Nokea
The external male genital organs are represented by the following structures, EXCEPT:
- A. penis;
- B. seminal ducts;
- C. corpus spongiosum;
- D. prostate
Correct Answer: D
Rationale: The correct answer is D: prostate. The prostate is an internal male reproductive organ located below the bladder. Step-by-step rationale: A - The penis is an external male genital organ. B - Seminal ducts are also known as vas deferens and are part of the male reproductive system. C - The corpus spongiosum is a spongy tissue structure found in the penis. Thus, the prostate is the only internal organ listed, making it the correct answer.
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With respect to the effects of testosterone in the male which statement is incorrect?
- A. testosterone inhibits the secretion of luteinising hormone
- B. testosterone stimulates the secretion of inhibin from leydig cells
- C. testosterone induces and maintains male sexual functions
- D. testosterone stimulates protein anabolism and bone growth.
Correct Answer: B
Rationale: The correct answer is B because inhibin is primarily secreted by Sertoli cells in the testes, not Leydig cells. Testosterone actually stimulates the secretion of inhibin from Sertoli cells. In contrast, Leydig cells produce testosterone in response to luteinising hormone (Choice A). Testosterone does play a key role in inducing and maintaining male sexual functions (Choice C) and also stimulates protein anabolism and bone growth (Choice D). Thus, Choice B is incorrect as Leydig cells do not secrete inhibin.
The following take part in the fecundation process:
- A. a single ovule;
- B. a single fecundated spermatozoon;
- C. one ovule with two nuclei, which means the pregnancy is monovitelline twin;
- D. two ovules, which means the pregnancy is bivitelline twin;
Correct Answer: C
Rationale: The correct answer is C, one ovule with two nuclei, which means the pregnancy is monovitelline twin. This is correct because during fertilization, a single sperm fertilizes an ovum, resulting in the formation of a zygote with two nuclei. Monovitelline twins originate from the splitting of a single fertilized egg, leading to two embryos with shared genetic material. The other choices, A and B, are incorrect as they do not accurately represent the process of fecundation. Choice A refers to a single ovule before fertilization, and choice B refers to a single spermatozoon, which is involved in fertilization but does not lead to the formation of twins. Choice D is also incorrect as it describes bivitelline twins, which result from the fertilization of two separate eggs by two different sperm, leading to genetically distinct individuals.
During the 12-hr period preceding ovulation, which of the following is true?
- A. The plasma concentration of estrogen is rising
- B. A surge of luteinizing hormone is secreted from the pituitary
- C. The surge occurs immediately after the formation of the corpus luteum
- D. The surge followed immediately by a fall in the plasma concentration of progesterone
Correct Answer: B
Rationale: The correct answer is B because a surge of luteinizing hormone (LH) is necessary for ovulation to occur, typically happening 24-36 hours before ovulation. This surge triggers the release of the mature egg from the ovarian follicle. Choices A, C, and D are incorrect as estrogen levels peak just before ovulation, the corpus luteum forms after ovulation, and progesterone levels rise after ovulation, not fall immediately after the LH surge.
Which of the following is a form of sexual reproduction?
- A. Fragmentation.
- B. Parthenogenesis.
- C. Budding.
- D. Hermaphroditism
Correct Answer: D
Rationale: Step 1: Define sexual reproduction as the process involving the fusion of gametes from two parents.
Step 2: Hermaphroditism refers to an organism having both male and female reproductive organs for self-fertilization.
Step 3: In hermaphroditism, there is still a fusion of gametes, fulfilling the criteria of sexual reproduction.
Step 4: Fragmentation, parthenogenesis, and budding are forms of asexual reproduction, not involving the fusion of gametes.
Step 5: Therefore, the correct answer is D (Hermaphroditism) as it aligns with the definition and process of sexual reproduction.
The helmet-like region of the sperm that is similar to a large lysosome and assists penetration of the egg is called the ________.
- A. flagellum
- B. midpiece
- C. spermatid
- D. acrosome
Correct Answer: D
Rationale: The correct answer is D: acrosome. The acrosome is a specialized organelle in the sperm head that contains enzymes necessary for penetrating the egg during fertilization. It releases these enzymes to help the sperm penetrate the egg's protective outer layer. The flagellum (choice A) is the tail of the sperm that provides motility. The midpiece (choice B) contains mitochondria for energy production. Spermatid (choice C) is an immature sperm cell formed during spermatogenesis.