Nokea
A scientist studying developmental physiology performs an experiment in which a substance is given to pregnant rats that give birth to pups that have XY chromosomes but female genital organs. What was the substance given to the rats?
- A. An antibody that blocked the effect of human chorionic gonadotropin in the embryo and fetus
- B. A large quantity of estrogen-like compounds
- C. Follicle-stimulating hormone
- D. Testosterone
Correct Answer: A
Rationale: The correct answer is A: An antibody that blocked the effect of human chorionic gonadotropin in the embryo and fetus. Human chorionic gonadotropin (hCG) is crucial for male sexual differentiation. Blocking its effects would lead to the development of female genital organs in pups with XY chromosomes. Estrogen-like compounds (B) and follicle-stimulating hormone (C) are not directly involved in male sexual differentiation. Testosterone (D) is responsible for male sexual development, so giving testosterone would not result in female genital organs in XY pups.
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Which of the following is the site of fertilization?
- A. Ureters
- B. Urethra
- C. Uterine tubes
- D. Ovaries
Correct Answer: C
Rationale: The correct answer is C, Uterine tubes. Fertilization occurs in the uterine tubes, also known as Fallopian tubes, where the sperm and egg meet to form a zygote. The uterine tubes provide a suitable environment for fertilization to take place.
A: Ureters - Incorrect, ureters are tubes that carry urine from the kidneys to the bladder, not involved in fertilization.
B: Urethra - Incorrect, the urethra is a tube that carries urine from the bladder out of the body, not involved in fertilization.
D: Ovaries - Incorrect, ovaries release eggs but fertilization does not occur in the ovaries; rather, it occurs in the uterine tubes.
How many fused parts form sacrum?
- A. 4
- B. 5
- C. 6
- D. 3
Correct Answer: A
Rationale: The sacrum is formed by the fusion of 5 originally separate sacral vertebrae. However, the coccyx is the result of the fusion of 4 originally separate coccygeal vertebrae. Therefore, the sacrum itself is formed by the fusion of 4 parts, making choice A correct. Choices B, C, and D are incorrect as they do not accurately reflect the anatomical structure of the sacrum.
Which of the following statements is incorrect.
- A. a female has approximately 2-4 million oocytes at birth
- B. a female has approximately 6 million oogonia during fetal development
- C. a female ovulates about 2,000 to 4,000 oocytes during her life
- D. only approximately 1-5 oocytes are fertilized
Correct Answer: C
Rationale: The correct answer is C because a female actually ovulates only about 400-500 oocytes during her lifetime, not 2,000 to 4,000. This is due to the process of follicular atresia where many oocytes are lost before ovulation. Choice A is correct as females have a finite number of oocytes at birth. Choice B is correct as oogonia differentiate into primary oocytes during fetal development. Choice D is incorrect as typically only one oocyte is fertilized during each menstrual cycle.
The vascularization of the Fallopian tubes is provided by branches off the following artery:
- A. uterine;
- B. ovarian;
- C. external iliac;
- D. abdominal aorta;
Correct Answer: A
Rationale: The correct answer is A: uterine artery. The uterine artery provides blood supply to the Fallopian tubes. It arises from the internal iliac artery and gives off branches that vascularize the tubes. The ovarian artery primarily supplies blood to the ovaries, not the Fallopian tubes. The external iliac artery supplies the lower extremities, not the reproductive organs. The abdominal aorta is a main artery that gives rise to multiple branches supplying various organs, but it does not directly supply the Fallopian tubes.
At what point in life does a female begin her monthly ovarian cycle?
- A. At birth
- B. At puberty
- C. At middle age
- D. At menopause
Correct Answer: B
Rationale: The correct answer is B: At puberty. The monthly ovarian cycle, also known as the menstrual cycle, begins at puberty when a female's body matures and starts ovulating. This is typically around the age of 11-14. At birth (A), females already have all their eggs but do not start ovulating until puberty. Middle age (C) refers to the period around 40-65, which is not when the cycle begins. Menopause (D) is the cessation of the menstrual cycle, marking the end of reproductive years, typically around the age of 45-55.