“Human Reproduction” MCQ with Answer Explanation : NEET 2025.

81. Which of the following is the correct sequence of events in the development of a zygote?
    a) Blastula → Morula → Gastrula
    b) Morula → Blastula → Gastrula
    c) Gastrula → Blastula → Morula
    d) Morula → Gastrula → Blastula

Answer: b) Morula → Blastula → Gastrula

Explanation:
After fertilization, the zygote undergoes cleavage to form a solid ball of cells called the morula. The morula then develops into a blastula (with a hollow cavity), which further differentiates into a gastrula during gastrulation, where the three germ layers are formed.

82. The site of implantation of the blastocyst in the female reproductive system is the:
    a) Ovaries
    b) Fallopian tube
    c) Uterine wall (endometrium)
    d) Cervix

Answer: c) Uterine wall (endometrium)

Explanation:
The blastocyst implants into the thickened endometrium of the uterus, where it establishes the placenta and continues its development into an embryo and later a fetus.

83. Which of the following is the correct function of the amniotic fluid?
    a) To provide nutrients to the fetus
    b) To facilitate gas exchange
    c) To protect the fetus from physical injury
    d) To help in the release of oxytocin

Answer: c) To protect the fetus from physical injury

Explanation:
Amniotic fluid surrounds the developing fetus in the amniotic sac, providing a cushion that protects the fetus from mechanical shocks, helps maintain a stable temperature, and allows for fetal movement.

84. Which of the following hormones is primarily responsible for preparing the mammary glands for lactation during pregnancy?
    a) Estrogen
    b) Progesterone
    c) Prolactin
    d) Oxytocin

Answer: c) Prolactin

Explanation:
Prolactin is produced by the anterior pituitary gland and plays a key role in stimulating the mammary glands to produce milk. While oxytocin aids in milk ejection, prolactin is responsible for milk production.

85. Which of the following is the process by which the mature egg is released from the ovary?
    a) Fertilization
    b) Ovulation
    c) Menstruation
    d) Parturition

Answer: b) Ovulation

Explanation:
Ovulation is the release of a mature egg from the ovarian follicle into the fallopian tube, where it may be fertilized by sperm. This typically occurs around the midpoint of the menstrual cycle.

86. The process of cleavage in the early stages of embryonic development results in:
    a) Increase in the size of cells
    b) Increase in the number of cells
    c) Formation of germ layers
    d) Development of organs

Answer: b) Increase in the number of cells

Explanation:
Cleavage is a series of rapid mitotic cell divisions that increase the number of cells (blastomeres) in the developing embryo without an increase in overall size. This process eventually leads to the formation of the morula and blastula.

87. Which of the following events happens first after the fusion of sperm and egg?
    a) Formation of the blastocyst
    b) Cleavage
    c) Gastrulation
    d) Implantation

Answer: b) Cleavage

Explanation:
Cleavage begins shortly after the fusion of sperm and egg, resulting in a rapid series of cell divisions. These divisions produce a multicellular structure, which will further develop into a blastocyst.

88. Which of the following hormones stimulates the development of secondary sexual characteristics in females?
    a) Progesterone
    b) Testosterone
    c) Estrogen
    d) Luteinizing hormone (LH)

Answer: c) Estrogen

Explanation:
Estrogen is responsible for the development of secondary sexual characteristics in females, such as breast development, widening of the hips, and the regulation of the menstrual cycle.

89. The process of embedding the blastocyst into the endometrial lining of the uterus is called:
    a) Fertilization
    b) Implantation
    c) Cleavage
    d) Gastrulation

Answer: b) Implantation

Explanation:
Implantation is the process by which the blastocyst embeds itself into the endometrium (the lining of the uterus) to establish a pregnancy. It occurs about 6-10 days after fertilization.

90. The hormone primarily responsible for the thickening of the endometrial lining after ovulation is:
    a) Estrogen
    b) Progesterone
    c) Follicle-stimulating hormone (FSH)
    d) Luteinizing hormone (LH)

Answer: b) Progesterone

Explanation:
After ovulation, the corpus luteum produces progesterone, which prepares the endometrium for potential implantation by thickening it and making it more glandular and vascularized.