GS Paper III · Science & Technology · Biology · Class XII NCERT
Human Reproduction
Complete UPSC notes — Male & Female Reproductive Systems, Gametogenesis, Menstrual Cycle, Fertilisation, Embryonic Development, Pregnancy, Parturition & Lactation — with PYQs, MCQs and Current Affairs.
🌱
Overview — Human Reproduction at a Glance
Key facts, events and one-line takeaways
Core Definition
Humans are sexually reproducing and viviparous (give birth to live young). Reproduction involves: formation of gametes → fertilisation → embryo development → delivery.
⚡
Key Events (6)
1. Gametogenesis → 2. Insemination → 3. Fertilisation → 4. Implantation → 5. Gestation → 6. Parturition
📍
Site of Fertilisation
Ampullary region of fallopian tube — NOT the uterus. This is a common UPSC trap!
📅
Key Numbers
Menstrual cycle: 28–29 days. Gestation: 9 months. Ovulation: Day 14. Sperms ejaculated: 200–300 million
🧫
Fertility Criteria
For normal fertility: ≥60% normal shape & size + ≥40% vigorous motility
🥚
Eggs at Puberty
60,000–80,000 primary follicles remain in each ovary at puberty (from ~2 million at birth)
🧬
Sex Determination
X or Y in sperm determines sex. XX = Female, XY = Male. Mother always gives X.
Mnemonic — 6 Reproductive Events
Gametogenesis → Insemination → Fertilisation → Implantation → Gestation → Parturition | "GIF I Go Public"
🔵
Male Reproductive System
Testes · Ducts · Accessory glands · Key functions
Fig. 3.1(b) Diagrammatic view of male reproductive system. Sperm path: Testicular lobules (seminiferous tubules) → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra. The testis is shown open to reveal the internal lobule structure.
Fig. 3.1(a) Sectional view of male pelvis. Note: urethra serves both urinary and reproductive systems. Ejaculatory duct forms where vas deferens joins seminal vesicle. The scrotum hangs outside abdomen to keep testes 2–2.5°C cooler than body temperature.
Why are testes outside the body?
Spermatogenesis requires temperature 2–2.5°C lower than body temperature. The scrotum maintains this. Cryptorchidism (undescended testes) → infertility because temperature is too high for sperm production.
| Structure | Function / Key Facts |
|---|---|
| Testes | Primary male sex organs. ~250 testicular lobules, each with 1–3 coiled seminiferous tubules where sperms are produced. |
| Sertoli cells (inside tubules) | Provide nutrition to developing germ cells. Also produce androgen-binding protein (ABP). Do NOT secrete androgens. |
| Leydig cells (outside tubules, interstitial) | Secrete androgens (testosterone). Stimulated by LH. NOT inside seminiferous tubules — a common UPSC trap. |
| Rete testis → Vasa efferentia | Collect and carry sperms from seminiferous tubules to epididymis. |
| Epididymis | Site of sperm maturation and temporary storage. Secretions aid motility. |
| Vas deferens | Carries mature sperms to ejaculatory duct. Loops over urinary bladder. Joins with seminal vesicle duct → ejaculatory duct. |
| Seminal vesicles | Secrete seminal plasma rich in fructose, calcium, enzymes — energy for sperms. |
| Prostate gland | Secretes fluid component of semen. Single gland. Prostate cancer common in older men. CA |
| Bulbourethral glands | Paired. Secrete lubricating fluid for penis. Also contributes to seminal plasma. |
| Semen | = Seminal plasma + Sperms. Semen ≠ Sperms alone. |
Mnemonic — Sperm Path
Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus
"Some Rare Vehicles Enable Very Easy Urinary Urgency"
"Some Rare Vehicles Enable Very Easy Urinary Urgency"
📋 PYQ — UPSC PrelimsClassic
Which cells synthesise and secrete testicular androgens (testosterone)?
- (a) Sertoli cells
- (b) Spermatogonia
- (c) Leydig cells (Interstitial cells) ✓ Correct
- (d) Primary spermatocytes
Explanation: Leydig cells (interstitial cells) are located in interstitial spaces OUTSIDE the seminiferous tubules and secrete androgens (testosterone). Sertoli cells are INSIDE the tubules and provide nutrition + ABP. This is one of the most frequently tested distinctions in Biology MCQs.
🌸
Female Reproductive System
Ovaries · Oviducts · Uterus · External genitalia · Mammary glands
Fig. 3.3(b) Diagrammatic sectional view of female reproductive system. Fallopian tube has 3 parts: Infundibulum (with fimbriae — collects ovum) → Ampulla (widest, site of fertilisation ⭐) → Isthmus (narrow, joins uterus). Uterus walls: Perimetrium (outer) → Myometrium (muscle) → Endometrium (inner lining, shed in menstruation).
Fig. 3.3(a) Sectional view of female pelvis. Uterus lies posterior to urinary bladder. Cervix opens into vagina. Clitoris lies at the upper junction of the two labia minora. Vaginal orifice is partially covered by hymen. The cervix + vagina form the birth canal.
| Structure | Function / Key Facts |
|---|---|
| Ovaries | Primary female sex organs. Produce ova + steroid hormones (estrogen, progesterone). One on each side; stroma divided into cortex (follicles) and medulla. |
| Infundibulum | Funnel-shaped, nearest to ovary. Fimbriae collect ovum after ovulation. |
| Ampulla ⭐ | Widest part. SITE OF FERTILISATION. Most UPSC-important structure of the oviduct. |
| Isthmus | Narrow lumen. Connects ampulla to uterus. |
| Uterus (Womb) | Inverted pear-shaped. Three layers: Perimetrium (outer thin membrane), Myometrium (middle smooth muscle — contracts during delivery), Endometrium (inner glandular — sheds during menstruation, site of implantation). |
| Cervix | Narrow neck connecting uterus to vagina. Cervical canal + vagina = birth canal. HPV causes cervical cancer — preventable by vaccine. |
| Mammary glands | 15–20 mammary lobes with alveoli (milk cells) → mammary tubules → mammary duct → lactiferous duct (milk out). Colostrum first secreted — rich in antibodies. |
NCERT Note on Hymen — Legal Significance
The hymen can be broken by sudden falls, sports, tampons — not only by coitus. Some women retain the hymen even after coitus. Presence or absence of hymen is NOT a reliable indicator of virginity or sexual experience. This has been used in legal proceedings in India — medically baseless.
Mnemonic — 3 Uterus Layers (outside → inside)
Perimetrium → Myometrium → Endometrium | "Please Make Everything"
🔬
Gametogenesis — Spermatogenesis & Oogenesis
Formation of male and female gametes · Meiosis · Chromosome numbers
Fig. 3.8 Schematic representation of (a) Spermatogenesis and (b) Oogenesis. Left side: Spermatogonia (46 chr) → mitosis → Primary spermatocytes (46) → 1st meiosis → Secondary spermatocytes (23) → 2nd meiosis → 4 Spermatids (23) → differentiation → 4 Spermatozoa. Right side: Oogonia form in fetal life → arrested as Primary oocytes at prophase I → at puberty, 1st meiosis completes (unequal) → Secondary oocyte + 1st polar body → only after fertilisation, 2nd meiosis completes → Ovum + 2nd polar body. Critical: Oogenesis produces 1 functional ovum; spermatogenesis produces 4 functional spermatozoa.
🔵 Spermatogenesis
1
Spermatogonia (2n=46) multiply by mitosis on inner wall of seminiferous tubules
2
Some → Primary spermatocytes (2n=46) → undergo 1st meiotic division
3
→ 2 Secondary spermatocytes (n=23) → undergo 2nd meiotic division
4
→ 4 equal Spermatids (n=23) → Spermiogenesis (spermatids → spermatozoa)
5
Spermiation: Release of sperms from Sertoli cells into seminiferous tubule lumen
Starts at puberty. GnRH → LH (→ Leydig → androgens) + FSH (→ Sertoli cells). Continuous throughout adult male life. Produces 4 equal, functional spermatozoa.
🌸 Oogenesis
1
Oogonia form during fetal/embryonic life. No new oogonia after birth. ~2 million at birth.
2
Oogonia → enter prophase I → arrested as Primary oocytes (from birth to puberty)
3
At puberty: 60,000–80,000 primary follicles/ovary remain (rest degenerated)
4
1st meiosis (unequal) → 1 large Secondary oocyte + 1 tiny 1st polar body
5
Secondary oocyte released at ovulation (arrested at metaphase II). Completes 2nd meiosis only if fertilised
6
After fertilisation → 1 Ovum (mature) + 1 Second polar body
Key difference: Starts fetal life, completes only after fertilisation. Produces 1 large ovum (retains all cytoplasm/nutrients) + non-functional polar bodies that degenerate.
| Feature | Spermatogenesis | Oogenesis |
|---|---|---|
| Starts | Puberty | Fetal/embryonic life |
| Completed | Continuous throughout adult life | Only after fertilisation |
| Products | 4 equal functional spermatids | 1 large ovum + 2–3 polar bodies |
| Division | Equal meiotic divisions | Unequal (ovum retains cytoplasm) |
| Location | Seminiferous tubules (testes) | Ovarian follicles |
| Arrest phase | None — continuous | Arrested twice: prophase I (birth→puberty); metaphase II (puberty→fertilisation) |
Sperm Structure — 4 Parts
Head (haploid nucleus + acrosome with fertilisation enzymes) → Neck → Middle piece (mitochondria = energy/ATP for movement) → Tail (flagellum for motility). Plasma membrane covers entire sperm.
📋 PYQ — UPSC Prelims2021
Which of the following is released during ovulation in humans?
- (a) Primary oocyte
- (b) Mature ovum (ootid)
- (c) Secondary oocyte ✓ Correct
- (d) Oogonium
Explanation: A secondary oocyte (arrested at metaphase II) is released during ovulation — NOT a mature ovum. The secondary oocyte completes meiosis II and becomes a mature ovum ONLY if a sperm fertilises it. Without fertilisation, the secondary oocyte degenerates. This is one of the most commonly tested facts in human reproduction.
📅
Menstrual Cycle
4 Phases · Hormones · LH Surge · Corpus Luteum
Fig. 3.9 Events during a 28–29 day menstrual cycle. Top panel: Pituitary hormones — FSH rises during follicular phase; LH surges sharply at day ~14 (LH surge = trigger for ovulation). Middle panels: Ovarian events — follicle matures into Graafian follicle → ovulation → corpus luteum forms → corpus luteum regresses if no fertilisation. Ovarian hormones — Estrogen peaks just before LH surge; Progesterone dominates the luteal phase. Bottom panel: Uterine events — menses (endometrium shed) → proliferative phase (endometrium rebuilds under estrogen) → secretory phase (endometrium maintained under progesterone for implantation). If fertilisation occurs, corpus luteum is maintained by hCG from placenta.
Menstrual Cycle — Definition
Reproductive cycle in female primates (monkeys, apes, humans). Average 28–29 days. First menstruation = menarche. Cessation ~50 years = menopause. Cyclic menstruation = indicator of normal reproductive health.
| Phase | Days | Events | Key Hormones |
|---|---|---|---|
| Menstrual Phase | 1–5 | Endometrium + blood vessels break down → menstrual flow through vagina. Only if ovum NOT fertilised (corpus luteum degenerates → progesterone falls). | All hormones low |
| Follicular Phase (Proliferative) | 6–13 | Primary follicles grow → Graafian follicle. Endometrium regenerates. Rising estrogen thickens endometrium. | FSH↑ → follicle growth → Estrogen↑ |
| Ovulatory Phase | Day 14 | LH surge → Graafian follicle ruptures → secondary oocyte released (ovulation). Window for fertilisation. | LH surge (peak), FSH peaks, Estrogen peaks |
| Luteal Phase (Secretory) | 15–28 | Ruptured follicle → Corpus Luteum → secretes progesterone → maintains endometrium for implantation. No fertilisation → CL degenerates → progesterone falls → menstruation. | Progesterone dominant; LH & FSH fall |
⭐
LH Surge — Most Tested Point
At day ~14, LH reaches its peak — the LH surge. This directly induces rupture of Graafian follicle (ovulation). Rapid secretion of LH is the trigger. Both LH and FSH peak mid-cycle.
🌕
Corpus Luteum
Formed from remnants of ruptured Graafian follicle. Secretes progesterone. If no fertilisation → degenerates (corpus albicans) → progesterone falls → menstruation. If fertilisation → maintained by hCG from placenta.
🔁
Estrous vs Menstrual Cycle
Estrous cycle (non-primates) — no menstrual bleeding; endometrium reabsorbed. Menstrual cycle (primates only) — endometrium shed with bleeding. UPSC trap: both are reproductive cycles but only primates menstruate.
🤰
During Pregnancy
Menstrual cycle stops during pregnancy. hCG maintains corpus luteum. Absence of menstruation may indicate pregnancy (but also stress, poor health, hormonal disorders).
🔗
Fertilisation & Implantation
Sperm meets ovum · Zygote → Blastocyst → Implantation · IVF
Fig. 3.10 Ovum surrounded by few sperms. Zona pellucida (inner membrane): sperm contact here induces membrane changes blocking additional sperms — polyspermy prevention. Corona radiata (outer cell layer). Perivitelline space (gap between zona pellucida and ovum membrane). Acrosomal enzymes of sperm digest through corona radiata and zona pellucida to reach the ovum.
Fig. 3.11 Transport of ovum, fertilisation, and passage of growing embryo through fallopian tube to uterus. (a) Ovum → (b) sperm meets ovum → (c) 2-cell → (d) 4-cell → (e) Morula (compact ball, 8–16 cells) → (f–g) Blastocyst (fluid-filled, trophoblast + ICM) → (H) Blastocyst implantation in endometrium of uterus. This entire journey takes several days.
Insemination
→
Sperms reach Ampulla
→
Fertilisation (Ampullary region)
→
Zygote (2n)
→
Cleavage → Morula
→
Blastocyst
→
Implantation in Endometrium
→
Pregnancy ✅
| Event | Key Facts |
|---|---|
| Fertilisation | Occurs at ampullary region of fallopian tube. Zona pellucida contact → membrane changes → polyspermy blocked (only 1 sperm fertilises). Acrosome enzymes penetrate zona pellucida. Nuclei fuse → Zygote (diploid, 46 chr). |
| Morula | Zygote → repeated mitotic cleavage → 8–16 cell compact ball = morula. Still moving through fallopian tube toward uterus. |
| Blastocyst | Fluid-filled structure. Trophoblast (outer layer — attaches to endometrium; forms placenta). Inner Cell Mass / ICM (attached to trophoblast — forms the embryo; contains stem cells). |
| Implantation | Trophoblast attaches to endometrium → uterine cells divide and cover blastocyst → embeds in endometrium. Pregnancy begins here. |
| Germ layers | ICM → Ectoderm (outer) + Endoderm (inner) → Mesoderm appears between them. These 3 germ layers form all adult tissues. ICM also has stem cells that can form any tissue. |
🧪 In Vitro Fertilisation (IVF) — Test Tube Babies
Indication: Women with blocked oviducts (sperms cannot reach egg naturally).
Process: Eggs collected + sperms collected → fertilised in lab → embryo cultured ~1 week → placed in mother's uterus → normal delivery.
"Test tube baby" = misnomer — baby develops in uterus; only fertilisation is done in vitro.
First IVF baby: Louise Brown (1978, UK) — Robert Edwards & Patrick Steptoe. Edwards → Nobel Prize in Physiology/Medicine 2010. Nobel Fact
Process: Eggs collected + sperms collected → fertilised in lab → embryo cultured ~1 week → placed in mother's uterus → normal delivery.
"Test tube baby" = misnomer — baby develops in uterus; only fertilisation is done in vitro.
First IVF baby: Louise Brown (1978, UK) — Robert Edwards & Patrick Steptoe. Edwards → Nobel Prize in Physiology/Medicine 2010. Nobel Fact
📋 PYQ — UPSC PrelimsClassic
In humans, fertilisation normally occurs in the:
- (a) Uterus
- (b) Cervix
- (c) Ampulla of the fallopian tube ✓ Correct
- (d) Isthmus of the fallopian tube
Explanation: Fertilisation occurs in the ampullary region of the fallopian tube (specifically the ampullary-isthmic junction). The uterus is the site of implantation, not fertilisation. Both ovum and sperms must reach the ampullary region simultaneously — this is why not all coitus results in fertilisation.
🤰
Pregnancy & Embryonic Development
Placenta · Pregnancy hormones · Foetal milestones · Sex determination
Fig. 3.12 The human foetus within the uterus. Placental villi (chorionic villi interdigitate with uterine tissue — forms the placenta, the structural and functional unit). Umbilical cord (connects foetus to placenta — carries O₂/nutrients to foetus, CO₂/waste away). Yolk sac (vestigial in humans). Cavity of uterus. Plug of mucus in cervix (seals the uterus during pregnancy, prevents infection). This figure is frequently asked in UPSC.
Placenta — Multi-Function Organ
Chorionic villi (from trophoblast) + uterine tissue = Placenta. Functions: (1) Supply O₂ & nutrients to foetus. (2) Remove CO₂ & waste from foetus. (3) Acts as endocrine gland (secretes pregnancy hormones). Connected to foetus by umbilical cord.
| Hormone | Source | Function |
|---|---|---|
| hCG (human chorionic gonadotropin) | Placenta | Maintains corpus luteum → progesterone continues. Detected in urine/blood = basis of pregnancy test. Only during pregnancy. |
| hPL (human placental lactogen) | Placenta | Prepares mammary glands for lactation. Regulates maternal metabolism. Only during pregnancy. |
| Relaxin | Ovary (later pregnancy) | Relaxes pelvic ligaments, softens cervix for delivery. Only during pregnancy. |
| Estrogens & Progestogens | Placenta + Ovary | Maintain pregnancy, support foetal growth. (Also present outside pregnancy.) |
| Cortisol, Prolactin, Thyroxine | Maternal glands (increased) | Support foetal growth and maternal metabolic changes. Several-fold increase during pregnancy. |
Only-During-Pregnancy Hormones (UPSC Trap)
hCG hPL Relaxin
— These 3 are produced EXCLUSIVELY during pregnancy. NCERT explicitly states this. All other hormones (estrogen, progesterone, cortisol, prolactin) exist outside pregnancy too.
| Time | Foetal Development Milestone |
|---|---|
| End of 1st month | Heart is formed. Heart sound detectable by stethoscope — first sign of growing foetus. |
| End of 2nd month | Limbs and digits develop. |
| End of 12 weeks (1st Trimester) | Most major organ systems formed. Limbs and external genital organs well developed. |
| 5th month | First foetal movements felt by mother (quickening). Hair appears on head. |
| End of 24 weeks (2nd Trimester) | Body covered with fine hair (lanugo). Eyelids separate. Eyelashes formed. |
| 9 months (3rd Trimester complete) | Foetus fully developed. Ready for delivery. |
Sex Determination — Mother always contributes X chromosome (XX female). Father contributes either X (→ daughter, XX) or Y (→ son, XY). Sex of child is determined by the father's sperm, not the mother. Blaming the mother for the sex of a child has no biological basis. In India, pre-natal sex determination is illegal under the PC&PNDT Act, 1994 — to combat female foeticide and the skewed Child Sex Ratio. CA Relevant
👶
Parturition & Lactation
Childbirth · Oxytocin positive feedback · Colostrum · Breastfeeding
Parturition — Childbirth Process
Gestation period = ~9 months. Delivery of foetus = parturition. Triggered by complex neuroendocrine mechanism. Signals come from fully developed foetus + placenta.
Foetus + placenta send signals
→
Mild uterine contractions (Foetal ejection reflex)
→
Oxytocin released (posterior pituitary)
→
Stronger contractions
→
More oxytocin secreted (positive feedback ♻️)
→
Baby delivered through birth canal
→
Placenta expelled
💉
Oxytocin — Positive Feedback
Secreted by posterior pituitary. Creates a positive feedback loop: contractions → more oxytocin → stronger contractions → delivery. Synthetic oxytocin (Pitocin/Syntocinon) used to induce or augment labour in hospitals. CA
🍼
Lactation & Colostrum
Mammary glands differentiate during pregnancy → milk production starts at end of pregnancy. First milk = colostrum: yellow, rich in IgA antibodies → passive immunity for newborn. WHO recommends exclusive breastfeeding for 6 months.
📋 PYQ — UPSC PrelimsClassic
Which hormone is responsible for the positive feedback mechanism during parturition?
- (a) Relaxin
- (b) Progesterone
- (c) Oxytocin ✓ Correct
- (d) Estrogen
Explanation: Oxytocin (posterior pituitary) creates the classic positive feedback loop of parturition: mild contractions → oxytocin → stronger contractions → more oxytocin → maximum contractions → delivery. Progesterone actually suppresses contractions during pregnancy (its fall before labour helps initiate parturition). Relaxin helps soften cervix and relax pelvic ligaments but does not create the positive feedback loop.
🔄
Asexual Reproduction — Budding & Binary Fission
Hydra · Amoeba · NCERT Class 8 Basics
Fig. 9.11 Budding in Hydra. Outgrowths (buds) develop from the body wall of the parent. Each bud grows into a miniature Hydra with tentacles, then detaches as a new independent organism. Only ONE parent involved — no gametes, no fertilisation. The bud is genetically identical to the parent.
Fig. 9.12 Binary fission in Amoeba. (a) Normal amoeba with nucleus. (b) Nucleus starts dividing (karyokinesis). (c) Cytoplasm divides (cytokinesis). (d) Two daughter amoebae, each genetically identical to parent. Simplest asexual reproduction. Also seen in bacteria, Paramecium.
| Type | Example | Key Point |
|---|---|---|
| Budding | Hydra, Yeast | New individual develops as outgrowth from parent. Genetically identical. Single parent. |
| Binary Fission | Amoeba, Bacteria, Paramecium | Single organism → two equal daughter cells. Nucleus divides first, then cytoplasm. |
| Multiple Fission | Plasmodium (malaria parasite) | Parent divides into many daughters simultaneously. Occurs during adverse conditions. |
| Regeneration | Planaria, Starfish | A fragment of organism grows into a complete new individual. Not the same as repair. |
| Parthenogenesis | Drones (male bees), some lizards | Development from unfertilised egg. Drones are haploid. Some organisms can switch between sexual and parthenogenetic reproduction. |
📰
Current Affairs — Reproductive Health & Technology
Indian Laws · ART · RISUG · HPV · Maternal Health Data
🇮🇳 India — Key Laws & Policies
PC&PNDT Act, 1994 — Bans prenatal sex determination and sex-selective abortion. Addresses female foeticide and skewed Child Sex Ratio. Amended 2003 to include preconception sex selection.
MTP Act 1971 (Amended 2021) — Legal abortion: up to 20 weeks (general); up to 24 weeks (special cases: rape survivors, minors, foetal abnormalities). Beyond 24 weeks: medical board approval. Unmarried women included.
ART (Regulation) Act 2021 — Regulates IVF clinics, gamete banks. Establishes National ART & Surrogacy Board. Minimum age: 21 (women), 26 (men) to use ART.
Surrogacy (Regulation) Act 2021 — Bans commercial surrogacy. Only altruistic surrogacy allowed (close relative, no payment). Protects surrogates from exploitation.
Beti Bachao Beti Padhao — Improves Child Sex Ratio. CSR improved from 918 (NFHS-4) to 929 (NFHS-5).
Janani Suraksha Yojana — Cash incentive for institutional deliveries. Institutional deliveries: 89% (NFHS-5, up from 79%).
MTP Act 1971 (Amended 2021) — Legal abortion: up to 20 weeks (general); up to 24 weeks (special cases: rape survivors, minors, foetal abnormalities). Beyond 24 weeks: medical board approval. Unmarried women included.
ART (Regulation) Act 2021 — Regulates IVF clinics, gamete banks. Establishes National ART & Surrogacy Board. Minimum age: 21 (women), 26 (men) to use ART.
Surrogacy (Regulation) Act 2021 — Bans commercial surrogacy. Only altruistic surrogacy allowed (close relative, no payment). Protects surrogates from exploitation.
Beti Bachao Beti Padhao — Improves Child Sex Ratio. CSR improved from 918 (NFHS-4) to 929 (NFHS-5).
Janani Suraksha Yojana — Cash incentive for institutional deliveries. Institutional deliveries: 89% (NFHS-5, up from 79%).
🔬 Science & Technology Advances
RISUG (Reversible Inhibition of Sperm Under Guidance) — Indian male contraceptive by Dr. Sujoy Guha, IIT Kharagpur. Polymer injected into vas deferens disables sperms. Reversible. Non-hormonal. Advanced clinical trials. US version: Vasalgel.
HPV Vaccine — Cervical Cancer — India launched free HPV vaccination for girls 9–14 years (Union Budget 2023). Cervical cancer = 2nd most common cancer in Indian women. Gardasil/Cervarix protect against HPV strains 16 & 18.
IVF / Preimplantation Genetic Testing (PGT) — Embryos screened for genetic disorders (β-thalassemia, Down syndrome) before implantation. Ethical debate on "designer babies."
CRISPR Babies Controversy (2018) — He Jiankui (China) created first gene-edited human babies (CCR5 gene). Global scientific outcry. India has no specific germline editing law yet. Ethics & CA
In Vitro Gametogenesis (IVG) — Experimental: stem cells converted to eggs/sperm in lab. 2023 milestone in mice (Japan). Could help infertile patients without gametes.
Artificial Oxytocin Misuse — Synthetic oxytocin misused in dairy cattle to increase milk yield. Banned for this use in India. Health concerns ongoing.
HPV Vaccine — Cervical Cancer — India launched free HPV vaccination for girls 9–14 years (Union Budget 2023). Cervical cancer = 2nd most common cancer in Indian women. Gardasil/Cervarix protect against HPV strains 16 & 18.
IVF / Preimplantation Genetic Testing (PGT) — Embryos screened for genetic disorders (β-thalassemia, Down syndrome) before implantation. Ethical debate on "designer babies."
CRISPR Babies Controversy (2018) — He Jiankui (China) created first gene-edited human babies (CCR5 gene). Global scientific outcry. India has no specific germline editing law yet. Ethics & CA
In Vitro Gametogenesis (IVG) — Experimental: stem cells converted to eggs/sperm in lab. 2023 milestone in mice (Japan). Could help infertile patients without gametes.
Artificial Oxytocin Misuse — Synthetic oxytocin misused in dairy cattle to increase milk yield. Banned for this use in India. Health concerns ongoing.
| Indicator | Current Value | Context / Target |
|---|---|---|
| Maternal Mortality Ratio (MMR) | ~97/1 lakh live births (SRS 2018–20) | SDG 3.1 target: <70. Declined from 254 (2004–06). Kerala: 19; UP: 167. |
| Infant Mortality Rate (IMR) | ~28/1,000 live births (2020) | SDG 3.2: <12 by 2030. Declined from 68 (2000). |
| Total Fertility Rate (TFR) | ~2.0 (NFHS-5, 2021) | Replacement level = 2.1. India is at/below replacement nationally. |
| Child Sex Ratio (CSR) | 929 girls/1,000 boys (NFHS-5) | Improved from 918 (NFHS-4). Target: 950. PC&PNDT Act impact. |
| Institutional Deliveries | ~89% (NFHS-5) | Up from 79% (NFHS-4). JSY, LaQshya programme impact. |
🎯
Practice MCQs — Human Reproduction
UPSC-style · Click any option to check answer · Full explanations
🧬 Click an option to reveal the answer and explanation
Q1. The corpus luteum is formed from the remnants of which structure after ovulation?
- (a) Primary follicle
- (b) Secondary follicle
- (c) Graafian follicle (mature follicle)
- (d) Primordial follicle
The Graafian follicle (fully mature follicle) ruptures during ovulation releasing the secondary oocyte. The remaining granulosa cells of the ruptured follicle luteinise and form the corpus luteum (Latin: "yellow body"). The corpus luteum secretes progesterone which maintains the endometrium. If no fertilisation → corpus luteum degenerates (becomes corpus albicans) → progesterone falls → menstruation. If fertilisation occurs → hCG from placenta maintains the corpus luteum through the first trimester.
Q2. Which of the following is the correct function of the acrosome in a sperm?
- (a) It is located in the middle piece and produces energy (ATP) for sperm motility
- (b) It is a cap-like structure on the anterior portion of the sperm head containing hydrolytic enzymes that help penetrate the ovum
- (c) It contains mitochondria that power flagellar movement
- (d) It is the flagellum of the sperm enabling swimming toward the ovum
The acrosome is a membrane-bound cap covering the anterior portion of the sperm head/nucleus. It contains hydrolytic enzymes (hyaluronidase, acrosin etc.) that are released during the acrosome reaction when sperm contacts the zona pellucida — these enzymes digest through the corona radiata and zona pellucida, allowing the sperm to penetrate the ovum. The middle piece (not acrosome) contains mitochondria for energy. The tail (flagellum) provides motility.
Q3. Consider the menstrual cycle. Which of these statements are correct?
1. FSH and LH both peak at mid-cycle around day 14.
2. Progesterone dominates the follicular phase.
3. LH surge directly triggers ovulation.
4. Corpus luteum secretes progesterone to maintain endometrium.
1. FSH and LH both peak at mid-cycle around day 14.
2. Progesterone dominates the follicular phase.
3. LH surge directly triggers ovulation.
4. Corpus luteum secretes progesterone to maintain endometrium.
- (a) 1, 2 and 4 only
- (b) 2, 3 and 4 only
- (c) 1, 3 and 4 only
- (d) All four
Statement 1 ✓ — Both LH and FSH peak at mid-cycle (~day 14). LH surge is sharp; FSH also peaks moderately. Statement 2 ✗ — Progesterone dominates the LUTEAL phase (post-ovulation). The follicular phase is dominated by rising estrogen (from follicle under FSH stimulation). Statement 3 ✓ — The sharp LH surge directly induces rupture of the Graafian follicle (ovulation). This is the direct causal link. Statement 4 ✓ — Corpus luteum (from ruptured Graafian follicle) secretes progesterone which maintains the endometrium for possible implantation. Answer: 1, 3, 4 → (c).
Q4. Which of the following hormone combinations is produced EXCLUSIVELY during pregnancy?
- (a) Estrogen, Progesterone, Oxytocin
- (b) hCG, Prolactin, Cortisol
- (c) hCG, hPL, Relaxin
- (d) Progesterone, hCG, FSH
NCERT explicitly states: "hCG, hPL and relaxin are produced in women ONLY during pregnancy." (1) hCG (human chorionic gonadotropin) — from placenta, maintains corpus luteum, detected in pregnancy tests. (2) hPL (human placental lactogen) — from placenta, prepares breasts for lactation. (3) Relaxin — from ovary in later pregnancy, softens cervix and relaxes pelvic ligaments. Estrogen, progesterone, cortisol and prolactin do increase significantly during pregnancy, but these hormones exist at baseline levels outside pregnancy too — they are NOT exclusively pregnancy hormones.
Q5. RISUG, a male contraceptive developed in India, works by:
- (a) Injecting a polymer into the vas deferens that disables sperms; reversible by injecting a solvent
- (b) Hormonal suppression of testosterone production in the testes
- (c) Surgical cutting of the vas deferens (vasectomy)
- (d) Raising scrotal temperature to temporarily halt spermatogenesis
RISUG (Reversible Inhibition of Sperm Under Guidance) developed by Dr. Sujoy K. Guha at IIT Kharagpur: A polymer gel (styrene maleic anhydride in DMSO) is injected into the vas deferens. The gel creates a positive electrostatic charge that damages sperm membranes as they pass through, preventing fertilisation. Reversible: DMSO injection dissolves the polymer and restores fertility. Key features: non-hormonal, long-lasting (years), low cost, reversible (unlike vasectomy). In advanced Phase III trials in India. The US version being developed is called Vasalgel. This is a significant Indian contribution to contraceptive science.
Q6. Which of the following correctly describes the path of a sperm from where it is produced to where it exits the body?
- (a) Seminiferous tubules → Epididymis → Rete testis → Vas deferens → Urethra
- (b) Rete testis → Seminiferous tubules → Vasa efferentia → Epididymis → Urethra
- (c) Seminiferous tubules → Rete testis → Epididymis → Vasa efferentia → Vas deferens → Urethra
- (d) Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra
The correct path is: Seminiferous tubules (where sperms are produced) → Rete testis (network collecting sperms) → Vasa efferentia (carry to epididymis) → Epididymis (maturation and storage) → Vas deferens (ascends to abdomen, loops over bladder) → Ejaculatory duct (formed where vas deferens joins seminal vesicle duct) → Urethra → outside via urethral meatus. Common trap: Vasa efferentia comes BEFORE epididymis, not after rete testis skipping to epididymis directly.
⚡ Quick Revision — Human Reproduction
| Topic | Key Facts for UPSC |
|---|---|
| Male system | Testes in scrotum (2–2.5°C cooler). 250 lobules → seminiferous tubules. Sertoli cells: nutrition + ABP. Leydig cells: androgens. Path: Seminiferous → Rete → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra. |
| Female system | Ovaries: gametes + hormones. Fallopian tube: Infundibulum (fimbriae) → Ampulla (fertilisation ⭐) → Isthmus. Uterus: Perimetrium → Myometrium → Endometrium. Cervix + Vagina = birth canal. |
| Spermatogenesis | Starts puberty. GnRH → LH (Leydig, androgens) + FSH (Sertoli). Spermatogonia(46) → Primary(46) → Secondary(23) → 4 Spermatids(23) → Spermiogenesis → Spermatozoa → Spermiation. Produces 4 equal sperms. |
| Oogenesis | Starts fetal life. Oogonia → Primary oocytes (arrested prophase I at birth). Puberty: 60,000–80,000/ovary. Ovulation: secondary oocyte (arrested metaphase II). Completes meiosis II ONLY if fertilised → 1 Ovum + polar bodies. |
| Menstrual cycle | 28–29 days. Menstrual(1–5) → Follicular/Proliferative(6–13, FSH↑, Estrogen↑) → Ovulatory(Day 14, LH surge → ovulation) → Luteal/Secretory(15–28, Corpus luteum → Progesterone↑ → maintains endometrium). Menarche = first period. Menopause ~50 yrs. |
| Fertilisation | Site: Ampullary region. Zona pellucida → polyspermy block (only 1 sperm). Acrosome enzymes penetrate layers. Zygote(2n) → cleavage → Morula → Blastocyst (Trophoblast + ICM) → Implantation in endometrium = pregnancy begins. |
| Pregnancy hormones | Placenta: hCG (pregnancy test), hPL (lactation prep), Estrogens, Progestogens. Ovary (late): Relaxin. ONLY during pregnancy: hCG + hPL + Relaxin. Placenta also: umbilical cord connects foetus. |
| Foetal milestones | 1 month: Heart. 2 months: Limbs. 12 weeks: Major organs. 5 months: Movements + head hair. 24 weeks: Body hair, eyelids. 9 months: Fully developed. |
| Parturition | Foetal ejection reflex → Oxytocin (posterior pituitary) → Positive feedback → Contractions → Baby out → Placenta expelled. |
| Lactation | Colostrum (first 2–5 days) = IgA antibodies → passive immunity. WHO: exclusive breastfeeding 6 months. Prolactin = milk production. Oxytocin = milk let-down (ejection). |
| Sex determination | Mother: always X. Father: X (→XX, girl) or Y (→XY, boy). Sex determined by father's sperm. |
| Key laws & CA | PC&PNDT Act 1994 (no sex determination). MTP Act 1971/2021 (legal abortion ≤20 wks; ≤24 special cases). ART Act 2021. Surrogacy Act 2021 (only altruistic). RISUG: Indian male contraceptive (IIT KGP). HPV vaccine free for girls 9–14 (2023). MMR: 97, TFR: 2.0 (NFHS-5). IVF Nobel 2010: Robert Edwards. |
🚨 6 UPSC TRAPS — Human Reproduction (Read Every One):
Trap 1 — "Fertilisation occurs in the uterus" → WRONG!
Fertilisation occurs in the AMPULLARY REGION of the fallopian tube. The uterus is the site of implantation. This is probably the single most tested fact in human reproduction MCQs.
Trap 2 — "A mature ovum is released at ovulation" → WRONG!
What is released at ovulation is a SECONDARY OOCYTE (arrested at metaphase II). A mature ovum only forms after the secondary oocyte is fertilised and completes meiosis II. Without fertilisation, no mature ovum ever forms.
Trap 3 — "Sertoli cells secrete androgens; Leydig cells give nutrition" → WRONG! (completely reversed!)
Sertoli cells = nutrition to germ cells + ABP (inside tubules). Leydig cells = androgens/testosterone (outside tubules, interstitial spaces). This reversal is one of the most common factual errors in MCQ options.
Trap 4 — "Progesterone dominates the follicular phase" → WRONG!
Progesterone dominates the LUTEAL PHASE (days 15–28). During the follicular phase, estrogen is the dominant hormone (rising due to follicle growth under FSH). Corpus luteum (progesterone source) only forms AFTER ovulation.
Trap 5 — "hCG, hPL, Relaxin are present throughout a woman's adult life" → WRONG!
These three are produced EXCLUSIVELY DURING PREGNANCY. hCG in urine is the basis of the pregnancy test — it would be useless if hCG were always present. NCERT states this explicitly.
Trap 6 — "Oogenesis begins at puberty, just like spermatogenesis" → WRONG!
Oogenesis begins during FETAL/EMBRYONIC LIFE. Primary oocytes are present and arrested from birth. Spermatogenesis, by contrast, begins only at puberty. Their timelines are fundamentally different — and both arrest points of oogenesis (prophase I, then metaphase II) are frequently tested.
Trap 1 — "Fertilisation occurs in the uterus" → WRONG!
Fertilisation occurs in the AMPULLARY REGION of the fallopian tube. The uterus is the site of implantation. This is probably the single most tested fact in human reproduction MCQs.
Trap 2 — "A mature ovum is released at ovulation" → WRONG!
What is released at ovulation is a SECONDARY OOCYTE (arrested at metaphase II). A mature ovum only forms after the secondary oocyte is fertilised and completes meiosis II. Without fertilisation, no mature ovum ever forms.
Trap 3 — "Sertoli cells secrete androgens; Leydig cells give nutrition" → WRONG! (completely reversed!)
Sertoli cells = nutrition to germ cells + ABP (inside tubules). Leydig cells = androgens/testosterone (outside tubules, interstitial spaces). This reversal is one of the most common factual errors in MCQ options.
Trap 4 — "Progesterone dominates the follicular phase" → WRONG!
Progesterone dominates the LUTEAL PHASE (days 15–28). During the follicular phase, estrogen is the dominant hormone (rising due to follicle growth under FSH). Corpus luteum (progesterone source) only forms AFTER ovulation.
Trap 5 — "hCG, hPL, Relaxin are present throughout a woman's adult life" → WRONG!
These three are produced EXCLUSIVELY DURING PREGNANCY. hCG in urine is the basis of the pregnancy test — it would be useless if hCG were always present. NCERT states this explicitly.
Trap 6 — "Oogenesis begins at puberty, just like spermatogenesis" → WRONG!
Oogenesis begins during FETAL/EMBRYONIC LIFE. Primary oocytes are present and arrested from birth. Spermatogenesis, by contrast, begins only at puberty. Their timelines are fundamentally different — and both arrest points of oogenesis (prophase I, then metaphase II) are frequently tested.
