Nokea
The spermatozoon contains:
- A. 11 pairs of somatic chromosomes;
- B. one sexual chromosome;
- C. the X sex chromosome;
- D. the Y sex chromosome;
Correct Answer: D
Rationale: The correct answer is D because the spermatozoon contains the Y sex chromosome, determining male characteristics. Sperm cells are haploid and carry only one set of chromosomes, including either an X or Y sex chromosome. The presence of the Y chromosome leads to the development of male offspring. Choice A is incorrect as sperm cells do not contain somatic chromosomes. Choice B is incorrect as sperm cells contain one pair of sex chromosomes, not just one. Choice C is incorrect because sperm cells can carry either the X or Y sex chromosome, not specifically the X chromosome.
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Spasm of sternocleidomastoid muscle in the neck causes:
- A. Talipes equinovarus
- B. Torticollis
- C. Cleft lip
- D. Kyphosis
Correct Answer: B
Rationale: The correct answer is B: Torticollis. Spasm of the sternocleidomastoid muscle in the neck causes the head to tilt to one side and the chin to rotate to the opposite side, leading to a condition known as torticollis. Talipes equinovarus (A) is a foot deformity, cleft lip (C) is a congenital facial anomaly, and kyphosis (D) is an abnormal curvature of the spine. These conditions are not directly related to the spasm of the sternocleidomastoid muscle in the neck.
Which hormone thickens the lining of the uterus?
- A. FSH
- B. estrogen
- C. LH
- D. progesterone
Correct Answer: B
Rationale: The correct answer is B: estrogen. Estrogen is responsible for thickening the lining of the uterus during the menstrual cycle in preparation for implantation of a fertilized egg. Follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles. Luteinizing hormone (LH) triggers ovulation. Progesterone helps maintain the uterine lining during the second half of the menstrual cycle. Estrogen plays a key role in the initial thickening of the uterine lining, making it the correct choice.
The result of oogenesis is _____.
- A. one secondary oocyte
- B. two secondary oocytes
- C. one ovum
- D. four ootids
Correct Answer: C
Rationale: The correct answer is C: one ovum. During oogenesis, a primary oocyte undergoes meiosis to produce one mature ovum and three polar bodies. The ovum contains the majority of the cytoplasm and organelles needed for fertilization. The other choices are incorrect because:
A: one secondary oocyte - After meiosis I, the primary oocyte develops into one secondary oocyte and one polar body.
B: two secondary oocytes - This is not a possible outcome of oogenesis as only one secondary oocyte is produced.
D: four ootids - Ootids are the immediate products of meiosis II in oogenesis and are not the final mature gametes like the ovum.
During pregnancy, the uterine smooth muscle is quiescent. During the 9th month of gestation the uterine muscle becomes progressively more excitable. What factors contribute to the increase in excitability?
- A. Placental estrogen synthesis rises to high rates
- B. Progesterone synthesis by the placenta decreases
- C. Uterine blood flow reaches its highest rate
- D. Prostaglandin E2 synthesis by the placenta decreases
Correct Answer: B
Rationale: The correct answer is B: Progesterone synthesis by the placenta decreases. Progesterone maintains uterine quiescence during pregnancy by inhibiting uterine contractions. As progesterone levels decline towards the end of pregnancy, the uterine muscle becomes more excitable. Placental estrogen synthesis (Choice A) does not directly affect uterine excitability. Uterine blood flow (Choice C) is not a direct factor in uterine muscle excitability. Prostaglandin E2 (Choice D) actually increases towards the end of pregnancy, contributing to uterine contractions rather than decreasing excitability.
Which situation would be part of the normal reproductive cycle of a human?
- A. the presence of testosterone regulating gamete production in a male
- B. estrogen in concentrations that would produce sperm in a female
- C. a high progesterone level in a male
- D. a low insulin level in either a male or a female
Correct Answer: A
Rationale: Step 1: Testosterone is a hormone primarily produced by the testes in males, regulating sperm production.
Step 2: Gametes are reproductive cells (sperm in males), crucial for the reproductive cycle.
Step 3: Therefore, the presence of testosterone regulating gamete production in a male is a normal part of the reproductive cycle.
Summary:
- Option B is incorrect as estrogen, a female sex hormone, does not produce sperm.
- Option C is incorrect as progesterone is a hormone mainly involved in the menstrual cycle and pregnancy, not in males.
- Option D is incorrect as insulin is a hormone related to glucose metabolism, not directly involved in the reproductive cycle.