Integument of rabbit-

Correct Answer: D

Rationale: The correct answer is D because the integument of a rabbit serves multiple functions. It conserves heat in winter by providing insulation, loses excess heat during summer through mechanisms like vasodilation, and regulates body temperature by adjusting blood flow and fur density. Choice A is correct but incomplete, as the integument also helps in thermoregulation. Choice B is incorrect as the integument helps in both heat conservation and dissipation. Choice C is also incorrect as the integument does more than just regulating body temperature, such as protecting against external factors and providing sensory functions.

Correct Answer: B

Rationale: The correct answer is B: Root of the hair. Huxley's layer is a layer of cells located in the outer root sheath of the hair follicle. It is named after Thomas Huxley, a renowned biologist. This layer plays a role in the formation and growth of the hair. The other choices are incorrect because Huxley's layer specifically refers to a layer found in the root of the hair, not in the shaft or wall of the hair follicle. Choice D is incorrect as it denies the existence of Huxley's layer in any part of the hair structure.

Correct Answer: B

Rationale: The correct answer is B: Stratum lucidum. This layer of the epidermis is characterized by its clear, transparent cytoplasm due to the presence of eleidin, a protein that replaces the keratohyalin in the granules of the stratum granulosum. Stratum malpighi (A) refers to the basal layer, stratum granulosum (C) contains granules with keratohyalin, and stratum corneum (D) is the outermost layer composed of dead keratinocytes. The transparency of cytoplasm is a unique feature of the stratum lucidum, making it the correct choice.

Correct Answer: A

Rationale: The correct answer is A because merocrine sweat glands produce odorless sweat. The body odor associated with sweating is caused by apocrine sweat glands, not merocrine glands. Merocrine sweat helps prevent bacterial growth (B) through its antimicrobial properties. It contains water and waste products (C) such as urea and salts. Merocrine sweat is mostly water (D), aiding in cooling the body through evaporation. Therefore, A is incorrect as merocrine sweat does not produce body odor.

Correct Answer: B

Rationale: The correct answer is B: Blood flow to the skin increases. When body temperature rises, blood vessels in the skin dilate to release heat through radiation. This increased blood flow helps cool the body. Melanocytes (A) are responsible for skin pigmentation and do not directly regulate body temperature. Circulation in the skin (C) actually increases to dissipate heat. Evaporative cooling (D) through sweat continues to help regulate body temperature.