Skin

Skin, which is, surprisingly, the largest human body organ, is located on the outside of the body of humans and other animals. It is a protective, sensory, and endocrine organ. Accumulating evidence also suggest it has a critical role in the whole body's homeostasis. Historically, skin color has also been, and often still is, a pretext for arbitrary distinctions between peoples, i.e. racism.

According to oriental medicine, the skin is composed of acupoints regulating the interaction of the body with the universe, and of a complex network of meridians coordinating the flow of Ch'i (Qi).

Physiology

By convention, the skin is divided into two subcomponents: the dermis and the epidermis.

Dermis

The protein content of the dermis is 90% collagen, or 75% of the total skin weight; the other major component is elastin, which provides elasticity to the skin.

Epidermis

(...) Drugs, physiologic molecules and pollutants can penetrate the body through the skin, in proportion to their lipophilicity (their affinity to fats).

In oriental medicine

Oriental philosophy views the body as a microcosm interacting with the macrocosm (the "outer" universe). Meridians and acupoints located in the skin are viewed as agents of this interaction. Although the scientific basis for acupuncture is unclear and its potential clinical uses are debated (see acupuncture for details), neuroimaging studies suggest that at least some points on the skin are distinct entities consistent with the oriental tradition (see acupuncture point for details).