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Anatomy of Hair

February 17, 2018

Hair is an essential part of your anatomy, providing warmth, protecting us from potentially harmful objects and it also impacts appearance and offers an opportunity for self expression.

Hair is a physically distinct feature known as a skin appendage. There are multiple appendages on our skin such as toenails, fingernails and sweat glands.

The anatomy of your hair begins with the skin.

Our skin is composed of three layers: epidermis, dermis, and subcutaneous fat and connective tissues.

The epidermis is the outer layer of skin that is less than a millimeter in thickness, composed of dead skin cells that are constantly shedding and replacing itself.

The dermis, located below the epidermis, is about two to three millimeter thick on the scalp, providing the skin with durability and protection. This region also contains the subcutaneous glands and sweat glands.

The subcutaneous fat and connective tissues, beneath the dermis, are a group of larger sensory nerve branches and blood vessels nourishing the skin with oxygen.

Hair Follicles and Hair Shaft: Found in the upper part of the subcutaneous fat are the hair follicles which are three to four millimeter in length, containing one to four hair shafts.

The hair shafts are composed of three layers:

Cuticle is the outer layer of the hair, the part of the shaft that are visible to us with our naked eye.

Cortex is the middle layer of the hair and provides the hair strength. It is composed of a protein called keratin. This protein is also found in the horns of rhinoceroses.

Medulla is the innermost layer of the hair and only present in terminal hair follicles.

Terminal hair is long, thick and dark compared to hairs that are vellus. During puberty, with the increase of androgenic hormone levels, the vellus hair will be replaced with terminal hair. The terminal hair is more common in men and found in regions such as the chest, arms, foot. Our scalps only contain terminal hair.

 

Dr. Stephen Mulholland, MD
Posted by Dr. Stephen Mulholland, MD
has been practicing plastic surgery for over 20 years. He is one of Canada’s most renowned and best plastic surgeons in Toronto with his wealth of experience, artistry, and humbleness towards his patients.

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