Integumentary System - Dermis, Hypodermis & Accessory Structures

Vocabulary flashcards covering key layers, cells, glands, structures, and functions of the integumentary system, emphasizing thermoregulation, epidermal strata, and accessory structures.

Epidermis

Outer protective layer of skin; produces new skin cells, retains moisture, and determines skin color.

Dermis

Middle skin layer containing collagen, blood vessels, glands, hair follicles, and nerve endings; supports epidermis and aids in sensation and thermoregulation.

Hypodermis (Subcutaneous Layer)

Innermost skin layer composed of loose connective and adipose tissue; stores energy, insulates, and anchors skin to muscles and bones.

Basement Membrane

Thin, fibrous layer that attaches the epidermis to the dermis.

Dermal Papillae

Wavy projections of dermis into epidermis that strengthen attachment and help regulate hair growth.

Stratum Corneum

Outermost epidermal stratum; layers of dead, keratin-filled cells forming first line of defense.

Stratum Lucidum

Clear, thin layer found only in thick skin (palms, soles) providing extra protection.

Stratum Granulosum

Epidermal layer where cells accumulate keratohyalin granules and form a waterproof barrier.

Stratum Spinosum

‘Prickle cell’ layer rich in keratinocytes connected by desmosomes, giving skin strength and flexibility.

Stratum Basale

Deepest epidermal layer containing stem cells; site of continual cell division attaching epidermis to dermis.

Keratinocytes

Primary epidermal cells that produce keratin for toughness and water resistance.

Melanocytes

Pigment-producing cells in stratum basale that synthesize melanin in response to UV-B radiation.

Merkel Cells

Touch-sensitive cells in the epidermis that connect to sensory neurons.

Fibroblasts

Dermal cells that synthesize collagen and extracellular matrix components.

Hair Follicle

Epidermal invagination in dermis where hair develops and grows.

Hair Bulb

Enlarged base of hair follicle containing dividing cells that form the hair shaft.

Dermal (Hair) Papilla

Connective tissue at base of hair bulb containing blood vessels and nerves that nourish growing hair.

Hair Shaft

Visible portion of hair above skin surface, composed of dead keratinized cells.

Arrector Pili Muscle

Band of smooth muscle attached to hair follicle that contracts to produce ‘goosebumps’ and move sebum.

Sebaceous Gland

Exocrine gland opening into hair follicle; secretes oily sebum to lubricate skin and hair.

Sebum

Oily mixture of triglycerides, proteins, cholesterol, and electrolytes that conditions hair and skin.

Sudoriferous (Sweat) Glands

Skin glands producing sweat for thermoregulation and excretion.

Eccrine Sweat Glands

Most numerous sweat glands; coiled tubes that open directly onto skin surface for cooling and waste removal.

Apocrine Sweat Glands

Sweat glands opening into hair follicles of axilla and genital regions; secretions may develop odor after bacterial action.

Cutaneous Plexus

Network of blood vessels at the dermis–hypodermis junction supplying skin structures.

Tactile (Meissner) Corpuscle

Dermal sensory receptor that detects light touch and texture.

Lamellated (Pacinian) Corpuscle

Deep dermal receptor sensitive to pressure and vibration.

Nail Body

Visible hard plate of the nail sitting atop the nail bed.

Nail Matrix

Proximal growth zone of nail where new nail cells form.

Nail Root

Portion of nail buried under skin, adjacent to bone, where growth begins.

Eponychium (Cuticle)

Extension of stratum corneum over proximal nail, providing a seal.

Vellus Hair

Fine, lightly pigmented hair covering most of the body.

Terminal Hair

Coarse, pigmented hair on scalp, eyebrows, and after puberty in axillary and pubic regions.

Conduction (Heat Loss)

Direct transfer of body heat to cooler objects through molecular contact.

Convection (Heat Loss)

Transfer of heat via movement of air or fluid across the skin.

Radiation (Heat Loss)

Emission of infrared heat from warmer body to cooler environment without direct contact.

Evaporation (Heat Loss)

Heat removal when sweat or water on skin surface changes to vapor.

Hypothalamus

Brain region that monitors body temperature and controls sweat glands and muscle activity for thermoregulation.

Vitamin D (Cholecalciferol)

Hormone precursor synthesized in skin by UV exposure; essential for calcium absorption and homeostasis.

Psoriasis

Skin disorder of rapid keratinocyte proliferation causing flaky, silvery scales.

Malignant Melanoma

Aggressive skin cancer arising from melanocytes.

Basement Membrane

Thin anchoring layer between epidermis and dermis (duplicate removed to keep unique).

Skin Thermoregulation

Process by which skin conserves or dissipates heat via blood flow, sweat, and insulation.

Cuticle (Hair)

Outermost layer of hair shaft composed of overlapping keratinized cells.

Keratohyalin Granules

Basophilic granules in stratum granulosum aiding keratin aggregation and waterproofing.

Desmosomes

Protein junctions connecting keratinocytes, giving strength to stratum spinosum.