Neonates that are kept in 100% oxygen incubators for several days become blind when they are removed from the incubator, a condition referred to as retrolental fibroplasia. What is the explanation for the loss of sight?

Correct Answer: C

Rationale: The correct answer is C because high oxygen concentration in neonates suppresses normal blood vessel growth in the retina. When oxygen therapy is stopped, oxygen levels fall, triggering excessive blood vessel growth in the retina and vitreous humor, leading to fibrous blockage of light. Option A suggests fibrous tissue growth due to oxygen, which is incorrect. Option B inaccurately states that oxygen causes vessel rupture. Option D is incorrect as oxygen does not directly destroy retinal neurons.

Correct Answer: D

Rationale: The correct answer is D: Prostate. The prostate gland surrounds the upper portion of the urethra just below the junction with the urinary bladder. It secretes a fluid that makes up a significant portion of semen. The other choices are incorrect because: A: Ejaculatory gland is not a correct anatomical structure. B: Seminal vesicles are located behind the bladder and contribute to semen production. C: Bulbourethral glands are located at the base of the penis and secrete a lubricating fluid during arousal.

Correct Answer: B

Rationale: The correct answer is B: zygote. A zygote is formed when a sperm cell fertilizes an egg cell, marking the beginning of a new individual's development. It is the first cell of the new organism with a full set of chromosomes. A: Blastocyst is a later stage of development after the zygote has undergone several cell divisions. C: Fetus refers to the later stages of development when the embryo has developed recognizable features. D: Embryo is the stage after the zygote when the cells start to differentiate into different tissues and organs.

Correct Answer: C

Rationale: The correct answer is C, the uterine (fallopian) tubes. This is where fertilization usually occurs as it is the site where the egg and sperm meet. The egg is released from the ovary and travels through the fallopian tube where it can be fertilized by sperm. If fertilization occurs, the resulting embryo will then travel to the uterus for implantation. The other choices are incorrect because fertilization does not typically occur in the ovary (A) or vesicular (Graafian) follicle (B). While the uterus (D) is where the embryo implants and develops into a fetus, fertilization itself does not occur there.

Correct Answer: C

Rationale: The correct answer is C: Progesterone. The corpus luteum is a temporary endocrine structure in the ovaries that forms after ovulation. Its main function is to produce progesterone, which helps prepare the uterine lining for implantation of a fertilized egg. Follicle stimulating hormone (FSH) is produced by the pituitary gland to stimulate follicle development, not by the corpus luteum. Testosterone is mainly produced by the testes in males and a small amount by the ovaries in females, not by the corpus luteum. Progesterone is the key hormone produced by the corpus luteum, making choice C the correct answer.