The Amazing Human Skin


By Joe Spivak

Quick question: What is the largest organ of the human body? If you said 'the skin', give yourself a +1. The skin, consisting of the epidermis, dermis and subcutaneous fat layer (hypodermis), is the largest organ of the human body... and arguably one of the most vital to your survival.

In a recent article, scientists outlined some critical functions of the skin. They are: diagnosis of disease, olfactory function, elasticity, temperature regulation, protection and immunity.

Health Monitor

The skin can be a very powerful indicator of an individual's health. Skin should be "warm, pink and elastic" to the touch. Pinch yourself. Go ahead, not too hard though. Did you notice how your skin turned white for a couple seconds and then returned to its natural color? That is called 'capillary refill' and it is a technique used to quickly assess a person's cardiovascular function. Two-to-three seconds indicates your heart and lungs are working efficiently. Any longer, and well, you should probably stop reading this and seek medical attention.

Olfactory Function

Who 'nose' what that means? That's right, scientist have shown that olfactory receptors embedded in the skin can help you perceive odors (smell) in your environment.


Ever wonder where your little brother or sister came from? Me too, although I am betting on Mars for my little sister. Anyway, skin has an amazing ability to stretch. This is best seen in a pregnant woman's belly. The elastic fibers that slowly stretch prevent the skin from tearing and allow it to bounce back after nine months.

Temperature Regulation

It only takes a few minutes of kickball before you notice the sweat starting to form on your skin. The dilation of blood vessels in response to heat allows water to escape the body as sweat. The water then evaporates from the skin, cooling the body as it does. Did you know you can sweat up to three gallons of water per day? It is a good thing, without it, you wouldn't last long in the summer heat!

Protection and Immunity

Arguably your skin's most important function is protection: from the sun, microbes and viruses. Your skin forms what is called 'The Primary Line of Defense' and is both a mechanical and chemical barrier against the world. You are constantly under assault from UV rays, bacteria and parasites. Your skin keeps them from harming you. Sebaceous glands in the skin secrete protective anti-bacterial oils, melanin blocks UV rays and skin continuity prevents harmful pathogens from entering your body.

Yep, the skin is a pretty amazing feat of biology. It protects you, keeps you cool, can indicate your overall health and, oh yeah, we would look pretty weird without it!

Classroom Discussion

  • How is the skin a chemical and mechanical 'primary line of defense'?
  • Can you think of any more functions of the skin? Communication? What diseases can it help diagnose?