Mucous glands are not found in the skin of mammals because-

Correct Answer: B

Rationale: The correct answer is B: Skin is not slimy. Mucous glands produce a slimy substance called mucus, which serves to lubricate and protect various surfaces in the body. Skin in mammals is not supposed to be slimy, as it needs to maintain a dry and protective barrier. A: Skin does respire through diffusion, but this does not relate to the presence of mucous glands. C: Skin does have blood vessels for nourishment and temperature regulation, but this does not explain the absence of mucous glands. D: The presence of strata of cells in the outer skin layer is related to its protective function and does not directly influence the absence of mucous glands.

Correct Answer: A

Rationale: The dermis is mainly composed of fibrous connective tissue, which provides structural support and flexibility to the skin. This tissue contains collagen and elastin fibers, giving the skin its strength and elasticity. Nerve fibers and receptors are present in the dermis for sensation, but they are not the main component. Blood capillaries supply nutrients and oxygen to the skin, but they are not the primary composition of the dermis. Elastin proteins are important for elasticity, but they are a component within the fibrous connective tissue in the dermis. Therefore, choice A is correct as it accurately represents the main composition of the dermis.

Correct Answer: B

Rationale: The correct answer is B: Tanning. Tanning is the process of converting raw animal hides into leather by treating them with chemicals to preserve and strengthen the material. Taxidermy is the preserving of animal bodies, not the formation of leather. Keratinization is the process of converting soft tissues into hard structures like hair and nails, not the formation of leather. So, tanning is the only choice directly related to the formation of leather from the skin.

Correct Answer: A

Rationale: The correct answer is A: End organs of Ruffini. These corpuscles are stimulated by hot temperatures due to their function as thermoreceptors. Ruffini corpuscles respond to sustained pressure and warmth, making them sensitive to hot temperatures. The other choices are incorrect because: B: Crases corpuscles respond to deep pressure. C: Bulb corpuscles, also known as Pacinian corpuscles, respond to deep pressure and vibration. D: Meissner's corpuscles respond to light touch and are located in the dermal papillae of hairless skin.

Correct Answer: D

Rationale: The correct answer is D: Acting as a receptor organ. Mammalian skin contains sensory receptors for touch, pressure, pain, temperature, and vibration. These receptors play a crucial role in detecting and responding to external stimuli, aiding in survival. Skin is not primarily meant for A: The removal of excess water, as this function is mainly carried out by the kidneys. Skin does not excrete urea, making B incorrect. Skin is not responsible for storage of food, making C an incorrect choice. Thus, the correct answer is D as skin primarily acts as a receptor organ for sensory perception.