Nokea
Ovulation is initiated by
- A. rising levels of follicle stimulating hormone
- B. rising levels of progesterone
- C. a drop in oestrogen levels
- D. rising levels of luteinizing hormone
Correct Answer: D
Rationale: The correct answer is D: rising levels of luteinizing hormone. Luteinizing hormone surge triggers ovulation by stimulating the release of the mature egg from the ovary. This surge is a crucial event in the menstrual cycle. A: Follicle stimulating hormone is involved in follicular development, not ovulation. B: Progesterone levels rise after ovulation, not before. C: Oestrogen levels actually rise before ovulation to trigger the LH surge, so a drop in oestrogen levels would not initiate ovulation.
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If a woman has a tumor secreting large amounts of estrogen from the adrenal gland, which of the following will occur?
- A. Progesterone levels in the blood will be very low
- B. Her luteinizing hormone secretion rate will be totally suppressed
- C. She will not have normal menstrual cycles
- D. Her bones will be normally calcified
Correct Answer: B
Rationale: Correct Answer: B - Her luteinizing hormone secretion rate will be totally suppressed
Rationale:
1. The tumor secretes large amounts of estrogen, which can lead to negative feedback on the hypothalamus and pituitary gland.
2. Luteinizing hormone (LH) is crucial for ovulation and normal menstrual cycles.
3. High estrogen levels can suppress LH secretion, disrupting ovulation and menstrual cycles.
Summary of other choices:
A: Progesterone levels may actually be elevated due to the tumor-induced high estrogen levels.
C: The disruption of LH secretion can lead to abnormal menstrual cycles.
D: High estrogen levels can lead to bone loss due to inhibition of bone formation and increased bone resorption.
Which of the following is an example of ovoviviparity?
- A. Honeybees lay soft eggs within the hive
- B. Sharks hatch from shell-covered fertilized eggs within the female's body.
- C. Birds hatch from shell covered fertilized eggs laid within a nest.
- D. Fetal mammals obtain nourishment from the mother through a placent
Correct Answer: C
Rationale: Ovoviviparity is a reproductive strategy where fertilized eggs develop within the female's body but are not nourished by the mother. Choice C is correct because birds lay fertilized eggs within a nest where they hatch, indicating the eggs were developed internally. Choice A is incorrect as honeybees do not exhibit ovoviviparity. Choice B is incorrect as sharks exhibit viviparity, where embryos develop inside the mother but are nourished directly. Choice D is incorrect as it describes placental nourishment in mammals, which is not characteristic of ovoviviparity.
Medial lower arm bone is
- A. Humerus
- B. Radius
- C. Ulna
- D. Carpals
Correct Answer: C
Rationale: The correct answer is C: Ulna. The ulna is the medial lower arm bone located on the pinky side. It articulates with the humerus at the elbow joint and with the radius at the wrist joint. The humerus (A) is the upper arm bone, not located in the lower arm. The radius (B) is the lateral lower arm bone, not the medial one. Carpals (D) refer to the wrist bones, not the lower arm bones. Therefore, the ulna is the correct answer as it is the specific bone that fits the description of being the medial lower arm bone.
The ovule that can be fecundated contains:
- A. 22 somatic chromosomes;
- B. 23 autosomes;
- C. a sex chromosome: X or Y;
- D. 11 pairs of somatic chromosomes;
Correct Answer: B
Rationale: The correct answer is B: 23 autosomes. The ovule contains half the number of chromosomes as the typical somatic cell, which is 46 in humans. This is because during meiosis, the number of chromosomes is reduced by half to ensure the correct chromosome number in the offspring. Therefore, the ovule contains 23 chromosomes, which are autosomes (non-sex chromosomes). Choices A, C, and D are incorrect because the ovule does not contain the same number of somatic chromosomes, a sex chromosome, or 11 pairs of somatic chromosomes.
Parenchymal tissue of the testes is
- A. Interstitial cells of Leydig
- B. Seminiferous tubules
- C. Spermatozoon
- D. Semen
Correct Answer: B
Rationale: The correct answer is B: Seminiferous tubules. These are the structures within the testes where sperm production occurs. This is the main function of testicular parenchymal tissue. Interstitial cells of Leydig (A) produce testosterone, spermatozoon (C) is a mature sperm cell, and semen (D) is a fluid that contains sperm and other substances. These choices are incorrect as they do not specifically represent the parenchymal tissue of the testes where sperm production takes place.