Epidermis (skin)

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Epidermis (skin)

The epidermis is the outermost layer of the skin

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
, composed of terminally differentiated stratified squamous epithelium

Epithelium

In biology and medicine, epithelium is a Biological tissue composed of cell s that line the cavities and surfaces of structures throughout the body....
, acting as the body's major barrier against an inhospitable environment.

epidermis is avascular, nourished by diffusion

Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
from the dermis

Dermis

File:EpidermisPainted.svgThe dermis is a layer of skin between the epidermis_ and subcutaneous tissues, and is composed of two layers, the papillary_dermis and reticular dermis....
, and composed for four cell types: keratinocyte

Keratinocyte

The keratinocyte is the major constituent of the epidermis , constituting 95% of the cells found there. Those keratinocytes found in the Stratum germinativum are sometimes referred to as "basal cells" or "basal keratinocytes."...
s, melanocyte

Melanocyte

Melanocytes are cell located in the bottom layer of the skin's epidermis , the middle layer of the eye , the inner ear, meninges, bones and heart....
s, Langerhans cell

Langerhans cell

Langerhans cells are dendritic cells in the Epidermis , containing large granules called Birbeck granules. They are normally present in lymph nodes and other organs, including the stratum spinosum layer of the epidermis....
s, and the Merkels cell. Keratinocytes are the major constituent, constituting 95% of the epidermis.

epidermis is composed of 4-5 layers depending on the region of skin being considered.

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Cellular components

The epidermis is avascular, nourished by diffusion

Diffusion

Dermis

Keratinocyte

Melanocyte

Melanocytes are cell located in the bottom layer of the skin's epidermis , the middle layer of the eye , the inner ear, meninges, bones and heart....
s, Langerhans cell

Langerhans cell

Layers

The epidermis is composed of 4-5 layers depending on the region of skin being considered. Those layers in descending order are the stratum corneum

Stratum corneum

The stratum corneum is the outermost layer of the epidermis , composed of large, flat, polyhedral, plate-like envelopes filled with keratin which are the dead cells that have migrated up from the stratum granulosum....
, stratum lucidum

Stratum lucidum

The stratum lucidum is a layer of the epidermis_ found only in palmoplantar skin , between the stratum granulosum and stratum corneum layers. It is composed of three to five layers of dead, flattened keratinocytes....
, stratum granulosum

Stratum granulosum

The stratum granulosum is a layer of the epidermis_ found between the stratum corneum and stratum spinosum. In this layer, keratinocytes are now called granular cells, and contain keratohyalin and lamellar granules....
, stratum spinosum

Stratum spinosum

The stratum spinosum is a layer of the epidermis_ found between the stratum granulosum and Stratum germinativum. This layer is also referred to as the "spinous" or "prickle-cell" layer....
, and stratum basale

Stratum germinativum

The Stratum germinativum is the deepest layer of the epidermis, a continuous layer of cells often described as one cell thick, though it may be two to three cells thick in glabrous skin and hyperproliferative epidermis....
. The term Malpighian layer

Malpighian layer

The Malpighian layer of the skin is composed of both the stratum germinativum and stratum spinosum....
refers to both the basal and spinosum layers.

Cellular kinetics

The stratified squamous epithelium is maintained by cell division within the basal layer. Differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where anucleate corneal cells are continually shed from the surface (desquamation

Desquamation

Desquamation is the shedding of the Epidermis s of the skin. The word comes from the Latin 'desquamare' , meaning "to scrape the scale off a fish"....
). In normal skin the rate of production equals the rate of loss, taking about two weeks for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.it also contains hair

Epidermis (skin)

Cellular components

Layers

Cellular kinetics

Additional images