Secretion of sebaceous glands help to keep-

Correct Answer: A

Rationale: The correct answer is A because sebaceous glands secrete sebum, an oily substance that lubricates the hair and skin, making them waterproof. Sebum also helps protect the skin from drying out and maintains its elasticity. Choice B is incorrect because sebum doesn't make the hair waterproof on its own. Choice C is incorrect because sebum also affects the skin, not just the hair. Choice D is incorrect as sebum plays a crucial role in skin and hair health.

Correct Answer: D

Rationale: The correct answer is D: Stratum corneum. This layer of skin is water-proof due to the presence of keratin, a protein that forms a protective barrier against water loss and external substances. The other choices, A, B, and C, do not have the same water-proofing properties. Stratum germinativum is the innermost layer responsible for cell division, stratum granulosum is involved in keratin production, and stratum lucidum is a thin, translucent layer found only in thick skin areas. Therefore, only the stratum corneum contains the necessary structures to make it water-proof, making it the correct choice.

Correct Answer: C

Rationale: The correct answer is C because the dermis is the layer of skin that provides strength, flexibility, and elasticity, making it suitable for shoe leather. Choice A is incorrect because the presence of cells alone doesn't determine leather quality. Choice B is incorrect as hardness is not a desirable quality for shoe leather. Choice D is incorrect as ecdysis refers to the shedding of skin by animals, not the process of obtaining leather.

Correct Answer: A

Rationale: The correct answer is A: Arrector muscles. Arrector muscles are responsible for pulling the hair follicles and hairs upright when the temperature is low, a response known as piloerection. This physiological response helps to trap heat and maintain body temperature. Abductor muscles (Choice B) are not involved in hair erection. Petrihydroid muscles (Choice C) and Contractor muscles (Choice D) are not anatomical terms related to hair erection.

Correct Answer: B

Rationale: The correct answer is B: Meissner's corpuscles. Meissner's corpuscles are responsible for detecting light touch and low-frequency vibration. They are located in the upper dermis and have rapidly adapting receptors, making them sensitive to changes in stimuli. Pacinian corpuscles (A) detect deep pressure and high-frequency vibration, Krause's bulbs (C) detect cold temperatures, and Corpuscles of Ruffini (D) detect skin stretching and continuous pressure. Meissner's corpuscles specifically match the description of touch receptors in mammalian skin, making it the correct choice.