The Integumentary System: Your Skin, Hair, Nails, and Glands

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The integumentary system is made up of several organs and structures including the skin, hair, nails, glands, and nerves. The primary function of the integumentary system is to protect the inside of the body from elements in the environment—like bacteria, pollution, and UV rays from the sun.

The skin and its associated structures also retain bodily fluids, eliminate waste products, and regulate the body’s temperature. The integumentary system works with all other bodily systems—such as the nervous, cardiovascular, and digestive systems—to accomplish all the jobs it performs in helping to maintain the stability of the internal body. 

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Anatomy of the Integumentary System

The integumentary system includes:

  • Skin
  • Hair
  • Nails
  • Exocrine glands
  • Sensory nerves

Skin

The skin is the largest and heaviest organ of the body. To function as a protective barrier, it must cover the entire outside of the body, from the top of a person’s head to the end of the toes. The skin is approximately 2 mm (0.079 inches) thick and in its entirety weighs nearly 6 pounds.

Although there may be some differences in the skin from one person to another (such as the color, texture, and thickness), all skin has a few primary similarities. For example, every person’s skin is comprised of different types, including:

  • Thick and hairless: Located on body parts that are frequently used and involve a lot of friction (such as the soles of the feet and palms of the hands).
  • Thin and hairy: The most predominant type of hair on the body, located everywhere, except areas covered by thick and hairless skin.

Layers of the Skin

There are two layers of the skin:

  • The epidermis: The outer layer of the skin that makes up its strong protective covering.
  • The dermis: Located under the epidermis; most of the structures of the skin are located in the dermis (such as various types of glands and hair follicles).

The fatty layer of the skin is a layer of subcutaneous (under the skin) tissue, also known as the hypodermis. The fatty layer serves many different functions, including:

  • Providing a cushion for the skin
  • Storing fuel for the body (in the form of fat cells)
  • Insulating the body, helping to maintain its stable temperature

Hair

Hair serves to:

  • Help protect the skin
  • Regulate body temperature
  • Lend itself to the evaporation and perspiration process
  • Help with the nerve sensing functions of the integumentary system

Hair is primarily comprised of a fibrous protein and contains a very small amount of lipids (fats) and water. Hair comes from follicles, which are simple organs made up of cells called epithelial cells. Epithelial cells are the cells that line the organs and function to provide a protective barrier. 

Nails

Just like other body parts, nails consist of several segments, including:

  • The nail plate: The part of the nail that is visible.
  • The nail bed: The skin that lies beneath the nail plate.
  • The cuticle: The thin line of tissue that is located at the base of the nail and overlaps the nail plate.
  • The nail folds: The folds of the skin located on the sides of the nail plate.
  • The lunula: The white-colored half-moon-shaped area located at the base of the nail plate.
  • The matrix: Part of the nail that is not visible, located underneath the cuticle, this is the area responsible for the growth of the fingernail.

The function of the nail is:

  • Protection: Protects the fingers and toes from injury or trauma.
  • Sensation: Assists with the sense of touch.

Glands

The integumentary system has four types of exocrine glands, which secrete some type of substance outside the cells and body.

The four exocrine glands associated with the integumentary system include:

  • Sudoriferous glands: Sweat glands that are hollow, cylindrical structures under the skin; they excrete sweat via very small openings at the skin’s surface. The purpose of sudoriferous glands is to emit perspiration to help cool the body off when the body temperature rises.
  • Sebaceous glands: Very small tubular-shaped glands, located in the dermis, which are responsible for releasing oil into the hair follicle to help lubricate and protect the hair shaft, keeping it from becoming hard and brittle. 
  • Ceruminous glands: Located in the ear canal, ceruminous glands function along with sebaceous glands to produce ear wax (medically coined cerumen). Cerumen is important in its role as a protective mechanism, keeping foreign invaders (such as bacteria and fungus) at bay and guarding the ear against any type of physical damage.
  • Mammary glands: There are two mammary glands located one at each side of the front of the chest wall. Both men and women have mammary glands, but in men, these glands are underdeveloped. In females, the glands function to produce breastmilk after giving birth. The mammary glands are semicircular in shape in young females, but later the glands begin to lose their shape. A single mammary gland weighs about 500 to 1000 grams (1.1 to 2.2 pounds).

Function of the Integumentary System

Overall, the integumentary system functions to guard the body, providing a barrier to infection and shielding the body against temperature changes and the adverse effects of potentially harmful substances (such as UV light).

The integumentary system has many specific roles in its involvement in helping to protect and regulate the body’s internal functions, Here are some ways that the skin, nails, hair, glands, and nerves of the integumentary system work:

  • Helps to protect the body’s tissues and organs
  • Protects against infections and foreign invaders
  • Keeps the body from becoming dehydrated (by storing water)
  • Helps to maintain a stable body temperature
  • Transports and gets rid of waste materials
  • Performs a receptor job for pressure, pain, heat, cold, or touch
  • Stores fat for a source of energy
  • Protects the body from trauma and serves as a shock absorber (due to the fatty layer of the integumentary system).
  • Protects the skin from damage caused by UV light from the sun (and other sources)

Protection From Injury

The skin is made up of a very tough type of protein called keratin that is the primary type of skin in the outermost layer, the epidermis.

Keratin helps protect tissues, organs, and structures from injury, like:

  • Cuts
  • Scratches
  • Abrasions

Fatty Layer Protection

The fatty layer of the skin helps protect against trauma to the underlying tissues and organs by serving as a shock absorber, buffering some of the impact of some types of injuries (such as those caused by blunt force).

Protection Against Infection

The skin creates an acidic pH environment in which microorganisms find it difficult to grow, therefore protecting from infection.

Protection With Sweat

Sweat from the sweat glands prevents an overgrowth of microorganisms on the skin by producing a substance called dermcidin, which is an anti-infective agent that has natural antibiotic properties.

Many different types of microorganisms encounter the skin, but these organisms are not able to penetrate healthy skin. However, when a cut or other injury that causes an opening in the skin occurs, the organisms on the skin are no longer harmless as they enter the skin’s barrier.

This may trigger the skin’s inflammatory response. The inflammatory response prompts the transportation of white blood cells and other cells—called macrophages—that engulf the invading organisms. 

Protection Against Ultraviolet Rays

Not only does the skin provide a very strong barrier against infections in the body, but it also prevents damage to the body from certain harmful substances, such as ultraviolet (UV) light from the sun (or other sources, such as tanning beds).

The skin responds to UV rays by producing the pigment melanin in cells called melanocytes. If overexposure to the sun occurs, inflammation occurs and the skin becomes reddened and flushed in response to dilatation of the blood vessels in the dermis. As melanin is produced, the skin begins to tan; the melanin absorbs the UV light, preventing damage to the DNA of the cell. 

How Hair Protects Your Skin

One study found that hair also provides a barrier against both UVB and UVA radiation. The study discovered that the more thickness and density a person’s hair was, the more protective the hair was in providing a better barrier against UV radiation.

Maintenance of Body Temperature

One of the most important functions of the skin is to help maintain the body’s core temperature.

The center in the brain that helps regulate temperature—called the hypothalamus—prompts skin changes in response to a change in the body’s internal temperature.

The vast blood supply in the skin can help regulate temperature; as the blood vessels dilate, it allows for heat loss. When the vessels constrict, heat is retained. This process lends itself to the regulation of the body’s core temperature.

Sensory Nerves

Sensory nerves are abundant in the top layer of the skin (the epidermis); these nerves transmit feelings of:

  • Pain
  • Heat
  • Other sensations experienced by the skin

Sign of Malfunctioning Sensory Nerves

When sensory nerves in the skin malfunction, the result is often a tingling feeling or a burning sensation.

The dermis contains nerve endings and an array of touch receptors. This allows the dermis to detect sensations such as pressure, heat, cold, and contact.

The nerve endings in the dermis detect sensations, and thus play a role in the protection of the skin, by sounding an alarm when the skin is exposed to things such as a potential burn. 

Metabolism

Skin metabolism is the rate at which new skin cells turn over; this occurs between the epidermal and dermal cells that work together to regulate collagen production and repair UV light damage, aging, and other damage caused to the skin. 

Absorption and Secretion

The skin is responsible for excreting various substances, including:

  • Small amounts of carbon dioxide
  • Sweat
  • Water
  • Waste products (such as excess sodium chloride and urea)

Absorption

The skin has been found to absorb many substances.

A study published by the American Journal of Public Health found that the skin absorbed 64% of the total contaminants found in regular tap water. The skin will absorb some types of medications including:

  • Hormones
  • Glyceryl trinitrate (to treat angina)
  • A wide range of other topical medicine applications

Medications that are given topically (via the skin) should be massaged into the skin and covered with an occlusive dressing for optimal absorption.

The skin also stores some substances, including:

  • Water, which is absorbed and stored in the skin
  • Nutrients, such as vitamin D

Interactions With Other Systems

The integumentary system is very active in working with other organ systems to maintain the body’s overall balance (called homeostasis). Examples of how the skin helps each body system maintain homeostasis include:

The Immune System

The skin interacts with the body’s immune system in many ways to protect the body from infection, serving as a physical barrier to disease-causing microorganisms.

The Digestive System

The skin synthesizes vitamin D (from exposure to the sun) therefore providing this vital nutrient to the digestive system. Vitamin D is required to absorb calcium and the skin works with the digestive system to ensure that calcium can be properly absorbed.

The Cardiovascular System

The skin works with the cardiovascular system by helping to conserve or release heat by constricting or dilating the blood vessels.

The Nervous System

The skin functions to transmit sensations from the environment via its nerve receptors. The nerve impulses (such as the perception of pain, heat, cold, and other sensations) are then transmitted to the nervous system to be interpreted by the brain.

The Musculoskeletal System

Vitamin D synthesis—which takes place in the skin—promotes calcium absorption. Calcium is needed for the growth and maintenance of bones, as well as for muscle contractions.

The Endocrine System

The endocrine system involves the body’s hormones. Vitamin D—produced by the skin–can act as a hormone in the body. Some hormone imbalances can have an adverse effect on the skin.

The Respiratory System

The small hairs in the nose (which are part of the integumentary system) act as a filter to remove harmful particles which may otherwise be inhaled into the lungs.

The Urinary System

The skin functions to excrete waste products (such as salts and some nitrogenous wastes) into the sweat; this helps the kidneys maintain the body’s proper balance of electrolytes as well as maintaining the normal pH balance.

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9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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