Integumentary system

Apocrine Sweat Gland

Organ made of specialized cells that produces and secretes sweat; its duct opens into a hair follicle.

Arrector Pili

Bundle of smooth muscle associated with each hair follicle; its contraction pulls the hair follicle upright.

Dendritic Cells

Immune system cell that resides in the epidermis; functions to ingest foreign substances and activate the immune system.

Dermal Papillae

Peg-like projections of dermis that indent the overlying epidermis.

Dermis

Deep layer of the skin.

Eccrine Sweat Glands

Organ made of specialized cells that produces and secretes sweat; its duct opens onto the surface of the skin.

Epidermis

Superficial layer of the skin.

Eponychium

Proximal nail fold that projects onto the nail body; also called the cuticle.

Free Edge (of Nail)

Distal part of the nail that protrudes beyond the nail plate or body.

Hair

Flexible strands consisting largely of dead, keratinized cells that protrude from the skin; also called pili.

Hair Bulb

Expanded deep end of the hair follicle.

Hair Follicle

Sheath of epidermis that surrounds the hair root.

Hair Matrix

Dividing cells that create the hair; lies adjacent to the hair papilla.

Hair Papilla

A dermal papilla that protrudes into the hair bulb; contains a knot of capillaries that feeds the hair matrix.

Hyponychium

Thickened region beneath the free edge of the nail that secures the free edge of the nail plate at the tip of the finger or toe.

Keratinocytes

Epidermal cell that produces keratin (a fibrous protective protein).

Lunule

The region of the nail plate or body that lies over the thick nail matrix and appears as a white crescent.

Melanocyte

Epidermal cell that synthesizes melanin (a pigment that protects against ultraviolet [UV] radiation).

Nail

Clear protective covering on the dorsal surface of the distal part of a finger or toe.

Nail Bed

Epidermis upon which the nail lies.

Nail Folds

Skin folds that overlap the proximal and lateral borders of the nail.

Nail Matrix

Thickened proximal portion of the nail bed responsible for nail growth.

Nail Plate or Body

Visible attached portion of a nail.

Papillary Layer

Thin, superficial layer of the dermis.

Pore

The opening of a sweat gland duct onto the skin's surface.

Reticular Layer

Thick, deep layer of the dermis.

Root (of Hair)

Part of the hair embedded in the skin.

Root (of Nail)

Proximal portion of the nail embedded in the skin.

Sebaceous Gland

Glands that secrete oil or sebum.

Shaft of Hair

Visible part of the hair that projects above the skin's surface.

Subcutaneous Tissue

Layer of tissue that lies deep to the skin, anchoring it to the underlying structures.

Tactile Cell

An epithelial cell present in the epidermal-dermal junction that is closely associated with a sensory nerve ending; functions as a sensory receptor for touch.

Hydrodermis

Areolar connective tissue

Papillary layer of dermis

the uppermost layer of the dermis, consisting of loose connective tissue that contains capillaries and sensory neurons, providing nutrients to the epidermis and aiding in touch sensation.

reticular layer

the deeper layer of the dermis, composed of dense irregular connective tissue, providing strength and elasticity to the skin.

Stratum Basale

the deepest layer of the epidermis, where new skin cells are generated, consisting of a single row of columnar or cuboidal keratinocytes.

Stratum Corneum

the outermost layer of the epidermis (outside layer), consisting of dead keratinized cells that provide a protective barrier against environmental damage and water loss.

Stratum Granulosum

(Middle layer) the layer of the epidermis above the stratum spinosum, characterized by the presence of granules that contain keratohyalin, contributing to the formation of a waterproof barrier.

Stratum Spinosum

(4th layer from superficial-deep) the layer of the epidermis above the stratum basale, characterized by spiny-shaped keratinocytes that provide strength and flexibility to the skin.

Stratum Lucidum

(Clear layer) (2nd layer from outer in) thin layer of the epidermis found only in thick skin, such as the palms and soles, providing an additional barrier and contributing to the overall thickness of the skin.