Integumentary System (Dermatology)

Vocabulary practice flashcards covering skin anatomy, epidermal and dermal layers, exocrine glands, tissue repair processes, burns, skin lesions, and dermatological pathologies based on the lecture transcript.

Integumentary System

The organ system comprising the skin and its accessory structures, serving as the first line of defense against the environment and making up approximately $16\%$ of total body weight.

Epidermis

The superficial, avascular layer of the cutaneous membrane composed of keratinized stratified squamous epithelium that receives nutrients via diffusion and takes approximately $5\text{ weeks}$ for cells to travel from bottom to top.

Keratinization

The process by which epidermal cells fill with keratin as they move upward, changing shape and forming a durable, water-resistant protein barrier.

Exfoliation (Desquamation)

The continuous sloughing off and shedding of dead, flattened keratinocytes from the surface of the skin.

Thick Skin

Skin containing five epidermal layers, found exclusively on high-friction areas such as the soles of the feet and palms of the hands.

Thin Skin

Skin containing four epidermal layers, covering most of the human body.

Stratum Basale (Stratum Germinativum)

The deepest single layer of epidermal cells resting on the basement membrane where active mitosis occurs; contains keratinocytes, stem cells, tactile cells, and melanocytes ($25\%$ of cells).

Melanin

A dark brown-to-black pigment synthesized by melanocytes that absorbs ultraviolet (UV) light to protect epidermal cell DNA from mutations.

Stratum Spinosum

An epidermal layer composed of several layers of keratinocytes with spiny processes connected by desmosomes; abundant in dendritic cells.

Stratum Granulosum

An epidermal layer consisting of $2\text{ to }5$ layers of cells containing dark-staining keratohyalin granules where cell keratinization begins.

Stratum Lucidum

A narrow, translucent band of dead, anucleate cells present only in thick skin to provide extra protection.

Stratum Corneum

The most superficial layer of the epidermis comprising $75\%$ of its total thickness, consisting of $20\text{ to }30$ layers of dead, flattened, fully keratinized cells.

Dermis

The deeper, thicker layer of fibrous connective tissue beneath the epidermis, richly endowed with blood vessels, nerve endings, sweat glands, and hair follicles.

Papillary Layer

The superficial one-fifth of the dermis composed of loose areolar tissue that forms projections called dermal papillae and contains capillaries and Meissner's corpuscles.

Reticular Layer

The deeper four-fifths of the dermis composed of dense irregular connective tissue containing blood vessels, glands, hair follicles, and Pacinian corpuscles.

Pacinian Corpuscle

A specialized sensory receptor located in the reticular layer of the dermis that detects pressure.

Meissner's Corpuscle

A tactile sensory receptor located in the papillary layer of the dermis that senses light touch.

Cleavage (Tension) Lines

Structural alignment patterns of collagen bundles in the dermis; incisions made parallel to these lines produce minimal scarring compared to perpendicular cuts.

Hypodermis (Subcutaneous Layer)

A layer of loose areolar and adipose connective tissue beneath the dermis that anchors skin to underlying structures, provides insulation, and stores energy.

Structural Classification of Exocrine Glands

Categorization of exocrine glands based on duct branching (simple vs. compound) and secretory unit shape (tubular vs. acinar/alveolar).

Types of Exocrine Gland Secretion

Classification of glands according to their mode of secretion: merocrine (exocytosis), apocrine (pinched-off cell portions), and holocrine (entire cell rupture).

Merocrine Gland

An exocrine gland that releases fluid secretions through the cell membrane via exocytosis without damaging the cell.

Apocrine Gland

An exocrine gland whose secretory cells release products by pinching off a portion of their apical cell membrane.

Holocrine Gland

An exocrine gland in which entire cells disintegrate and rupture to release their secretory product.

Sebaceous (Oil) Glands

Exocrine holocrine glands in the dermis that secrete oily sebum into hair follicles to coat, condition, and protect hair shafts.

Eccrine (Merocrine) Sweat Glands

Abundant coiled tubular glands in the dermis that discharge sweat directly onto the skin surface via pores for thermoregulation.

Apocrine Sweat Glands

Large sweat glands located in the axillae and external genitalia that empty into hair follicles and secrete water, salts, fatty acids, and proteins during stress or arousal.

Arrector Pili Muscle

A band of smooth muscle attached to a hair follicle that contracts in response to cold or stress, erecting the hair and forming goosebumps.

Regeneration

Tissue repair where damaged tissue is replaced by identical, fully functional cell types via mitosis.

Fibrosis

Tissue repair where destroyed parenchymal tissue is replaced by dense connective tissue and collagen matrix, creating permanent scar tissue.

Keloid

A firm, raised, overgrown scar resulting from excessive accumulation of granulation tissue during wound healing.

First-Degree Burn

A partial-thickness burn involving only the epidermis, causing localized pain, redness, and slight swelling without blisters.

Second-Degree Burn

A partial-thickness burn damaging the epidermis and upper dermis, causing redness, pain, inflammation, and blister formation.

Third-Degree Burn

A full-thickness burn destroying the epidermis, entire dermis, and underlying tissues; characterized by charred tissue and absence of pain due to destroyed nerve endings.

Rule of Nines

A clinical estimation method (Lund-Browder system) that divides body surface area into multiples of $9\%$ to assess the severity of burns.

Types of Skin Lesions

Morphological classification of visible skin abnormalities caused by disease or injury, including macules, papules, vesicles, cysts, and ulcers.

Macule

A flat, discolored skin lesion that does not project above the surface of the skin, such as a freckle or age spot.

Papule

A small, solid, elevated skin lesion measuring less than $1\,cm$ in diameter.

Vesicle

A small, elevated skin lesion filled with clear fluid, such as a blister seen in herpes or chickenpox.

Pustule

A small, raised skin lesion containing pus.

Wheal

A red, itchy, slightly elevated skin elevation caused by localized edema, characteristic of hives or insect bites.

Cyst

An elevated, thick-walled sac containing fluid or semisolid material.

Ulcer

An open sore or erosion of the skin surface extending into deeper tissue layers.

Scale

A dry, thin flake of dead epidermis sloughing off the skin surface.

Alopecia

Partial or complete loss of hair.

Cellulitis

An acute bacterial infection of connective tissue causing localized erythema, swelling, and severe pain, commonly on the face or legs.

Acne Vulgaris

A common skin condition in which excessive sebum production clogs pores, facilitating bacterial accumulation and inflammation.

Furuncle (Boil)

A localized abscess centered on a hair follicle or sebaceous gland resulting from a bacterial infection.

Onychomycosis

A fungal infection of the nail plate causing discoloration, crumbling, and thickening of the nail.

Tinea

A fungal skin infection (commonly called ringworm) categorized by location: Tinea Corporis (body), Tinea Capitis (scalp), Tinea Cruris (groin), and Tinea Pedis (foot).

Vitiligo

An autoimmune disorder in which melanocytes lose function, resulting in unpigmented white patches across various body regions.

Gangrene

Necrosis (death) of tissue caused by severe ischemia, frostbite, or advanced infection.

Decubitus Ulcer

A pressure sore or bedsore caused by prolonged pressure against skin over a bony prominence, leading to ischemia and tissue destruction.

Eczema

An inflammatory epidermal disease characterized by severe pruritus (itching), redness, weeping vesicles, and rough, scaly patches.

Psoriasis

A chronic autoimmune skin condition in which keratinocytes divide $10\times$ faster than normal, producing silvery scales and thick red plaques.

Actinic Keratoses

Precancerous scaly pink or red papules caused by chronic sun exposure that may progress to squamous cell carcinoma.

Basal Cell Carcinoma

The most common and least aggressive form of skin cancer, originating from stratum basale cells that slowly invade the dermis.

Squamous Cell Carcinoma

The second most common skin cancer, arising from keratinocytes in the stratum spinosum and presenting as scaly red lesions.

Melanoma

The most aggressive, fast-growing, and highly metastatic form of skin cancer, resulting from malignant transformation of melanocytes.

ABC's of Skin Lesions

Clinical guidelines used to evaluate skin lesions for malignancy: Asymmetry, Border irregularity, Color variation, and Diameter greater than $6\,mm$.

Debridement

The surgical removal of dead, damaged, or infected necrotic tissue from a wound, burn, or ulcer to facilitate healing.

Punch Biopsy

A diagnostic procedure using a circular tubular blade to remove a cylindrical core sample of tissue including epidermis, dermis, and subcutis.

Culture and Sensitivity (C&S)

A diagnostic test where fluid exudate or pus is cultured in a Petri dish to identify the specific infectious bacteria and test its response to various antibiotics.