The Human Body: Skin Biology and Structure

Organs are groups of tissues that work together to achieve a special purpose. Organs keep the body functioning and maintain life. Your skin is considered an organ, and its purpose is to protect the body from outside contaminants such as germs and pollution. The skin also helps keep your body temperature consistent, receives and processes sensory information, and stores fat, water, and vitamin D.

Most researchers agree that the skin is the largest organ. Skin covers the entire body, making up approximately 16 percent of the body’s total mass. Recently, some scientists have changed their thinking about the classification of organs and have shifted to calling the interstitium the largest organ in the body. This would make the skin the second-largest organ in the body. The interstitium contains fluid-filled spaces in flexible connective tissues, and this network exists beneath the skin, around arteries and veins, and in the linings of the lungs, digestive tract, and urinary system. Not all scientists agree about the classification of the interstitium as an organ, however.

The three layers of the skin, beginning with the outside layer, are the epidermis, the dermis, and the subcutaneous or hypodermis tissues. The epidermis doesn’t contain any blood vessels, so it relies on the dermis to deliver nutrients and get rid of waste. The epidermis is made of skin cells that are held together by lipids. The epidermis is the physical and biological barrier that prevents allergens and irritants from penetrating into the body. The epidermis also prevents the loss of too much fluid. The dermis is thicker than the epidermis and lies immediately under it. The dermis supports the epidermis, further protecting, cushioning, nourishing, and helping to heal wounds when they occur. The dermis contains nerve endings and hair roots, and this layer is also where sweat glands and blood vessels are. Below the dermis lies the subcutaneous layer that is made mostly of fat. This is where the main support and structure for the skin comes from, and this layer also helps insulate the body from cold. The subcutaneous layer has both nerves and blood vessels in it.

The skin is a fascinating organ. There are six main types of skin, ranging from fair to dark, and melanin is the pigment in the skin that determines skin’s color. Skin color is mostly determined by a person’s genetics. The skin cells produce melanin with exposure to the sun, so the more skin is exposed to the sun, the more melanin the skin contains.

Sebaceous glands are present around hair follicles, and the scalp and face have the highest concentration of sebaceous glands. In fact, the face may have up to 900 sebaceous glands in every square centimeter of skin. At puberty, the sebaceous glands begin producing more sebum, which tends to cause acne. Sometimes, people also have health conditions that make sebaceous glands more active. If oily skin is a problem, it may help to see a physician. Some medications are available by prescription that can help lower sebum production.

As a person ages, their skin starts showing signs of aging, including sagging, wrinkles, and dark spots. This happens naturally, but it can happen earlier for people who have overexposed their skin to ultraviolet radiation on a regular basis. The dermis layer contains special proteins that help keep the skin supple and smooth. With aging, the body produces lesser amounts of these proteins, which reduces elasticity of the skin. The amount of fat in the hypodermis also shrinks with aging, which contributes to saggy skin.

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