Integumentary System

Epidermis

Avascular, stratified squamous epithelial layer.

Stratum Basale

Mitotically active cuboidal-low columnar cell layer.

Stratum Spinosum

Layer where keratinocytes appear spiny under microscopy.

Stratum Granulosum

Layer with keratinocytes showing dark-staining granules.

Stratum Corneum

Outermost layer with keratin granules and lipids.

Stratum Lucidum

Layer seen in thick, hairless skin.

Melanocytes

Cells producing melanin for UV protection.

Melanin

Pigment that protects skin from UV radiation.

Merkel Cells

Touch sensors sending impulses to nerves.

Langerhans Cells

Phagocytic cells presenting antigens to T lymphocytes.

Nails

Compacted keratinized cells forming protective plates.

Nail Bed

Vascular layer beneath the nail plate.

Nail Root

Proximal part fitting into the nail fold.

Dermis

Deeper skin layer with connective tissue.

Papillary Layer

Upper 20% of dermis with loose connective tissue.

Reticular Layer

Lower 80% of dermis with dense fibrous network.

Epidermal-Dermal Junction

Area where dermal papillae contact the epidermis.

Hair Follicles

Epidermal derivatives pushing into the dermis.

Arrector Pili Muscle

Smooth muscle causing hair to stand erect.

Sebaceous Glands

Glands producing sebum, surrounding hair follicles.

Sebum

Oily product providing waterproofing for skin.

Sweat Glands

Coiled glands producing sweat for cooling.

Sweat Composition

Mainly salt water with urea and other molecules.