The most deadly skin cancer is:

Correct Answer: B

Rationale: Among skin cancers, malignant melanoma is the most deadly due to its aggressive nature and high metastatic potential. Originating in melanocytes, the pigment-producing cells in the epidermis, it can spread rapidly to lymph nodes, lungs, and brain if untreated, with a 5-year survival rate dropping significantly in advanced stages (e.g., below 30% for stage IV). Basal cell carcinoma, the most common skin cancer, arises from basal cells in the epidermis and rarely metastasizes, making it highly treatable with surgery. Squamous cell carcinoma, from squamous cells, can metastasize but does so less frequently and aggressively than melanoma, with better prognosis if caught early. Melanoma's lethality stems from its ability to invade deeper tissues and its link to UV exposure, which triggers mutations (e.g., in the BRAF gene). Statistics show it causes the majority of skin cancer deaths despite being less common, emphasizing its severity over the slower-growing, less invasive basal and squamous types.

Correct Answer: C

Rationale: Sebaceous glands are located in the dermis, the thick layer of skin beneath the epidermis, where they produce sebum, an oily substance that lubricates hair and skin. They are typically associated with hair follicles, which are embedded in the dermis, and secrete sebum into the follicle to reach the surface. The digestive system is unrelated to skin glands, ruling it out entirely. The hypodermis, or subcutaneous layer, contains fat and connective tissue, not sebaceous glands. The stratum corneum, the outermost epidermal layer, consists of dead, keratinized cells and lacks glands or living structures. Anatomical studies of skin consistently place sebaceous glands in the dermis, making this the correct location due to their functional and structural integration with dermal components like hair follicles and blood vessels.

Correct Answer: A

Rationale: Sudiferous glands are sweat glands (eccrine and apocrine), secreting sweat, not sebum, which is an oily substance produced by sebaceous glands. Sebaceous glands correctly secrete oil (sebum) to lubricate skin and hair. Apocrine glands, a type of sudiferous gland, secrete sweat into hair follicles. Ceruminous glands in the ear canal secrete cerumen (earwax). The incorrect statement is that sudiferous glands secrete sebum, as their function is sweat production, a distinction clear in skin physiology, making this the error to identify.

Correct Answer: A

Rationale: Transdermal administration involves applying a drug (e.g., via a patch) to the skin for systemic absorption into the bloodstream, affecting the whole body, like fentanyl patches. Topical administration targets local skin effects, like antibiotic creams. Intradermal injections deliver into the dermis, not surface application. Subcutaneous administration goes beneath the skin via injection. 'Trans' (across) indicates crossing the skin barrier for systemic action, a method reliant on the skin's permeability, making this the correct term.

Correct Answer: D

Rationale: Skin functions include producing melanin (via melanocytes) for UV protection, secreting sebum (via sebaceous glands) to lubricate, and minimizing water loss via the stratum corneum's barrier. Storing fat occurs in the hypodermis, not skin. Bile excretion is a liver function, not skin. Keratin production and immunity (via Langerhans cells) are true, but lymphocytes are made in lymphoid organs, not skin. The trio of melanin, sebum, and water retention reflects core integumentary roles, making this the accurate set.