The anatomy of the skin

The anatomy of the skin

Skin Anatomy

The skin makes up around 12% of an adult’s body weight. Skin is made up of 3 major layers known as the Epidermis, Dermis and the Subcutaneous.

The Epidermis

This is the outermost layer of the skin. There are various layers of cells within the epidermis, the outermost of which is called the stratum corneum (or horny layer). The layers can be seen clearly in the diagram of the skin. The surface layer is composed of twenty-five to thirty sub-layers of flattened scale-like cells, that are continually being exfoliated off by friction and replaced by the cells beneath.

The surface layer is considered the real protective layer of the skin. Cells are called keratinised cells because the living matter within the cell (protoplasm) has changed to form a protein (keratin) which helps to give the skin its protective properties.

New skin cells are formed in the deepest layer of the epidermis. This layer is known as the stratum basale. New cells being to gradually move from this layer towards the stratum corneum to be shed. As they move towards the surface, the cells undergo a process of change from a round, living cell to a flat, hardened cell.

The layers of the epidermis from top to bottom are known as:

  • Stratum Corneum/Horny Layer
  • Stratum Lucidum/Clear Layer (only found in the palms on the hands and soles of the feet)
  • Stratum Granulosum/Granular Layer
  • Stratum Spinosum/Prickle Cell Layer
  • Stratum Basale/Basal or Germinative Layer

 

 

Dermis Layer

The dermis is a tough and elastic layer containing white fibrous tissue interlaced with yellow elastic fibres.

The dermis is an expanse layer and contains:

  • Blood vessels
  • Lymphatic capillaries and vessels
  • Sweat glands and their ducts
  • Sebaceous glands
  • Sensory nerve endings
  • The erector pili – which involuntary activates tiny muscles attached to the hair follicle in cold weather to trap heat.
  • Hair follicles, hair bulbs and hair roots

Subcutaneous Layer

This is the deepest layer of the skin and located beneath the dermis. It connects the dermis to the underlying organs. The subcutaneous layer is mainly composed of loose fibrous connective tissue and fat (adipose) cells interlaced with blood vessels. This layer is generally around 8% thicker in females than in males. The functions of this layer include insulation, storage of lipids, cushioning of the body and temperature regulation.