Integumentary System and Thermoregulation (3B) - Bio & Biochem

Which skin appendage produces sebum, and what is its primary effect on skin?

Sebaceous gland; lubricates and provides antimicrobial barrier. Associated with hair follicles, it secretes oily sebum that moisturizes skin and inhibits microbial growth via fatty acids.
Which epidermal cell type functions as a mechanoreceptor for light touch?

Merkel cells. Associated with sensory nerve endings, these cells transduce mechanical stimuli into neural signals for tactile discrimination.
Which hypothalamic region is most associated with heat conservation and generation responses?

Posterior hypothalamus. This area detects hypothermia and activates shivering and vasoconstriction to generate and conserve body heat.
Which epidermal layer is present only in thick skin (palms and soles)?

Stratum lucidum. Present in areas of high friction, this translucent layer of dead cells adds extra protection and thickness to withstand mechanical stress.
Which sweat gland is associated with hair follicles and activates at puberty?

Apocrine sweat gland. Located in axillary and anogenital regions, these glands secrete viscous fluid influenced by hormones, contributing to scent signaling.
What is the main structural protein produced by keratinocytes?

Keratin. This fibrous protein forms intermediate filaments in keratinocytes, conferring mechanical strength and water resistance to the epidermis.
Which epidermal layer contains actively dividing keratinocytes?

Stratum basale (germinativum). This deepest layer houses mitotic stem cells that continuously generate new keratinocytes to replace those shed from the surface.
What is the most effective mechanism of heat loss during vigorous exercise in humans?

Evaporation of sweat. As sweat vaporizes, it absorbs latent heat from the skin, providing efficient cooling when other mechanisms are insufficient.
What is the primary barrier function of the stratum corneum?

Limits water loss and blocks pathogen/chemical entry. As the outermost layer of dead, keratinized cells, it forms an impermeable shield that prevents dehydration and invasion by external threats.
What are the three major layers of the skin from superficial to deep?

Epidermis, dermis, hypodermis (subcutaneous tissue). These layers form the skin's structure, with the epidermis as the protective outer barrier, dermis providing support and elasticity, and hypodermis offering insulation and anchorage.
Identify the heat transfer mechanism: heat exchange by direct physical contact with a surface.

Conduction. This direct transfer occurs when the skin touches a cooler object, allowing heat to flow down the temperature gradient.
What is the primary function of melanocytes in the epidermis?

Produce melanin to protect against ultraviolet radiation. These cells synthesize pigment that absorbs harmful UV rays, shielding DNA in keratinocytes from mutations and damage.
What is the primary effect of cutaneous vasoconstriction on body temperature?

Decreases heat loss by reducing skin blood flow. By narrowing vessels, it limits warm blood exposure to cold skin, minimizing heat dissipation to maintain core warmth.
Which hypothalamic region is the primary thermostat for heat dissipation responses?

Anterior hypothalamus (preoptic area). This region senses elevated core temperature and initiates sweating and vasodilation to promote heat loss.
What is the formula for body mass index (BMI) in SI units?

$BMI = \frac{m}{h^2}$ . Using mass in kilograms and height in meters squared, it quantifies adiposity for assessing health risks.
Which autonomic division primarily controls eccrine sweating?

Sympathetic nervous system (cholinergic fibers). These fibers release acetylcholine to stimulate sweat secretion, enabling rapid cooling responses to heat or stress.
What is the primary effect of cutaneous vasodilation on body temperature?

Increases heat loss by raising skin blood flow. By expanding vessels, it enhances convective and radiative heat transfer from blood to the environment.
What type of sweat gland is most important for thermoregulation?

Eccrine sweat gland. Widely distributed, these glands produce watery sweat that evaporates to dissipate heat and maintain core temperature.
Which dermal layer contains most hair follicles, glands, and blood vessels?

Reticular dermis. As the deeper, denser layer, it supports skin appendages and vasculature crucial for nutrient delivery and sensory functions.
What is piloerection, and which muscle causes it?

Hair standing; contraction of arrector pili muscle. Sympathetic activation causes this smooth muscle to contract, erecting hairs to trap insulating air in cold conditions.
What type of epithelium composes the epidermis?

Keratinized stratified squamous epithelium. This epithelial type provides a tough, waterproof barrier due to multiple layers of flattened cells filled with keratin, ideal for protection against environmental stressors.
What is the primary tissue type of the dermis?

Dense irregular connective tissue. With collagen and elastin fibers oriented randomly, this tissue resists multidirectional stresses while providing flexibility and strength.
What is the main composition and role of the hypodermis (subcutaneous tissue)?

Adipose and areolar CT; insulation, cushioning, energy storage. These loose connective tissues store fat for thermal regulation, absorb shocks, and serve as an energy reserve.
Identify the heat transfer mechanism: heat loss to moving air or water across skin.

Convection. This process involves heat transfer from the body to surrounding fluid in motion, enhanced by wind or water flow.
Identify the epidermal cell type that provides immune surveillance via antigen presentation.

Langerhans cells (dendritic cells). Derived from bone marrow, these immune cells capture skin antigens and migrate to lymph nodes to activate T-cell responses.

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