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Skin: Layers of Skin, Functions, Disease, and Layers of skin


The biggest organ of our human body is the skin accounting for approximately 16% of total body weight. The skin protects us from pathogens i.e. bacteria, fungi, UV radiations, and restricts the loss of fluid and electrolytes. Along with that it also plays an important role in the maintenance of temperature via the process of thermoregulation.

What are the functions of skin?

Following are some important functions of the skin:

  1. To protect us from mechanical trauma, pathogens, and ultraviolet radiations. 
  2. It also prevents fluid and electrolyte loss.
  3. To balance the fluid and electrolyte level.
  4. Maintains the temperature via thermoregulation.
  5. Give the sensation of pain, pressure, and temperature using sensory receptors.
  6. The skin is also involved in the synthesis of vitamin D.

The Production of Vitamin D:


The skin starts producing vitamin D in the presence of sunlight. Vitamin D is then converted into Calcitriol in the liver and kidneys. Calcitriol monitors the production of calcium and phosphorus in the body. These both are the building blocks of the bones. 

Calcium is very important as it is associated with the normal functioning of the nervous system, maintenance of bone density as well as bone growth, insulin secretion, immune system, cell proliferation, and blood pressure.  

What are the causes of skin disease?

Sunlight contains three types of ultraviolet radiation and these are responsible for skin diseases. These radiations are UVA, UVB, and UVC.

UVA: Among all three types, UVA is the most common and responsible for skin aging and wrinkling.

UVB: These rays cause sunburns, cataracts, and damage the immune system.

UVC: These are the most dangerous among all the sunlight radiations and are absorbed by the ozone layer.

Ultraviolet radiations are good or bad?


All three types of UV radiations are responsible for damaging the collagen fibers and thus boost skin aging. Vitamin is damaged with the striking of UVA and UVB. UVA is also responsible for skin cancer, and along with UVB, UVA can also destroy vitamin A.

How skin fights with UV radiations: 

To guard against the UV radiations, the skin uses melanin pigment which absorbs the  UV radiations and resisting it from damaging the skin tissue. The quantity of melanin increases in the skin when exposed to UV radiation and this process is called suntan. 

Layers of the skin: There are three layers of skin.

  1.  Epidermis
  2.  Dermis
  3.  Hypodermis

Epidermis: The top layer of the epidermis is composed of epithelial cells usually keratinocytes. None of the blood vessels is present in the epidermis. It gives protection and absorbs nutrients. It is also involved in homeostasis. 

What are the layers of the epidermis?

The epidermis also has five layers and these are: 

  1.  Stratum Corneum
  2.  Stratum Lucidum
  3.  Startum Granulosum
  4.  Stratum Spinosum
  5.  Stratum basale.

What are the cells of the epidermis? 

There are five types of cells present in the epidermis and these are: 

  1.  Squamous cells 
  2.  Basal cells
  3.  Melanocytes
  4.  Langerhan's cells
  5.  Markel cells

Dermis: Dermis is a vital part of the skin and is also called true skin. The dermis contains two layers, which are composed of collagen and elastin fibers. Collagen gives strength to the skin whereas elastin makes the skin flexible. These layers are:

  1.  Papillary Dermis
  2.  Reticular dermis.

Papillary Dermis: Papillary dermis is the top layer of the dermis containing the capillaries which give nourishment. The pain and touch receptors are also there. With the unique pattern of the papillary dermis, we can identify the fingerprints of each individual.

Reticular Dermis: The sweat glands, hair follicles, nerves, and blood are present reticular dermis. 

What are the functions of the dermis?

The six important functions of the dermis are: 

  1. Supply the nutrients i.e. blood, and oxygen 
  2. To restrict the shearing force 
  3. To lubricate the skin
  4. To give the inflammatory response
  5. To protect muscles, bones, and other organs
  6. To retain the moisture.

What are the contents of the dermis?

  • The contents of the dermis are: 
  • Sebaceous glands producing sebum or oil.
  • Sweat glands
  • Bases of hair follicles.
  • Specialized nerve cells i.e. Meissner's corpuscle, Pacinian corpuscles, Ruffini corpuscle, Krause's end bulb, Free nerve endings.

Hypodermis:

The hypodermis is a build-up of connective and fatty tissue which is at top of the muscles and lie directly underneath the dermis. The vessels, nerves, and lymph channels are present here. 

What are the functions of hypodermis?

The three important functions of hypodermis are: 

  1. To store the energy in adipose or fat tissue.
  2. To anchor the skin.
  3. To give the protection and isolate from the external environment.

how we can assess the skin?

To assess the skin, we use these five parameters:

  1. Temperature 
  2. Color 
  3. Moisture 
  4. Turgor 
  5. Integrity

Temperature: The temperature of the skin is usually warm. If the temperature is warmer than normal then these are signs of inflammation. If the temperature is cooler than normal, then these are the signs of poor vasoconstriction. 

Color: The pale color indicates poor circulation. The variation of melanin deposits or blood flow are the reflections of hyperpigmentation and hyperpigmentation. If the palm of the hand is pale and warm then these are the signs of anemia and if the hands are cold the these are the signs of vasoconstriction. 

Moisture: We can diagnose the skin disorder while touching the skin to check whether it is dry or moist. The dryness will indicate hyperkeratosis, whereas the moisture indicates eczema and inflammation of the epidermis. 

Turgor: The skin turgor is the elasticity of the skin. Skin with poor turgor takes too much time to return back to the normal position, and that indicates dehydration or aging. High turgor skin comes back to its original shape within seconds. 

Integrity: Integrity means the health of the skin. With aging, the skin loses its integrity and likely causes a pressure injury. 



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