Scalp is the soft tissue layer covering the Bony vault over the brain. Scalp is a fusion of 5 layers of soft tissue.
- S: Skin
- C: Superfacial Fascia or Sub Cutaneous Tissue
- A: Musculo Aponeurotic layer
- L: Loose sub Aponeurotic layer
- P: Periosteum
S – Skin: It is the layer of the scalp which consists of many hair follicles, sabeceous glands and sweat glands.
C – Sub Cutaneous layer or Superfacial fascia: This layer contains Blood Vessels and Nerves of the scalp. The walls of the blood vessels have fibrous strands fixed to them which prevents retraction of blood vessels when injured.
A – Musculo Aponeurotic layer or galea aponeurotica: As the name suggests it consists of frontal and occipital bellies of occipitofrontalis muscle. The frontal belly causes horizontal wrinkles on the forehead and help in raising eyebrows. As the first, second and third layers of the scalp are fused together the movement caused by the galea aponeurotica leads to the forward and backward movement of the scalp.
L – Loose sub aponeurotic layer: It form a space filled with loose areolar tissue. Emissary veins pass through this space. This is called teh dangerous area of scalp as it is closed on all sides except anteriorly which opens into the upper eyelid.
P – Periosteum or Pericarnium: It is the loose covering over bones of the vault. It covers the complete bones of the vault except the sutures where it is continuous with the endocranium.
Which layer is called safety layer?
Great picture, Varun! I’m a junior doctor and I found it so hard to find online photos demonstrating a nicely dissected scalp! Anyway, may I suggest that the structure labelled “P” is actually Dura, since it is beneath the cranium (look at the frontal and occipital pole). I think some Periosteum is included in the “L” structure. Next layer beneath Dura is Arachnoid, and next to it is Brain.
Cheers.
Very good observation Creski, P is below the cranium and looks more like Dura, an epidural hematoma develops above this layer and a subdural hematoma would be below the dura