Which of the following matches the definition: A full thickness skin loss involving damage or necrosis of subcutaneous tissue that may extend down to but not through underlying fascia, infection and/or necrosis may be present?

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: 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.

Correct Answer: D

Rationale: Sebaceous glands are integral to skin function, producing sebum, an oily substance. They do not secrete sebum directly to the skin's surface; instead, they release it into hair follicles, which then reach the surface, making the first option inaccurate. They derive from the epidermis (ectoderm), not mesoderm, which forms the dermis, ruling out the second. They are exocrine glands, secreting sebum externally via ducts, not endocrine glands, which release hormones into the blood, eliminating the third. The correct description is that they are compound saccular (or alveolar) glands, with multiple acini (sac-like structures) branching from a duct, a histological classification fitting their structure and holocrine secretion mode (cells disintegrate to release sebum). This aligns with their role in lubricating skin and hair, their epidermal origin, and their anatomical complexity, distinguishing them from simpler gland types.

Correct Answer: D

Rationale: The hair matrix is the actively growing part of the hair bulb, located at the base of the hair follicle, and it contains a layer of basal cells (stem cells) that divide to produce the hair shaft and inner root sheath. The hair follicle is the entire structure surrounding the hair, not a component of the matrix. The hair shaft is the visible, dead portion of the hair, formed by the matrix but not part of it. The glassy membrane is a basement membrane-like structure around the follicle, not within the matrix. The basal cells in the matrix are critical for hair growth, as they differentiate and keratinize to form the hair, making this the accurate description.