The scalp is normally defined as the zone between the face on the front and the neck on the back and the other sides. Anatomically, it is considered to consist of five separate layers.
The third layer is scientifically named the aponeurosis (also known as epicranial aponeurosis or galea aponeurotica). This also consists of dense fibrous tissues. It starts from the frontalis muscle and ends at the occipitalis one.
Under it, there is a thicker layer of connective tissue that is not as dense and can be torn more easily, during scalping for example. It serves as a buffer zone between the top three layers and the final one. Since it is easier to cut through it, it is used by surgeons during neurosurgery and craniofacial interventions. However, it is also very vulnerable to infections, and pathogens can quickly reach the brain using blood vessels, which is why surgeons nickname this layer "the danger zone". It consists of areolar tissue built from collagen I and collagen III. It is not fibrous and its structure is more like a matrix, with a high amount of GAGs (glycosaminoglycans). One of the main purposes of this loose scalp layer is to allow the top ones to be flexible and move a bit when needed.
The final layer is the periosteum of the bones in the skull and is named the pericranium. Its main role is to feed the skull bone and to repair any damage done to it. During some surgical interventions like craniotomy, this layer has to be detached from the bones.
The scalp of humans consists of an area on the top and the back of the head, with smaller parts on the sides. It can basically be defined as all parts of the head except the face and the neck. Commonly, the scalp term designates the entire head, even if anatomically only the area where the hair grows should be considered as the scalp. The skin on the scalp can be affected by numerous problems. Usually, the hair hides all of these symptoms and many people are unaware of them.
Other frequent problems hidden under the hair are the inflammation of the scalp or even swelling under its skin. These can affect all people, regardless of sex, age, race or the length or color of their hair. Many of these problems can cause hair loss and baldness if they remain untreated for a long period of time. Most people don't understand that baldness is usually not a separate issue, but rather the effect of another condition that was not addressed and is now causing various complications.
There can be many diseases of the scalp, which have very different symptoms and warning signs. Some of these issues are specific to the hair or the scalp, while others are more general diseases that affect the entire body or several parts of it. These conditions are not easy to diagnose and treat. Professional medical help is required, the specialists in scalp problems are the dermatologists and sometimes the trichologists. It must be said that hair and scalp problems are frequently caused by poor lifestyle choices. These can be quite simple and are easily be corrected without the help of a doctor.
Hygiene is important for all parts of the body and the hair is no exception and needs to be cleaned often. Unlike other areas, the hair is constantly exposed to outside factors. It tends to collect dust and other particles from the air, which mix with the sebum naturally produced by the scalp. Without washing, the dirt irritates the scalp. Using hair gel and other similar cosmetic products makes things worse, since these have to be washed off as well. In time, irritation causes scratching, which leads to small wounds and infection.
There are many scalp problems, we will mention some of the most common ones. Probably the most frequent one is dry scalp skin. This has many possible causes, like very dry weather or aging. However, it can also be the result of excessive hair washing or using too many hair cosmetics. These remove the natural oils that protect and moisture the scalp. Dry skin is also a genetic factor and some people are more vulnerable to the chemicals in hair care products than others. Skin dryness usually causes a host of other problems, starting with local infections. It can also be caused by severe skin diseases, like psoriasis.
Another common scalp problem is the infection of hair follicles, or folliculitis. Usually, the infection is caused by bacteria, the most common one being Staphylococcus aureus. It can be transmitted from one person to another and the disease is also known as hot tub folliculitis, due to the dangers of washing in common with others. People who shave their head are more likely to be infected. A special case is folliculitis keloidalis, an infection that starts at the back of the head and usually affects men of African ancestry. In general, folliculitis begins with small red eruptions, which later become yellow and fill up with pus. It can spread rapidly and leaves ugly scars if untreated for a long time. The scars left by folliculitis keloidalis are known as keloid scars.
The scalp can also be attacked by fungus. Infection with dermatophytes fungi causes a round rash that looks like a ring, this is why the disease is named the scalp ringworm. In science, the condition is known as tinea capitis. Yeast is another type of fungus that can cause a ringworm infection. However, Pityosporum ovale (Malassezia furfur) normally leads to dandruff, probably the most common of all scalp problems.