Physiology of cellular turnover

Physiology of cellular turnover:

The skin is the largest organ of the body and has two layers: the epidermis and the dermis. Beneath is the subcutaneous layer. Because of it’s exposure to the environment, skin plays an important role in protecting the body.

The functions of the skin include:

  1. Sensation: temperature, touch, pressure, pain
  2. Heat regulation: sweating, vasoconstriction, vasodilation
  3. Absorption
  4. Protection
  5. Excretion – sweat
  6. Secretion – sebum
  7. Production of vitamin D

The epidermis is the outer covering of the skin. There are no blood vessels; nourishment comes from interstitial fluid. The epidermis is divided into 5 layers where cells are formed through mitosis at the basal layer. These cells migrate through the epidermis changing shape as they differentiate and become filled with keratin. They eventually reach the top layer and are sloughed off.

There are five layers:

  1. The stratum corneum/horny layer
  2. The stratum lucidum/clear layer
  3. The stratum granulosum/granular layer
  4. The stratum spinosum/prickle layer
  5. The stratum germinativum/basal layer


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