The skin is the largest organ in the human body, and is a part of the integumentary system. In an average human being, the skin has a total surface area of about 1.5 to 2.0 square meters. For cosmetic reasons, it can be said that the skin is one of the most pampered organs in the human body. A clear, glowing skin is always admired for its appearance. A healthy skin performs various vital bodily functions.
Layers of the Skin
The human skin is made up of three layers - the outermost epidermis, followed by dermis, and the innermost hypodermis. The epidermis is made up of keratinocytes, melanocytes, Langerhans cells, and Merkel cells. This layer lacks blood vessels, and so, it gets nourishment from the superficial layers of the dermis. The layer beneath the epidermis is called dermis, and this layer is attached to the former by a basement membrane. The dermis has nerve endings, blood vessels, hair follicles, sebaceous glands, and lymphatic vessels. The hypodermis that lies beneath the dermis serves the purpose of attaching the other skin layers to the underlying bones or muscles. It is this layer, that contains a major part of the body fat. While epidermis plays a vital role in the function of maintaining body temperature, and in providing a waterproof outer covering; the dermis with connective tissues, protects the body from stress and strain. The hypodermis with fat provides insulation, and also cushions the inner parts.
- Protects the body: As the skin is exposed to the environment, it comes into contact with pathogens and other toxins. The Langerhans cells in the skin are responsible for destroying such pathogens. The skin protects the body from radiation and chemicals.
- Identifies sensations: It is a common fact that the skin is responsible for the sensation of touch. This is because of the presence of numerous nerve endings, that react to sensations, like pressure, pain, heat, and cold.
- Regulates Temperature: One of the important functions of the skin is maintaining the normal body temperature. This is accomplished with the help of sweat glands, that expel waste products as well as water, so as to cool the body. The fat in the dermis provides insulation from cold. Even dilation of the small blood vessels in the skin results in cooling of the body. Likewise, constriction of these blood vessels reduce heat loss from the body.
- Controls Evaporation: The skin also prevents loss of water and nutrients from the body, through evaporation, as it acts as a barrier.
- Absorbs Substances: The skin can also absorb small amounts of oxygen, carbon dioxide, and nitrogen. Some medicines are meant for absorption through the skin only.
- Produces vitamin D: While the skin stores water and lipids, this organ can also synthesize vitamin D, when it is exposed to sunlight.
- Excretes wastes: The skin performs excretion of urea, water, uric acid, and ammonia, in small amounts, through the sweat.