Skin - The integumentary system

What you need to know about our largest organ?

Well we all know that an onion has several layers......so does our skin.  Our skin mightn't have as many layers as an onion but each layer has a specific role.


Like an onion we start with an outer layer that is our protective layer which can be smooth or flaky depending on our age or what we have been exposed too.


The most outer layer is the epidermis which is about 20-30 cells thick. The part of the epidermis that is exposed to the external environment,  is composed of 15–20 layers of flattened cells with no nuclei and cell organelles. These are dead cells form a barrier to protect underlying tissue from infection, dehydration, chemicals, and mechanical stress. 


Within the epidermis there are also special cells that are part of your immune system to further protect you from external invaders like bacteria, fungi, and viruses.


The last main function of the epidermis is to make new skin cells. This happens at the very bottom of the epidermis. The skin cells travel up to the top layer and flake off, about a month after they form.


The second layer is the dermis layer. It is made up of tough connective tissue as well as different types of cells and glands that have many important functions.


First, the dermis contains blood vessels that provide nourishment and waste removal for both dermal and epidermal cells.


During wound healing, these blood vessels dilate in order to deliver nutrients and immune cells to the wound site in order to facilitate healing. When this happens, you will notice signs of inflammation, such as swelling, redness, and warmth.


The dermis also contains hair follicles, sweat glands, sebaceous glands, and nerves. 


  • Hair follicles are the root of each hair on your skin. Each root attaches to a small muscle that tightens and gives you goose bumps when you are cold or scared.
  • Sweat glands produce sweat that travels up tubes and comes out of the pores on the surface of skin. Sweating keeps you cool and helps you get rid of bad stuff your body doesn't need. 
  • Sebaceous glands secrete sebum (oil) in order to keep your skin soft, smooth and waterproof.
  • Nerve endings in the dermis that help you to feel things by sending signals to your brain including sense of touch and sense of heat.


Lastly, the dermis contains a structural network of collagen and elastin fibres embedded in an extracellular matrix. 


This is what gives the skin strength as well as elasticity. Scars form as a result of damage to this layer of skin. 


When the skin is wounded, collagen and elastin fibres must regenerate in order to seal the wound, and the extracellular matrix must be remodelled.


The third layer, hypodermis, also referred to as the subcutaneous tissue, is made up of fat and connective tissue This layer plays many important roles in your body. 


  1. It has a special connecting tissue known as fibrous bands that attach the dermis to your muscles and bones. There are also collagen and elastin fibers that attach this layer of skin to the dermis.
  2. It stores fat. While many people seek to rid their bodies of fat through diet and exercise, our body does need some fat to act as padding and as an energy reserve, as well as providing some minor thermoregulation via insulation.
  3. The blood vessels and nerve cells from the dermis extend into the hypodermis, although they are larger in the hypodermis and continue on to the rest of the body.

It also functions to insulate the body to maintain body temperature. 


When dermis is richly supplied with blood vessels, sweat and oil glands, and nerve endings our skin is smooth, with no breaks in the surface. It is warm (not hot or red) and neither dry and flaky nor moist and wrinkled. Healthy skin is a mirror of a healthy body.


The most common causes of unhealthy skin stem from chronic dehydration, poor nutrition and poor blood flow. Combined, these factors reduce the oxygen and nutrient delivery to the inner layers of the skin.


Your skin is a natural detoxifier. If its not getting the oxygen and nutrients it needs then it cannot do this function properly. This means your cells are constantly fighting to get rid of the bad stuff.

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