Integumentary System Vocabulary

Vocabulary flashcards generated from Chapter 5 (The Integumentary System) notes.

Cutaneous membrane

The skin, composed of an outer superficial epithelium (epidermis) and an inner deep connective tissue layer (dermis).

Epidermis

The superficial, avascular stratified squamous epithelium layer of the cutaneous membrane where nutrients and oxygen diffuse from dermal capillaries.

Keratinocytes

The most abundant epithelial cells in the body, containing large amounts of the protective protein keratin.

Stratum basale (stratum germinativum)

The deepest epidermal layer attached to the basement membrane by hemidesmosomes, containing basal stem cells, melanocytes, and tactile cells.

Tactile cells (Merkel cells)

Specialized epidermal cells located in the stratum basale that associate with sensory nerve endings to detect touch in hairless skin.

Melanocytes

Pigment-producing cells located in the stratum basale that synthesize melanin and package it into vesicles called melanosomes.

Stratum spinosum

The "spiny layer" of the epidermis containing 8 to 10 layers of keratinocytes bound by desmosomes and containing dendritic (Langerhans) cells active in immune response.

Dendritic (Langerhans) cells

Immune cells located in the stratum spinosum that participate in coordinating the immune response to pathogens and skin cancers.

Stratum granulosum

The "granular layer" of the epidermis consisting of 3 to 5 layers of keratinocytes producing keratin and keratohyalin before undergoing cellular death.

Keratohyalin

A protein produced in the stratum granulosum that forms dense granules, promoting cellular dehydration and cross-linking of keratin fibers.

Stratum lucidum

The "clear layer" of the epidermis found exclusively in thick skin (such as the palms and soles), situated superficial to the stratum granulosum.

Stratum corneum

The exposed, water-resistant outer layer of skin composed of 15 to 30 layers of dead, flattened, keratinized cells.

Keratinization

The formation of protective, dead surface layers of epidermal cells filled with keratin protein.

Insensible perspiration

Unnoticed water loss caused by water diffusing across the stratum corneum and evaporating, averaging approximately $500\,\text{mL}$ per day.

Sensible perspiration

Active water secretion produced directly by sweat glands onto the skin surface.

Epidermal growth factor (EGF)

A peptide growth factor produced by the salivary glands and duodenum that promotes basal cell division, accelerates keratin production, stimulates epidermal repair, and stimulates glandular secretion.

Papillary layer

The outer layer of the dermis composed of areolar tissue containing capillaries, lymphatic vessels, sensory neurons, and dermal papillae.

Reticular layer

The deeper layer of the dermis composed of dense irregular connective tissue containing collagen and elastic fiber networks.

Skin turgor

The flexibility and resilience of skin provided by water content and dermal connective tissue fibers.

Tension lines (cleavage lines)

Parallel bundles of collagen and elastic fibers in the dermis that resist forces applied to the skin.

Cutaneous plexus

A deep network of blood vessels located along the reticular layer of the dermis.

Subpapillary plexus

A network of small arteries in the papillary layer of the dermis that provides capillary loops to dermal papillae.

Carotene

An orange-yellow pigment found in orange vegetables that accumulates in epidermal cells, deep dermis, and subcutaneous layer, and can be converted to vitamin A.

Cyanosis

A bluish discoloration of the skin resulting from dark red, oxygen-released hemoglobin or reduced blood flow to the skin.

Calcitriol

A hormone converted by the liver and kidneys from vitamin D3 (cholecalciferol) that is essential for calcium and phosphate ion absorption by the small intestine.

Root hair plexus

Sensory nerve fibers surrounding the base of a hair follicle that detect movement of the hair shaft.

Arrector pili muscle

Involuntary smooth muscle attached to a hair follicle whose contraction pulls the hair upright, causing "goose bumps".

Hair matrix

A layer of epithelial cells at the base of the hair bulb surrounding the hair papilla whose cell division produces hair.

Club hair

An inactive hair formed when a hair follicle ceases growth prior to entering a new growth cycle and shedding.

Vellus hairs

Soft, fine hairs that cover most of the body surface.

Terminal hairs

Heavy, deeply pigmented hairs found on the scalp, eyebrows, and eyelashes, and appearing in other body areas after puberty.

Sebaceous glands

Holocrine exocrine glands in the skin that discharge an oily lipid secretion (sebum) into hair follicles or directly onto the skin surface.

Sebum

A lipid secretion produced by sebaceous glands that lubricates and protects the hair shaft, conditions skin, and inhibits bacterial growth.

Apocrine sweat glands

Sweat glands in the armpits, nipples, and pubic region that secrete sticky, cloudy, odorous fluid into hair follicles via merocrine secretion.

Eccrine (merocrine) sweat glands

Coiled tubular glands widely distributed over the body surface (especially palms and soles) that secrete a watery fluid ($99\%$ water plus salt) directly onto the skin surface for thermoregulation.

Ceruminous glands

Modified glands in the ear canal that produce cerumen (earwax) to prevent foreign particles from reaching the eardrum.

Eponychium

The cuticle; a narrow fold of stratum corneum over the proximal portion of the visible nail plate.

Lunula

The pale, crescent-shaped area near the root of a nail where underlying blood vessels are obscured.

Granulation tissue

The combination of blood clot, fibroblasts, and an extensive capillary network formed during the migratory phase of skin repair.