Which cells produce the pigment that contributes to hair colour?

Correct Answer: B

Rationale: Hair color arises from melanin, a pigment produced by melanocytes. Located in the hair follicle's bulb, melanocytes synthesize eumelanin (brown/black) or pheomelanin (red/yellow), injecting it into surrounding keratinocytes, which form the hair shaft's keratin structure. The amount and type of melanin determine color more eumelanin darkens hair, while pheomelanin lightens it. Keratinocytes, the majority cells in hair and epidermis, build the hair but don't produce pigment; they receive it from melanocytes. Langerhans cells are immune cells in the epidermis, unrelated to pigmentation. Merkel cells, at the epidermal-dermal junction, sense touch, not color. Melanocytes' role in hair, skin, and eye pigmentation is genetically regulated, with activity declining in graying hair. Histological studies of follicles confirm melanocytes as the pigment source, distinguishing them from structural or sensory cells in hair development.

Correct Answer: D

Rationale: Keratin is the fibrous protein that fills the dead cells of the stratum corneum, the outermost epidermal layer, providing toughness and resistance to abrasion. Granstein and dermin are not recognized proteins in skin anatomy likely distractors. Melanin, produced by melanocytes deeper in the epidermis, is a pigment for UV protection, not a structural filler in dead cells. Keratin, produced by keratinocytes as they move upward and die, hardens the corneum, forming a protective barrier, a process well-documented in histology as essential to skin's durability and waterproofing.

Correct Answer: B

Rationale: Melanocytes, located in the stratum basale, produce melanin, a pigment that absorbs UV radiation, protecting skin cells from DNA damage and reducing cancer risk. Darkening (tanning) enhances this shield. Keratinocytes make keratin, a structural protein, not pigment. Dendrocytes (likely dendritic cells) are immune-related, not pigment-producing. Merkel cells detect touch, not UV protection. Melanin's role in UV defense, distributed to surrounding keratinocytes, is a well-established skin adaptation, making melanocytes the correct cell type.

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: A

Rationale: Sebaceous glands are the skin's oil glands, secreting sebum into hair follicles to lubricate skin and hair, distinct from sweat glands. Eccrine (merocrine) glands secrete watery sweat to the surface. Apocrine glands secrete sweat into follicles. The term 'sebaceous' directly refers to oil production, a role not shared by the others, all of which are sudiferous glands. This specificity in skin histology identifies sebaceous glands as the oil producers, making them the correct synonym.