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    skin condition due to infected sebaceous glands
    genetic disorder that affects the skin, in which there is no melanin production
    active phase of the hair growth cycle
    apocrine sweat gland
    type of sweat gland that is associated with hair follicles in the armpits and genital regions
    arrector pili
    smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up”
    basal cell
    type of stem cell found in the stratum basale and in the hair matrix that continually undergoes cell division, producing the keratinocytes of the epidermis
    basal cell carcinoma
    cancer that originates from basal cells in the epidermis of the skin
    sore on the skin that develops when regions of the body start necrotizing due to constant pressure and lack of blood supply; also called decubitis ulcers
    thickened area of skin that arises due to constant abrasion
    transitional phase marking the end of the anagen phase of the hair growth cycle
    type of callus that is named for its shape and the elliptical motion of the abrasive force
    in hair, the second or middle layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb
    in hair, the outermost layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb
    dermal papilla
    (plural = dermal papillae) extension of the papillary layer of the dermis that increases surface contact between the epidermis and dermis
    layer of skin between the epidermis and hypodermis, composed mainly of connective tissue and containing blood vessels, hair follicles, sweat glands, and other structures
    structure that forms an impermeable junction between cells
    eccrine sweat gland
    type of sweat gland that is common throughout the skin surface; it produces a hypotonic sweat for thermoregulation
    skin condition due to an allergic reaction, which resembles a rash
    elastin fibers
    fibers made of the protein elastin that increase the elasticity of the dermis
    clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss
    outermost tissue layer of the skin
    nail fold that meets the proximal end of the nail body, also called the cuticle
    external root sheath
    outer layer of the hair follicle that is an extension of the epidermis, which encloses the hair root
    first-degree burn
    superficial burn that injures only the epidermis
    fourth-degree burn
    burn in which full thickness of the skin and underlying muscle and bone is damaged
    glassy membrane
    layer of connective tissue that surrounds the base of the hair follicle, connecting it to the dermis
    keratinous filament growing out of the epidermis
    hair bulb
    structure at the base of the hair root that surrounds the dermal papilla
    hair follicle
    cavity or sac from which hair originates
    hair matrix
    layer of basal cells from which a strand of hair grows
    hair papilla
    mass of connective tissue, blood capillaries, and nerve endings at the base of the hair follicle
    hair root
    part of hair that is below the epidermis anchored to the follicle
    hair shaft
    part of hair that is above the epidermis but is not anchored to the follicle
    connective tissue connecting the integument to the underlying bone and muscle
    thickened layer of stratum corneum that lies below the free edge of the nail
    integumentary system
    skin and its accessory structures
    internal root sheath
    innermost layer of keratinocytes in the hair follicle that surround the hair root up to the hair shaft
    type of scar that has layers raised above the skin surface
    type of structural protein that gives skin, hair, and nails its hard, water-resistant properties
    cell that produces keratin and is the most predominant type of cell found in the epidermis
    granulated protein found in the stratum granulosum
    Langerhans cell
    specialized dendritic cell found in the stratum spinosum that functions as a macrophage
    basal part of the nail body that consists of a crescent-shaped layer of thick epithelium
    in hair, the innermost layer of keratinocytes originating from the hair matrix
    Meissner corpuscle
    (also, tactile corpuscle) receptor in the skin that responds to light touch
    pigment that determines the color of hair and skin
    cell found in the stratum basale of the epidermis that produces the pigment melanin
    type of skin cancer that originates from the melanocytes of the skin
    intercellular vesicle that transfers melanin from melanocytes into keratinocytes of the epidermis
    Merkel cell
    receptor cell in the stratum basale of the epidermis that responds to the sense of touch
    spread of cancer cells from a source to other parts of the body
    nail bed
    layer of epidermis upon which the nail body forms
    nail body
    main keratinous plate that forms the nail
    nail cuticle
    fold of epithelium that extends over the nail bed, also called the eponychium
    nail fold
    fold of epithelium at that extend over the sides of the nail body, holding it in place
    nail root
    part of the nail that is lodged deep in the epidermis from which the nail grows
    Pacinian corpuscle
    (also, lamellated corpuscle) receptor in the skin that responds to vibration
    papillary layer
    superficial layer of the dermis, made of loose, areolar connective tissue
    reticular layer
    deeper layer of the dermis; it has a reticulated appearance due to the presence of abundant collagen and elastin fibers
    disease in children caused by vitamin D deficiency, which leads to the weakening of bones
    collagen-rich skin formed after the process of wound healing that is different from normal skin
    sebaceous gland
    type of oil gland found in the dermis all over the body and helps to lubricate and waterproof the skin and hair by secreting sebum
    oily substance that is composed of a mixture of lipids that lubricates the skin and hair
    second-degree burn
    partial-thickness burn that injures the epidermis and a portion of the dermis
    squamous cell carcinoma
    type of skin cancer that originates from the stratum spinosum of the epidermis
    stratum basale
    deepest layer of the epidermis, made of epidermal stem cells
    stratum corneum
    most superficial layer of the epidermis
    stratum granulosum
    layer of the epidermis superficial to the stratum spinosum
    stratum lucidum
    layer of the epidermis between the stratum granulosum and stratum corneum, found only in thick skin covering the palms, soles of the feet, and digits
    stratum spinosum
    layer of the epidermis superficial to the stratum basale, characterized by the presence of desmosomes
    stretch mark
    mark formed on the skin due to a sudden growth spurt and expansion of the dermis beyond its elastic limits
    sudoriferous gland
    sweat gland
    resting phase of the hair growth cycle initiated with catagen and terminated by the beginning of a new anagen phase of hair growth
    third-degree burn
    burn that penetrates and destroys the full thickness of the skin (epidermis and dermis)
    vitamin D
    compound that aids absorption of calcium and phosphates in the intestine to improve bone health
    skin condition in which melanocytes in certain areas lose the ability to produce melanin, possibly due an autoimmune reaction that leads to loss of color in patches

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