The condition of our scalp influences the condition of our hair. A healthy scalp stimulates hair growth and promotes a flourishing head of hair. Conversely, scalp disease, infections, and skin disorders can lead to hair thinning and loss.
Layers of the Scalp
The scalp consists of five tissue layers: skin, connective tissue, aponeurosis, loose connective tissue, and periosteum (conveniently, the layers can be remembered as SCALP). Together, the layers create an intricate anatomical structure that runs from the face to the back of the neck and covers the cranial vault.
- Skin – The thick outermost layer that contains hair follicles and sebaceous glands, which secretes an oil-like substance that lubricates the skin and hair.
- Connective tissue – The layer beneath the skin (subcutaneous layer) that consists of fibrous tissue and fat. It contains the main blood vessels and nerves of the scalp, which notably give the scalp the richest blood supply of any area of the skin on the body.
- Aponeurosis – A tough, fibrous layer that connects the frontalis muscle to the occipitalis muscle, two muscles that cover the front and back of the skull, respectively.
- Loose connective tissue – A thin layer that separates the lowest layer (periosteum) from the upper three layers and gives the scalp its mobility.
- Periosteum – The dense layer of connective tissue that nourishes and adheres to the bone.
The skin is the layer of the scalp that contains the mechanism that is responsible for manufacturing hair: the hair follicle.
Hair Follicles in the Scalp
Hair follicles, found in the dermal portion of the skin, are the structures responsible for producing hair. At any given point, normal hair follicles are in one of three phases of the hair growth cycle. A complex system contains nutrients delivered in the bloodstream and nerves that receive biological signals. Patients who suffer from hair loss can be diagnosed as having genetic reasons for the condition and/or hair follicles damaged by inflammation.
Damaged Hair Follicles
Bacterial or fungal infections can cause inflammation of the hair follicles (known as folliculitis), which, if severe and persistent, can destroy hair follicles. Skin conditions such as psoriasis or dandruff can irritate the scalp and lead to incessant scratching – a habit that can exacerbate the problem, damage hair and impede growth. Lupus and Lichen Plano Pilaris cause inflammation which destroys the follicle. Follicles may also be injured and possibly destroyed by certain processing procedures such as straightening and tight braids or extensions. If the scalp becomes injured, scar tissue can develop and permanent hair loss may result. To prevent hair loss, scalp conditions should be evaluated and appropriately treated, especially where an injury or inflammation is present.