Anatomy and Physiology - Layers of the Skin

Comprehensive vocabulary flashcards covering the anatomical structures, epidermal layers, cell types, dermal components, hypodermis, pigmentation mechanisms, and clinical conditions discussed in Section 5.1: Layers of the Skin.

Integumentary System

The organ system consisting of the skin and its accessory structures, working together as a single structure to provide overall protection to the body.

Epidermis

The avascular outermost layer of the skin, composed of keratinized, stratified squamous epithelium arranged in four or five layers of epithelial cells.

Dermis

The well-vascularized "core" layer of the integumentary system beneath the epidermis, made of dense, irregular connective tissue housing blood vessels, hair follicles, and sweat glands.

Hypodermis

Also known as the subcutaneous layer or superficial fascia; a well-vascularized layer of loose areolar connective tissue and adipose tissue beneath the dermis that anchors skin to underlying muscle and bone fascia.

Thin Skin

Skin covering most of the body that consists of four epidermal layers: the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum.

Thick Skin

Skin found exclusively on the palms of the hands and soles of the feet that contains a fifth epidermal layer, the stratum lucidum, located between the stratum corneum and stratum granulosum.

Keratinocyte

A predominant cell found in all layers of the epidermis except the stratum basale that manufactures and stores the intracellular fibrous protein keratin.

Keratin

An intracellular fibrous protein that confers hardness and water-resistant properties to hair, nails, and skin.

Stratum Basale

Also called the stratum germinativum; the deepest epidermal layer consisting of a single layer of cuboidal basal stem cells that constantly undergoes mitosis to produce new keratinocytes.

Basal Cell

A cuboidal-shaped stem cell located in the stratum basale that serves as the precursor to all keratinocytes of the epidermis.

Dermal Papilla

A finger-like projection or fold of the superficial dermis that interlocks with the stratum basale to strengthen epidermal-dermal attachment and forms fingerprint ridges.

Merkel Cell

A specialized receptor cell dispersed in the stratum basale, abundant in the hands and feet, that stimulates sensory nerves perceived as touch.

Melanocyte

A cell found in the stratum basale that produces the pigment melanin to color hair and skin and protect DNA from ultraviolet (UV) radiation.

Stratum Spinosum

An epidermal layer composed of 8 to 10 layers of keratinocytes that exhibit a spiny appearance caused by interlocking desmosomes, and which contains dendritic Langerhans cells.

Desmosome

A cell structure with protruding processes that interlocks adjacent keratinocytes in the stratum spinosum to strengthen mechanical bonds between cells.

Langerhans Cell

A dendritic macrophage found interspersed in the stratum spinosum that engulfs bacteria, foreign particles, and damaged cells.

Stratum Granulosum

An epidermal layer 3 to 5 cell layers deep where keratinocytes flatten, thicken cell membranes, and accumulate large amounts of keratin and keratohyalin as nuclei and organelles disintegrate.

Keratohyalin

A protein accumulated as granules within keratinocytes of the stratum granulosum that aggregates, cross-links, and bundles keratin precursors.

Stratum Lucidum

A smooth, translucent layer of flattened, dead keratinocytes located between the stratum granulosum and stratum corneum, present solely in the thick skin of the palms, soles, and digits.

Eleidin

A clear protein derived from keratohyalin that densely packs dead keratinocytes in the stratum lucidum to give them a transparent appearance.

Stratum Corneum

The most superficial layer of the epidermis, comprising 15 to 30 layers of dead, cornified keratinocytes that prevent microbial entry, limit dehydration, and protect against mechanical abrasion.

Papillary Layer

The superficial layer of the dermis composed of loose areolar connective tissue forming dermal papillae and containing fibroblasts, adipocytes, blood vessels, phagocytes, and Meissner corpuscles.

Meissner Corpuscle

A tactile touch receptor found in the papillary layer of the dermis.

Reticular Layer

The deeper, thicker layer of the dermis composed of dense irregular connective tissue with a meshwork of elastin fibers for elasticity and collagen fibers for structural strength and hydration.

Adipocyte

A fat-storing cell found in the hypodermis that serves as an energy reserve, insulates against heat loss, and cushions underlying structures from trauma.

Melanosome

A cellular vesicle produced by melanocytes that packages and transfers melanin into neighboring keratinocytes.

Eumelanin

A primary form of melanin pigment that exists as black and brown shades.

Pheomelanin

A primary form of melanin pigment that provides a red color.

Albinism

A genetic disorder characterized by the complete or partial lack of melanin production by melanocytes, causing pale coloring of skin, hair, and eyes, along with increased UV sensitivity and vision issues.

Vitiligo

A condition in which melanocytes lose the ability to produce melanin in certain areas, possibly due to an autoimmune reaction, causing light-colored depigmented skin patches.

Cyanosis

A bluish tint of the skin occurring when restricted oxygen supply leads to the dominance of dark red deoxyhemoglobin in the blood.

Jaundice

A yellow discoloration of the skin caused by liver disease or cancer that results in the accumulation of bile and the yellow pigment bilirubin.