🌸 Chapter 2
Human Reproduction
(3 Marks )
1. Describe the structure of a human
sperm.
Answer:
A sperm has three parts:
- Head: Contains the haploid nucleus
and acrosome (with enzymes for ovum penetration).
- Middle piece: Contains mitochondria that
provide ATP for motility.
- Tail: A flagellum for movement.
The acrosome helps the sperm enter the ovum during fertilization.
2. Explain the role of male
accessory glands.
Answer:
The seminal vesicles, prostate gland, and bulbourethral glands
secrete fluids that:
- Provide nutrition
(fructose, calcium, citric acid).
- Facilitate sperm motility.
- Neutralize vaginal acidity.
- Form semen, which is
essential for fertilization.
3. What are the major functions of
the testis?
Answer:
1.
Production
of sperm (spermatogenesis)
in seminiferous tubules.
2.
Secretion
of testosterone
by Leydig cells.
3.
Regulation
of male secondary sexual characteristics and libido.
4. Differentiate between primary and
secondary sexual characteristics in males.
Answer:
- Primary: Organs directly involved in
reproduction (testes, penis, vas deferens).
- Secondary: Features influenced by
hormones (deep voice, facial hair, broad shoulders).
5. Explain the process of
spermatogenesis.
Answer:
1.
Spermatogonia divide by mitosis → Primary
spermatocytes.
2.
Primary
spermatocytes undergo meiosis I → Secondary spermatocytes.
3.
Secondary
spermatocytes undergo meiosis II → Spermatids.
4.
Spermatids
undergo spermiogenesis → mature spermatozoa.
6. What is spermiogenesis? What
happens to sperms after formation?
Answer:
Spermiogenesis is the transformation of spermatids into spermatozoa.
After formation, sperms are released into the lumen of seminiferous tubules
(spermiation) and stored in the epididymis for maturation.
7. Describe the structure of the
human ovary.
Answer:
Each ovary is almond-shaped, enclosed by a germinal epithelium
and tunica albuginea.
The cortex contains follicles in different stages (primordial to
Graafian), and the medulla contains blood vessels and nerves.
8. Explain the process of oogenesis.
Answer:
1.
Oogonia → Primary oocytes (arrested in
prophase I).
2.
After
puberty, one primary oocyte completes meiosis I → Secondary oocyte + Polar
body.
3.
Meiosis
II completes only after fertilization → Ovum + Polar body.
9. Differentiate between
spermatogenesis and oogenesis.
Answer:
|
Feature |
Spermatogenesis |
Oogenesis |
|
Site |
Testes |
Ovaries |
|
Duration |
Continuous after puberty |
Starts before birth, completes after fertilization |
|
Result |
4 sperms |
1 ovum + 3 polar bodies |
10. Describe the structure of a
Graafian follicle.
Answer:
A Graafian follicle consists of:
- Oocyte surrounded by zona
pellucida and corona radiata.
- Antrum: Fluid-filled cavity.
- Theca layers: Secrete estrogen.
It ruptures during ovulation to release the ovum.
11. Write the role of FSH and LH in the
menstrual cycle.
Answer:
- FSH: Stimulates follicle growth and
estrogen secretion.
- LH: Induces ovulation and
maintains the corpus luteum.
Their combined action regulates the 28-day menstrual cycle.
12. Explain the four phases of the
menstrual cycle.
Answer:
1.
Menstrual
Phase (1–5 days):
Shedding of endometrium.
2.
Follicular
Phase (6–13 days):
Follicle matures, estrogen rises.
3.
Ovulation
(14th day):
LH surge releases ovum.
4.
Luteal
Phase (15–28 days):
Corpus luteum secretes progesterone; if no fertilization, menstruation begins
again.
13. What are the functions of the
corpus luteum?
Answer:
- Secretes progesterone to
maintain endometrium.
- Supports early pregnancy.
- Degenerates if fertilization
doesn’t occur.
14. What changes occur in the ovary
and uterus during the menstrual cycle?
Answer:
- Ovary: Follicle growth →
Ovulation → Corpus luteum formation.
- Uterus: Endometrium thickens →
Prepares for implantation → Sheds if no fertilization.
15. Where does fertilization occur
in humans? Describe the process briefly.
Answer:
Fertilization occurs in the ampullary-isthmic junction of the fallopian
tube.
Steps:
1.
Sperm
reaches ovum.
2.
Acrosomal
enzymes digest zona pellucida.
3.
Sperm
and ovum nuclei fuse → Zygote.
16. What is implantation and when
does it occur?
Answer:
Implantation is the attachment of the blastocyst to the endometrium,
usually around the 7th day after fertilization, establishing pregnancy.
17. Describe the structure of a
blastocyst.
Answer:
A blastocyst has:
- Trophoblast: Outer layer forming the
placenta.
- Inner cell mass: Forms embryo.
- Blastocoel: Fluid-filled cavity.
18. What are the functions of the
placenta?
Answer:
1.
Nutrient
and gas exchange
between mother and fetus.
2.
Waste
removal.
3.
Secretion
of hormones
– hCG, hPL, estrogen, progesterone.
19. What is the role of hCG and hPL
hormones during pregnancy?
Answer:
- hCG: Maintains corpus luteum and
progesterone secretion.
- hPL: Prepares mammary glands and
regulates fetal nutrition.
20. Mention the role of oxytocin in
parturition.
Answer:
Oxytocin induces strong uterine contractions, stimulates expulsion of
the baby, and promotes milk ejection during lactation.
21. What are the changes in hormones
during pregnancy?
Answer:
- hCG, progesterone, and estrogen levels rise.
- FSH and LH are inhibited.
- These maintain endometrial
growth and prevent new ovulation.
22. Define gestation and
parturition.
Answer:
- Gestation: Period of embryonic
development inside the uterus (about 9 months).
- Parturition: Process of childbirth
initiated by oxytocin and fetal signals.
23. Explain the process of
lactation.
Answer:
After childbirth:
- Prolactin stimulates milk secretion.
- Oxytocin helps in milk ejection.
- The first milk (colostrum)
provides immunity to the infant.
24. What is the role of relaxin
hormone during pregnancy?
Answer:
Relaxin relaxes pelvic ligaments and cervix during late pregnancy to
facilitate childbirth.
25. How does the placenta act as an
endocrine organ?
Answer:
Placenta secretes hCG, hPL, estrogen, and progesterone, which regulate
fetal growth, maternal metabolism, and pregnancy maintenance.
26. What are the barriers to
polyspermy in humans?
Answer:
- Zona pellucida hardens after first sperm entry.
- Cortical granules release enzymes preventing
additional sperm binding.
27. What are monozygotic and
dizygotic twins?
Answer:
- Monozygotic: One zygote divides into two
embryos → Identical twins.
- Dizygotic: Two separate ova fertilized by
two sperms → Fraternal twins.
28. Name three hormonal
contraceptive methods.
Answer:
1.
Oral
pills (Saheli, Mala-D)
2.
Injectable
hormones (Depo-Provera)
3.
Implants
(Norplant)
They prevent ovulation by inhibiting LH and FSH secretion.
29. What is vasectomy?
Answer:
A surgical sterilization method in males where vas deferens is
cut and tied to prevent sperm transport.
30. What is tubectomy?
Answer:
A surgical sterilization method in females where fallopian tubes
are cut and tied to prevent ovum-sperm contact.
31. What is infertility? State one
cause in males and females.
Answer:
Inability to conceive after one year of unprotected intercourse.
- Male: Low sperm count.
- Female: Blocked fallopian tubes or
hormonal imbalance.
32. List any three sexually
transmitted diseases (STDs).
Answer:
1.
Syphilis
2.
Gonorrhea
3.
AIDS
(HIV infection)
33. Mention three methods to prevent
STDs.
Answer:
1.
Use
of condoms during intercourse.
2.
Avoiding
multiple sexual partners.
3.
Regular
medical check-ups.
34. What are assisted reproductive
technologies (ART)? Give examples.
Answer:
Techniques to assist infertile couples to conceive.
Examples: IVF (test-tube baby), GIFT, ZIFT, ICSI, AI (Artificial
Insemination).
35. What is IVF?
Answer:
In In Vitro Fertilization, ova and sperms are fused outside the body.
The formed zygote/blastocyst is transferred to the uterus for
implantation.
36. Explain ZIFT and GIFT.
Answer:
- ZIFT (Zygote Intra-Fallopian
Transfer):
Zygote formed outside is transferred to fallopian tube.
- GIFT (Gamete Intra-Fallopian
Transfer):
Gametes are directly placed in fallopian tube for fertilization.
37. What is ICSI?
Answer:
Intracytoplasmic Sperm Injection – A single sperm is injected directly
into an ovum to assist fertilization, useful in cases of male infertility.
38. What are the functions of the
amniotic sac and fluid?
Answer:
- Amniotic sac encloses fetus.
- Amniotic fluid cushions against mechanical
shocks, maintains temperature, and prevents dehydration.
39. Mention three differences
between sperms and ova.
Answer:
|
Feature |
Sperm |
Ovum |
|
Number |
Millions per ejaculation |
One per cycle |
|
Motility |
Motile |
Non-motile |
|
Size |
Small |
Large with cytoplasm |
40. Name three functions of
estrogen.
Answer:
1.
Stimulates
endometrial growth.
2.
Promotes
female secondary sexual characters.
3.
Helps
in ovulation.
41. Mention three functions of
progesterone.
Answer:
1.
Maintains
endometrium.
2.
Prevents
uterine contractions.
3.
Prepares
mammary glands for lactation.
42. Explain the importance of
colostrum.
Answer:
Colostrum is rich in antibodies (IgA) that provide passive immunity
and protect newborns from infections.
43. What is the difference between
fertilization and implantation?
Answer:
- Fertilization: Fusion of sperm and ovum →
zygote formation.
- Implantation: Embedding of blastocyst in
endometrium for nutrition.
44. Explain the role of the
pituitary gland in reproduction.
Answer:
Pituitary secretes FSH and LH, which control gametogenesis and
hormonal secretion in both sexes.
45. Mention three differences
between male and female gametogenesis.
Answer:
|
Feature |
Spermatogenesis |
Oogenesis |
|
Starts |
Puberty |
Before birth |
|
Number |
4 sperms |
1 ovum + 3 polar bodies |
|
Duration |
Continuous |
Cyclic |
46. What are the two main functions
of the ovaries?
Answer:
1.
Oogenesis – production of ova.
2.
Secretion
of hormones
– estrogen and progesterone.
47. What are the changes in the
uterus after fertilization?
Answer:
- Endometrium thickens.
- Blood supply increases.
- Placenta forms.
- Menstrual cycle stops.
48. What is the importance of the
amnion during pregnancy?
Answer:
Amnion encloses the fetus and protects it from mechanical injury,
dehydration, and temperature changes.
49. What is the significance of the
menstrual cycle?
Answer:
It prepares the uterus for implantation each month, ensuring readiness
for possible pregnancy.
50. Explain how hormonal balance
maintains pregnancy.
Answer:
High levels of progesterone and estrogen maintain endometrial growth, hCG
supports corpus luteum, and hPL aids fetal development.
