The Anatomy and Function of Hair and Nails in the Integumentary System

Apart from serving cosmetic functions, hair and nails play various important functions in the body. Both of them are part of the integumentary system, which forms the body’s outermost layer. The integumentary system is made up of hair, nails, skin, glands, and nerves. Its main function is to protect the insides of the body from harmful elements like pathogens and environmental factors like pollution. Read on to find out more about the anatomy and function of hair and nails.

We have hair on many parts of our bodies. The hair on our heads plays a big role in how we look and feel about ourselves. However, this is not the only role that hair plays in our body, even the hair on our heads. The hair on our heads actually plays a very important role in keeping us warm by preventing the loss of heat from the scalp. At the same time, hair present in the ears, nose, and the very tiny almost invisible hair present around our eyes keep these sensitive areas safe from dust and other small particles that can cause harm. Even our eyebrows and eyelashes protect our eyes by reducing the amount of debris particles and light that enter them. Apart from this, the fine hair that covers our body also provides warmth and protects the delicate skin.^(1,2)

Let us look at the different parts of human hair:

1. Anatomy of Hair

   Human hair is made up of three distinct parts. These include:⁽³⁾

   • Hair shaft, which is the part that is visible to us and sticks out from the surface of the skin. The shaft of the hair is considered to be dead and has no biochemical activity.
   • Root, which is a soft, thickened bulb located at the base of the hair. This is the only living part of the hair.
   • Follicle, which is a sac-like pit located in a pit in the skin from where the hair actually grows.

   At the bottom of the hair follicle is located the papilla, where the main hair growth takes place. The papilla, in turn, is made up of an artery that provides nourishment to the hair root. As the cells grow, multiply, and produce the protein keratin to harden the structure, they get pushed upwards from the follicle and through the surface of the skin, thus producing a shaft of the hair.^(4,5,6)

   Each strand of hair is made up of three layers. These are:

   • The medulla, which is the central part and is soft.
   • The cortex, which surrounds the medulla and is the main part of the hair strand.
   • The cuticle, which is that hard outer layer that keeps the shaft safe.

   Your hair grows by developing new cells at the base of the root. These cells divide quickly to multiply and form a sort of rod of tissue in the skin. The rods of cells then start to move upward through the skin while the new cells continue to multiply and form under them. As they move upward, they get cut off from the supply of nutrients and nourishment. They then begin to make a hard protein known as keratin through a process known as keratinization. When the process of keratinization happens, the hair cells begin to die. These dead cells and the protein keratin form the shaft of the hair.⁽⁷⁾

   As we already know, hair grows all over the body except for the palms of the hands, lips, and soles of the feet. Hair tends to grow faster in the summer season than in winter, and the growth slows down at night as compared to the growth rate during the day.

2. Functions of Hair

   One of the most important functions of the hair on our head is to provide insulation and ensure that the head retains heat. The hair on the head also keeps the skin on the head safe from damage caused by the sun’s ultraviolet (UV) light.⁽⁸⁾

   Now, what is interesting to note is that the function of hair in other parts of the body is often debated. One theory is that the hair on the body helps keep us warm in cold environments. When you feel too cold, there are arrector pili muscles underneath the body hair that contract and cause the body hair to stand up. This traps the layer of warm air above the outermost layer of the skin known as the epidermis. However, this function of body hair has been found to be more effective in mammals that have thick fur or hair than it is in humans, especially in women who have relatively less body hair.^(9,10)

   Hair also has a critical sensory function in the body. There are sensory receptors located in the hair follicles that are able to sense when the hair moves and whether it is moving because of being touched by a physical object or due to a breeze. These receptors also provide us with sensory awareness of the presence of any parasites or insects on the skin. Some hairs, especially the eyelashes, are very sensitive to the presence of any harmful debris. The eyebrows also keep the eyes safe from sweat, rain, dirt, and any other harmful particles. Apart from this, the hair on the eyebrows also plays a key role in non-verbal communication as they help express emotions on the face such as anger, surprise, sadness, or excitement. Hair in the nose and ears also protects the body by trapping dust particles that may contain microbes and allergens.^(11,12)

Just like any other body part, your nails are also made up of several segments. Nails can best be described as accessory organs of the skin that are made up of layers or sheets of dead keratinocytes (a type of cell) and can be found on the distal ends of the toes and fingers. There is keratin present in your nails, which makes them hard, but at the same time, they remain flexible. Nails serve a variety of purposes in the body, right from cosmetic ones to providing protection to the fingers and toes, enhancing the sensations we feel, and they also act like tools.^(13,14)

While we do not need our nails to survive, but they do provide protection and support to the tips of the toes and fingers, keeping them safe from injury and helping us pick up objects. Without nails, we would have a very difficult time indeed while trying to scratch an itch or trying to untie a knot. Nails can also be an important indicator of a person’s overall health and many illnesses often affects the growth of your nails.^(15,16)

1. Anatomy of Nails

   A nail is made up of three main parts. These are the root, plate, and free margin. There are several other structures under and around the nail, including the nail bed, the nail fold, and the cuticle. Nails grow from the nail matrix, which is a deep layer of living epidermal tissue located at the proximal end of the nail. It is the nail matrix that surrounds the nail root and contains stem cells that form keratinocytes after diving. Keratinocytes are cells that are responsible for the production of the protein keratin and also make up the nail.⁽¹⁷⁾

   The anatomy of the nail is as follows:⁽¹⁸⁾

   • The nail root, which is the part of the nail that can be found under the surface of the skin at the proximal end of the nail. This is where the nail actually starts.⁽¹⁹⁾
   • The nail plate, also known as the body of the nail, is the part of the nail that remains external to the skin and visible to us. This is the visible part on which many people like to apply various shades of nail colors.
   • The free margin, which is the part of the nail that protrudes outward beyond the distal end of the toe or finger. This is the part that is usually filed or cut to keep the nail neatly trimmed.
   • The nail bed, which is the area of skin located under the nail plate. The nail bed is pink in color because of the presence of capillaries in the dermis layer of the skin, which is the second layer under the topmost epidermis layer. You will notice a whitish crescent-shaped area located at the base of the nail. This is known as the lunula.
   • The cuticle, which is a layer of dead epithelial cells that quickly overlaps and covers the edges of the nail plate. The cuticle is responsible for sealing off the edges of the nail. This helps prevent infections of the tissues located underneath.⁽²⁰⁾
   • The nail fold, which is a fold or groove in the skin where the side edges or part of the nail plate remains embedded.

   Nails grow out of the deep folds or grooves in the skin of the toes and fingers. In any healthy individual, as the epidermal cells located under the nail root start to move upward toward the surface of the skin, the cells increase in number and the ones located closest to the nail root end up getting flat and pressed together tightly. Each cell ends up becoming a thing plate, which then piles up into layers to form the nail.

   As is the process with hair, nails also form by the process of keratinization, and when the nail cells begin to accumulate, the nail starts to push forward and grow.

   Fingernails tend to grow faster than toenails, and just like hair, nails also grow faster in the summer season than in winter. In cases of injury to the nail, if a nail gets torn off, it will manage to grow back, but only if the nail matrix is not badly damaged or injured.⁽²¹⁾

2. Functions of Nails

   Nails play an important role in helping doctors understand your overall health. Doctors, especially Emergency Medical Technicians (EMTs) often look at the fingernail beds to use the color of the same as a quick indicator of oxygen saturation of the blood or to determine how much blood is reaching the extremities of a person. If the nail beds are of a purplish or bluish color, it is usually taken as a sign of low oxygen saturation. To determine if blood is flowing properly to the extremities such as the fingers and toes of a person, a blanch test might be carried out. During this test, a fingernail is depressed just for a brief moment to make the nail bed turn white by forcing the blood to go out of the capillaries. Once the pressure is released, they should take only a second or two for the nail bed to return to its normal color. This indicates that there is normal blood flow to the extremities. If, however, the return of the nail bed to its normal pinkish color takes longer than a second or two, it can be an indication that there is low blood volume because of shock or dehydration.

   Remember that nails, especially toenails, are one of the most common sites on the body to be affected by fungal infections. This causes the nails to turn yellow in color and become thick. Toenails are most often infected as compared to the fingernails since your feet remain confined inside shoes for longer periods of time. Remaining enclosed inside shoes provides the perfect dark, warm, and moist environment for fungi to grow and thrive. Toes also have lesser blood flowing to them as compared to fingers, which makes it more challenging for your immune system to easily detect and prevent infections from developing in the toenails.^(22,23)

   Even though nails appear to be tougher and harder than your skin, they are actually far more permeable than the skin, making it easy for harmful substances such as chemicals and other toxins to get absorbed through the nails and cause various health problems. This is why it is important to take good care of your nails.

Hair and nails are important parts of the body that serve various critical functions. Hair helps to keep the skin safe, regulates skin temperature, and also protects our head from the sun’s UV rays while preventing heat loss. Hair in the nose and ears, as well as the eyelashes, defends the body and trap dust particles that may cause harm to the body. Similarly, nails also play a protective role in the body. Apart from protecting the delicate tips of our fingers and toes, nails also help enhance our grip, allowing us to pick up things. While both hair and nails play protective roles in the body, it is equally important for us to keep these parts safe from infection and other diseases by taking good care. Practicing good hygiene and avoiding using too many chemical-loaded cosmetics on our hair and nails will prevent damage to these parts and ensure overall well-being.

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