A voyage through our skin

Skin is the human body’s biggest organ. What does it mean? 
It means that skin is 4 to 6% of the body weight and an adult carries about 8 pounds or 3,6 Kg and 22 square feet or 2 square meters of it. 

Skin has important functions 

  • BARRIER FUNCTION against microorganisms, ultraviolet radiation, and some environmental pollution. 
  • PROTECTION from impact, infection and dehydration. 
  • SYNTHESIS molecules and some vitamins. 
  • THERMOREGULATION 
  • SKIN SENSATION
  • EXCRETION AND ABSORPTION.

When you think about your skin, first think about these 3 layers

  1. Epidermis
  2. Dermis
  3. Hypodermis 

These three work in synergy to keep us well-protected. 

EPIDERMIS - The skin’s first layer. 

Epidermis

It consist of trees different and important types of cells. 

1. KERATINOCYTES 
Keratinocytes represent the major cell type of the epidermis, the outermost of the layers of the skin, making up about 90 percent of the cells there. They originate in the deepest layer of the epidermis, the stratum basale and move up to the final barrier layer of the skin, the stratum corneum. There, keratinocytes are found as nucleus-free, flat, and highly keratinized squamous cells 
FUNCTIONS: They play an essential role in protection, as they form a tight barrier that prevents foreign substances from entering the body, while minimizing the loss of moisture, heat, and other constituents. These cells have also a structural role, forming tight bonds with the other cells in the epidermis and maintaining them in their locations. In addition, keratinocytes function as immunomodulators following skin injuries.
2. MELANOCYTES
Make the pigment Melanin. This chemical is what makes the skin tan. A melanocyte produces the pigment then injects particles of it into the cytoplasm of adjacent keratinocytes. These melanin particles cluster together and absorb the sun’s rays as they pass through the upper layers of the epidermis. They then form a protective shield over the keratinocytes. 
3. LANGERHANS CELLS 
Form about 2-4% of the total cells in the epidermis; these cells are very important for the immune defence system of the body. When foreign materials come into contact with the skin, the tentacles of the langerhans cells stick to any particles of foreign matter. They then carry them to other parts of the body. 

DERMIS - The second skin’s layer 

DERMIS

The dermis is a connective tissue layer sandwiched between the epidermis and the hypodermis. It is a tough elastic layer which houses blood vessels, sensory nerve endings, hair follicles, and sebaceous glands. The role of the dermis is to support and protect the skin and deeper layers, assist in thermoregulation, and aid in sensation. There are fewer cells in the Dermis than the Epidermis, but its principal is the Fibroblast which are elastic fibers that make the Collagen. 

The dermis has 3 mains functions 

  • Skin Support and Protection

The structure of the dermis provides a connective tissue framework for strength, flexibility, and protection of the deeper anatomical structures. Collagen and extracellular components like hyaluronic acid fortify the skin. Elastic tissue also helps support the skin and provide flexibility. The blood vessels in the dermis are crucial for maintenance of the epidermis and epidermal appendages. Nutrients via blood support the epidermis, hair follicles, and sweat glands. The dermal blood supply also plays a role in temperature regulation. 

  • Thermoregulation

Vasoactive dermal vessels regulate body temperature. Specialized structures called glomus bodies also take part in thermoregulation. Glomus bodies are complexes of glomus cells, vessels, and smooth muscle cells that predominate in the digits, palms, and soles.

  • Sensation

Nerve endings in the dermis surround hair follicles. These nerve endings sense hair movement and act as mechanoreceptors allowing sensation to extend beyond the skin's surface. 

HYPODERMIS the third skin’s layer.

HYPODERMIS

It is the innermost and thickest layer of skin and also known as the subcutaneous layer or the subcutaneous tissue. This layer contains the root of our hair, larger nerves and blood vessels but also fat, the fat that concerns people when they are trying to keep their weight under control. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma.
The hypodermis also has a special connecting tissue that attaches the dermis to our muscles and bones.