Squamous cell carcinomas are the second most common of the skin cancers and are capable of metastasizing if not treated. This cancer affects which cells?

Correct Answer: C

Rationale: Squamous cell carcinoma (SCC) originates from keratinocytes, the predominant cells of the epidermis, specifically in the stratum spinosum, where they begin to differentiate. Basal cell carcinoma affects basal cells of the stratum basale, not SCC. Melanocytes in the basale produce melanin, linked to melanoma, not SCC. Langerhans cells are immune cells, not cancerous in SCC, and the stratum lucidum lacks them. SCC arises from spinosum keratinocytes due to UV-induced DNA damage, enabling it to invade deeper layers and metastasize if untreated, making this the correct cell type.

Correct Answer: B

Rationale: Accessory components of the skin are structures derived from the epidermis, enhancing its function. Nails, formed from keratinized epidermal cells at the nail matrix, protect fingertips. Hair, also epidermal, grows from follicles, aiding sensation and insulation. Mammary glands, modified sweat glands of epidermal origin, produce milk and are considered integumentary appendages. Subcutaneous tissue (hypodermis), however, is not an accessory structure; it's a connective tissue layer beneath the dermis, composed of adipose and areolar tissue, anchoring skin to underlying structures and storing fat. While integral to the integumentary system, it's mesoderm-derived, not an epidermal appendage like nails, hair, or glands. Anatomical definitions classify accessory structures as epidermis-derived, excluding the hypodermis, which supports rather than extends skin function, clarifying its distinct role.

Correct Answer: A

Rationale: Transdermal delivery involves a medicine being applied via a patch on the skin, allowing it to penetrate through the skin layers into the bloodstream for systemic effects, such as nicotine or pain relief patches. Subcutaneous delivery requires an injection beneath the skin into the hypodermis, not a patch. Topical application refers to medicines like creams that act locally on the skin surface, not systemically. Intramuscular delivery involves injection into muscle tissue, far deeper than skin application. The term 'transdermal' specifically denotes crossing the skin barrier for absorption into circulation, distinguishing it from other methods and aligning with the use of adhesive patches in pharmacology.

Correct Answer: D

Rationale: Nociceptors are free nerve endings in the skin, particularly in the dermis and epidermis, with large receptive fields that detect pain (from 'noci,' Latin for harm), responding to heat, chemicals, or injury. Hair follicle movement is sensed by root hair plexuses, not nociceptors. Lamellated corpuscles (e.g., Pacinian) detect pressure, not pain. Merkel cells, linked to touch via Merkel discs, don't sense pain. Nociceptors' role in pain perception, via unmyelinated nerve endings, is a fundamental aspect of skin's sensory system, making this the accurate description.

Correct Answer: B

Rationale: The papillary dermal layer, the uppermost part of the dermis, is the most superficial integument layer with capillaries, lymphatics, and sensory neurons, supporting the avascular epidermis above it. The reticular dermal layer, deeper in the dermis, has these structures too but isn't as superficial. The stratum granulosum and lucidum are epidermal layers, lacking blood vessels or nerves. The papillary layer's loose connective tissue and rich vascularity, just below the epidermis, make it the correct answer, balancing superficiality with functional components.