dermis

subcutaneous layer

a continuous sheet of areolar connective tissue and adipose tissue between the dermis of the skin and the deep fascia of the muscles

internal root sheath

a covering of epithelium produced by the matrix that surrounds the root of the hair

external root sheath

a downward continuation of the epidermis that surrounds the root of the hair

dermal papillae

a fingerlike projection of the dermis that may contain blood capillaries or Meissner corpuscles (of touch)

hair matrix

a germinal layer of cells responsible for the growth of existing hairs and the production of new hairs when old hairs are shed

dermis

a layer of dense irregular connective tissue lying deep to the epidermis

stratum lucidum

a layer of the epidermis found only in the thick skin of the fingers, palms, and soles

stratum granulosum

a layer of the epidermis that marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata

stratum spinosum

a layer of the epidermis that provides strength and flexibility to the skin

papilla of the hair

a nipple-shaped indentation which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle

arrector pili

a smooth muscle attached to hair follicles that causes "goose bumps" to appear on the skin when contracted

hair follicle

a structure composed of epithelium that surrounds the root of a hair

Meissner corpuscle

a tactile nerve ending receptor in the dermal papillae that is sensitive to touch

pacinian corpuscle

a type of nerve ending located in the subcutaneous layer that is sensitive to pressure; also described as "lamellated"

sebaceous gland

an exocrine gland in the dermis associated with a hair follicle that secretes oil

free nerve ending

dendrites that lack any obvious structural specialization; used to generate sensations of warmth, coolness, pain, tickle, and itch

apocrine sudoriferous gland

found in the skin of the axilla, groin, and areolae; secretes a viscous, lipid- and protein-rich product into a hair follicle upon stimulation during emotional distress or sexual excitement

eccrine sudoriferous gland

found throughout the skin of most regions of the body, especially in skin of forehead, palms, and soles; secretes a less viscous product consisting of water, ions, urea, and ammonia; regulates body temperature and removal of metabolic wastes

bulb

the base of a hair follicle and its surrounding dermal root sheath, containing the papilla of the hair and matrix

stratum basale

the deepest layer of the epidermis consisting of stem cells capable of undergoing cell division to form new cells

stratum corneum

the most superficial layer of the epidermis consisting of dead cells

root

the portion of a hair that penetrates into the dermis and sometimes the subcutaneous layer

shaft

the superficial portion of the hair

epidermis

the superficial, thinner layer of skin, composed of keratinized stratified squamous epithelium