What is Skin?

Skin is the body's biggest organ. When people think of organs, most often the heart, lungs and brain come to mind but typically not the skin. Like these and other organs inside the body, skin is made up of different types of tissues and these tissues are made up of cells.

Much like the roof on a house, the skin plays an important role in protecting our bodies. It keeps bodily fluids inside while at the same time carefully controlling the release of waste product. It also helps keep our internal body parts safe from the potentially harmful effects of the environment including the sun, light and bacteria and also from injury.

Several different layers make up the skin, but perhaps because the underlying layers are not visible, they're not thought of very often. We spend much of our lives worrying about acne and wrinkles but don't realize that these types of skin issues have a lot to do with the workings of the layers below.

If you were to look at a cross-section of skin, you'd see that skin consists of 3 different layers: the epidermis, the dermis and the hypodermis or subcutis layer. Let's take a closer look at each.

Epidermis

This is the outermost layer of skin - the one that is visible. It covers the entire body, from the head down to the feet. The epidermis itself consists of 3 layers and is made up of tightly-woven connective tissues of varying thickness. For example, the skin covering your feet is much thicker than that below the eye. The epidermis acts like a barrier, keeping the good in and the bad out.

The top layer of the epidermis is constantly being shed. It's the layer that acts as the gatekeeper keeping fluids in and dangers out. Although not easily visible, most of this layer is covered with thousands of tiny pores and hair shafts. New skin is continually being generated by the bottom layer to replace the skin that has been shed. The epidermis also contains melanin, the cells responsible for skin pigmentation (coloring) and protecting against the sun's damaging rays.

Dermis

This layer of connective tissue tucked in between the innermost and outermost layers is the site of much activity. The dermis is home to blood vessels, lymph vessels, nerve tissue, hair follicles, bundles of collagen and sweat glands. Much activity happens in the middle layer. Blood vessels supply nutrients. Nerve tissues give skin the ability to feel. And the muscle tissues in this layer when they are activated are what cause a person to develop goose bumps in response to cold or fear. This layer also has the ability to trap bacteria that manages to penetrate the epidermis.

Hypodermis or subcutis layer

The innermost layer of skin helps to regulate our body temperature. It is here that insulating fat and collagen can be found which is why this layer helps keep us warm. This layer also acts as a cushion or shock absorber, protecting the body from injury. The connective tissue that makes up this important layer is also known as adipose tissue.