Skin Cells and Skin Layers

Papillary Region

A thin layer of areolar connective tissue that is deep in the stratum basale of the epidermis and the basement membrane.

Melanocytes

Comprise 8% of the epidermal cells and produce and secrete the pigment melanin.

Keratinocytes

Comprise 90% of cells of the epidermis and produce keratin, a tough fibrous protein that protects the skin and deeper tissues from chemicals, microbes, and heat. These cells also produce granules that secrete lipid-rich product that helps to waterproof the skin.

Dermis

Connective tissue. Contains two layers: Papillary and Reticular

Stratum Basle

Contain a single row of cells attached to the basement membrane, contains stem cells that divide to form keratinocytes. Older cells are pushed toward the surface and undergo a process called keratinization, which produces tough, dead cells in the superficial layer. Melanocytes, Langerhans cells, and Merkel cells are also found within this layer.

Stratum Lucidum

Contains 3 to5 rows of flat, dead keratinocytes. This layer is translucent in specimens of fresh skin.

Stratum Spinosum

Contains 8 to 10 rows of cells, mainly keratinocytes. Cells in this layer have thorn-like projections caused by tissue preparation process.

Langerhans Cells

Immune system cells that attack pathogens that enter the skin. Comprise 2% of epidermal cells.

Stratum Granulosum

Keratinocytes contain granules in this layer. This layer contains 3 to 5 rows of flattened keratinocytes that are beginning to die. No dividing cells are present in this layer or in more superficial layers.

Hypodermis

Located below the skin, major storage site for adipose tissue.

Reticular Layer

The deeper and much thicker region of the dermis. Composed mainly of dense, irregular connective tissue whose collagen fibers provide the skin with strength and whose elastic fibers provide elasticity.

Merkel Cells

The least abundant cell type and are only found in the deepest layer of the epidermis. These cells function as touch receptors and are associated with sensory neurons.

Epidermis

The outer layer of the skin, is composed of stratified squamous epithelial tissue.

Stratum Corneum

The outermost layer of skin. A very thick layer containing 25 to 30 or more rows of dead, squamous shaped keratinocytes. This layer is tough and water resistant. These cells continuously fall off and are replaced by cells in the adjacent layer.