Which type of sensory receptor in the skin is responsible for detecting changes in temperature?

Correct Answer: D

Rationale: Thermoreceptors, specialized nerve endings in the dermis and epidermis, detect temperature changes, signaling heat or cold to maintain homeostasis. Meissner's corpuscles sense light touch, Ruffini endings detect stretch and sustained pressure, and Merkel cells (via discs) sense continuous touch, none primarily temperature-focused. Thermoreceptors' sensitivity to thermal stimuli, distinct from mechanical or tactile roles, makes them the correct receptor type, essential for skin's sensory function.

Correct Answer: A

Rationale: The epidermis is primarily keratinocytes, epithelial cells that produce keratin, forming its stratified layers from basale to corneum, comprising about 90% of its cells. Fibroblasts, in the dermis, make collagen. Adipocytes, fat cells, dominate the hypodermis. Chondrocytes form cartilage, not skin. Keratinocytes' prevalence and role in barrier formation define the epidermis, making them the correct cell type.

Correct Answer: B

Rationale: Collagen, abundant in the dermis's reticular layer, provides strength and resilience, resisting stretching and supporting skin structure, produced by fibroblasts. Melanin is an epidermal pigment, keratin fills epidermal cells, and sebum is an oily secretion, none structural in the dermis. Collagen's fibrous network, paired with elastin, ensures skin durability, making it the main protein.

Correct Answer: B

Rationale: The dermis contains blood vessels that dilate (to release heat) or constrict (to retain heat) in response to temperature changes, aiding thermoregulation. The epidermis is avascular, the hypodermis (subcutaneous tissue) has fewer vessels and focuses on insulation, not active regulation. The dermis's vascular network, adjusting blood flow, makes it the correct layer.