Human Reproduction - NCERT Solutions

Chapter Overview

Human Reproduction is a crucial chapter for NEET that covers the male and female reproductive systems, gametogenesis, menstrual cycle, fertilization, pregnancy, and reproductive health. This chapter has high weightage in NEET examinations.

Key Concepts:

• Male Reproductive System: Testes, accessory ducts, glands, and external genitalia
• Female Reproductive System: Ovaries, fallopian tubes, uterus, vagina, and external genitalia
• Gametogenesis: Spermatogenesis and oogenesis
• Menstrual Cycle: Hormonal regulation and phases
• Fertilization and Implantation: Formation of zygote and embryo development

NCERT Exercise Solutions

Exercise 3.1

Question: Fill in the blanks: (a) Humans reproduce _____________ (asexually/sexually) (b) Humans are _____________ (oviparous/viviparous/ovoviviparous) (c) Fertilisation is _____________ (external/internal) in humans (d) Male and female gametes are called _____________ and _____________ respectively. (e) Zygote divides to form _____________ which gets implanted in uterine wall. (f) The structure formed for attachment of foetus to uterine wall is called _____________.

Solution: (a) Humans reproduce sexually (asexually/sexually) (b) Humans are viviparous (oviparous/viviparous/ovoviviparous) (c) Fertilisation is internal (external/internal) in humans (d) Male and female gametes are called sperm and ovum respectively. (e) Zygote divides to form blastocyst which gets implanted in uterine wall. (f) The structure formed for attachment of foetus to uterine wall is called placenta.

Exercise 3.2

Question: Draw a labelled diagram of male reproductive system.

Solution:

Male Reproductive System Components:

External Genitalia:

• Penis: Male copulatory organ
• Scrotum: Pouch containing testes, maintains temperature 2-3°C below body temperature

Internal Organs:

1. Testes: Primary sex organs

   • Produce sperm (spermatogenesis)
   • Secrete testosterone
   • Contains seminiferous tubules and Leydig cells

2. Accessory Ducts:

   • Rete testis: Network of tubules
   • Epididymis: Storage and maturation of sperm
   • Vas deferens: Transport sperm from epididymis to urethra
   • Ejaculatory duct: Formed by vas deferens and seminal vesicle

3. Accessory Glands:

   • Seminal vesicles: Produce seminal plasma (60% of semen)
   • Prostate gland: Produces prostatic fluid (30% of semen)
   • Bulbourethral glands: Produce lubricating fluid

4. Urethra: Common passage for urine and semen

Exercise 3.3

Question: Draw a labelled diagram of female reproductive system.

Solution:

Female Reproductive System Components:

Internal Organs:

1. Ovaries: Primary sex organs (pair)

   • Produce ovum (oogenesis)
   • Secrete estrogen and progesterone
   • Contains ovarian follicles at different stages

2. Fallopian Tubes (Oviducts):

   • Infundibulum: Funnel-shaped opening with fimbriae
   • Ampulla: Site of fertilization
   • Isthmus: Connects to uterus
   • Transport ovum from ovary to uterus

3. Uterus (Womb):

   • Fundus: Upper portion
   • Body: Main portion
   • Cervix: Lower narrow portion opening into vagina
   • Three layers: perimetrium, myometrium, endometrium

4. Vagina: Receives penis during copulation and serves as birth canal

External Genitalia (Vulva):

• Labia majora: Outer folds of skin
• Labia minora: Inner folds
• Clitoris: Erectile tissue, sensitive organ
• Hymen: Thin membrane partially covering vaginal opening

Exercise 3.4

Question: Write two major functions each of testis and ovary.

Solution:

Functions of Testis:

1. Spermatogenesis: Production of male gametes (sperm) in seminiferous tubules
2. Hormone Secretion: Production of testosterone by Leydig cells, which:
   • Maintains primary and secondary sexual characteristics
   • Stimulates spermatogenesis
   • Controls development of male accessory organs

Functions of Ovary:

1. Oogenesis: Production of female gametes (ova) through the development of ovarian follicles
2. Hormone Secretion: Production of estrogen and progesterone, which:
   • Regulate menstrual cycle
   • Maintain pregnancy
   • Develop secondary sexual characteristics
   • Prepare uterus for implantation

NCERT Highlights for NEET

🎯 High-Yield Topics for NEET:

1. Spermatogenesis: Process, duration, and hormonal control
2. Oogenesis: Process with specific timing and numbers
3. Menstrual Cycle: Phases and hormonal regulation
4. Placenta: Structure and functions
5. Hormonal Control: FSH, LH, estrogen, progesterone

🧬 Important Points to Remember:

1. Sperm Production: 200-300 million sperm per day, 60-120 million per ejaculation
2. Ovulation Release: Only one ovum per menstrual cycle
3. Fertilization Site: Ampulla region of fallopian tube
4. Implantation: 6-7 days after fertilization
5. Gestation Period: 280 days (40 weeks)

NEET Practice Questions

Question 1 (NEET Level)

Statement: Spermatogenesis results in the formation of: (A) 2 spermatozoa (B) 4 spermatozoa (C) 3 spermatozoa (D) 1 spermatozoa

Solution: Spermatogenesis is the process of sperm formation from spermatogonia.

Process:

1. Spermatogonia (2n) → Primary spermatocytes (2n) [Mitosis]
2. Primary spermatocytes (2n) → Secondary spermatocytes (n) [Meiosis I]
3. Secondary spermatocytes (n) → Spermatids (n) [Meiosis II]
4. Spermatids (n) → Spermatozoa (n) [Spermiogenesis]

Each primary spermatocyte produces 4 spermatozoa.

Answer: Option (B) 4 spermatozoa

Question 2 (NEET Level)

Statement: The hormone secreted by corpus luteum is: (A) Estrogen (B) Progesterone (C) LH (D) FSH

Solution: Corpus luteum is formed from the ruptured Graafian follicle after ovulation.

Functions of Corpus Luteum:

• Secretes progesterone (main hormone)
• Also secretes some estrogen
• Maintains endometrium for implantation
• If pregnancy occurs, continues to function until placenta takes over

Answer: Option (B) Progesterone

Question 3 (NEET Level)

Statement: Fertilization in humans occurs in: (A) Ovary (B) Uterus (C) Fallopian tube (D) Vagina

Solution: Fertilization in humans occurs in the ampulla region of the fallopian tube.

Process:

1. Ovum released from ovary
2. Sperm travels through cervix, uterus, and reaches fallopian tube
3. Fertilization occurs in ampulla (widest part of fallopian tube)
4. Zygote moves toward uterus for implantation

Answer: Option (C) Fallopian tube

Menstrual Cycle Details

Phases of Menstrual Cycle (28 days):

1. Menstrual Phase (Days 1-5):

• Endometrial shedding
• Low estrogen and progesterone levels
• FSH starts increasing

2. Follicular Phase (Days 6-13):

• Follicle development under FSH stimulation
• Estrogen secretion by growing follicle
• Endometrial regeneration
• LH starts increasing

3. Ovulatory Phase (Day 14):

• LH surge causes ovulation
• Graafian follicle ruptures
• Secondary oocyte released

4. Luteal Phase (Days 15-28):

• Corpus luteum formation
• Progesterone secretion (dominant hormone)
• Endometrium becomes secretory
• If no fertilization: corpus luteum degenerates

Hormonal Control:

Gametogenesis Comparison

Spermatogenesis vs Oogenesis:

Important Values for NEET

Sperm Characteristics:

• Length: 60 μm (head 5 μm, middle piece 5 μm, tail 50 μm)
• Motility: 40-50% motile in normal semen
• Count: 60-120 million per ejaculation
• Viability: 24-48 hours in female reproductive tract

Ovum Characteristics:

• Size: 0.1 mm (largest cell in human body)
• Viability: 24 hours after ovulation
• Release: One per menstrual cycle
• Structure: Surrounded by zona pellucida and corona radiata

Pregnancy Timeline:

• Fertilization: Day 14 (approximately)
• Implantation: Days 6-7 after fertilization
• Heartbeat: Week 6
• Movement felt: Week 18-20
• Viability: Week 28 onwards
• Full term: 40 weeks (280 days)

Success Tips

1. Diagrams are Crucial: Practice labeled diagrams of reproductive systems
2. Hormonal Control: Master the feedback mechanisms
3. Numerical Values: Remember important numbers and durations
4. Comparative Study: Compare male and female systems

Master Human Reproduction

This chapter is extremely important for NEET. Focus on understanding the processes and hormonal control!

Remember: Every diagram, every process, and every hormone mentioned in NCERT is important for NEET. Study this chapter thoroughly!

For additional practice, explore our Biology Practice Problems section.