Integumentary System Flashcards

Vocabulary flashcards covering the anatomy, epidermal strata, skin cell types, dermal regions, pigmentary mechanics, and accessory organs of the integumentary system based on the lecture notes.

Integumentary System General Dimensions

The total surface area and mass of the human skin, which covers approximately $2\,\text{m}^2$, has a thickness of $1\text{--}2\,\text{mm}$, and weighs $4.5\text{--}5\,\text{kg}$ ($10\,\text{lbs}$).

Epidermis

The superficial, thin, avascular layer of the skin composed entirely of keratinized stratified squamous epithelium.

Dermis

The deeper, thicker, vascular layer of the skin composed of dense irregular connective tissue containing blood vessels, nerves, glands, and hair follicles.

Subcutaneous Layer (Hypodermis)

A layer of adipose connective tissue located beneath the dermis that serves as a fat depot, anchors skin, and contains large blood vessels and lamellar (Pacinian) corpuscles.

Keratinocytes

The primary cells of the epidermis ($85\text{--}90\%$ of epidermal cells) arranged in $4\text{--}5$ layers, which produce tough keratin protein and water-repelling lamellar granules.

Melanocytes

Specialized cells comprising $8\%$ of epidermal cells, located in the stratum basale, that produce melanin pigment and transfer it to keratinocytes via long projections.

Intraepidermal Macrophages (Dendritic / Langerhans Cells)

Immune cells originating from red bone marrow that migrate to the epidermis to recognize and assist in destroying invading microbes.

Tactile Epithelial Cells (Merkel Cells)

Cells located in the deepest layer of the epidermis (stratum basale) that connect to sensory neuron tactile discs to detect light touch.

Stratum Basale (Stratum Germinativum)

The deepest layer of the epidermis, consisting of a single row of cuboidal or columnar stem cells attached to the basement membrane that continuously divide to produce new keratinocytes.

Stratum Spinosum

The thickest layer of the epidermis, containing $8\text{--}10$ rows of many-sided keratinocytes joined by desmosomes and thick bundles of keratin intermediate filaments.

Stratum Granulosum

An epidermal layer consisting of $3\text{--}5$ rows of flattened keratinocytes undergoing apoptosis, containing dark-staining keratohyalin granules and lipid-releasing lamellar granules.

Stratum Lucidum

A clear, dead epidermal layer composed of $4\text{--}6$ rows of flat keratinocytes found exclusively in thick skin areas such as fingertips, palms, and soles.

Stratum Corneum

The outermost epidermal layer consisting of $25\text{--}30$ (or up to $50$ or more) rows of dead, flat, nucleus-free keratinocytes completely filled with keratin and surrounded by lipids.

Keratohyalin

A protein present in the stratum granulosum that functions to assemble keratin intermediate filaments into dense clumps of mature keratin.

Lamellar Granules

Membrane-enclosed vesicles in keratinocytes that secrete a lipid-rich, water-repellent secretion to reduce water loss and inhibit entry of foreign materials.

Callus

An abnormal thickening of the stratum corneum resulting from persistent or repeated mechanical friction.

Eumelanin

A type of melanin pigment produced by melanocytes that imparts brown to black coloration to skin and hair.

Pheomelanin

A type of melanin pigment produced by melanocytes that imparts yellow to red coloration to skin and hair.

Albinism

An inherited genetic condition characterized by the inability to produce melanin due to a lack or defect of the enzyme tyrosinase.

Vitiligo

An autoimmune disorder causing the partial or complete loss of functional melanocytes, resulting in depigmented white patches on the skin.

Nevus (Mole)

A benign, localized overgrowth of melanocytes that typically appears during childhood or adolescence.

Papillary Region

The superficial one-fifth ($20\%$) of the dermis composed of loose connective tissue, dermal papillae, capillaries, corpuscles of touch, and free nerve endings.

Reticular Region

The deeper four-fifths of the dermis composed of dense irregular connective tissue with netlike collagen and elastic fibers, housing hair follicles, oil glands, and sweat gland ducts.

Arrector Pili Muscle

A small smooth muscle extending from the papillary dermis to the hair follicle sheath that contracts to pull hair upright, forming goosebumps.

Eponychium (Cuticle)

A narrow band of stratum corneum at the proximal border of the nail that adheres to the nail wall.

Sebaceous Glands

Simple branched acinar exocrine glands located in the dermis that usually open into hair follicles to secrete oily sebum.

Sebum

An oily secretion containing lipids, cholesterol, proteins, and salts that keeps hair and skin soft, reduces evaporation, and inhibits bacterial growth.

Eccrine Sweat Glands

Widespread sudoriferous glands that produce watery sweat directly onto the skin surface primarily for body temperature regulation via evaporation.

Apocrine Sweat Glands

Sudoriferous glands found in the armpits, pubic region, and areolae that secrete a thick, protein- and lipid-rich fluid into hair follicles starting at puberty during stress or excitement.