The scalp extends from the supra-orbital margins anteriorly to the superior nuchal line posteriorly & slopes on each side to the superior temporal line. The forehead is common to both the scalp & face. The scalp is composed of 5 layers indicated by the letters of the word SCALP:
Skin: the skin of the scalp is the thickest in the body with numerous hairs & abundant sebaceous glands.
Connective tissue: a dense fibro-fatty connective tissue binds the overlying skin to the underlying aponeurosis. It contains the vessels & nerves of the scalp.
Aponeurosis: the epicranial aponeurosis of occipitofrontalis (galeaaponeurotica) is a thin tendinous sheet that extends between the occipital & frontal bellies of occipitofrontalis muscle. Laterally it blends with the temporalis fascia just above the zygomatic arch. The subaponeurotic space is the potential space beneath the epicranial aponeurosis.
Loose areolar tissue: this tissue occupies the subaponeurotic space. It extends anteriorly into the upper eyelids & bleeding anywhere beneath the aponeurosis may appear as a black eye by the blood tracking down through the space. This area also called the dangerous area of the scalp because the emissary veins which open here may transmit the infection from the scalp to the cranial venous sinuses.
Pericranium: is the outer periosteum of the cranial vault. It becomes continuous with the inner periosteum of the bones (endocranium) at the sutures & thus a subperiosteal haematoma outlines the concerned bone.
Occipitofrontalis is the muscle of the scalp. It consists of 2 bellies on each side connected by the epicranial aponeurosis. Occipitalis (posterior belly) arises from the superior nuchal line and attaches to the back of the aponeurosis. It’s supplied by the posterior auricular branch of the facial nerve. Frontalis (anterior belly) arises from the skin & superficial fascia of the eyebrow & attaches to the front of the aponeurosis.
It’s supplied by the temporal branch of the facial nerve. Frontalis elevates the eyebrows & produces wrinkles in the skin of the forehead. Occipitalis mainly anchors the aponeurosis posteriorly.
The supratroclear& supraorbital arteries: are branches of the opthlamic artery. They wind around the supra-orbital margin & ascend the forehead & scalp as far backwards as the vertex of the skull, accompanied by the corresponding nerves. The supratrochlear artery lies closer to the midline.
The superficial temporal artery: is the smaller terminal branch of the external carotid artery. It ascends from the level of the neck of the mandible deep to the zygomatic arch & in front of the auricle & auriculotemporal nerve. It ends by dividing into frontal & parietal branches to the supply the skin of the scalp over the corresponding eminences. Before its final division, it gives 3 branches:
The transverse facial branch: runs forwards on masseter below the zygomatic arch.
The zygomatico-orbital branch: runs above the zygoatic arch between the 2 layers of the temporal fascia.
The middle temporal branch: ascends vertically across the root of the zygomatic arch to pierce the temporal fascia & groove the skull above the external auditor meatus.
The posterior auricular artery: is a branch from the external carotid artery. It runs along the level of the upper border of the posterior belly of digastric muscle to reach the outer surface of the mastoid process. It gives cutaneous branches to the scalp behind the auricle. In addition it gives muscular & glandular (to parotid gland) branches and a stylomastoid branch (through the stylomastoid foramen to the facial nerve).
The occipital artery: is a branch from the external carotid artery. It runs along lower border of the posterior belly of digastric to reach the inner surface of the mastoid process.it runs across the apex of the posterior triangle of the neck , then it pierces trapezius 2-3 cm from the midline & runs with the greater occipital nerve to supply the back of the scalp as high as the vertex. Nerves & Arteries of the Scalp