Huxley's layer is found in -

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: 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.

Correct Answer: C

Rationale: The correct answer is C: skin oil. Sebum is a waxy, oily substance produced by the sebaceous glands in the skin. It helps to lubricate and waterproof the skin and hair. Regular sweat (option A) is produced by sweat glands and is primarily composed of water and electrolytes. Milk (option B) is produced by mammary glands in mammals. Odiferous sweat (option D) refers to sweat that may have a strong odor due to bacterial activity, not sebum. Therefore, the correct term for the substance produced by the sebaceous glands is skin oil, making option C the correct answer.

Correct Answer: A

Rationale: When the arrector pili muscles contract, they pull on the hair follicles, causing the hair to stand upright, resulting in goosebumps. This physiological response is triggered by emotions or cold temperature to trap air and increase insulation. The other choices are incorrect because sweat release is controlled by sweat glands, skin color changes are unrelated to arrector pili muscles, and shivering is a response to generate heat, not directly caused by arrector pili muscle contraction.