A drug that is administered 'transdermally' is one that:

Correct Answer: C

Rationale: Transdermal drugs are applied to the epidermis (e.g., via patches) and absorbed through the skin into the bloodstream for systemic effects, not limited to local action (topical). Muscle injection is intramuscular, and anal insertion is rectal, both unrelated. Application to the epidermis initiates the transdermal process, relying on diffusion through skin layers, a common delivery method in pharmacology, making this the precise definition.

Correct Answer: B

Rationale: Normal flora (bacteria) reside on the epidermis, particularly the stratum corneum, the skin's surface exposed to the environment. The dermis, beneath, is internal and sterile unless breached. 'Microdermis' isn't a term; likely a typo. The hypodermis, deeper still, isn't a flora habitat. The epidermis, as the outermost layer, hosts these microbes, which thrive without penetrating living tissue, making it the correct location.

Correct Answer: C

Rationale: The skin regulates temperature via sweat glands and blood vessels, senses stimuli through receptors, and protects against pathogens with its physical barrier and immune cells, but hormone production isn't a primary skin function. Hormones like cortisol or testosterone are produced by endocrine glands (e.g., adrenals, gonads), not skin. While skin synthesizes vitamin D, a prohormone, this is a metabolic process, not hormone production in the endocrine sense. Temperature regulation involves sweating and vasodilation, sensation uses nerve endings, and pathogen protection relies on the stratum corneum and Langerhans cells. Hormone production's absence from skin's core roles distinguishes it as the incorrect function here.

Correct Answer: B

Rationale: The stratum corneum, the epidermis's outermost layer, is a barrier of dead, keratinized cells and lipids that prevents pathogen entry and water loss, protecting the body from infection and dehydration. Sensation involves dermal receptors, not this dead layer. Melanin is produced in the stratum basale, not corneum. Temperature regulation uses sweat and vessels, not this passive shield. Its tough, waterproof structure, constantly shedding to renew protection, defines its primary role, a cornerstone of skin defense.

Correct Answer: C

Rationale: Sebum, an oily secretion from sebaceous glands, lubricates skin and hair, preventing dryness and brittleness while adding a minor protective layer. UV protection is melanin's role, not sebum's. Temperature regulation involves sweat and vessels, not oil. Melanin production is melanocytes' task, not glands'. Sebum's lipid content, delivered via hair follicles, maintains skin suppleness and waterproofing, making lubrication its primary function, per skin physiology.