The structure partly responsible for 'goosebumps' is known as the ...

Correct Answer: B

Rationale: Goosebumps occur when small muscles attached to hair follicles contract, causing hairs to stand upright and skin to pucker. These are the arrector pili muscles, smooth muscles in the dermis anchored to the hair follicle base and the epidermal-dermal junction. When stimulated by cold or emotion (via the sympathetic nervous system), they contract, pulling hairs erect, an evolutionary vestige from furrier ancestors to trap heat or signal threat. Sebaceous glands secrete sebum to lubricate hair and skin, not to cause goosebumps. 'Cappilary' (likely a typo for capillary) refers to blood vessels, which adjust for temperature but don't directly produce goosebumps. Collagen provides dermal strength but is a passive fiber, not a muscle. The arrector pili's action is involuntary, linked to thermoregulation and emotional response, and its distinct role in piloerection visible as goosebumps sets it apart as the key structure in this phenomenon.

Correct Answer: B

Rationale: Sweat, from eccrine glands, contains water (99%), urea, lactic acid, and salts like sodium chloride, but not calcium in significant amounts. Water is the primary component, cooling the body via evaporation. Urea, a metabolic waste, is excreted in trace amounts, reflecting sweat's minor excretory role. Lactic acid, from muscle activity, appears during exertion, lowering sweat pH. Sodium, potassium, and chloride ions maintain electrolyte balance, but calcium, critical in blood and bone, is conserved by the kidneys, not sweat glands. Analysis of sweat composition shows negligible calcium unlike urine, where it's excreted. This reflects sweat's focus on thermoregulation and minor waste removal, not mineral loss. Physiological studies confirm calcium's absence as a standard component, distinguishing it from other substances routinely detected in sweat.

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.