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 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 color of the skin of the individual.
  • Melanin also helps to protect the body from ultraviolet (UV) radiation present in sunlight that 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 percent 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 skins' specialized cells and structures.

Q1) What is haemoglobin?

Hemoglobin (abbreviated Hgb or Hb) is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. Hemoglobin is made up of four protein molecules (globulin chains) that are connected together. 

Source: Discovery of haemoglobin in epidermis throws light on skin's protective features: Study