperms from
the testes towards the outside through the urethra; secretions of
epididymis and vas deferens contribute to sperm maturation and
motility.
Accessory glands: add seminal secretions; seminal vesicles, prostate and bulbourethral glands contribute to seminal plasma, and bulbourethral secretion helps lubricate the penis.
Accessory glands: add seminal secretions; seminal vesicles, prostate and bulbourethral glands contribute to seminal plasma, and bulbourethral secretion helps lubricate the penis.
12What is oogenesis? Give a brief account.
Oogenesis is the process of formation of a mature female gamete.
It begins during embryonic development. Oogonia form primary
oocytes that enter prophase-I and remain temporarily arrested. The
primary oocyte becomes part of a primary follicle, which develops
through secondary and tertiary follicle stages. The tertiary
follicle has an antrum and the theca becomes organised into theca
interna and theca externa. The primary oocyte completes meiosis I
to form a large haploid secondary oocyte and a small first polar
body. The tertiary follicle becomes a Graafian follicle, whose
rupture releases the secondary oocyte by ovulation.
13Draw a labelled section through ovary.
The ovary should show the
peripheral cortex, inner medulla and ovarian
follicles at different developmental stages as described in the
chapter.
14Draw a labelled Graafian follicle.
Show the
secondary oocyte, zona pellucida, granulosa cell region,
antrum, theca interna and theca externa
in an appropriate sectional view.
Exercise 15 — Functions
| Structure | Function |
|---|---|
| Corpus luteum | Secretes large amounts of progesterone, which is essential for maintenance of the endometrium. |
| Endometrium | Inner glandular layer of the uterus; it undergoes cyclical changes and provides the uterine lining important for implantation and pregnancy maintenance. |
| Acrosome | Cap-like structure on the sperm head containing enzymes that help the sperm enter the ovum during fertilisation. |
| Sperm tail | Facilitates sperm motility so that the sperm can move through the female genital tract. |
| Fimbriae | Finger-like projections of the infundibulum that help in collection of the ovum after ovulation. |
Exercise 16 — True / False with correction
16aAndrogens are produced by Sertoli cells.
16bSpermatozoa get nutrition from Sertoli cells.
16cLeydig cells are found in ovary.
16dLeydig cells synthesise androgens.
16eOogenesis takes place in corpus luteum.
16fMenstrual cycle ceases during pregnancy.
16gPresence or absence of hymen is not a reliable indicator of
virginity or sexual experience.
Exercise 17–21 — Long / conceptual answers
17What is menstrual cycle? Which hormones regulate it?
The menstrual cycle is the reproductive cycle in female primates
such as monkeys, apes and human beings. In humans it repeats at an
average interval of about 28/29 days. It includes menstrual,
follicular, ovulatory and luteal phases. The cyclical changes are
induced by changes in pituitary and ovarian hormones. LH and FSH
increase during the follicular phase; an LH surge around the
middle of the cycle induces ovulation. The corpus luteum then
secretes progesterone, which helps maintain the endometrium.
18What is parturition? Which hormones are involved in its
induction?
Parturition is the process of delivery of the foetus (childbirth).
The source describes a neuroendocrine mechanism involving signals
from the fully developed foetus and placenta, the foetal ejection
reflex and oxytocin release from the maternal pituitary. Oxytocin
strengthens uterine contractions, which further stimulates
oxytocin secretion in a positive feedback loop. The chapter
summary also mentions the involvement of cortisol, estrogens and
oxytocin.
19Why is blaming women for giving birth to daughters
scientifically incorrect?
The ovum produced by the female carries an X sex chromosome. The
male produces sperms carrying either X or Y. If an X-bearing sperm
fertilises the ovum, the zygote is XX; if a Y-bearing sperm
fertilises it, the zygote is XY. Therefore, the chromosome
contributed by the sperm determines whether the resulting zygote
is XX or XY. The mother does not produce an ovum carrying either X
or Y in the sex-chromosome system described in this chapter.
20How many eggs are released by a human ovary in a month? What
about identical and fraternal twins?
Normally, one ovum is released during a menstrual
cycle. Identical twins arise when one fertilised egg/embryo gives
rise to two individuals, so they originate from
one ovulated egg. Fraternal twins arise when
two ova are fertilised, so two ova are released
in that cycle.
21How many eggs might have been released by the ovary of a female
dog that gave birth to six puppies?
For this textbook-style reasoning question, the expected answer is
six eggs, assuming each puppy developed from a
separately fertilised ovum.
Exam tip: In long answers, write the definition
first, then the sequence/mechanism, and finish with the key result.
For diagram questions, keep labels clear and use the same terminology
as the chapter.
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