Which of the following is another name for blackheads associated with acne?

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: 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.

Correct Answer: C

Rationale: Langerhans cells, found mainly in the stratum spinosum, are dendritic immune cells that detect and engulf bacteria, presenting antigens to trigger an immune response. Merkel cells sense touch, not infection. Keratinocytes form the skin barrier and produce keratin, but they don't directly fight bacteria. Melanocytes produce melanin for pigment, not immunity. When bacteria breach a wound, Langerhans cells act as the epidermis's first line of immune defense, migrating to lymph nodes to alert the immune system, making them the critical cells in this scenario.