Skin is the outermost organ that protects and incases the tendons, ligaments, bones, muscles, etc. It is also the largest organ of the human body.

Formation and Orientation

Healthy skin consists of vitamins A, C, D and E, but in all skin, there are melanocytes which produce mesodermal cells. These cells allow for the absorption of UV rays. There are five main pigments that provide color in the skin’s many levels. Although not found in the skin, Oxyhemoglobin is found in the blood, causing a red coloration. Hemoglobin is also found in the blood but gives off a purple color. Melanin and melanoid are both found in the epidermis and give a brown color. Keratin is in the fat cells of the dermis (skin), the superficial fascia, and stratum corneum, giving off a yellow or orange color.

It has been estimated that there are anywhere from 50 million to 500 billion bacteria on one square inch of skin. There are two types of skin; glabrous and hairy skin. Each provides a different environment for microbes. The type of skin flora present is dependent on the area; moist, dry, sebaceous. In moist areas, such as the underarms, corynebacteria and staphylococci are prevalent. In dry areas like forearms, there are mainly b-proteobacteria and flavobacteriales. In the areas around the nostrils and around the back (sebaceous areas), propionibacteria and staphylococci are dominate. Along with these bacteria, yeast grows on the surface of the skin. Throughout the day, dead skin cells mix with sweat, dust and other sebaceous gland secretions. This makes it easier for skin to become damaged, infected and unhealthy.

Skin is made of three layers. The epidermis consists of five sub-layers; stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and the stratum germinativum. These layers work to weather-proof and protect the body’s contents as it is the outermost layer of the skin. The dermis cushions the body and its appendages from stress and strain with connective tissues. The hypodermis is used mostly for the storage of water and lipids (fats).


Skin works to protect the body from external forced. The countless nerve endings present in the skin work to sense temperature, pressure, pain and vibration. The skin also works to maintain homeostasis. When overheated, the sweat glands excrete sweat in order to cool the body. When cold, the skin produces a twitch giving the sensation of “goosebumps”. The skin stores water and lipids, while working to absorb vitamin D. The skin has a resistance to water that prevents essential nutrients from being washed out of the body. Because of the skin’s low permeability, toxins are prohibited from touching tissues hidden away in the body.

Image Caption: Anatomy of the human skin. Credit: US-Gov / Wikipedia