The integument consists of which of the following layers?

Correct Answer: A

Rationale: The integumentary system officially includes the epidermis and dermis. The epidermis is the outer protective layer, while the dermis beneath it contains connective tissue, glands, and nerves. The hypodermis, though adjacent, is the subcutaneous layer, not part of the integument proper. Listing epidermal sublayers (germinativum to corneum) excludes the dermis, incomplete for the integument. Combining the corneum with dermal layers omits other epidermal parts. Standard anatomy defines the integument as epidermis and dermis, aligning with their integrated protective roles.

Correct Answer: C

Rationale: The hypodermis, or superficial fascia, is the subcutaneous layer of fat and connective tissue beneath the dermis, not part of the integument (epidermis and dermis). It's not the outer layer (epidermis) or inner layer of the skin proper (dermis is deeper within the integument). It is vascularized, with blood vessels supplying it, not reliant solely on diffusion like the epidermis. Its exclusion from the integument and role as a cushion and insulator define it anatomically, making this the correct characterization.

Correct Answer: B

Rationale: Keratinocytes, originating in the stratum basale, migrate upward, producing keratin and dying to form the stratum corneum, the dead, keratin-filled outer layer. Melanocytes produce melanin, not the corneum's structure. Dendrocytes (dendritic cells) are immune-related, not structural. Lymphocytes are in blood or lymph, not forming skin layers. Keratinocytes' differentiation into the corneum's protective barrier is a core epidermal process, making them the responsible cell type.

Correct Answer: B

Rationale: The integument comprises the epidermis and dermis, with the dermis as the deeper layer, including the papillary and reticular sublayers. The epidermis is superficial, with the stratum corneum as its topmost part. The papillary dermal layer is the upper dermis, not the deepest. The dermis, extending beneath the epidermis to the hypodermis boundary, is the integument's deepest component, housing glands and connective tissue, making it the correct answer.

Correct Answer: C

Rationale: Melanin, produced by melanocytes in the stratum basale, is the pigment responsible for skin color, ranging from light to dark tones, and absorbs UV radiation to protect underlying cells from DNA damage. Melatonin, a hormone from the pineal gland, regulates sleep, not skin color. Hemoglobin, in red blood cells, gives a pinkish hue via dermal blood vessels but isn't a skin pigment or UV shield. Collagen, a dermal protein, provides structure, not pigmentation or UV protection. Melanin's dual role in coloration and photoprotection, darkening with UV exposure (tanning), makes it the correct pigment, per dermatological understanding.