I. INTRODUCTION — OVERVIEW
A REPRODUCTIVE EVENTS IN HUMANS
↔ Swipe table sideways to view full columns
| EVENT | DETAIL |
|---|---|
| Gametogenesis | Formation of gametes — sperms (males) & ovum (females) ⭐ |
| Insemination | Transfer of sperms into female genital tract ⭐ |
| Fertilisation | Fusion of male & female gametes → formation of zygote ⭐ |
| Implantation | Attachment of blastocyst to uterine wall ⭐ |
| Gestation | Embryonic development ⭐ |
| Parturition | Delivery of the baby ⭐ |
B KEY DIFFERENCE BETWEEN MALE & FEMALE
↔ Swipe table sideways to view full columns
| FEATURE | MALE | FEMALE |
|---|---|---|
| Gamete formation | Sperm formation continues even in old men ⭐⭐ | Formation of ovum ceases around age 50 years ⭐⭐ |
| Reproduction type | Sexually reproducing & viviparous ⭐ | Sexually reproducing & viviparous ⭐ |
II. MALE REPRODUCTIVE SYSTEM
A OVERVIEW & B. TESTES
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Location | Pelvic region ⭐ |
| Components | A pair of testes + Accessory ducts + Glands + External genitalia ⭐ |
| Testes Location | Situated outside abdominal cavity within a pouch called Scrotum ⭐⭐⭐ |
| Scrotum function | Maintains low temperature of testes — 2–2.5°C lower than normal internal body temperature ⭐⭐⭐ |
| Why low temp needed | Necessary for spermatogenesis ⭐⭐ |
| Size (adult) | Length: 4–5 cm; Width: 2–3 cm ⭐ |
| Covering | Dense covering ⭐ |
| Compartments | Each testis has about 250 compartments called testicular lobules ⭐⭐ |
| Each lobule contains | 1–3 highly coiled seminiferous tubules → where sperms are produced ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2011: Scrotum maintains temperature 2–2.5°C lower than body temperature for spermatogenesis.
C SEMINIFEROUS TUBULES & D. INTERSTITIAL SPACE
• Lined inside by two types of cells ⭐⭐⭐:
| CELL TYPE | FUNCTION |
|---|---|
| Male germ cells (Spermatogonia) | Undergo meiotic divisions → form sperms ⭐⭐⭐ |
| Sertoli cells | Provide nutrition to germ cells ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2010: Seminiferous tubules lined by spermatogonia & Sertoli cells.
Interstitial Space ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Location | Outside seminiferous tubules ⭐⭐ |
| Contains | Small blood vessels & Interstitial cells (Leydig cells) ⭐⭐⭐ |
| Leydig cells function | Synthesise & secrete testicular hormones called Androgens ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2020, 2012: Leydig cells = interstitial cells; synthesise & secrete androgens.
⚡ EXAM TRAP
NEET 2024: LH acts on Leydig cells → stimulates synthesis & secretion of androgens. Androgens are produced by Leydig cells, NOT by Sertoli cells!
E MALE SEX ACCESSORY DUCTS
↔ Swipe table sideways to view full columns
| DUCT | DETAIL |
|---|---|
| Rete testis | Seminiferous tubules open into rete testis ⭐⭐ |
| Vasa efferentia | Leave testis → open into epididymis ⭐⭐ |
| Epididymis | Located along posterior surface of each testis ⭐⭐ |
| Vas deferens | Ascends to abdomen → loops over urinary bladder ⭐⭐ |
| Ejaculatory duct | Vas deferens receives duct from seminal vesicle → opens into urethra as ejaculatory duct ⭐⭐⭐ |
| Function | Store & transport sperms from testis to outside through urethra ⭐⭐ |
PATH OF SPERM ⭐⭐⭐ (MOST ASKED)
🔑 SEQUENCE: Seminiferous Tubules → Rete Testis → Vasa Efferentia → Epididymis → Vas Deferens → Ejaculatory Duct → Urethra → Urethral Meatus
⚡ EXAM TRAP
NEET 2019, 2016, 2011, 2023: Correct sequence of sperm transport — ST → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus.
⚡ EXAM TRAP
NEET 2015, 2014: Urethra = shared terminal duct of reproductive & urinary system in human male.
F MALE ACCESSORY GLANDS & G. EXTERNAL GENITALIA
↔ Swipe table sideways to view full columns
| GLAND / GENITALIA | DETAIL |
|---|---|
| Paired Seminal vesicles | Contribute to seminal plasma ⭐ |
| Prostate gland (single) | Contributes to seminal plasma ⭐ |
| Paired Bulbourethral glands | Secretions help in lubrication of penis ⭐⭐ |
| Seminal plasma | Rich in fructose, calcium & certain enzymes ⭐⭐⭐ |
| Semen = | Seminal plasma + Sperms ⭐⭐ |
| Penis | Male external genitalia ⭐ |
| Special tissue | Helps in erection of penis → facilitates insemination ⭐ |
| Glans penis | Enlarged end of penis ⭐ |
| Foreskin | Loose fold of skin covering glans penis ⭐ |
⚡ EXAM TRAP
NEET 2010: Seminal plasma rich in fructose, calcium & enzymes.
⚡ EXAM TRAP
NEET 2023: Vas deferens receives duct from seminal vesicle → opens into urethra as ejaculatory duct (TRUE).
III. FEMALE REPRODUCTIVE SYSTEM
A OVERVIEW & B. OVARIES
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Location | Pelvic region ⭐ |
| Components | A pair of ovaries + a pair of oviducts + Uterus + Cervix + Vagina + External genitalia + Mammary glands ⭐⭐ |
| Ovaries Function | Primary female sex organ ⭐⭐ |
| Produce | Female gamete (Ovum) + several steroid hormones (ovarian hormones) ⭐⭐ |
| Size | 2–4 cm in length ⭐ |
| Connected to | Pelvic wall & Uterus by ligaments ⭐ |
| Covering | Thin epithelium ⭐ |
| Encloses | Ovarian stroma ⭐ |
| Stroma divided into | Peripheral cortex & Inner medulla ⭐⭐ |
⚡ EXAM TRAP
NEET 2023: Female reproductive system — ovaries, oviducts, uterus, cervix, vagina, external genitalia.
C OVIDUCTS (FALLOPIAN TUBES)
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Length | 10–12 cm ⭐ |
| Extends from | Periphery of ovary → to uterus ⭐ |
| Are | Female accessory ducts (along with uterus & vagina) ⭐ |
THREE PARTS OF FALLOPIAN TUBE ⭐⭐⭐
↔ Swipe table sideways to view full columns
| PART | DETAIL |
|---|---|
| (i) Infundibulum | Part closer to ovary; funnel-shaped ⭐⭐⭐ • Edges possess finger-like projections called Fimbriae ⭐⭐⭐ • Fimbriae help in collection of ovum after ovulation ⭐⭐⭐ |
| (ii) Ampulla | Infundibulum leads to this wider part of oviduct ⭐⭐ • Site of fertilisation ⭐⭐⭐ |
| (iii) Isthmus | Last part of oviduct; has narrow lumen ⭐⭐ • Joins the uterus ⭐⭐ |
⚡ EXAM TRAP
NEET 2024, RE-NEET 2024: Fallopian tube = Infundibulum + Ampulla + Isthmus. Infundibulum — funnel-shaped; fimbriae collect ovum.
⚡ EXAM TRAP
NEET 2024: Uterine fundus is NOT a component of Fallopian tube!
D UTERUS
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Number | Single ⭐ |
| Also called | Womb ⭐ |
| Shape | Like an inverted pear ⭐⭐ |
| Support | Ligaments attached to pelvic wall ⭐ |
| Opens into | Vagina through narrow cervix ⭐⭐ |
| Cervical canal | Cavity of cervix ⭐ |
| Birth canal | Cervical canal + Vagina ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2023: Cervical canal along with vagina forms birth canal (TRUE).
THREE LAYERS OF UTERINE WALL ⭐⭐⭐
↔ Swipe table sideways to view full columns
| LAYER | POSITION | TYPE | FUNCTION |
|---|---|---|---|
| Perimetrium | External | Thin, membranous ⭐⭐ | Outer covering |
| Myometrium | Middle | Thick layer of smooth muscle ⭐⭐⭐ | Exhibits strong contractions during delivery ⭐⭐ |
| Endometrium | Inner | Glandular layer ⭐⭐⭐ | Lines uterine cavity; undergoes cyclical changes during menstrual cycle ⭐⭐⭐ |
E FEMALE EXTERNAL GENITALIA
↔ Swipe table sideways to view full columns
| STRUCTURE | DETAIL |
|---|---|
| Mons pubis | Cushion of fatty tissue covered by skin & pubic hair ⭐⭐ |
| Labia majora | Fleshy folds of tissue; extend down from mons pubis; surround the vaginal opening ⭐⭐⭐ |
| Labia minora | Paired folds of tissue under labia majora ⭐ |
| Hymen | Membrane partially covering vaginal opening ⭐⭐ |
| Clitoris | Tiny finger-like structure; lies at upper junction of two labia minora above urethral opening ⭐⭐⭐ |
⚡ EXAM TRAP
RE-NEET 2024: Match — Mons pubis = fatty cushion; Clitoris = tiny finger-like structure above labia minora; Hymen = thin membrane; Labia majora = fleshy fold surrounding vaginal opening.
HYMEN — Important Statement ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Often torn during | First coitus (intercourse) ⭐⭐ |
| Can also be broken by | Sudden fall/jolt, vaginal tampon insertion, sports (horseback riding, cycling) ⭐⭐ |
| In some women | Hymen persists even after coitus ⭐⭐⭐ |
| KEY STATEMENT | Presence or absence of hymen is NOT a reliable indicator of virginity or sexual experience ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2024: Statement I (hymen not reliable indicator of virginity) = TRUE; Statement II (hymen torn during first coitus ONLY) = FALSE (can also be broken by other means!).
F MAMMARY GLANDS
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Type | Paired structures (breasts) ⭐ |
| Contain | Glandular tissue + variable amount of fat ⭐ |
| Glandular tissue divided into | 15–20 mammary lobes ⭐⭐ |
| Each lobe contains | Clusters of cells called Alveoli ⭐⭐⭐ |
| Alveoli function | Cells of alveoli secrete milk → stored in cavities (lumens) of alveoli ⭐⭐ |
PATH OF MILK ⭐⭐⭐
🔑 SEQUENCE: Alveoli → Mammary Tubules → Mammary Duct → Mammary Ampulla → Lactiferous Duct → Nipple
⚡ EXAM TRAP
RE-NEET 2024, NEET 2022: Correct path of milk = Alveoli → Mammary Tubules → Mammary Duct → Mammary Ampulla → Lactiferous Duct.
IV. GAMETOGENESIS
A SPERMATOGENESIS
1. Overview ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Definition | Process by which immature male germ cells (Spermatogonia) produce sperms ⭐⭐⭐ |
| Location | Inside seminiferous tubules of testis ⭐⭐ |
| Begins at | Puberty ⭐⭐⭐ |
| Spermatogonia are | Diploid (2n) — contain 46 chromosomes ⭐⭐ |
| Multiply by | Mitotic division → increase in numbers ⭐ |
⚡ EXAM TRAP
NEET 2018: Spermatogenesis begins at puberty.
2. Steps of Spermatogenesis ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STAGE | DETAIL |
|---|---|
| Spermatogonia (2n, Diploid) | Mitosis → increase in numbers ⭐ |
| Primary Spermatocyte (2n, Diploid) | Undergoes MEIOSIS I (Reduction division) ⭐⭐ |
| Secondary Spermatocyte (n, Haploid) | TWO equal cells; undergoes MEIOSIS II ⭐⭐ |
| Spermatids (n, Haploid) | FOUR equal cells ⭐⭐ |
| Spermatozoa (n, Haploid) | After SPERMIOGENESIS (transformation) ⭐⭐⭐ |
| Released from | Seminiferous Tubules via SPERMIATION ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2013, 2015, 2020: Correct sequence = Spermatogonia → Spermatocyte → Spermatid → Spermatozoa. Spermatogonia normally diploid; Haploid cells = Secondary spermatocyte, First polar body, Ovum.
⚡ EXAM TRAP
NEET 2022: 1 secondary spermatocyte → 2 spermatids → 2 spermatozoa; 200 million secondary spermatocytes needed for 400 million spermatozoa.
3. KEY DEFINITIONS ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TERM | DEFINITION |
|---|---|
| Spermiogenesis | Transformation of spermatids into spermatozoa (sperms) ⭐⭐⭐ |
| Spermiation | Release of sperms from Sertoli cells into the cavity of seminiferous tubules ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2022, 2018: Spermiogenesis = spermatids → spermatozoa; Spermiation = release of spermatozoa from Sertoli cells into seminiferous tubules. TRAP: 'Spermiogenesis = formation of sperms from spermatogonia' is INCORRECT!
4. Hormonal Regulation of Spermatogenesis ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STEP | DETAIL |
|---|---|
| 1 | Hypothalamus secretes GnRH (significant increase at puberty) ⭐⭐ |
| 2 | GnRH acts on ANTERIOR PITUITARY GLAND ⭐⭐ |
| 3 | Stimulates secretion of TWO GONADOTROPINS: LH & FSH ⭐⭐ |
| 4a | LH acts on LEYDIG CELLS → stimulates synthesis & secretion of ANDROGENS ⭐⭐⭐ |
| 4b | FSH acts on SERTOLI CELLS → stimulates secretion of FACTORS that help in SPERMIOGENESIS ⭐⭐⭐ |
| 5 | ANDROGENS stimulate SPERMATOGENESIS ⭐⭐ |
⚡ EXAM TRAP
NEET 2024, 2022: LH → Leydig cells → Androgens → Spermatogenesis; FSH → Sertoli cells → factors → Spermiogenesis. TRAP: FSH acts on Sertoli cells in males, NOT Leydig cells!
5. Statements True for Spermatogenesis but NOT Oogenesis ⭐⭐
• (B) Differentiation of gamete occurs after completion of meiosis ✅
• (C) Meiosis occurs continuously in a mitotically dividing stem cell population ✅
• (E) It is initiated at puberty ✅
🔑 NEET 2022: Answer: B, C and E only.
B STRUCTURE OF SPERM
↔ Swipe table sideways to view full columns
| PART | DETAIL |
|---|---|
| Overall | Microscopic structure ⭐ |
| Covering | Plasma membrane envelops the whole body of sperm ⭐⭐ |
| Head | Contains elongated haploid nucleus ⭐⭐; anterior portion covered by Acrosome (cap-like structure) ⭐⭐⭐ |
| Acrosome | Filled with enzymes that help in fertilisation ⭐⭐⭐ |
| Neck | Connects head to middle piece ⭐ |
| Middle piece | Possesses numerous Mitochondria → produce energy for sperm motility → essential for fertilisation ⭐⭐⭐ |
| Tail | Facilitates sperm motility ⭐⭐ |
⚡ EXAM TRAP
NEET 2010: Acrosome filled with enzymes for fertilisation; Middle piece = mitochondria → energy for motility.
Sperm Count, Fertility, Maturation & Motility ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Ejaculate | 200–300 million sperms during a coitus ⭐⭐ |
| For normal fertility | At least 60% must have normal shape & size; At least 40% must show vigorous motility ⭐⭐ |
| Secretions essential for maturation & motility | Epididymis, Vas deferens, Seminal vesicle, Prostate ⭐⭐ |
| Functions maintained by | Testicular hormones (Androgens) ⭐ |
C CAPACITATION
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Definition | Changes in sperm BEFORE fertilisation ⭐⭐⭐ |
| Where it occurs | Female reproductive tract ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2017, 2015: Capacitation refers to changes in the sperm BEFORE fertilisation; occurs in female reproductive tract.
D OOGENESIS
1. Overview ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Definition | Process of formation of mature female gamete (ovum) ⭐⭐ |
| Markedly different from | Spermatogenesis ⭐ |
| Initiated during | Embryonic development stage ⭐⭐⭐ |
| Gamete mother cells | A couple of million oogonia formed within each foetal ovary ⭐⭐ |
| Key fact | No more oogonia are formed & added after birth ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2022: Oogenesis initiated during embryonic development stage (NOT at puberty, birth, or adulthood).
2. Steps of Oogenesis ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STAGE | DETAIL |
|---|---|
| Oogonia (2n, Diploid) | Formed during embryonic development; start division → enter Prophase-I of meiosis ⭐⭐ |
| Primary Oocytes (2n, Diploid) | Get TEMPORARILY ARRESTED at Prophase-I ⭐⭐⭐; each surrounded by a layer of GRANULOSA CELLS ⭐⭐ |
| Primary Follicle | Primary oocyte + layer of granulosa cells ⭐⭐ |
| Secondary Follicle | More granulosa layers + new THECA ⭐⭐ |
| Tertiary Follicle | Fluid-filled cavity = ANTRUM appears ⭐⭐⭐ |
| Meiosis I completed | Primary oocyte → UNEQUAL division → SECONDARY OOCYTE (n) + FIRST POLAR BODY ⭐⭐⭐ |
| Graafian Follicle | Tertiary follicle → mature; secondary oocyte forms ZONA PELLUCIDA ⭐⭐⭐ |
| Ovulation | Graafian follicle RUPTURES → release of SECONDARY OOCYTE ⭐⭐⭐ |
| Meiosis II | Completed only AFTER sperm entry/fertilisation → OOTID (OVUM) + SECOND POLAR BODY ⭐⭐⭐ |
3. Key Facts of Follicle Development ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STAGE / FEATURE | DETAIL |
|---|---|
| Primary follicle | Primary oocyte + layer of granulosa cells ⭐⭐ |
| Secondary follicle | More layers of granulosa + new theca ⭐⭐ |
| Tertiary follicle | Characterised by fluid-filled cavity called Antrum ⭐⭐⭐ |
| Theca organisation | Inner theca interna + Outer theca externa ⭐⭐ |
| Graafian follicle | Mature follicle ⭐⭐ |
| Zona pellucida | New membrane formed by secondary oocyte in Graafian follicle ⭐⭐⭐ |
| Zona pellucida nature | Acellular layer ⭐⭐⭐ |
| At puberty | Only 60,000–80,000 primary follicles left in each ovary ⭐⭐ |
⚡ EXAM TRAP
NEET 2016, 2023, 2015: Tertiary follicle characterised by fluid-filled cavity = Antrum. Zona pellucida = acellular layer in an antral follicle. Antrum is characteristic of tertiary follicle, NOT secondary!
⚡ EXAM TRAP
NEET 2019, 2020, 2015: Extrusion of second polar body from egg occurs after entry of sperm but BEFORE fertilisation (before nuclear fusion). Meiosis-II is not complete until fertilisation!
V. MENSTRUAL CYCLE
A OVERVIEW
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Found in | Female primates (monkeys, apes, humans) ⭐ |
| First menstruation called | Menarche → begins at puberty ⭐⭐⭐ |
| Average interval | About 28/29 days ⭐⭐ |
| Ceases around | 50 years of age → termed Menopause ⭐⭐⭐ |
| Cyclic menstruation extends between | Menarche & Menopause ⭐⭐ |
| One ovum released per | Menstrual cycle (during ovulation at mid-cycle) ⭐ |
⚡ EXAM TRAP
NEET 2023: Cyclic menstruation extends between menarche & menopause (TRUE); First menstrual cycle at puberty is menarche, NOT menopause.
B FOUR PHASES OF MENSTRUAL CYCLE
PHASE 1: MENSTRUAL PHASE (Days 1–5) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Duration | 3–5 days ⭐⭐ |
| What happens | Breakdown of endometrial lining of uterus & its blood vessels ⭐⭐⭐ |
| Result | Liquid (blood + tissue) comes out through vagina = menstrual flow ⭐⭐ |
| Occurs when | Released ovum is NOT fertilised ⭐⭐⭐ |
| Lack of menstruation | May indicate pregnancy ⭐⭐ |
| But also caused by | Stress, poor health etc. ⭐⭐ |
| Menstrual flow due to lack of | Progesterone ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2013: Menstrual flow occurs due to lack of Progesterone.
PHASE 2: FOLLICULAR PHASE (Proliferative Phase) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| In ovary | Primary follicles grow to become fully mature Graafian follicle ⭐⭐⭐ |
| In uterus | Endometrium regenerates through proliferation ⭐⭐ |
| Induced by | Changes in levels of pituitary & ovarian hormones ⭐⭐ |
| Gonadotropins (LH & FSH) | Increase gradually during follicular phase ⭐⭐ |
| Stimulate | Follicular development + secretion of Estrogen by growing follicles ⭐⭐⭐ |
PHASE 3: OVULATORY PHASE (≈ Day 14) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| When | Both LH & FSH attain peak level in middle of cycle (about 14th day) ⭐⭐⭐ |
| LH surge | Rapid secretion of LH leading to its maximum level during mid-cycle ⭐⭐⭐ |
| Result | LH surge induces rupture of Graafian follicle → release of ovum = OVULATION ⭐⭐⭐ |
⚡ EXAM TRAP
RE-NEET 2024, NEET 2016, 2011, 2024: Ovulation on ≈14th day; induced by LH surge → rupture of Graafian follicle → release of ovum. Both A & R correct and R explains A.
⚡ EXAM TRAP
NEET 2020, 2015: Release of ovum caused by high concentration of Estrogen (which triggers the LH surge). Decrease in estradiol is NOT associated with ovulation.
PHASE 4: LUTEAL PHASE (Secretory Phase) ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| After ovulation | Remaining parts of Graafian follicle transform into Corpus Luteum ⭐⭐⭐ |
| Corpus Luteum secretes | Large amounts of Progesterone ⭐⭐⭐ |
| Progesterone essential for | Maintenance of endometrium ⭐⭐⭐ |
| Such endometrium necessary for | Implantation of fertilised ovum & other events of pregnancy ⭐⭐⭐ |
| During pregnancy | All events of menstrual cycle stop → no menstruation ⭐⭐ |
| If NO fertilisation | Corpus luteum degenerates → disintegration of endometrium → menstruation → new cycle ⭐⭐⭐ |
⚡ EXAM TRAP
RE-NEET 2024, NEET 2023, 2018, 2017, 2014, 2013, 2012: Corpus luteum = temporary endocrine gland; secretes progesterone → essential for maintenance of endometrium → necessary for implantation.
INHIBIN ⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Produced by | Granulosa cells in ovary ⭐⭐⭐ |
| Inhibits secretion of | FSH ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2016 (II): Inhibin = produced by granulosa cells in ovary; inhibits secretion of FSH.
VI. FERTILISATION AND IMPLANTATION
A INSEMINATION & B. SITE OF FERTILISATION
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| During copulation (coitus) | Semen released by penis into vagina ⭐ |
| Sperm movement | Swim rapidly → through cervix → into uterus → reach ampullary region of fallopian tube ⭐⭐ |
| Site of fertilisation | Ampullary region of fallopian tube (ampullary-isthmic junction) ⭐⭐⭐ |
| Condition | Fertilisation can only occur if ovum & sperms are transported simultaneously to ampullary region ⭐⭐⭐ |
| Therefore | Not all copulations lead to fertilisation & pregnancy ⭐ |
⚡ EXAM TRAP
NEET 2016 (I): Fertilisation feasible only if ovum & sperms transported simultaneously to ampullary-isthmic junction of fallopian tube.
C PROCESS OF FERTILISATION
↔ Swipe table sideways to view full columns
| STEP | DETAIL |
|---|---|
| 1 | Sperm comes in contact with ZONA PELLUCIDA of ovum ⭐⭐⭐ |
| 2 | Induces CHANGES IN MEMBRANE → BLOCKS ENTRY of additional sperms ⭐⭐⭐ |
| 3 | Ensures ONLY ONE SPERM fertilises an ovum ⭐⭐ |
| 4 | ACROSOME secretions help sperm enter cytoplasm of ovum through zona pellucida & plasma membrane ⭐⭐⭐ |
| 5 | Induces COMPLETION of MEIOTIC DIVISION of secondary oocyte ⭐⭐ |
| 6 | 2nd meiotic division (UNEQUAL) → Forms SECOND POLAR BODY + HAPLOID OVUM (OOTID) ⭐⭐ |
| 7 | Haploid sperm nucleus + Haploid ovum nucleus FUSE → DIPLOID ZYGOTE ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2017, 2020: Sperm contacts zona pellucida → changes in membrane → blocks additional sperms → only 1 sperm fertilises.
⚡ EXAM TRAP
NEET 2021: Receptors for sperm binding in mammals present on zona pellucida.
D SEX DETERMINATION
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Sex decided at | Stage of fertilisation itself ⭐⭐ |
| All ova carry | X chromosome ⭐ |
| 50% sperms carry | X chromosome ⭐ |
| 50% sperms carry | Y chromosome ⭐ |
| XX zygote → | Female baby ⭐ |
| XY zygote → | Male baby ⭐ |
| KEY STATEMENT | Sex of baby determined by father (sperm), NOT by mother ⭐⭐⭐ |
E CLEAVAGE, BLASTOCYST & IMPLANTATION
↔ Swipe table sideways to view full columns
| STAGE / COMPONENT | DETAIL |
|---|---|
| Zygote (in isthmus) | MITOTIC DIVISION starts = CLEAVAGE ⭐⭐⭐; Moves towards UTERUS |
| Blastomeres | 2, 4, 8, 16 daughter cells formed by cleavage ⭐⭐ |
| Morula | Embryo with 8–16 blastomeres ⭐⭐⭐ |
| Blastocyst | Morula continues to divide → transforms into blastocyst as it moves into UTERUS ⭐⭐⭐ |
| Trophoblast | Outer layer of blastomeres ⭐⭐⭐; gets attached to endometrium ⭐⭐ |
| Inner Cell Mass (ICM) | Inner group of cells attached to trophoblast ⭐⭐⭐; gets differentiated as embryo ⭐⭐ |
| Implantation | Blastocyst becomes embedded in the endometrium of uterus ⭐⭐⭐ • After trophoblast attachment → uterine cells divide rapidly → cover the blastocyst ⭐ • Leads to pregnancy ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2023: Implantation = blastocyst embedded in endometrium → leads to pregnancy.
VII. PREGNANCY AND EMBRYONIC DEVELOPMENT
A PLACENTA
1. Formation ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| After implantation | Finger-like projections appear on trophoblast = Chorionic villi ⭐⭐⭐ |
| Chorionic villi surrounded by | Uterine tissue & maternal blood ⭐⭐ |
| Placenta = | Chorionic villi + Uterine tissue become interdigitated → jointly form structural & functional unit between developing embryo & maternal body ⭐⭐⭐ |
2. Functions of Placenta ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FUNCTION | DETAIL |
|---|---|
| Supply | Oxygen & nutrients to embryo ⭐⭐⭐ |
| Removal | CO₂ & excretory/waste materials produced by embryo ⭐⭐ |
| Connection | Connected to embryo through umbilical cord ⭐⭐⭐ |
| Endocrine tissue | Acts as endocrine tissue → produces several hormones ⭐⭐⭐ |
3. Hormones Produced by Placenta ⭐⭐⭐
↔ Swipe table sideways to view full columns
| HORMONE | FULL FORM / DETAIL |
|---|---|
| hCG | Human Chorionic Gonadotropin ⭐⭐⭐ |
| hPL | Human Placental Lactogen ⭐⭐⭐ |
| Estrogens | Increased several-fold ⭐⭐ |
| Progestogens | Increased several-fold ⭐⭐ |
| Relaxin | Produced by ovary in later phase of pregnancy ⭐⭐ |
| Produced ONLY during pregnancy | hCG, hPL & Relaxin ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2020, 2018, 2016: Placenta produces hCG, hPL, estrogens, progestogens; acts as endocrine tissue. Relaxin is secreted by Corpus luteum (ovary) during later phase of pregnancy. High level of hCG stimulates synthesis of estrogen & progesterone.
4. Hormones Increased During Pregnancy ⭐⭐
↔ Swipe table sideways to view full columns
| HORMONES INCREASED | PURPOSE |
|---|---|
| Estrogens, Progestogens, Cortisol, Prolactin, Thyroxine | Support foetal growth, metabolic changes in mother, maintain pregnancy ⭐⭐ |
B EMBRYONIC DEVELOPMENT — GERM LAYERS & C. STEM CELLS
↔ Swipe table sideways to view full columns
| EVENT / FEATURE | DETAIL |
|---|---|
| Immediately after implantation | ICM differentiates into outer Ectoderm & inner Endoderm ⭐⭐⭐ |
| Soon appears | Mesoderm — between ectoderm & endoderm ⭐⭐⭐ |
| These three layers | Give rise to all tissues & organs in adults ⭐⭐ |
| Stem Cells located in | Inner cell mass ⭐⭐ |
| Potency | Have potency to give rise to all tissues & organs ⭐⭐⭐ |
⚡ EXAM TRAP
NEET 2018: Amnion of mammalian embryo derived from Ectoderm & Mesoderm.
D DEVELOPMENTAL MILESTONES
↔ Swipe table sideways to view full columns
| TIME | MILESTONE |
|---|---|
| After 1 month | Embryo's heart is formed ⭐⭐ |
| End of 2nd month | Foetus develops limbs & digits ⭐⭐ |
| End of 12 weeks (1st trimester) | Most major organ systems formed (limbs & external genital organs well-developed) ⭐⭐⭐ |
| During 5th month | First movements of foetus; hair on head ⭐⭐ |
| End of 24 weeks (2nd trimester) | Body covered with fine hair; eyelids separate; eyelashes formed ⭐⭐ |
| End of 9 months | Foetus fully developed → ready for delivery ⭐⭐ |
⚡ EXAM TRAP
NEET 2020: At end of 12 weeks (first trimester) = most major organ systems formed.
VIII. PARTURITION AND LACTATION
A PARTURITION (CHILDBIRTH)
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Gestation period | Average 9 months of human pregnancy ⭐⭐ |
| Definition | Process of delivery of the foetus (childbirth) ⭐⭐ |
| Mechanism | Complex neuroendocrine mechanism ⭐ |
Mechanism of Parturition ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STEP | DETAIL |
|---|---|
| 1 | Signals originate from FULLY DEVELOPED FOETUS + PLACENTA ⭐⭐⭐ |
| 2 | Induce mild uterine contractions = FOETAL EJECTION REFLEX ⭐⭐⭐ |
| 3 | Triggers release of OXYTOCIN from maternal pituitary ⭐⭐⭐ |
| 4 | Oxytocin acts on UTERINE MUSCLE → causes STRONGER uterine contractions ⭐⭐ |
| 5 | Stronger contractions STIMULATE FURTHER OXYTOCIN secretion = POSITIVE FEEDBACK loop ⭐⭐⭐ |
| 6 | Stronger & stronger contractions → EXPULSION of baby through BIRTH CANAL ⭐⭐ |
| 7 | After baby → PLACENTA also expelled ⭐ |
⚡ EXAM TRAP
NEET 2021, 2015, 2024: Release of Prolactin is NOT an important component of initiation of parturition. Parturition = Foetal ejection reflex from foetus + placenta!
B LACTATION
↔ Swipe table sideways to view full columns
| FEATURE | DETAIL |
|---|---|
| Mammary glands | Undergo differentiation during pregnancy ⭐⭐ |
| Start producing milk | Towards the end of pregnancy ⭐⭐ |
| Process called | Lactation ⭐⭐ |
| Colostrum | Milk produced during initial few days of lactation ⭐⭐⭐ |
| Colostrum contains | Several antibodies ⭐⭐⭐ |
| Antibodies essential for | Developing resistance in new-born babies ⭐⭐⭐ |
| Recommendation | Breast-feeding during initial period of infant growth recommended for healthy baby ⭐⭐ |
⚡ EXAM TRAP
NEET 2024, RE-NEET 2024: Lactation = mammary glands differentiate during pregnancy → produce milk; Colostrum = initial milk with several antibodies for newborn resistance. Both A (breast-feeding recommended) & R (colostrum contains antibodies) are correct AND R explains A!
IX. RAPID REVISION — KEY COMPARISON TABLES
TABLE 1: Male vs Female Reproductive System ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | MALE | FEMALE |
|---|---|---|
| Primary sex organ | Testes | Ovaries |
| Gamete | Sperm | Ovum |
| Hormones | Androgens (from Leydig cells) | Estrogen, Progesterone (from ovaries) |
| Accessory ducts | Rete testis, Vasa efferentia, Epididymis, Vas deferens | Oviducts, Uterus, Vagina |
| Accessory glands | Seminal vesicles, Prostate, Bulbourethral | — |
| External genitalia | Penis | Mons pubis, Labia majora/minora, Hymen, Clitoris |
| Gamete formation | Continues in old age | Ceases ≈50 years (menopause) |
TABLE 2: Spermatogenesis vs Oogenesis ⭐⭐⭐
↔ Swipe table sideways to view full columns
| FEATURE | SPERMATOGENESIS | OOGENESIS |
|---|---|---|
| Starts | At puberty | During embryonic development |
| Continuous? | Yes — continuous throughout life | No — arrested at prophase-I; resumes at puberty |
| New germ cells after birth? | Yes (spermatogonia divide by mitosis) | No — no more oogonia after birth |
| Meiosis I result | 2 equal secondary spermatocytes | 1 large secondary oocyte + 1 tiny first polar body (unequal) |
| Meiosis II result | 4 equal spermatids | 1 ootid (ovum) + 1 second polar body (unequal) |
| Final product | 4 functional sperms from 1 spermatogonium | 1 functional ovum from 1 oogonium |
| Meiosis II completed | Before release | Only after fertilisation |
TABLE 3: Key Terms — Spermatogenesis ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TERM | DEFINITION |
|---|---|
| Spermatogenesis | Entire process: spermatogonia → sperms |
| Spermiogenesis | Spermatids → Spermatozoa (transformation; NO division) |
| Spermiation | Release of sperms from Sertoli cells into seminiferous tubule cavity |
| Capacitation | Changes in sperm in female reproductive tract BEFORE fertilisation |
TABLE 4: Follicle Development ⭐⭐⭐
↔ Swipe table sideways to view full columns
| STAGE | KEY FEATURE |
|---|---|
| Primary follicle | Primary oocyte + 1 layer of granulosa cells |
| Secondary follicle | More granulosa layers + new theca |
| Tertiary follicle | Antrum (fluid-filled cavity); theca interna + theca externa |
| Graafian follicle | Mature follicle; secondary oocyte + zona pellucida |
| Ovulation | Rupture of Graafian follicle → release of secondary oocyte |
| Corpus luteum | Remaining part of Graafian follicle after ovulation |
TABLE 5: Four Phases of Menstrual Cycle ⭐⭐⭐
↔ Swipe table sideways to view full columns
| PHASE | DAYS | KEY EVENTS | HORMONES |
|---|---|---|---|
| Menstrual | 1–5 | Endometrium breaks down; menstrual flow | Low progesterone; corpus luteum degenerated |
| Follicular / Proliferative | 6–13 | Primary follicle → Graafian follicle; Endometrium regenerates | ↑ FSH & LH (gradually); ↑ Estrogen |
| Ovulatory | ≈14 | LH surge → Graafian follicle ruptures → Ovulation | Peak LH & FSH |
| Luteal / Secretory | 15–28 | Corpus luteum forms → secretes Progesterone; Endometrium maintained | ↑ Progesterone |
TABLE 6: Hormonal Regulation Summary ⭐⭐⭐
↔ Swipe table sideways to view full columns
| HORMONE | SOURCE | TARGET | EFFECT |
|---|---|---|---|
| GnRH | Hypothalamus | Anterior pituitary | Stimulates LH & FSH secretion |
| LH | Anterior pituitary | Leydig cells (♂); Ovarian follicles (♀) | Androgen synthesis (♂); LH surge → Ovulation (♀) |
| FSH | Anterior pituitary | Sertoli cells (♂); Ovarian follicles (♀) | Spermiogenesis factors (♂); Follicular devt + Estrogen (♀) |
| Androgens | Leydig cells | Seminiferous tubules | Stimulates spermatogenesis |
| Estrogen | Growing ovarian follicles | Uterus; Hypothalamus-Pituitary | Endometrium proliferation; triggers LH surge |
| Progesterone | Corpus luteum | Uterus | Maintains endometrium for implantation |
| Inhibin | Granulosa cells (♀) | Anterior pituitary | Inhibits FSH secretion |
| hCG | Placenta | Corpus luteum | Maintains corpus luteum → progesterone |
| Oxytocin | Maternal pituitary | Uterine muscle | Stronger contractions during parturition |
TABLE 7: Three Layers of Uterine Wall ⭐⭐⭐
↔ Swipe table sideways to view full columns
| LAYER | POSITION | TYPE | FUNCTION |
|---|---|---|---|
| Perimetrium | External | Thin, membranous | Outer covering |
| Myometrium | Middle | Thick smooth muscle | Strong contractions during delivery |
| Endometrium | Inner | Glandular | Lines uterine cavity; cyclical changes; breaks down during menstruation |
TABLE 8: Three Parts of Fallopian Tube ⭐⭐⭐
↔ Swipe table sideways to view full columns
| PART | FEATURE | FUNCTION |
|---|---|---|
| Infundibulum | Funnel-shaped; has fimbriae | Collection of ovum after ovulation |
| Ampulla | Wider part | Site of fertilisation |
| Isthmus | Narrow lumen; joins uterus | Passage for zygote; cleavage occurs here |
TABLE 9: Placental Hormones ⭐⭐⭐
↔ Swipe table sideways to view full columns
| HORMONE | PRODUCED ONLY DURING PREGNANCY? |
|---|---|
| hCG | ✅ Yes |
| hPL | ✅ Yes |
| Relaxin | ✅ Yes (by ovary in later phase) |
| Estrogens | No (increased several-fold) |
| Progestogens | No (increased several-fold) |
TABLE 10: Developmental Milestones ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TIME | MILESTONE |
|---|---|
| 1 month | Heart formed |
| 2 months | Limbs & digits |
| 12 weeks (1st trimester) | Major organ systems; external genitalia |
| 5th month | Foetal movements; hair on head |
| 24 weeks (2nd trimester) | Fine hair; eyelids separate; eyelashes |
| 9 months | Fully developed; ready for delivery |
TABLE 11: Path of Sperm vs Path of Milk ⭐⭐⭐
↔ Swipe table sideways to view full columns
| PATH OF SPERM | PATH OF MILK |
|---|---|
|
Seminiferous Tubules → Rete Testis → Vasa Efferentia → Epididymis → Vas Deferens → Ejaculatory Duct → Urethra → Urethral Meatus |
Alveoli → Mammary Tubules → Mammary Duct → Mammary Ampulla → Lactiferous Duct → Nipple |
X. COMMON EXAM TRAPS — QUICK REFERENCE
CONSOLIDATED PYQ Q&A TABLE ⭐⭐⭐
↔ Swipe table sideways to view full columns
| TRAP / QUESTION | CORRECT ANSWER |
|---|---|
| Scrotum — temperature difference? | 2–2.5°C lower than normal body temperature ⭐⭐ |
| How many testicular lobules? | About 250 per testis ⭐ |
| Each lobule contains? | 1–3 seminiferous tubules ⭐ |
| Sertoli cells function? | Nutrition to germ cells ⭐⭐ |
| Androgens produced by? | Leydig cells (NOT Sertoli cells) ⭐⭐⭐ |
| LH acts on which cells in males? | Leydig cells ⭐⭐⭐ |
| FSH acts on which cells in males? | Sertoli cells (NOT Leydig cells) ⭐⭐⭐ |
| LH → Leydig cells → ? | Androgens → stimulate spermatogenesis ⭐⭐ |
| FSH → Sertoli cells → ? | Factors that help in spermiogenesis ⭐⭐ |
| Path of sperm (correct sequence)? | ST → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra ⭐⭐⭐ |
| Shared terminal duct (male)? | Urethra ⭐⭐ |
| Seminal plasma rich in? | Fructose, Calcium, Enzymes ⭐⭐ |
| Semen = ? | Seminal plasma + Sperms ⭐ |
| Bulbourethral gland function? | Lubrication of penis ⭐ |
| Cervical canal + Vagina = ? | Birth canal ⭐⭐ |
| Uterus shape? | Inverted pear ⭐ |
| Endometrium — what happens during menstruation? | Breaks down ⭐⭐ |
| Myometrium — what happens during delivery? | Strong contractions ⭐⭐ |
| Hymen — reliable indicator of virginity? | NO ⭐⭐⭐ |
| Hymen torn only during first coitus? | NO — can be broken by fall, jolt, sports, tampon ⭐⭐⭐ |
| Clitoris location? | Upper junction of two labia minora above urethral opening ⭐⭐ |
| Mammary lobes per breast? | 15–20 ⭐ |
| Milk secreted by? | Cells of alveoli ⭐ |
| Path of milk? | Alveoli → M. Tubules → M. Duct → Ampulla → Lactiferous Duct ⭐⭐⭐ |
| Fallopian tube parts? | Infundibulum, Ampulla, Isthmus ⭐⭐ |
| Is uterine fundus part of Fallopian tube? | NO ⭐⭐ |
| Fimbriae function? | Collection of ovum after ovulation ⭐⭐ |
| Site of fertilisation? | Ampullary region (ampullary-isthmic junction) ⭐⭐⭐ |
| Spermatogenesis begins at? | Puberty ⭐⭐ |
| Spermatogonia — diploid or haploid? | Diploid (2n, 46 chromosomes) ⭐⭐ |
| Spermiogenesis = ? | Spermatids → Spermatozoa ⭐⭐⭐ |
| Spermiation = ? | Release of sperms from Sertoli cells into seminiferous tubule cavity ⭐⭐⭐ |
| Spermiogenesis = spermatogonia → sperms? | NO — it is spermatids → sperms ⭐⭐⭐ |
| Capacitation = ? | Changes in sperm before fertilisation ⭐⭐ |
| Capacitation occurs in? | Female reproductive tract ⭐⭐⭐ |
| Acrosome — location & content? | Anterior portion of sperm head; filled with enzymes for fertilisation ⭐⭐ |
| Middle piece of sperm contains? | Mitochondria → energy for motility ⭐⭐ |
| Number of sperms per ejaculate? | 200–300 million ⭐ |
| For normal fertility — shape/size? | At least 60% normal ⭐ |
| For normal fertility — motility? | At least 40% vigorous ⭐ |
| Oogenesis initiated at? | Embryonic development stage (NOT puberty/birth) ⭐⭐⭐ |
| Oogonia formed after birth? | NO — no more oogonia added after birth ⭐⭐⭐ |
| Primary oocytes arrested at? | Prophase-I of meiosis ⭐⭐ |
| Antrum found in? | Tertiary follicle (NOT secondary) ⭐⭐⭐ |
| Zona pellucida — cellular or acellular? | Acellular ⭐⭐⭐ |
| Ovulation releases? | Secondary oocyte (NOT primary oocyte or ovum) ⭐⭐⭐ |
| At puberty — follicles left per ovary? | 60,000–80,000 primary follicles ⭐ |
| Meiosis II of secondary oocyte completed when? | After fertilisation (sperm entry) ⭐⭐⭐ |
| Second polar body extrusion when? | After entry of sperm but before nuclear fusion ⭐⭐ |
| First menstruation = ? | Menarche ⭐⭐ |
| Menstrual cycle interval? | 28/29 days ⭐ |
| Menopause = ? | Cessation of menstrual cycles around 50 years ⭐⭐ |
| Menstrual flow occurs due to lack of? | Progesterone ⭐⭐⭐ |
| Menstruation occurs if? | Ovum is NOT fertilised ⭐⭐ |
| Ovulation — what day? | ≈14th day ⭐⭐⭐ |
| Ovulation triggered by? | LH surge ⭐⭐⭐ |
| Corpus luteum = temporary endocrine gland? | Yes ⭐⭐⭐ |
| Corpus luteum secretes? | Large amounts of Progesterone ⭐⭐⭐ |
| Progesterone essential for? | Maintenance of endometrium → implantation ⭐⭐⭐ |
| No fertilisation → corpus luteum? | Degenerates → endometrium disintegrates → menstruation ⭐⭐ |
| Inhibin produced by? | Granulosa cells in ovary ⭐⭐ |
| Inhibin inhibits? | FSH secretion ⭐⭐ |
| Decrease in estradiol associated with ovulation? | NO — estradiol actually increases ⭐⭐ |
| Prolactin involved in parturition initiation? | NO — NOT an important component ⭐⭐⭐ |
| Fertilisation — sperm contacts which layer? | Zona pellucida ⭐⭐⭐ |
| Block to polyspermy? | Membrane changes block entry of additional sperms ⭐⭐ |
| Sex determined by? | Father (sperm carries X or Y) ⭐⭐ |
| Cleavage = ? | Mitotic divisions of zygote as it moves through isthmus ⭐⭐ |
| Morula = ? | Embryo with 8–16 blastomeres ⭐⭐ |
| Blastocyst outer layer? | Trophoblast ⭐⭐ |
| Blastocyst inner group? | Inner cell mass (ICM) → differentiates as embryo ⭐⭐ |
| Implantation = ? | Blastocyst embedded in endometrium ⭐⭐⭐ |
| Placenta functions? | O₂/nutrient supply; waste removal; endocrine tissue ⭐⭐ |
| Hormones produced ONLY during pregnancy? | hCG, hPL, Relaxin ⭐⭐⭐ |
| Relaxin secreted by? | Corpus luteum (ovary) in later phase ⭐⭐ |
| hCG stimulates? | Synthesis of estrogen & progesterone ⭐⭐ |
| After implantation — ICM differentiates into? | Outer Ectoderm + Inner Endoderm + Mesoderm (between) ⭐⭐ |
| Amnion derived from? | Ectoderm & Mesoderm ⭐⭐ |
| Stem cells found in? | Inner cell mass ⭐⭐ |
| Heart formed — when? | After 1 month ⭐ |
| Limbs & digits — when? | End of 2nd month ⭐ |
| Major organs formed — when? | End of 12 weeks (1st trimester) ⭐⭐ |
| First movements — when? | 5th month ⭐ |
| Gestation period? | 9 months ⭐ |
| Parturition = ? | Delivery of foetus (childbirth) ⭐ |
| Foetal ejection reflex — signals from? | Fully developed foetus + Placenta ⭐⭐ |
| Foetal ejection reflex triggers? | Release of Oxytocin from maternal pituitary ⭐⭐⭐ |
| Oxytocin — positive or negative feedback? | Positive feedback ⭐⭐ |
| Colostrum = ? | Milk produced during initial few days of lactation ⭐⭐⭐ |
| Colostrum contains? | Several antibodies for developing resistance in newborns ⭐⭐⭐ |
| 200 million secondary spermatocytes produce how many spermatozoa? | 400 million (each gives 2 spermatids → 2 spermatozoa) ⭐⭐ |