🌸 Chapter 2
Human Reproduction
(4 Marks )
🧬 Human Reproduction – 4
Marks Questions with Answers
1. Describe the structure of the human
male reproductive system.
Answer:
The male reproductive system includes:
1.
Testes: Paired oval organs located in the
scrotum; produce sperm and testosterone.
2.
Ducts: Epididymis (sperm storage), vas
deferens (transports sperm), ejaculatory duct, and urethra (common passage for
urine and semen).
3.
Accessory
glands: Seminal
vesicles, prostate, and bulbourethral glands secrete seminal fluid that
nourishes and activates sperms.
4.
External
genitalia: Penis
aids in copulation.
2. Describe the structure and functions
of the female reproductive system.
Answer:
The female reproductive system includes:
1.
Ovaries: Produce ova and hormones (estrogen,
progesterone).
2.
Oviducts
(fallopian tubes):
Carry ova from ovary to uterus; site of fertilization.
3.
Uterus: Thick-walled muscular organ where
embryo develops.
4.
Vagina: Receives penis during copulation
and serves as birth canal.
5.
External
genitalia: Include
labia and clitoris; protect reproductive organs.
3. Explain the process of
spermatogenesis and spermiogenesis.
Answer:
- Spermatogenesis:
- Spermatogonia (diploid) divide
→ Primary spermatocytes.
- Meiosis I → Secondary
spermatocytes.
- Meiosis II → Spermatids.
- Spermiogenesis: Spermatids → mature sperms by
developing a tail, acrosome, and mitochondria.
- Sperms are released into the
seminiferous tubule lumen (spermiation) and move to the epididymis.
4. Explain the process of oogenesis.
Answer:
- Begins before birth: Oogonia →
Primary oocytes (arrested in prophase I).
- Puberty onwards: One primary
oocyte per cycle completes meiosis I → Secondary oocyte + Polar body.
- Secondary oocyte released
during ovulation.
- Meiosis II completes only after
fertilization → Ovum + Polar body.
5. Explain the structure of the
seminiferous tubule.
Answer:
- Each testis contains seminiferous
tubules lined by two types of cells:
- Spermatogenic cells: Undergo spermatogenesis.
- Sertoli cells: Provide nourishment and
hormonal support.
- Interstitial (Leydig) cells between tubules secrete
testosterone.
6. Describe the hormonal regulation
of spermatogenesis.
Answer:
1.
GnRH from hypothalamus → stimulates
anterior pituitary.
2.
Pituitary
releases FSH and LH.
o FSH: Acts on Sertoli cells to promote
spermatogenesis.
o LH: Acts on Leydig cells to release
testosterone.
3.
Testosterone
regulates secondary sexual characters and maintains spermatogenesis.
7. Explain the structure of the
human sperm.
Answer:
- Head: Contains nucleus (haploid DNA)
and acrosome with enzymes for ovum penetration.
- Middle piece: Has mitochondria for energy.
- Tail: Flagellum that enables motility.
These structures together ensure fertilization capability.
8. Describe the histological
structure of a human ovary.
Answer:
- Germinal epithelium: Outer layer.
- Tunica albuginea: Connective tissue below
epithelium.
- Cortex: Contains follicles in
different stages (primordial to Graafian).
- Medulla: Contains blood vessels and
nerves.
9. Draw and label the structure of a
Graafian follicle. Explain its function.
Answer:
- Contains secondary oocyte,
surrounded by zona pellucida and corona radiata.
- Antrum: Fluid-filled cavity.
- Theca interna/externa: Secrete estrogen.
- Function: Releases ovum during
ovulation.
10. Explain the hormonal regulation
of the menstrual cycle.
Answer:
1.
FSH: Stimulates follicle growth and
estrogen secretion.
2.
Estrogen: Stimulates endometrial thickening.
3.
LH
surge: Causes
ovulation on 14th day.
4.
Progesterone: From corpus luteum, maintains
endometrium.
If no fertilization occurs, hormones drop → menstruation.
11. Describe the different phases of
the menstrual cycle.
Answer:
1.
Menstrual
Phase (1–5 days):
Shedding of endometrium.
2.
Follicular
Phase (6–13 days):
Follicle growth, estrogen rise.
3.
Ovulation
(14th day):
LH surge releases ovum.
4.
Luteal
Phase (15–28 days):
Corpus luteum secretes progesterone; if no fertilization, cycle restarts.
12. Write a note on ovulation and
its hormonal control.
Answer:
Ovulation is the rupture of the Graafian follicle releasing the secondary
oocyte.
It is triggered by a surge in LH around the 14th day of the menstrual
cycle, following high estrogen levels. LH also helps in corpus luteum
formation.
13. Explain the process of
fertilization in humans.
Answer:
- Occurs in the ampullary-isthmic
junction of fallopian tube.
Steps:
1.
Sperm
reaches ovum.
2.
Acrosomal
enzymes digest zona pellucida.
3.
Plasma
membranes fuse → zygote forms.
4.
Meiosis
II completes, restoring diploid condition.
14. Describe the process of
implantation.
Answer:
- The blastocyst formed
after fertilization travels to the uterus.
- Trophoblast attaches to the endometrium
around the 7th day.
- The endometrium thickens and
forms maternal part of the placenta.
15. What are the functions of the
placenta?
Answer:
1.
Supplies
nutrients and oxygen to the fetus.
2.
Removes
waste and CO₂.
3.
Acts
as an endocrine gland, secreting hCG, hPL, estrogen, and progesterone.
4.
Protects
fetus from certain harmful substances.
16. What is the role of hormones
during pregnancy?
Answer:
- hCG: Maintains corpus luteum.
- Progesterone: Maintains endometrium and
prevents contractions.
- Estrogen: Stimulates uterine growth.
- hPL: Prepares mammary glands and
regulates fetal nutrition.
17. Explain the role of oxytocin
during parturition.
Answer:
- Fetal ejection reflex triggers oxytocin
release.
- Causes uterine contractions,
pushing baby out.
- Also helps in milk ejection
from mammary glands.
18. Explain the stages of
parturition.
Answer:
1.
Dilation
stage: Cervix
dilates; amniotic sac ruptures.
2.
Expulsion
stage: Baby is
delivered.
3.
Afterbirth
stage: Placenta
expelled from uterus.
19. Describe the process of
lactation and its importance.
Answer:
- Prolactin: Stimulates milk production.
- Oxytocin: Helps milk ejection.
- Colostrum: First milk rich in antibodies
(IgA).
Provides nutrition and immunity to newborn.
20. Describe the development of the
zygote up to blastocyst formation.
Answer:
1.
Zygote
→ 2-cell → 4-cell → Morula → Blastocyst.
2.
Blastocyst
has trophoblast (outer) and inner cell mass (embryo).
3.
Trophoblast
implants in the endometrium.
21. Explain the structure and
function of the placenta as an endocrine organ.
Answer:
- Structure: Formed from chorionic villi
(fetal) and uterine tissue (maternal).
- Functions:
- Gas and nutrient exchange.
- Hormonal secretion: hCG, hPL,
estrogen, progesterone.
- Protection of fetus.
22. Describe how the menstrual cycle
is linked with pregnancy.
Answer:
If fertilization occurs:
- Corpus luteum persists,
secretes progesterone.
- Menstruation stops.
If no fertilization: - Corpus luteum degenerates.
- Progesterone drops →
menstruation resumes.
23. What is the significance of the
corpus luteum?
Answer:
Corpus luteum secretes progesterone, maintaining endometrium and
pregnancy.
If fertilization fails, it degenerates into corpus albicans.
24. Explain the steps of
gametogenesis in humans.
Answer:
- Spermatogenesis: In testes → 4 sperms.
- Oogenesis: In ovaries → 1 ovum + 3 polar
bodies.
Both are regulated by FSH and LH hormones.
25. Write the functions of FSH, LH,
estrogen, and progesterone in the female body.
Answer:
- FSH: Stimulates follicle
development.
- LH: Triggers ovulation.
- Estrogen: Promotes endometrial growth.
- Progesterone: Maintains pregnancy.
26. Explain how hormonal
contraceptives work.
Answer:
They contain estrogen and progesterone, which:
- Inhibit FSH and LH →
prevent ovulation.
- Thicken cervical mucus → block
sperm entry.
Examples: Mala-D, Saheli.
27. What is IVF and how is it
performed?
Answer:
In Vitro Fertilization:
1.
Ova
and sperm collected.
2.
Fertilization
outside the body.
3.
Zygote
grown till 8-cell/blastocyst stage.
4.
Transferred
to uterus (test-tube baby).
28. Explain ZIFT and GIFT
techniques.
Answer:
- ZIFT: Zygote formed outside →
transferred into fallopian tube.
- GIFT: Gametes placed directly in
fallopian tube for fertilization.
29. What is ICSI and when is it
used?
Answer:
Intracytoplasmic Sperm Injection (ICSI):
A single sperm is injected into an ovum.
Used in severe male infertility (low sperm count or motility).
30. What are the main features of
the human menstrual cycle?
Answer:
- 28-day cyclic process.
- Ovulation on 14th day.
- Hormonal control by FSH, LH,
estrogen, progesterone.
- Ensures periodic preparation of
uterus for pregnancy.
31. Describe hormonal changes during
the ovarian and uterine cycles.
Answer:
- FSH rises → follicle growth →
estrogen rises.
- LH surge → ovulation.
- Progesterone dominates luteal phase.
- Drop in progesterone →
menstruation.
32. Explain the role of hormones
during childbirth.
Answer:
- Estrogen: Increases uterine sensitivity
to oxytocin.
- Oxytocin: Triggers contractions.
- Relaxin: Softens cervix.
These coordinate for smooth delivery.
33. What are the physiological
changes in females during pregnancy?
Answer:
- Increased hormone levels (hCG,
estrogen, progesterone).
- Enlarged uterus.
- Increased blood volume.
- Breast enlargement and milk
gland development.
34. Explain the role of the amniotic
sac and fluid.
Answer:
- Protect fetus from mechanical
shock.
- Maintain constant temperature.
- Allow free movement and prevent
adhesion.
35. What are the types of twins and
how are they formed?
Answer:
- Monozygotic: Single zygote divides →
identical twins.
- Dizygotic: Two ova fertilized → fraternal
twins.
36. What is the significance of the
menstrual cycle for reproduction?
Answer:
- Prepares uterus monthly for
implantation.
- Indicates reproductive health.
- Failure of fertilization leads
to menstruation.
37. Explain the feedback control of
hormones in the menstrual cycle.
Answer:
- Estrogen inhibits FSH,
preventing multiple follicle growth.
- High estrogen stimulates LH surge.
- Progesterone inhibits both FSH
and LH post-ovulation.
38. Describe the mechanism of
fertilization and prevention of polyspermy.
Answer:
- Acrosomal enzymes digest egg
coverings.
- One sperm fuses with ovum.
- Zona pellucida hardens → blocks
additional sperm entry.
39. Describe the structure and
function of mammary glands.
Answer:
- Consist of lobes, lobules, and
alveoli.
- Alveoli secrete milk into ducts
→ nipple.
- Controlled by prolactin
and oxytocin.
40. Explain how hormones regulate
pregnancy and lactation.
Answer:
- Progesterone and estrogen: Maintain uterus.
- hCG: Maintains corpus luteum.
- Prolactin: Milk production.
- Oxytocin: Milk ejection.
41. What are the various stages of
embryonic development?
Answer:
Zygote → 2-cell → 4-cell → Morula → Blastocyst → Implantation → Gastrulation →
Organ formation.
42. Explain the functions of Sertoli
and Leydig cells.
Answer:
- Sertoli cells: Nourish developing sperms and
secrete inhibin.
- Leydig cells: Secrete testosterone for
spermatogenesis and secondary sexual traits.
43. Write short notes on any four
male accessory glands.
Answer:
- Seminal vesicles: Fructose-rich secretion.
- Prostate: Alkaline fluid.
- Bulbourethral: Lubrication.
- Together form semen that
nourishes sperms.
44. What are the key features of
human fertilization?
Answer:
- Internal fertilization in
fallopian tube.
- Single sperm entry.
- Zygote formation and cleavage.
- Restores diploid number.
45. Describe how the placenta is
formed.
Answer:
- Formed from chorionic villi
(fetal part) and endometrial tissue (maternal part).
- Establishes connection for
nutrient exchange.
46. Explain the importance of
colostrum in the newborn.
Answer:
- First milk after birth.
- Rich in antibodies (IgA).
- Provides passive immunity
and aids digestion.
47. Explain the differences between
menstrual and estrous cycles.
Answer:
|
Feature |
Menstrual |
Estrous |
|
Species |
Humans, primates |
Non-primates |
|
Endometrium |
Shed during menstruation |
Reabsorbed |
|
Periodicity |
Monthly |
Seasonal |
48. Explain how the hypothalamus
controls human reproduction.
Answer:
Hypothalamus secretes GnRH, stimulating pituitary → secretes FSH and
LH, which act on gonads to produce gametes and sex hormones.
49. Explain the significance of
hormonal feedback in male reproduction.
Answer:
- High testosterone inhibits GnRH
and LH secretion.
- Maintains hormonal balance and
sperm production rate.
50. Describe the main functions of
the female reproductive hormones.
Answer:
- FSH: Follicle development.
- LH: Ovulation.
- Estrogen: Uterine growth.
- Progesterone: Endometrial maintenance.
- Relaxin: Cervical dilation during
childbirth.
