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Human skin which is also called the integument, or the cutaneous membrane is made of two layers: the Epidermis, and the Dermis (OpenStax, 2018).
The Epidermis consists of four to five layers depending on the type of skin. Thick skin has five layers, and it is found in the palms of the hands and on the soles of the feet. Thin skin has four layers and is what covers most of the body.
Layer 1: The bottom of the five-layer skin or deep layer is called the Stratum Basale. It is made up of single layer of cells attached to the basement membrane. The three types of cells in this layer are Keratinocytes, Melanocytes, and Tactile cells (OpenStax, 2018). Keratinocytes go through cell division to replace cells that are shed from the surface of the skin. These cells produce structural protein called keratin which strengthens the skin and makes it almost waterproof. Melanocytes are scattered among the keratinocytes, and they produce the pigment melanin in reaction to exposure to ultraviolet light. Tactile cells are also scattered among the keratinocytes, and they serve as light tough receptors (OpenStax, 2018).
Layer 2: The Stratum Spinosum layer is made up of daughter keratinocytes from dividing cells in the Stratum Basale layer below, and epidermal dendritic cells. The daughter cells desmosomes, which are one of the ways cells connect to one another (OpenStax, 2018).
Layer 3: The Stratum Granulosum is comprised of three layers of keratinocytes. The process keratinization begins in this layer of epidermis (OpenStax, 2018).
Layer 4: The Stratum Lucidum layer is only found in the thick skin in the palms and soles of the feet. The keratinocytes in this layer are clear, flat, closely packed, and have no nucleus or organelles. They are also filled with the protein called Eleidin (OpenStax, 2018).
Layer 5: The Stratum Corneum (the top layer) is comprised of dead keratinized cells. It takes about two weeks for the new keratinocytes to reach the Stratum Corneum, and it remains in this layer for about another two weeks before it is shed (OpenStax, 2018).
Clinical condition related to Epidermis layer of skin
1. Epidermolysis Bullosa -- is a group of rare diseases that cause fragile, blistering skin. The blister may appear in response to injury, even from heat, rubbing, scratching or adhesive tape. In severe cases, the blister may occur inside the body, such as the lining of the mouth or the stomach. Most type of epidermolysis bullosa are inherited and has no cure (Mayo Clinic Staff, 2020).
The various types of epidermolysis bullosa are largely defined by which layer the blister form in. Complications include infection, sepsis, fusion of fingers and changes in the joints, problems with nutrition, constipation, dental problems, skin cancer, and death (Mayo Clinic Staff, 2020)
2. Albinism is a genetic disorder that affects the production of melanin, the pigment that colors skin, hair, and eyes. It's a lifelong condition, but it does not get worse over time (OpenStax, 2018). People with