- acne
- skin condition due to infected sebaceous glands
- albinism
- genetic disorder that affects the skin, in which there is no melanin production
- anagen
- 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
- bedsore
- 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
- callus
- thickened area of skin that arises due to constant abrasion
- catagen
- transitional phase marking the end of the anagen phase of the hair growth cycle
- corn
- type of callus that is named for its shape and the elliptical motion of the abrasive force
- cortex
- in hair, the second or middle layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb
- cuticle
- 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
- 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
- desmosome
- 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
- eczema
- 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
- eleiden
- clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss
- epidermis
- outermost tissue layer of the skin
- eponychium
- 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
- hair
- 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
- hypodermis
- connective tissue connecting the integument to the underlying bone and muscle
- hyponychium
- 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
- keloid
- type of scar that has layers raised above the skin surface
- keratin
- type of structural protein that gives skin, hair, and nails its hard, water-resistant properties
- keratinocyte
- cell that produces keratin and is the most predominant type of cell found in the epidermis
- keratohyalin
- granulated protein found in the stratum granulosum
- Langerhans cell
- specialized dendritic cell found in the stratum spinosum that functions as a macrophage
- lunula
- basal part of the nail body that consists of a crescent-shaped layer of thick epithelium
- medulla
- 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
- melanin
- pigment that determines the color of hair and skin
- melanocyte
- cell found in the stratum basale of the epidermis that produces the pigment melanin
- melanoma
- type of skin cancer that originates from the melanocytes of the skin
- melanosome
- 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
- metastasis
- 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
- rickets
- disease in children caused by vitamin D deficiency, which leads to the weakening of bones
- scar
- 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
- 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
- telogen
- 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
- vitiligo
- 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