Folder upper part of dermis is known as-

Correct Answer: D

Rationale: The correct answer is D because the folder upper part of the dermis is composed of both skin papilla and hair papilla. Skin papilla plays a role in nourishing the epidermis, while hair papilla supports hair growth. Choice A, skin papilla only, is incorrect as it does not account for the hair papilla's presence. Choice B, hair papilla only, is also incorrect as it neglects the role of the skin papilla. Choice C, dermal papilla only, is incorrect as it does not specify the individual components involved in the upper part of the dermis. Thus, the correct answer is D, which accurately reflects the presence of both skin papilla and hair papilla in the folder upper part of the dermis.

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: Keratin. Keratin is a fibrous structural protein found in the horns, nails, hairs, and feathers of birds. It provides strength and flexibility to these structures. Collagen (A) is a different protein found in connective tissues. Mucin (C) is a glycoprotein found in mucus. Cuticle (D) is a protective outer layer found in plants and insects, not in the mentioned structures. Therefore, based on the composition and function of horns, nails, hairs, and feathers, keratin is the most appropriate choice.

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.