Chapter 5- Module 4 The Integumentary System Notes

Vocabulary practice flashcards covering key terms, cell types, tissue layers, glands, appendages, and pathologies from Chapter 5: The Integumentary System.

Epidermis

The outermost protective shield of the body, composed of keratinized stratified squamous epithelial tissue, receiving nutrients via diffusion from the underlying dermis.

Dermis

The region underlying the epidermis that makes up the bulk of the skin; composed mostly of vascularized, fibrous connective tissue.

Hypodermis

Also known as superficial fascia, this subcutaneous layer deep to the skin is mostly composed of adipose tissue that absorbs shock, insulates, and anchors the skin to underlying structures.

Keratinocytes

The primary cell type of the epidermis whose major function is producing keratin; they are tightly connected by desmosomes and renew every $25\text{ to }45$ days.

Keratin

A fibrous protein that gives the epidermis its protective properties, formed by intermediate filaments containing one Type I (acidic) and one Type II (basic) protein family member.

Melanocytes

Cells comprising $10\text{–}25|\text{\%}$ of the deepest epidermis (stratum basale) that synthesize melanin and accumulate it in melanosomes to protect keratinocyte nuclei from UV damage.

Dendritic (Langerhans) Cells

Star-shaped immune cells arising in bone marrow that migrate to the epidermis to ingest foreign substances and activate the immune system.

Tactile (Merkel) Cells

Sensory touch receptors located at the epidermal-dermal junction, each associated with a disc-like sensory nerve ending.

Stratum Basale

The deepest epidermal layer (also called stratum germinativum), consisting of a single row of actively mitotic stem cells firmly attached to the dermis.

Stratum Spinosum

An epidermal layer several cell thick containing a web-like system of intermediate prekeratin filaments attached to desmosomes, as well as abundant melanosomes and dendritic cells.

Stratum Granulosum

A thin epidermal layer ($4\text{ to }6$ cell layers) where keratinization begins, cell nuclei and organelles disintegrate, and keratohyaline and lamellar granules accumulate.

Stratum Lucidum

A thin, translucent band superficial to the stratum granulosum consisting of a few rows of flat, dead keratinocytes, present only in thick skin.

Stratum Corneum

The most superficial epidermal layer consisting of $20\text{–}30$ rows of dead, flat, anucleate keratinized membranous sacs that protect deeper cells against water loss, abrasion, and penetration.

Papillary Layer

The superficial layer of the dermis composed of loose areolar connective tissue containing collagen, elastic fibers, blood vessels, and dermal papillae.

Dermal Papillae

Peg-like projections of the papillary dermis into the epidermis that contain capillary loops, Meissner's corpuscles (touch receptors), or free nerve endings (pain receptors).

Reticular Layer

The deeper dermal layer accounting for approximately $80\%$ of dermal thickness, composed of dense irregular fibrous connective tissue.

Cleavage Lines

Externally invisible lines formed by separations between collagen fiber bundles in the reticular dermis; incisions made parallel to these lines gap less and heal faster.

Flexure Lines

Dermal folds located at or near joints where the dermis is tightly secured to deeper structures, creating deep creases visible on hands, wrists, fingers, soles, and toes.

Eumelanin

A reddish-yellow to brownish-black form of melanin pigment that acts as an effective UV-blocking pigment.

Pheomelanin

A red or blond form of melanin pigment that is UV-permeable and may promote the formation of free radicals.

Carotene

A yellow-to-orange pigment found in plant products that accumulates in the stratum corneum and hypodermis fat, convertible to Vitamin A for vision and epidermal health.

Hemoglobin

An oxygen-binding pigment in red blood cells that gives a pinkish hue to fair skin with low melanin concentration.

Eccrine Sweat Glands

Also called merocrine sweat glands, these abundant glands function in thermoregulation by secreting sweat ($99\%$ water, salts, metabolic wastes) directly onto skin pores.

Apocrine Sweat Glands

Large sweat glands confined to axillary and anogenital areas that secrete a viscous, fatty sweat into hair follicles, becoming functional at puberty.

Sebaceous Glands

Branched alveolar holocrine glands widely distributed in skin (except palms/soles) that secrete oily sebum into hair follicles to lubricate hair and skin.

Sebum

An oily holocrine secretion produced by sebaceous glands consisting of lipids and cell fragments, possessing bactericidal properties and softening hair and skin.

Arrector Pili

A smooth muscle ribbon attached to a hair follicle whose contraction pulls the hair follicle upright, dimpling the skin to produce goosebumps.

Hair Matrix

The actively dividing area of the hair bulb that produces new hair cells.

Nail Matrix

The thickened proximal portion of the nail bed responsible for continuous nail growth.

Basal Cell Carcinoma

The least malignant and most common skin cancer, occurring when stratum basale cells proliferate and invade the dermis and hypodermis.

Squamous Cell Carcinoma

The second most common skin cancer, involving the keratinocytes of the stratum spinosum and presenting as scaly reddened papules.

Melanoma

The most dangerous and highly metastatic cancer of melanocytes, resistant to chemotherapy and characterized clinically by the ABCD rule.

Rule of Nines

A clinical calculation tool dividing the body into percentages of $9\%$ to estimate total body surface area burned and calculate volume of fluid loss.

First-Degree Burn

A partial-thickness burn causing damage confined only to the epidermis, presenting with localized redness, edema, and pain.

Second-Degree Burn

A partial-thickness burn that injures the epidermis and upper layer of the dermis, characterized by blister formation.

Third-Degree Burn

A full-thickness burn involving the entire depth of the skin, resulting in gray-white, cherry red, or blackened tissue with destroyed nerve endings.