Function of the skin

Functions of the integumentary system

The integumentary system plays an important role in protecting the body from the outside world. Healthy skin is a strong and resilient protective barrier. Skin and its accessory structures help the body to maintain homeostasis. The body is constantly being exposed to environmental threats which include:

Primary functions of the integumentary system

The primary function of skin is to provide protection for all of the underlying tissues. It is a waterproof and insulating shield that creates a physical, chemical, and biological barrier to the outside world. Skin provides protection against injury and infection, and serves as storage of fat that can be used for fuel.

Physical barrier
Intact skin is one of the body’s best defenses against injury and infection. Skin creates a physical barrier primarily due to the keratinized cells. These cells in addition to glycolipids create a waterproof surface that also protects the body from water loss (dehydration). Hair protects the scalp from UV radiation. The adipose of the hypodermis protects the body from temperature changes. Epithelial tissue of the skin is able to heal after being injured.

Chemical barrier
Skin serves as a chemical barrier to infection due the secretions like sebum that creates a slightly acidic surface which slows down growth of foreign bacteria. The chemical pigment melanin creates UV protection.

Biological barrier

The skin provides protection from infectious organisms. Langerhans cells are a type of dendritic cell that protects the body from infection. Skin also contains phagocytic cells and skin flora which protect the body from pathogens.

The integumentary system has cutaneous sensory receptors for detection of pain, temperature, pressure, vibration and movement.

The integumentary system helps the body to maintain an optimal temperature through thermoregulation. The dermis layer contains the majority of the blood vessels of the skin, and is able to assist with thermoregulation. Adipose tissue in the hypodermis also serves as an insulator.

The skin can help the body to dissipate heat and cool down by dilating the superficial blood vessels (arterioles) to lose heat through evaporation. Dilating of blood vessels is called vasodilation. This is why skin becomes flushed when hot. This process is assisted by sweat which speeds up the evaporation process.

When the body is cold, the blood vessels constrict (vasoconstriction) in order to reduce heat loss. The arrector pili (erector pili) muscle will cause the hair to stand up. It is involuntary skeletal muscle tissue attached to the hair follicle. This creates more of a dead air space around the body to slow heat loss through evaporation and creates goosebumps.

Other ways that the integumentary system can help the body with thermoregulation includes using thermoreceptors in the skin to detect cold or heat. This sends a message to the nervous system to respond accordingly. This response could include:

Long-term exposure can also produce adaptive changes within the skin to help with thermoregulation. For example, people living in higher latitudes will develop more blood vessels at the extremities to prevent frostbite. People living in hot climates will develop more efficient cooling mechanisms. This can occur over a timeframe of hours to weeks in a process called acclimatization. And it can occur over generations in a process called adaptation.

Even though the skin is waterproof due to keratin and skin oils, some substances can pass through the skin. The skin can absorb fat soluble molecules, organic solvents, resins from certain plants and topical medications. The skin is able to assist the body with eliminating some waste materials like ammonia, urea and excess salts and water by sweating.

The integumentary system works with the immune system to protect the body from infection. Skin has dendritic cells called Langerhans cells in the epidermis. These cells are a type of white blood cell that triggersimmune reactions. Secretions from the sebaceous glands (sebum) reduce surface bacterial growth by creating a slightly acidic environment. The surface of healthy skin has a layer of microorganisms called skin flora or skin microbiota. These microorganisms are usually bacteria or fungal, and are either not harmful, or are beneficial. They colonize the skin so that foreign microorganisms have a hard time taking over.

Skin can synthesize vitamin D when exposed to sunlight. Vitamin D is a fat soluble vitamin that regulates the levels of calcium and phosphate in bones. It is also a hormone that regulates calcium absorption from dietary sources.