Part 6: Implantation, Pregnancy and Placenta Formation

Part 6: Implantation, Pregnancy and Placenta Formation

Q1. Implantation of the blastocyst normally occurs in the:

a) Fallopian tube
b) Uterine endometrium
c) Cervix
d) Ovary

Answer: b) Uterine endometrium
Explanation:

• (b) Correct. Normal implantation site = endometrium of uterine body/fundus.
• Others are ectopic and abnormal.

Q2. Implantation usually takes place on which day after fertilisation?

a) Day 1–2
b) Day 5–7
c) Day 10–12
d) Day 20

Answer: b) Day 5–7
Explanation:

• (b) Correct. Blastocyst attaches to endometrium around 6th–7th day.

Q3. The outer layer of blastocyst that invades endometrium is:

a) Inner cell mass
b) Trophoblast
c) Zona pellucida
d) Blastocoel

Answer: b) Trophoblast
Explanation:

• (b) Correct. Trophoblast invades maternal tissue and forms placenta.

Q4. Successful implantation requires:

a) Thin endometrium
b) Proliferative endometrium
c) Secretory endometrium
d) Atretic follicle

Answer: c) Secretory endometrium
Explanation:

• (c) Correct. Progesterone-dominated secretory endometrium is receptive to implantation.

Q5. hCG is secreted by:

a) Corpus luteum
b) Placental trophoblast cells
c) Ovary
d) Pituitary

Answer: b) Placental trophoblast cells
Explanation:

• (b) Correct. hCG secreted by syncytiotrophoblast after implantation.

Q6. The function of hCG is to:

a) Stimulate ovulation
b) Maintain corpus luteum
c) Induce menstruation
d) Stimulate lactation

Answer: b) Maintain corpus luteum
Explanation:

• (b) Correct. hCG prevents corpus luteum degeneration in early pregnancy.

Q7. Corpus luteum of pregnancy secretes mainly:

a) FSH and LH
b) Progesterone
c) Estrogen only
d) Oxytocin

Answer: b) Progesterone
Explanation:

• (b) Correct. Progesterone maintains endometrium and pregnancy.

Q8. The placenta is formed by contributions from:

a) Fetus only
b) Mother only
c) Both trophoblast and maternal endometrium
d) Amniotic sac only

Answer: c) Both trophoblast and maternal endometrium
Explanation:

• (c) Correct. Placenta = chorionic (fetal) + decidual (maternal) tissues.

Q9. Which of the following is not a function of placenta?

a) Exchange of nutrients
b) Exchange of gases
c) Excretion of wastes
d) Production of gametes

Answer: d) Production of gametes
Explanation:

• (d) Correct. Placenta never produces gametes.

Q10. The hormone mainly responsible for maintaining pregnancy after first trimester is:

a) Progesterone from corpus luteum
b) Progesterone from placenta
c) Estrogen from ovary
d) FSH from pituitary

Answer: b) Progesterone from placenta
Explanation:

• (b) Correct. Placenta takes over progesterone secretion after ~12 weeks.

Q11. Which hormone is tested in urine for pregnancy diagnosis?

a) Estrogen
b) Progesterone
c) hCG
d) Prolactin

Answer: c) hCG
Explanation:

• (c) Correct. Urinary hCG forms basis of pregnancy tests.

Q12. Human placenta is classified as:

a) Epitheliochorial
b) Endotheliochorial
c) Haemochorial
d) Synepitheliochorial

Answer: c) Haemochorial
Explanation:

• (c) Correct. In humans, maternal blood is in direct contact with chorionic villi.

Q13. Chorionic villi are structures that:

a) Form embryo proper
b) Facilitate exchange between mother and fetus
c) Produce gametes
d) Induce ovulation

Answer: b) Facilitate exchange between mother and fetus
Explanation:

• (b) Correct. Chorionic villi increase surface area for exchange.

Q14. Which hormone is known as “pregnancy hormone”?

a) LH
b) hCG
c) Oxytocin
d) Estrogen

Answer: b) hCG
Explanation:

• (b) Correct. hCG confirms and maintains pregnancy.

Q15. Human placental lactogen (hPL) is secreted by:

a) Ovary
b) Placenta
c) Pituitary
d) Corpus luteum

Answer: b) Placenta
Explanation:

• (b) Correct. hPL modulates maternal metabolism and prepares mammary glands.

Q16. Function of human placental lactogen (hPL):

a) Maintains corpus luteum
b) Promotes mammary gland development and fetal nutrition
c) Causes uterine contractions
d) Initiates fertilisation

Answer: b) Promotes mammary gland development and fetal nutrition
Explanation:

• (b) Correct. hPL ensures nutrient supply to fetus.

Q17. Which hormone relaxes pelvic ligaments during parturition?

a) Relaxin
b) Oxytocin
c) Progesterone
d) Prolactin

Answer: a) Relaxin
Explanation:

• (a) Correct. Relaxin from ovary/placenta softens pelvic ligaments.

Q18. Which extraembryonic membrane contributes to placenta formation?

a) Amnion
b) Chorion
c) Yolk sac
d) Allantois

Answer: b) Chorion
Explanation:

• (b) Correct. Chorion forms fetal part of placenta.

Q19. The decidua basalis refers to:

a) Fetal component of placenta
b) Maternal endometrial component beneath embryo
c) Amniotic cavity
d) Yolk sac

Answer: b) Maternal endometrial component beneath embryo
Explanation:

• (b) Correct. Decidua basalis = maternal placenta contribution.

Q20. Placenta allows passage of all except:

a) Oxygen
b) Glucose
c) Antibodies
d) Erythrocytes

Answer: d) Erythrocytes
Explanation:

• (d) Correct. Cells like RBCs don’t cross placenta under normal conditions.

Q21. Which immunoglobulin crosses placenta to provide passive immunity to fetus?

a) IgM
b) IgG
c) IgA
d) IgE

Answer: b) IgG
Explanation:

• (b) Correct. IgG crosses placenta → passive immunity.

Q22. Which hormone prevents uterine contractions during pregnancy?

a) Oxytocin
b) Estrogen
c) Progesterone
d) Relaxin

Answer: c) Progesterone
Explanation:

• (c) Correct. Progesterone keeps myometrium relaxed during gestation.

Q23. An ectopic pregnancy most commonly occurs in:

a) Cervix
b) Fallopian tube
c) Ovary
d) Abdominal cavity

Answer: b) Fallopian tube
Explanation:

• (b) Correct. Tubal pregnancies are most common ectopic pregnancies.

Q24. Assertion (A): Placenta is both a structural and functional unit between mother and fetus.

Reason (R): It acts as a temporary endocrine organ and exchange surface.
a) Both A and R true; R correct explanation
b) Both A and R true; R not explanation
c) A true, R false
d) Both false

Answer: a) Both A and R true; R correct explanation

Q25. Assertion (A): High levels of hCG are maintained throughout pregnancy.

Reason (R): hCG continuously stimulates corpus luteum throughout gestation.
a) Both A and R true; R correct explanation
b) Both A and R true; R not explanation
c) A true, R false
d) Both false

Answer: c) A true, R false
Explanation:

• A is true: hCG high in early pregnancy, then declines.
• R is false: Placenta takes over progesterone production after 1st trimester; corpus luteum regresses.

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