What is the main structural protein found in the dermis that provides strength and resilience to the skin?

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: C

Rationale: A Stage III wound is defined as full-thickness skin loss with damage or necrosis of subcutaneous tissue that may extend down to, but not through, the underlying fascia, and it may include infection or necrosis. Stage I involves only the epidermis (non-blanchable redness), Stage II extends into the dermis (partial thickness, like a blister), and Stage IV goes beyond the fascia into muscle, bone, or supporting structures. The description matches Stage III precisely, as it specifies subcutaneous involvement without breaching the fascia, making it the correct classification.

Correct Answer: D

Rationale: Comedones are the technical term for blackheads (open comedones) and whiteheads (closed comedones) in acne, caused by clogged hair follicles with sebum and dead skin. Pustules are pus-filled pimples, distinct from blackheads. Sebaceous refers to oil glands, not a lesion type. Eccrine relates to sweat glands, unrelated to acne. Blackheads are specifically open comedones, where the pore remains open, oxidizing the contents to a dark color, making comedones the correct term.

Correct Answer: D

Rationale: The skin is the largest organ of the human body, and its weight relative to total body weight is a well-established fact in anatomy. It constitutes approximately 7% of an average person's body weight, though this can vary slightly depending on factors like hydration, fat content, and individual size. For a 70 kg (154 lb) person, this equates to about 4.9 kg (11 lb) of skin, including the epidermis, dermis, and hypodermis. Options suggesting 2% or less than 2% significantly underestimate the skin's mass, as even the epidermis alone, though thin, covers a vast surface area (about 1.5-2 square meters in adults). A 10% estimate overshoots the typical range, as it would imply an unrealistically heavy skin mass for most individuals. The 7% figure is widely accepted in medical and biological contexts, reflecting the skin's substantial role in protection, thermoregulation, and sensation, and accounting for its multiple layers and associated structures like glands and hair.

Correct Answer: B

Rationale: The integumentary system's components derive from specific embryonic layers and exhibit distinct tissue types. The epidermis arises from the ectoderm and consists of stratified squamous epithelium, a multilayered structure of flat cells that keratinize to form a protective barrier. This matches perfectly as a developmental and histological coupling. The mesoderm forms the dermis, not the epidermis, and while the dermis underlies stratified squamous epithelium, it is connective tissue, not epithelial. The hypodermis, also mesoderm-derived, contains adipose tissue for insulation and energy storage, but not ectoderm. The dermis, vascular and mesodermal, has no endodermal origin, as the endoderm forms internal linings. The correct trio links the epidermis's ectodermal origin with its stratified squamous composition, reflecting embryology (ectoderm differentiation) and anatomy (epithelial layering), making it the most coherent and accurate combination among the options.