Cortex: thicker and denser than other parts of the body, containing a large number of hair follicles, sebaceous glands and sweat glands. There are abundant blood vessels and lymphatic vessels, and there is much bleeding during trauma, but it heals quickly.
Subcutaneous layer: It is composed of fat and thick and vertical fiber bundles, which are closely connected with the skin layer and the cap aponeurosis layer through short fibers. It is the key to combine the scalp and is rich in blood vessels and nerves.
Cap aponeurosis layer: Cap aponeurosis layer is a large aponeurosis membrane structure covering the upper part of skull top, which is connected with frontalis muscle and occipital muscle in front, tough and tense.
Subaponeurosis: It consists of thin and loose connective tissue.
Subaponeurosis space: it is a thin layer of loose connective tissue between the aponeurosis of the cap and the adventitia of the skull. The gap is wide, located in front of the superior orbital margin and behind the nape line. The scalp is loosely connected with the skull adventitia through this layer, so it has great fluidity, and scalp tearing often occurs with this layer. When aponeurosis space is bleeding or suppurating, blood can spread along this space. The vein in this space can communicate with the cranial vein and dural sinus of the skull through several guide veins, so the infection in this space can be secondary to osteomyelitis of the skull or spread to the skull through the above channels. Therefore, this space is called the "danger zone" at the top of the skull.
Periosteal layer: cling to the outer plate of skull and can be peeled off from the surface of skull.
Excessive scalp oil secretion is mostly related to hormone secretion disorder, high pressure, excessive modification and frequent eating of high-fat foods.
People with oily hair are most likely to be caught by seborrheic alopecia if they are not properly cared for and pay insufficient attention to their lives.