The Integumentary System: Your Skin, Hair, Nails, and Glands (2024)

The integumentary system is the body's outermost layer. Composed of skin, hair, nails, glands, and nerves, its main job is to protect your insides from elements in your environment, like pollution and bacteria. It also helps retain bodily fluids, eliminate waste products, and regulate body temperature.

This article digs into the specifics about each part of the integumentary system, exactly what it does, how it interacts with other body systems, and some of the medical conditions that can affect it.

The Integumentary System: Your Skin, Hair, Nails, and Glands (1)

What Makes Up 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 skin 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.

Hair also has a bio-psycho-social function, influencing how we interact with others.

Nails

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

Glands

The integumentary system has four types of exocrine glands, which are glands that secrete some type of substance outside the cells and body, such as onto the skin.

The four exocrine glands associated with the integumentary system include:

Sudoriferous glands (sweat glands): Sweat glands 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.People of all sexes have mammary glands, but in males, these glands are underdeveloped.In females, the glands function to produce breast milk after giving birth.A single mammary gland weighs about 500 to 1,000 grams (1.1 to 2.2 pounds).

What Does the Integumentary System Do?

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 epidermis is composed of skin cells that contain a high content of keratin, a protein that provides protection from the external environment.

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 sometypes 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 dilation 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.

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, which is chest pain related to a lack of oxygen delivery to the heart tissue)
A wide range of other topical medicine applications

The skin also stores some substances, including:

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

How Does it Work 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:

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.

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.

Cardiovascular System

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

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.

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.

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.

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.

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.

What Conditions Affect the Integumentary System?

Conditions that affect the integumentary system include those caused by external triggers such as allergens and irritants as well as conditions that are acquired or genetic. A few of the most common are:

Skin Disorders

Acne: This condition occurs when hair follicles become blocked by oil and dead skin cells, causing pimples and blackheads.
Atopic dermatitis: This common skin condition causes red, dry, itchy skin that can become inflamed.
Eczema: This is an inflammatory skin condition that causes patches of dry, scaly, itchy skin.
Ichthyosis: This skin condition causes dry, itchy skin that may look rough or scaly. It is usually an inherited condition but can also occur with other diseases such as Hodgkin's lymphoma.
Psoriasis: People with psoriasis have itchy, scaly patches of skin, typically on the elbows, knees, and scalp. Psoriasis is distinguished from eczema by thick scales (called plaques) that may look silvery and tend to have well-defined borders.
Rosacea: This common condition causes flushing and small, visible blood vessels on the face. People with this condition may also develop small, red bumps in the affected area.
Vitiligo: This skin condition occurs when pigment-producing cells stop working. It causes patches of colorless skin, which can appear on any part of the body.

Skin cancer: Types of skin cancer include basal cell carcinoma, squamous cell carcinoma, Merkel cell, and melanoma. Of these, Merkel cell and melanoma are the most aggressive.

Nail Disorders

Beau's lines: These are indentations that appear on the surface of the nails. They happen when growth under the cuticle is interrupted, usually due to injury or illness.
Brittle nail syndrome: This is a common condition of the fingernails. People with brittle nail syndrome have nails that easily break or split, or are abnormally soft.
Longitudinal melanonychia: This condition causes a lengthwise black or brown streak on the nail plate. It can be caused by a benign deposit of pigment, but it can also be a sign of melanoma.
Nail psoriasis: This type of psoriasis usually occurs along with other psoriasis symptoms. It causes the nails to split or lift.
Onychomycosis: This is a fungal infection of the nail. It usually appears on the toenails and may cause them to become thickened, discolored, and brittle.

Hair Disorders

Alopecia: Alopecia is a condition that causes hair loss. There are a few different types, including male pattern baldness (the most common) and alopecia areata, where the immune system attacks the hair follicle, causing hair loss.
Anagen effluvium or telogen: This is hair shedding that happens due to an infection, autoimmune disorder, or exposure to certain chemicals or drugs, such as chemotherapy drugs.
Head lice: These parasites infect the head and lay eggs on the hair shaft. Head lice are common in childhood.
Hirsutism: This condition causes an overgrowth of coarse body and facial hair in women.

Gland Disorders

Medical conditions can affect any of the four gland types in the integumentary system. Some of these conditions include:

Hyperhidrosis: This describes excessive sweating that may occur even at comfortable temperatures or when you are not exercising.
Bromhidrosis: People with bromhidrosis have unusually offensive body odor. The condition can be caused by poor hygiene but it can also be related to diet, medication, or a medical condition.
Miliaria: This is a mild form of heat rash, where the sweat ducts become blocked and/or sweat becomes trapped under the skin.
Sebaceous gland hyperplasia: People with this condition develop small, yellowish bumps on the face. Sebaceous gland hyperplasia is most common in middle age and older adults.
Nevus sebaceous: This is a birthmark that is made up of extra oil glands. It typically begins as a slightly raised pink or orange area of skin. It is usually benign, but some can develop into malignancies.
Mammary gland hyperplasia:This is a benign condition of the breast that causes an overgrowth of cells in the ducts or lobules, the milk-producing glands in the breast.
Lobular carcinoma of the breast: This common type of breast cancer begins in the cells of the lobules.

Summary

The integumentary system is the outermost layer of your body. It includes the skin, hair, nails, glands, and sensory nerves. Its function is to provide a barrier to infection and protect the body from temperature changes and potentially harmful external substances.

The integumentary system works together with the body's other systems to maintain homeostasis. Like other body systems, there are certain conditions that can affect the integumentary system, such as skin disorders, autoimmune conditions, and certain cancers.