What is Epidermis?

About Epidermis:

• It is the outermost layer of the skin and protects the body from the environment.
• The thickness of the epidermis varies in different types of skin; it is only .05 mm thick on the eyelids and 1.5 mm thick on the palms and the soles of the feet.
• The epidermis layer itself is made up of five sublayers that work together to continually rebuild the surface of the skin:
• The various cells present in the epidermis are Keratinocytes, Melanocytes, Langerhans cells, and Merkel cells.
• Keratinocytes:
  • They are the most common type of cell in the epidermis and are responsible for the synthesis of the protein keratin.
  • These cells exist in progressive stages of differentiation from the deepest to the superficial layers of cells.
  • Moreover, keratinocytes originate from the basal layer, which is the deepest layer of the epidermis, and gradually move up to the outside layer of the epidermis.
  • Here, keratinocytes are shed from the skin and replaced by new maturing cells.
• Melanocytes:
  • They are another type of cell in the epidermis that is present throughout the basal layer.
  • These cells are responsible for the production of melanin, which contributes to the colour of the skin of an individual.
  • Melanin also helps to protect the body from ultraviolet (UV) radiation present in sunlight which can damage the DNA of the skin cells.
• Langerhans cells:
  • Langerhans cells produced in the bone marrow are also present in the epidermis and work to detect foreign substances and infections as part of the immune system of the skin.
  • These cells are also thought to be involved in the development of skin allergies.
• Merkel cells:
  • Merkel cells originate from neural crest cells and are responsible for the perception of gentle touch.
  • These cells are present in the epidermis in specific areas of the skin, such as the nail beds and genitalia.

What is Dermis?

• It is located beneath the epidermis and is the thickest of the three layers of the skin (1.5 to 4 mm thick), making up approximately 90 per cent of the thickness of the skin.
• The main functions of the dermis are to regulate temperature and to supply the epidermis with nutrient-saturated blood. 
• Much of the body's water supply is stored within the dermis. This layer contains most of the skin's specialized cells and structures.