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13.15: Nails and Hair

Difficulty Level: At Grade Created by: CK-12
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Would you believe this is a close-up of your hair and scalp?

Well maybe not yours. But some other person's. Hair is an integral part of the integumentary system. And although many people may lose some or all of the hair on top of their head, they still have hair on their arms and legs that perform important functions.

Nails and Hair

In addition to the skin, the integumentary system includes the nails and hair. Like the skin, these organs help the body maintain homeostasis.


Fingernails and toenails consist of specialized epidermal cells that are filled with keratin. The keratin makes them tough and hard, which is important for the functions they serve. Fingernails prevent injury by forming protective plates over the ends of the fingers. They also enhance sensation by acting as a counterforce to the sensitive fingertips when objects are handled.


Hair is a fiber that is found only in mammals. Its main component is keratin. A hair shaft consists of dead, keratin-filled cells that overlap each other like the shingles on a roof (see Figure below). Like roof shingles, the overlapping cells help shed water from the hair.

Shaft of Human Hair. This shaft of hair is magnified to show its overlapping cells.

Magnification of a human hair. The hair shaft is composed of dead, keratin-filled (keratinized) skin cells that overlap each other like the shingles, or tiles on a roof. You can see the overlapping cells in this image.

Hair helps to insulate and protect the body. Head hair is especially important in preventing heat loss from the body. Eyelashes and eyebrows protect the eyes from water, dirt, and other irritants. Hairs in the nose trap dust particles and microorganisms in the air and prevent them from reaching the lungs. Hair also provides sensory input when objects brush against it or it sways in moving air.


  • Nails and hair contain mostly keratin. They protect the body and enhance the sense of touch.

Practice I

Use this resource to answer the questions that follow.

  1. What is the role of nails?
  2. What does hair do?
  3. What are exocrine glands?

Practice II


1. A certain disease causes the loss of all body hair. How might homeostasis of the body be disturbed by the absence of hair? (Hint: What are the functions of hair?)

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keratin Tough, fibrous protein in skin, nails, and hair.

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Difficulty Level:
At Grade
Date Created:
Feb 24, 2012
Last Modified:
Aug 28, 2016
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