Four organ systems work to remove wastes from the body: the integumentary system (skin), the respiratory system (lungs), the digestive system (liver) and the urinary system (kidneys and bladder). Together, they comprise what is known as the excretory system functioning to maintain homeostasis, the stability of the body's internal environment. During the process of metabolism, the body produces fuel to keep it functioning in a state of health. Substances that cannot be used, such as toxins and the byproducts of metabolism, are eliminated via the excretory organs. Of the four excretory systems, skin plays the smallest role, but it is vital to our survival.
Skin
Most people do not realize that skin is an organ---the largest and heaviest organ in the body as per the Internet FAQ Archives for Online Education in its article, "The Integumentary System." Skin not only provides a protective covering for the body, but it also plays a small role in the excretion of metabolic wastes through perspiration.
Perspiration
Perspiration is a continual process serving to cool the body when it becomes overheated. It generally goes unnoticed unless it occurs as the result of excessive muscular activity or emotional stress, at which time the flow increases. "The Integumentary System" also states that perspiration serves as a means of elimination for metabolic wastes composed of water, which makes up the largest portion, salts and urea. The source of perspiration is the eccrine sweat glands.
Eccrine Sweat Glands
Skin contains approximately 2.5 million sweat glands located in the dermis, the second layer of skin that lies beneath the outer layer, the epidermis. They are coiled tubes with a straight portion extending outward and ending at the opening of one of the pores located in the epidermis. The blood vessels in the dermis release extracellular fluid, the fluid that surrounds the cells, that is absorbed into the sweat glands. This fluid containing metabolic wastes makes its way through the coils and up the tube to exit the body as perspiration.
Epidermis
The University of Virginia School of Medicine states that the epidermis, the outer layer of skin, lacks a blood supply and must obtain its nourishment from the dermis, the inner layer of skin. This epidermis is waterproof as the result of an insoluble protein, keratin, manufactured by cells contained within this layer of skin. Pores, small openings in the skin's surface, provide the means for perspiration to be released from the body to regulate its temperature and eliminate wastes.
Dermis
The dermis, the second layer of skin, contains hair, sweat glands, blood vessels and nerves, according to the University of Virginia School of Medicine. In addition to its function as the source of nourishment for the epidermis, this layer of skin also helps, through its vascular system (blood vessels), to regulate body temperature as well as being the location of the eccrine sweat glands that function as part of the skin's excretory system.
Tags: layer skin, sweat glands, blood vessels, metabolic wastes, dermis second