Epidermis

Epidermis

The top layer of the skin composed of stratified squamous epithelial tissue.

Stratum corneum

A layer of dead cells that is thick and keratinized, protecting the deeper layers of the skin. Regularly shed from the body.

Stratum lucidum

A thin layer of translucent cells found only in the thick skin of the palms and soles of feet.

Stratum granulosum

A layer where cells begin to flatten and disintegrate, accumulating keratin granules responsible for waterproofing the skin.

Stratum spinosum

A layer named for the irregular shape of its cells, several cells thick, and containing pre-keratin filaments.

Stratum basale

The bottom layer of the epidermis that is constantly dividing and pushing up cells into the next layer.

Melanocytes

Spider-shaped epithelial cells found in the bottom two layers of the epidermis that produce the pigment melanin.

Melanin

A pigment produced by melanocytes that is absorbed by nearby epidermal cells, protecting the skin against harmful UV rays.

Skin cancer

Uncontrolled division of skin cells due to DNA mutations caused by UV radiation.

Functions of epidermis

Protection from water, air, infection, chemicals, UV radiation. Sensations such as pressure, heat, cold, and pain. Temperature regulation - body can be heated or cooked by sweat and blood flow near surface. Excretion of waste through sweat. Production of Vitamin D.

Types of major cells in epidermis

Keratinocytes, melanocytes, intraepidermal macrophages (langerhans cells), tactile epithelial cells (merkel cells)

Difference of melanocytes in dark and light-skinned people

The number of melanocytes is the same. The difference is the amount of melanin produced.

Types of skin cancer

Melanoma, squamous cell carcioma, basal cell carcinoma

Melanoma

uncontrolled division of melanocytes

Basal cell carcinoma

Uncontrolled division of cells in the stratum basale layer.

Squamous cell carcinoma

Uncontrolled division of cells in the stratum spinosum layer.