Glossary


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A

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”


B

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


C

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


D

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


E

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


F

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


G

glassy membrane

layer of connective tissue that surrounds the base of the hair follicle, connecting it to the dermis


H

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


I

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


K

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


L

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


M

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



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