🧬 Human Reproductive System – NEET Notes

🔹 1. Introduction

• Reproduction is a biological process by which organisms produce offspring.

• Humans show sexual reproduction and are dioecious (separate sexes).

• Fertilization is internal.

🔹 2. Male Reproductive System

📍 Parts:

1. Testes

2. Accessory ducts

3. Accessory glands

4. External genitalia (Penis)

🟢 Testes

• Located in scrotum (2–2.5°C lower than body temperature)

• Function:

  • Produce sperms

  • Secrete hormone testosterone

🟢 Structure of Testis

• Contains seminiferous tubules

• Lined by:

  • Spermatogonia (produce sperm)

  • Sertoli cells (nourishment)

• Leydig cells → secrete testosterone

🟢 Accessory Ducts

• Rete testis → Vasa efferentia → Epididymis → Vas deferens → Urethra

👉 Function: Transport and maturation of sperms

🟢 Accessory Glands

• Seminal vesicles → fructose (energy)

• Prostate gland → activates sperms

• Bulbourethral gland → lubrication

👉 Semen = Sperm + Seminal fluid

🔹 3. Female Reproductive System

📍 Parts:

1. Ovaries

2. Oviducts (Fallopian tubes)

3. Uterus

4. Vagina

5. External genitalia

🟣 Ovaries

• Produce ova (eggs)

• Secrete:

  • Estrogen

  • Progesterone

🟣 Oviduct (Fallopian Tube)

• Parts:

  • Infundibulum (with fimbriae)

  • Ampulla (site of fertilization ⭐)

  • Isthmus

🟣 Uterus

• Site of implantation and development

• Layers:

  • Perimetrium (outer)

  • Myometrium (muscle)

  • Endometrium (inner lining)

🟣 Vagina

• Receives sperm during intercourse

• Birth canal

🔹 4. Gametogenesis

🟢 Spermatogenesis (in males)

• Occurs in seminiferous tubules

• Starts at puberty

Steps:

1. Spermatogonia → Primary spermatocyte

2. Meiosis I → Secondary spermatocyte

3. Meiosis II → Spermatids

4. Spermiogenesis → Spermatozoa

👉 Controlled by:

• FSH (acts on Sertoli cells)

• LH (stimulates Leydig cells → testosterone)

🟣 Oogenesis (in females)

• Begins before birth

• Completed after puberty

Steps:

1. Oogonia → Primary oocyte

2. Meiosis I → Secondary oocyte

3. Meiosis II (after fertilization)

👉 Produces:

• One ovum + polar bodies

🔹 5. Menstrual Cycle (28 days)

📅 Phases:

1. Menstrual Phase (Day 1–5)

   • Shedding of endometrium

2. Follicular Phase (Day 6–14)

   • Follicle development

   • Estrogen increases

3. Ovulation (Day 14) ⭐

   • Release of ovum

4. Luteal Phase (Day 15–28)

   • Corpus luteum forms

   • Progesterone increases

👉 If no fertilization → menstruation starts again

🔹 6. Fertilization

• Fusion of sperm and ovum

• Occurs in ampulla of fallopian tube ⭐

• Forms zygote (diploid)

🔹 7. Implantation

• Zygote → blastocyst → embeds in uterus

• Occurs ~ 6–7 days after fertilization

🔹 8. Pregnancy and Placenta

• Duration: ~9 months (280 days)

🟡 Placenta functions:

• Nutrient exchange

• Gas exchange

• Waste removal

• Hormone secretion (hCG, progesterone)

🔹 9. Parturition (Childbirth)

• Controlled by hormones:

  • Oxytocin

  • Relaxin

🔹 10. Lactation

• Milk production by mammary glands

• Hormone: Prolactin

⭐ Important NEET Points (Must Revise)

• Fertilization site → Ampulla

• Ovulation → Day 14

• Hormone for milk → Prolactin

• Testosterone → from Leydig cells

• Nourishment of sperms → Sertoli cells

• Human sperm count → ~200–300 million/ejaculation