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  • Epidermis is the outermost layer of the skin, which forms an outer protective covering of the body.
  • It contains no blood vessels but has many small nerve endings.
  • Consists of Stratified epithelial cells.
  • The free surface of the epidermis is marked by linear furrows and ridges of variable sizes.
  • The thickness of the epidermis varies from 0.4 – 1.5 mm.
  • Keratinocytes account for 80% of the cells in the epidermis, the other resident epidermal cells are Melanocytes, Langerhans & Merkel cells.

It is arranged in 5 layers, as listed below from Deepest to most superficial layer:

  • Stratum Germinativium/basal cell layer
  • Stratum Spinosum
  • Stratum Granulosum
  • Stratum Lucidum
  • Stratum Corneum



Stratum Germinativum/Basal cell Layer


This is the deepest layer of epidermis, which is in contact with the dermis below from which it gets nutrient fluid from the blood capillaries. This layer is regenerative. It is the living layer of skin. It has 1-2 layers of columnar cells. It has a nucleus & dense cytoplasm. As new cells are produced the older cells are pushed upwards to the next layer. The shape of the cells changes as they move upwards from one layer to the other. As there is no blood supply to the layers above stratum germinativum the cells gradually die.

One in every 10 cells is melanocyte which produces melanin. Melanin, the substance that gives colour to the skin includes a series of chemical reaction with the amino acid tyrosine.

Melanin also protects the underlying layer of skin from harmful effect of certain U.V.Rays.

  • New cells take about 3 weeks time to reach from the basal layer to the stratum corneum layer.

Stratum Spinosum / Prickle Cell layer

8 – 10 layers of cells. These cells are polyhedral with a round nucleus. It contains very fine filamentous structures called Tonofilaments, which consist of long chain of amino acids. The cells in the layer have specialized cell wall structure called the desmosomes, through which they are attached to each other as well as to the cells of basal cell layer. Tonofilaments are attached to desmosome and form a criss cross pattern in the cytoplasm of the cell and provide a sort of skeleton to the cells.

The Basal layer & the Spinous layer together are also known as Malpighian Layer.

Stratum Granulosum or Granular cell layer

This layer varies in the thickness e.g. it is thickest in the palms of hands and soles of feet. These flattened cells have evidence of kerotohyaline granules, which reflect light and give the skin its shiny look. The nucleus starts disintegrating & keratin deposit begins in the cytoplasm. The 1st stage of keratinisation begins at this layer.

Stratum Lucidum

 The thick epidermis of the palms & soles has an additional layer i.e. translucent. It is a thin, clear, glossy layer of dead skin. No nucleus & no cytoplasm, only Keratin. It reduces friction between St.Corneum and St.Granulosum. This layer acts as a barrier controlling the transmission of water through the skin and composed of 3-5 layers of dead flattened cells.

Stratum Corneum or the Corneal Cell Layer

 It contains dead flattened keratinised cells. Cells are generated in the Stratum Germinativum and old cells fall from the surface of stratum corneum. The function of Stratum Corneum is to keep the skin waterproof and prevent the skin from cracking and becoming open to bacterial infection. The continuous outward movement of epidermal cells constitutes a barrier for the agents which tend to penetrate the skin from outside. It takes 30 days for the cells to be reproduced in the stratum germinativum and move upwards to replace the cells on the skin surface.





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