What you will learn in this chapter
- Describe the male and female reproductive systems of humans with labelled diagrams.
- Compare spermatogenesis and oogenesis, including the ploidy of each stage.
- Explain the phases of the menstrual cycle and the role of FSH, LH, estrogen and progesterone.
- Explain fertilisation, cleavage, blastocyst formation and implantation.
- Describe the structure and functions of the placenta, including its hormones.
- Explain parturition and lactation, including the role of oxytocin and colostrum.
📘 Open this chapter on NCERT official website (ncert.nic.in) · The same NCERT chapter is taught in both CBSE and UP Board.
Human Reproduction — Notes
🖼️ Diagrams are now right inside the notes. Tap any picture to zoom and see the name and job of each part; 🧊 3D opens the 3D model.डायग्राम अब नोट्स के अंदर ही हैं। किसी भी चित्र पर टैप करें — ज़ूम करें और हर भाग का नाम व कार्य देखें; 🧊 3D से 3D मॉडल खुलता है।Diagrams ab notes ke andar hi hain. Kisi bhi picture par tap kijiye — zoom kijiye aur har part ka naam aur kaam dekhiye; 🧊 3D se 3D model khulta hai.
Revise these first (prerequisites)
- Cell division: mitosis and meiosis (Class 11 level)
- What a hormone is and how glands work (basic idea)
- Gametes (sperm/ovum) are haploid, the zygote is diploid
- Basic organ systems of the human body
The complete journey of human reproduction
Human reproduction occurs in a few steps: formation of gametes (gametogenesis), transfer of sperm into the female tract (insemination), fertilisation, attachment of the embryo to the uterus (implantation), pregnancy (gestation) and birth of the baby (parturition / प्रसव). If you understand each step separately, the chapter will feel easy.
Male system: factory + pipeline
The testis (वृषण) is the sperm-producing factory, located outside the body in the scrotum because sperm formation needs a temperature 2–2.5°C lower than body temperature. Sperms travel out through ducts (the pipeline), and glands (seminal vesicle, prostate, bulbourethral) provide fluid for them.
Male reproductive system (testis opened)नर जनन तंत्र (वृषण खुला हुआ)Male reproductive system (testis opened)NCERT Fig 2.1 (b)Follow the sperm route: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral.शुक्राणु का रास्ता देखें: शुक्रजनक नलिकाएँ → वृषण जालिका → शुक्रवाहिकाएँ → अधिवृषण → शुक्रवाहक → स्खलन वाहिनी → मूत्रमार्ग। ग्रंथियाँ: शुक्राशय, प्रोस्टेट, बल्बोयूरेथ्रल।Sperm ka raasta dekhiye: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral.🧊 See in 3D: male reproductive system3D में देखें: नर जनन तंत्र3D dekhiye: male reproductive system Female system: ovary, oviduct, uterus
The ovary (अंडाशय) produces the ovum. The oviduct / fallopian tube is the passage where fertilisation takes place. The uterus (गर्भाशय) is the 'home' where the baby grows for 9 months — its inner lining, the endometrium, is prepared every month.
Female reproductive system (sectional view)मादा जनन तंत्र (काट का दृश्य)Female reproductive system (sectional view)NCERT Fig 2.3 (b)Oviduct parts: fimbriae → infundibulum → ampulla → isthmus → uterus. Uterine wall: perimetrium, myometrium, endometrium; cervical canal + vagina = birth canal.अंडवाहिनी: झालर → कीपक → तुंबिका → संकीर्ण पथ → गर्भाशय। गर्भाशय भित्ति: पेरिमेट्रियम, मायोमेट्रियम, एंडोमेट्रियम; ग्रीवा नाल + योनि = जन्म नाल।Oviduct: fimbriae → infundibulum → ampulla → isthmus → uterus. Uterus wall: perimetrium, myometrium, endometrium; cervical canal + vagina = birth canal.🧊 See in 3D: female reproductive system3D में देखें: मादा जनन तंत्र3D dekhiye: female reproductive system Menstrual cycle = monthly preparation
Roughly every 28/29 days, the female body releases an ovum and prepares the uterus for pregnancy. If fertilisation does not occur, the prepared endometrium layer breaks down and comes out — this is called menstruation (आर्तव). It is a normal, healthy process.
Menstrual cycle (28 days)आर्तव चक्र (28 दिन)Menstrual cycle (28 days)NCERT Fig 2.9 (schematic)Match the 4 rows: hormone levels (LH surge ~day 14), follicle growth, ovulation, and endometrium thickness through 28 days.4 पंक्तियाँ मिलाएँ: हॉर्मोन स्तर (~14वें दिन LH उछाल), पुटक वृद्धि, अंडोत्सर्ग और 28 दिनों में एंडोमेट्रियम की मोटाई।4 rows milaiye: hormone levels (~day 14 LH surge), follicle growth, ovulation aur 28 din mein endometrium ki thickness. From fertilisation to baby
The sperm and ovum meet in the ampullary region of the fallopian tube → zygote. The zygote divides to form a ball-like structure (morula → blastocyst), which attaches to the uterine wall (implantation). Then the placenta (अपरा) forms, which supplies food and oxygen from the mother to the baby.
Fertilisation, cleavage and implantationनिषेचन, विदलन और अंतर्रोपणFertilisation, cleavage and implantationNCERT Fig 2.11Ovum is fertilised in the ampullary–isthmic junction; cleavage → morula → blastocyst, which implants in the endometrium.अंडाणु का निषेचन तुंबिका–संकीर्ण पथ संधि पर; विदलन → मोरुला → ब्लास्टोसिस्ट, जो एंडोमेट्रियम में रोपित होता है।Ovum ka fertilisation ampullary–isthmic junction par; cleavage → morula → blastocyst, jo endometrium mein implant hota hai.🧊 See in 3D: fertilisation → implantation3D में देखें: निषेचन → रोपण3D dekhiye: fertilisation → implantation Birth and milk
At the end of pregnancy, strong contractions of the uterus lead to the birth of the baby; the hormone oxytocin plays a major role in this. The milk produced in the first few days after birth, colostrum, is rich in antibodies (IgA) and acts like the baby's first 'vaccine'.
Mammary gland (sectional view)स्तन ग्रंथि (काट का दृश्य)Mammary gland (sectional view)NCERT Fig 2.4Milk route: alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct → nipple.दूध का रास्ता: कूपिकाएँ → स्तन नलिकाएँ → स्तन वाहिनी → स्तन तुंबिका → दुग्ध वाहिनी → चूचुक।Doodh ka raasta: alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct → nipple.🧊 See in 3D: mammary gland3D में देखें: स्तन ग्रंथि3D dekhiye: mammary gland
Quick check ✔
1. Where does fertilisation normally take place in humans?
2. Why are the testes located outside the body in the scrotum?
Basics clear? Now move on to Learn in Detail 👆
As per NCERT 2026-27 — every point you need for the board exam.
Steps of human reproduction
Gametogenesis → insemination → fertilisation → cleavage + blastocyst → implantation → gestation → parturition. Humans are viviparous.
Male reproductive system
Testes lie in the scrotum (testis temperature is ~2–2.5°C lower than body temperature). Each testis has ~250 lobules, each lobule has 1–3 seminiferous tubules. Tubules contain spermatogonia + Sertoli cells (nutrition). Between the tubules are Leydig cells → androgens (testosterone).
Male reproductive system (testis opened)नर जनन तंत्र (वृषण खुला हुआ)Male reproductive system (testis opened)NCERT Fig 2.1 (b)Follow the sperm route: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral.शुक्राणु का रास्ता देखें: शुक्रजनक नलिकाएँ → वृषण जालिका → शुक्रवाहिकाएँ → अधिवृषण → शुक्रवाहक → स्खलन वाहिनी → मूत्रमार्ग। ग्रंथियाँ: शुक्राशय, प्रोस्टेट, बल्बोयूरेथ्रल।Sperm ka raasta dekhiye: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral. Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Seminiferous tubule (sectional view)NCERT Fig 2.2, 2.5Spermatogonia near the wall divide towards the lumen into spermatocytes, spermatids and sperms; Sertoli cells nourish them; Leydig cells lie outside.भित्ति के पास शुक्राणुजन कोशिकाएँ गुहा की ओर शुक्राणुकोशिका, शुक्रप्रसू और शुक्राणु बनाती हैं; सर्टोली कोशिकाएँ पोषण देती हैं; लीडिग कोशिकाएँ बाहर।Wall ke paas spermatogonia lumen ki taraf spermatocytes, spermatids aur sperms banate hain; Sertoli cells khana dete hain; Leydig cells bahar.🧊 See in 3D: male reproductive system3D में देखें: नर जनन तंत्र3D dekhiye: male reproductive system🧊 See in 3D: seminiferous tubule3D में देखें: शुक्रजनक नलिका3D dekhiye: seminiferous tubule Male ducts & glands
Rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles (pair), prostate, bulbourethral (pair).
Male reproductive system (testis opened)नर जनन तंत्र (वृषण खुला हुआ)Male reproductive system (testis opened)NCERT Fig 2.1 (b)Follow the sperm route: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral.शुक्राणु का रास्ता देखें: शुक्रजनक नलिकाएँ → वृषण जालिका → शुक्रवाहिकाएँ → अधिवृषण → शुक्रवाहक → स्खलन वाहिनी → मूत्रमार्ग। ग्रंथियाँ: शुक्राशय, प्रोस्टेट, बल्बोयूरेथ्रल।Sperm ka raasta dekhiye: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral. Female reproductive system
Ovaries (estrogen, progesterone), oviduct (infundibulum, fimbriae, ampulla — site of fertilisation, isthmus), uterus (perimetrium, myometrium, endometrium), cervix, vagina. Mammary glands are also female accessory organs.
Female reproductive system (sectional view)मादा जनन तंत्र (काट का दृश्य)Female reproductive system (sectional view)NCERT Fig 2.3 (b)Oviduct parts: fimbriae → infundibulum → ampulla → isthmus → uterus. Uterine wall: perimetrium, myometrium, endometrium; cervical canal + vagina = birth canal.अंडवाहिनी: झालर → कीपक → तुंबिका → संकीर्ण पथ → गर्भाशय। गर्भाशय भित्ति: पेरिमेट्रियम, मायोमेट्रियम, एंडोमेट्रियम; ग्रीवा नाल + योनि = जन्म नाल।Oviduct: fimbriae → infundibulum → ampulla → isthmus → uterus. Uterus wall: perimetrium, myometrium, endometrium; cervical canal + vagina = birth canal.🧊 See in 3D: female reproductive system3D में देखें: मादा जनन तंत्र3D dekhiye: female reproductive system Spermatogenesis (शुक्राणुजनन)
Begins at puberty. Spermatogonia (2n) → primary spermatocyte (2n) → meiosis I → secondary spermatocytes (n) → meiosis II → spermatids (n) → spermiogenesis → spermatozoa. 1 primary spermatocyte → 4 sperms.
Gametogenesis: spermatogenesis vs oogenesisयुग्मकजनन: शुक्राणुजनन व अंडजननGametogenesis: spermatogenesis vs oogenesisNCERT Fig 2.8Compare side by side: one primary spermatocyte gives 4 sperms, one primary oocyte gives 1 ovum + polar bodies.साथ-साथ तुलना करें: एक प्राथमिक शुक्राणुकोशिका से 4 शुक्राणु, एक प्राथमिक अंडक से 1 अंडाणु + ध्रुवीय पिंड।Side by side compare kijiye: 1 primary spermatocyte se 4 sperms, 1 primary oocyte se 1 ovum + polar bodies. Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Seminiferous tubule (sectional view)NCERT Fig 2.2, 2.5Spermatogonia near the wall divide towards the lumen into spermatocytes, spermatids and sperms; Sertoli cells nourish them; Leydig cells lie outside.भित्ति के पास शुक्राणुजन कोशिकाएँ गुहा की ओर शुक्राणुकोशिका, शुक्रप्रसू और शुक्राणु बनाती हैं; सर्टोली कोशिकाएँ पोषण देती हैं; लीडिग कोशिकाएँ बाहर।Wall ke paas spermatogonia lumen ki taraf spermatocytes, spermatids aur sperms banate hain; Sertoli cells khana dete hain; Leydig cells bahar. Hormones (male)
GnRH from the hypothalamus → LH and FSH from the pituitary. LH → Leydig cells (androgens). FSH → Sertoli cells → help in spermiogenesis.
Sperm structure
Head (acrosome + nucleus), neck, middle piece (mitochondria = energy), tail. One ejaculation contains 200–300 million sperms; for normal fertility, ~60% must have normal shape and at least 40% must show vigorous motility.
Structure of a spermशुक्राणु की संरचनाStructure of a spermNCERT Fig 2.6Head (acrosome + nucleus), neck, middle piece full of mitochondria (energy), and tail for swimming.सिर (अग्रपिंडक + केंद्रक), ग्रीवा, माइटोकॉन्ड्रिया से भरा मध्य भाग (ऊर्जा) और तैरने के लिए पूँछ।Head (acrosome + nucleus), neck, mitochondria se bhara middle piece (energy) aur tairne ke liye tail.🧊 See in 3D: sperm3D में देखें: शुक्राणु3D dekhiye: sperm Oogenesis (अंडजनन)
Begins during foetal life itself — oogonia are formed, and primary oocytes get arrested in prophase of meiosis I. Primary follicle → secondary → tertiary (antrum) → Graafian follicle. Secondary oocyte + 1st polar body. Ovulation occurs at the secondary oocyte stage; meiosis II is completed upon sperm entry.
Gametogenesis: spermatogenesis vs oogenesisयुग्मकजनन: शुक्राणुजनन व अंडजननGametogenesis: spermatogenesis vs oogenesisNCERT Fig 2.8Compare side by side: one primary spermatocyte gives 4 sperms, one primary oocyte gives 1 ovum + polar bodies.साथ-साथ तुलना करें: एक प्राथमिक शुक्राणुकोशिका से 4 शुक्राणु, एक प्राथमिक अंडक से 1 अंडाणु + ध्रुवीय पिंड।Side by side compare kijiye: 1 primary spermatocyte se 4 sperms, 1 primary oocyte se 1 ovum + polar bodies. Section of ovary: follicles to corpus luteumअंडाशय की काट: पुटिका से पीत पिंड तकSection of ovary: follicles to corpus luteumNCERT Fig 2.7Go round the ovary: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum.अंडाशय में घूमकर देखें: प्राथमिक → द्वितीयक → तृतीयक → ग्राफी पुटक → अंडोत्सर्ग → पीत पिंड।Ovary mein ghoom kar dekhiye: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum.🧊 See in 3D: ovary section3D में देखें: अंडाशय काट3D dekhiye: ovary section Menstrual cycle (आर्तव चक्र)
~28 days. Menstrual phase (3–5 days) → follicular/proliferative phase (FSH, LH increase; estrogen) → ovulation on the 14th day (LH surge) → luteal/secretory phase (corpus luteum → progesterone, endometrium prepared). If fertilisation does not occur, the corpus luteum degenerates → menstruation. Menarche = first menstruation; menopause at ~50 years.
Menstrual cycle (28 days)आर्तव चक्र (28 दिन)Menstrual cycle (28 days)NCERT Fig 2.9 (schematic)Match the 4 rows: hormone levels (LH surge ~day 14), follicle growth, ovulation, and endometrium thickness through 28 days.4 पंक्तियाँ मिलाएँ: हॉर्मोन स्तर (~14वें दिन LH उछाल), पुटक वृद्धि, अंडोत्सर्ग और 28 दिनों में एंडोमेट्रियम की मोटाई।4 rows milaiye: hormone levels (~day 14 LH surge), follicle growth, ovulation aur 28 din mein endometrium ki thickness. Fertilisation & implantation
In the ampullary region, sperm + ovum → zygote. The sperm decides the sex (X or Y). Cleavage → morula (8–16 cells) → blastocyst (trophoblast + inner cell mass). The trophoblast attaches to the endometrium = implantation → pregnancy.
Fertilisation, cleavage and implantationनिषेचन, विदलन और अंतर्रोपणFertilisation, cleavage and implantationNCERT Fig 2.11Ovum is fertilised in the ampullary–isthmic junction; cleavage → morula → blastocyst, which implants in the endometrium.अंडाणु का निषेचन तुंबिका–संकीर्ण पथ संधि पर; विदलन → मोरुला → ब्लास्टोसिस्ट, जो एंडोमेट्रियम में रोपित होता है।Ovum ka fertilisation ampullary–isthmic junction par; cleavage → morula → blastocyst, jo endometrium mein implant hota hai.🧊 See in 3D: fertilisation → implantation3D में देखें: निषेचन → रोपण3D dekhiye: fertilisation → implantation Placenta
Chorionic villi + uterine tissue. Exchange of nutrition, O₂ and wastes. Hormones: hCG, hPL, estrogens, progestogens; relaxin from the ovary in late pregnancy. Inner cell mass → ectoderm, mesoderm, endoderm (stem cells).
Embryo development
1 month: heart. End of 2nd month: limbs and digits. By 12 weeks (1st trimester): major organ systems. 5th month: first movements, hair on the head. 24 weeks: fine hair on the body, eyelids separate. Pregnancy lasts ~9 months.
Parturition & lactation
Foetal ejection reflex → oxytocin → uterine contractions → birth of the baby. The milk produced in the first few days = colostrum — rich in antibodies (IgA), essential for the newborn's immunity.
Mammary gland (sectional view)स्तन ग्रंथि (काट का दृश्य)Mammary gland (sectional view)NCERT Fig 2.4Milk route: alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct → nipple.दूध का रास्ता: कूपिकाएँ → स्तन नलिकाएँ → स्तन वाहिनी → स्तन तुंबिका → दुग्ध वाहिनी → चूचुक।Doodh ka raasta: alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct → nipple.🧊 See in 3D: mammary gland3D में देखें: स्तन ग्रंथि3D dekhiye: mammary gland
The concept in depth — the why and the how. Everything stays within the NCERT syllabus.
Hormonal control of spermatogenesis
At puberty, GnRH from the hypothalamus increases → LH and FSH from the pituitary. LH acts on Leydig cells to stimulate production of androgens (testosterone), which stimulate spermatogenesis. FSH acts on Sertoli cells and causes release of factors that help in spermiogenesis. In other words, one hormone signals the 'factory owner' and the other signals the 'support staff'.
Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Seminiferous tubule (sectional view)NCERT Fig 2.2, 2.5Spermatogonia near the wall divide towards the lumen into spermatocytes, spermatids and sperms; Sertoli cells nourish them; Leydig cells lie outside.भित्ति के पास शुक्राणुजन कोशिकाएँ गुहा की ओर शुक्राणुकोशिका, शुक्रप्रसू और शुक्राणु बनाती हैं; सर्टोली कोशिकाएँ पोषण देती हैं; लीडिग कोशिकाएँ बाहर।Wall ke paas spermatogonia lumen ki taraf spermatocytes, spermatids aur sperms banate hain; Sertoli cells khana dete hain; Leydig cells bahar. How many gametes from one meiocyte?
After meiosis, one primary spermatocyte forms 4 sperm. But one primary oocyte forms only 1 ovum; the rest become polar bodies — due to unequal cytoplasmic division, the ovum gets more cytoplasm and food. So 100 primary spermatocytes → 400 sperm, but 100 primary oocytes → only 100 ova.
Gametogenesis: spermatogenesis vs oogenesisयुग्मकजनन: शुक्राणुजनन व अंडजननGametogenesis: spermatogenesis vs oogenesisNCERT Fig 2.8Compare side by side: one primary spermatocyte gives 4 sperms, one primary oocyte gives 1 ovum + polar bodies.साथ-साथ तुलना करें: एक प्राथमिक शुक्राणुकोशिका से 4 शुक्राणु, एक प्राथमिक अंडक से 1 अंडाणु + ध्रुवीय पिंड।Side by side compare kijiye: 1 primary spermatocyte se 4 sperms, 1 primary oocyte se 1 ovum + polar bodies. LH surge and ovulation
In the follicular phase, the Graafian follicle secretes estrogen. In the middle of the cycle (~day 14), both LH and FSH peak; the rapid LH surge ruptures the Graafian follicle and releases the ovum (secondary oocyte). The remaining follicle then becomes the corpus luteum, which secretes progesterone that maintains the endometrium. If fertilisation does not occur, the corpus luteum degenerates → progesterone falls → menstruation.
Menstrual cycle (28 days)आर्तव चक्र (28 दिन)Menstrual cycle (28 days)NCERT Fig 2.9 (schematic)Match the 4 rows: hormone levels (LH surge ~day 14), follicle growth, ovulation, and endometrium thickness through 28 days.4 पंक्तियाँ मिलाएँ: हॉर्मोन स्तर (~14वें दिन LH उछाल), पुटक वृद्धि, अंडोत्सर्ग और 28 दिनों में एंडोमेट्रियम की मोटाई।4 rows milaiye: hormone levels (~day 14 LH surge), follicle growth, ovulation aur 28 din mein endometrium ki thickness. Section of ovary: follicles to corpus luteumअंडाशय की काट: पुटिका से पीत पिंड तकSection of ovary: follicles to corpus luteumNCERT Fig 2.7Go round the ovary: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum.अंडाशय में घूमकर देखें: प्राथमिक → द्वितीयक → तृतीयक → ग्राफी पुटक → अंडोत्सर्ग → पीत पिंड।Ovary mein ghoom kar dekhiye: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum. 'Pause' points of oogenesis
Oogenesis begins during the embryonic stage itself; primary oocytes are arrested in prophase-I. The secondary oocyte released at ovulation is in meiosis-II, and meiosis-II is completed only when a sperm enters it — forming the ovum and the second polar body. Hence, 'the true ovum is formed only after fertilisation' — a favourite board exam concept.
Gametogenesis: spermatogenesis vs oogenesisयुग्मकजनन: शुक्राणुजनन व अंडजननGametogenesis: spermatogenesis vs oogenesisNCERT Fig 2.8Compare side by side: one primary spermatocyte gives 4 sperms, one primary oocyte gives 1 ovum + polar bodies.साथ-साथ तुलना करें: एक प्राथमिक शुक्राणुकोशिका से 4 शुक्राणु, एक प्राथमिक अंडक से 1 अंडाणु + ध्रुवीय पिंड।Side by side compare kijiye: 1 primary spermatocyte se 4 sperms, 1 primary oocyte se 1 ovum + polar bodies. Placenta — supply line + endocrine gland
The placenta is formed by chorionic villi (embryo's part) and uterine tissue (mother's part), and is connected to the embryo by the umbilical cord. It supplies O₂ and nutrients and removes CO₂ and wastes. It also produces hormones — hCG, hPL, estrogens, progestogens; in the later stage of pregnancy, relaxin is also secreted by the ovary. These hormones increase only during pregnancy.
Inner cell mass = stem cells
The outer layer of the blastocyst, the trophoblast, attaches to the uterus, and the inner cell mass forms the embryo. The inner cell mass contains stem cells that can give rise to any tissue/organ; these form the ectoderm, mesoderm and endoderm.
Fertilisation, cleavage and implantationनिषेचन, विदलन और अंतर्रोपणFertilisation, cleavage and implantationNCERT Fig 2.11Ovum is fertilised in the ampullary–isthmic junction; cleavage → morula → blastocyst, which implants in the endometrium.अंडाणु का निषेचन तुंबिका–संकीर्ण पथ संधि पर; विदलन → मोरुला → ब्लास्टोसिस्ट, जो एंडोमेट्रियम में रोपित होता है।Ovum ka fertilisation ampullary–isthmic junction par; cleavage → morula → blastocyst, jo endometrium mein implant hota hai.
Common confusions — cleared up
Spermatogenesis vs Spermiogenesis
Spermatogenesis = the whole process (spermatogonia → sperm). Spermiogenesis = only the final step, in which a spermatid changes into a sperm; their release is called spermiation.
Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Seminiferous tubule (sectional view)NCERT Fig 2.2, 2.5Spermatogonia near the wall divide towards the lumen into spermatocytes, spermatids and sperms; Sertoli cells nourish them; Leydig cells lie outside.भित्ति के पास शुक्राणुजन कोशिकाएँ गुहा की ओर शुक्राणुकोशिका, शुक्रप्रसू और शुक्राणु बनाती हैं; सर्टोली कोशिकाएँ पोषण देती हैं; लीडिग कोशिकाएँ बाहर।Wall ke paas spermatogonia lumen ki taraf spermatocytes, spermatids aur sperms banate hain; Sertoli cells khana dete hain; Leydig cells bahar. Structure of a spermशुक्राणु की संरचनाStructure of a spermNCERT Fig 2.6Head (acrosome + nucleus), neck, middle piece full of mitochondria (energy), and tail for swimming.सिर (अग्रपिंडक + केंद्रक), ग्रीवा, माइटोकॉन्ड्रिया से भरा मध्य भाग (ऊर्जा) और तैरने के लिए पूँछ।Head (acrosome + nucleus), neck, mitochondria se bhara middle piece (energy) aur tairne ke liye tail. In ovulation: ovum or secondary oocyte?
In ovulation, it is actually the secondary oocyte that is released; the mature ovum forms only after sperm entry, when meiosis-II is completed.
Leydig vs Sertoli cells
Leydig (interstitial) cells produce androgens (under LH). Sertoli cells provide nourishment to germ cells (under FSH).
Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Seminiferous tubule (sectional view)NCERT Fig 2.2, 2.5Spermatogonia near the wall divide towards the lumen into spermatocytes, spermatids and sperms; Sertoli cells nourish them; Leydig cells lie outside.भित्ति के पास शुक्राणुजन कोशिकाएँ गुहा की ओर शुक्राणुकोशिका, शुक्रप्रसू और शुक्राणु बनाती हैं; सर्टोली कोशिकाएँ पोषण देती हैं; लीडिग कोशिकाएँ बाहर।Wall ke paas spermatogonia lumen ki taraf spermatocytes, spermatids aur sperms banate hain; Sertoli cells khana dete hain; Leydig cells bahar. Corpus luteum vs Graafian follicle
The Graafian follicle is the mature follicle before ovulation (estrogen). After ovulation, the remaining part becomes the corpus luteum (progesterone).
Section of ovary: follicles to corpus luteumअंडाशय की काट: पुटिका से पीत पिंड तकSection of ovary: follicles to corpus luteumNCERT Fig 2.7Go round the ovary: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum.अंडाशय में घूमकर देखें: प्राथमिक → द्वितीयक → तृतीयक → ग्राफी पुटक → अंडोत्सर्ग → पीत पिंड।Ovary mein ghoom kar dekhiye: primary → secondary → tertiary → Graafian follicle → ovulation → corpus luteum.
Video
▶ Human Reproduction Class 12 One Shot 🔥 | NCERT + Diagrams + PYQs | Biology Chapter 2 · 39 min
Diagrams (tap & zoom)
All 9 diagrams of this chapter — tap one to open itइस अध्याय के सभी 9 डायग्राम — खोलने के लिए टैप करेंIs chapter ke saare 9 diagrams — kholne ke liye tap kijiye
Seminiferous tubule (sectional view)शुक्रजनक नलिका (काट)Fig 2.2, 2.5
Fertilisation, cleavage and implantationनिषेचन, विदलन और अंतर्रोपणFig 2.11
Gametogenesis: spermatogenesis vs oogenesisयुग्मकजनन: शुक्राणुजनन व अंडजननFig 2.8
Structure of a spermशुक्राणु की संरचनाFig 2.6
Section of ovary: follicles to corpus luteumअंडाशय की काट: पुटिका से पीत पिंड तकFig 2.7
Menstrual cycle (28 days)आर्तव चक्र (28 दिन)Fig 2.9 (schematic)
Male reproductive system (testis opened)नर जनन तंत्र (वृषण खुला हुआ)Fig 2.1 (b)
Female reproductive system (sectional view)मादा जनन तंत्र (काट का दृश्य)Fig 2.3 (b)
Mammary gland (sectional view)स्तन ग्रंथि (काट का दृश्य)Fig 2.4Important questions with answers
Q1. What is the difference between spermatogenesis and oogenesis?
Spermatogenesis begins in the testis at puberty, and one primary spermatocyte forms 4 sperms. Oogenesis begins in the ovary during foetal life itself, and one primary oocyte forms only 1 ovum (plus polar bodies).
Q2. What is the LH surge?
In the middle of the menstrual cycle (around the 14th day), the LH level reaches its peak — this is called the LH surge. It causes the Graafian follicle to rupture and release the ovum (ovulation).
Q3. Which hormones does the placenta produce?
The placenta produces hCG (human chorionic gonadotropin), hPL (human placental lactogen), estrogens and progestogens. Relaxin is secreted by the ovary in late pregnancy.
Q4. Why is colostrum important?
The milk produced during the first few days of lactation is colostrum. It contains several antibodies (IgA) that give resistance to the newborn baby — this is why breast-feeding is recommended.
UP Board previous year questions (2022–2026)
These questions are from real UP Board Intermediate papers (copies from a third-party archive, read and verified by SLH). Also shown: in how many 2022–2026 papers (different sets) a question from this topic appeared. See year-wise papers →
- “Testosterone hormone is synthesized and secreted by: (A) Epididymis (B) Sertoli cells (C) Sperm (D) Leydig cells”
UP Board 20261 marksQuestions from this topic: 12 papers (2022, 2023, 2024, 2025, 2026) - “Define spermatogenesis. Describe the process of spermatogenesis with the help of schematic diagram.”
UP Board 20265 marksQuestions from this topic: 11 papers (2022, 2023, 2025, 2026) - “Which hormone is secreted from the corpus luteum?”
UP Board 20261 marksQuestions from this topic: 7 papers (2023, 2024, 2025, 2026) - “Which of the following hormones is secreted by the placenta? (A) Progestogen (B) Relaxin (C) Prolactin (D) Growth hormone”
UP Board 20261 marksQuestions from this topic: 6 papers (2022, 2023, 2024, 2025, 2026) - “What are the finger-like projections on the edges of the infundibulum called?”
UP Board 20251 marksQuestions from this topic: 6 papers (2022, 2023, 2025) - “The process of fertilization occurs in which part of the female reproductive system? (A) In ampulla area (B) In sertoli cells (C) In isthmus (D) In fallopian tube”
UP Board 20261 marksQuestions from this topic: 5 papers (2023, 2024, 2026) - “Define oogenesis. Describe the process of oogenesis with a diagram.”
UP Board 20265 marksQuestions from this topic: 4 papers (2023, 2024, 2026)
Practice quiz
Tap an option — get instant right/wrong feedback and an explanation. Wrong answers are saved in "My mistakes".
1. Which cells produce testosterone?
2. In which part of the oviduct does fertilisation take place?
3. The surge of which hormone causes ovulation?
4. How many sperms are formed from one primary spermatocyte?
5. Which layer of the blastocyst carries out implantation?
6. Which hormone increases uterine contractions during parturition?
7. Which hormone is produced by the corpus luteum?
8. What is the first milk, rich in antibodies, called?
Quick revision checklist
Before the exam — try explaining each topic aloud for 1 minute. If you get stuck, reread it in the notes above.
- Steps of human reproduction
- Male reproductive system
- Male ducts & glands
- Female reproductive system
- Spermatogenesis (शुक्राणुजनन)
- Hormones (male)
- Sperm structure
- Oogenesis (अंडजनन)
- Menstrual cycle (आर्तव चक्र)
- Fertilisation & implantation
- Placenta
- Embryo development
- Parturition & lactation