Skin
The skin of the scalp is thick and hair bearing and contains numerous sebaceous glands. As a result, the scalp is a common site for sebaceous cysts.
Connective tissue (superficial fascia)
The superficial fascia is a fibrofatty layer that connects skin to the underlying aponeurosis of the occipitofrontalis muscle and provides a passageway for nerves and blood vessels. Blood vessels are attached to this fibrous connective tissue. If the vessels are cut, this attachment prevents vasospasm, which could lead to profuse bleeding after injury.
Epicranial aponeurosis (galea aponeurotica)
The epicranial aponeurosis is a thin tendinous structure that provides an insertion site for the occipitofrontalis muscle. Posterolaterally, the epicranial aponeurosis attachment extends from the superior nuchal line to the superior temporal line. Laterally, the epicranial aponeurosis continues as the temporal fascia. Anteriorly, the subaponeurotic space extends to the upper eyelids due to the lack of a bony insertion. This loose areolar tissue provides a potential subaponeurotic space that allows fluids and blood to pass from the scalp to the upper eyelids.
Loose areolar tissue
Areolar tissue loosely connects the epicranial aponeurosis to the pericranium and allows the superficial 3 layers of the scalp to move over the pericranium. Scalp flaps are elevated along a relatively avascular plane in craniofacial and neurosurgical procedures. However, certain emissary veins traverse this layer, which connects the scalp veins to the diploic veins and intracranial venous sinuses.
Pericranium
The pericranium is the periosteum of the skull bones. Along the suture lines, the pericranium becomes continuous with the endosteum. A subperiosteal hematoma, therefore, forms in the shape of the skull bones.
Occipitofrontalis muscle
Origin: The occipitofrontalis muscle consists of 2 occipital bellies and 2 frontal bellies. The occipital bellies arise from the superior nuchal lines on the occipital bone. The frontal bellies originate from the skin and superficial fascia of the upper eyelids.
Insertion: The occipital and frontal bellies inserted into the epicranial aponeurosis.
Nerve supply: Each occipital belly is innervated by the posterior auricular branch of the facial nerve, and each frontal belly is innervated by the frontal branch of the facial nerve.
Action: The frontal bellies can raise the eyebrows.
Nerve Supply
Sensory supply
Six sensory nerve branches of either the trigeminal nerve or the cervical nerve supply the scalp.
The supratrochlear nerve is a branch of the ophthalmic division of the trigeminal nerve. This nerve supplies the scalp in the medial plane at the frontal region up to the vertex.
The supraorbital nerve is also a branch of the ophthalmic division of the trigeminal nerve. This nerve supplies the scalp at the front, lateral to the supratrochlear nerve distribution, up to the vertex.
The zygomaticotemporal nerve is a branch of the maxillary division of the trigeminal nerve and supplies the scalp over the temple region.
The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve and supplies the skin over the temporal region of the scalp.
The lesser occipital nerve is a branch of the cervical plexus (C2), which supplies the scalp over the lateral occipital region.
The greater occipital nerve is a branch of the posterior ramus of the second cervical nerve. This nerve supplies the scalp in the median plane at the occipital region up to the vertex.
Motor supply
The frontal branch of the facial nerve supplies the frontal bellies of the occipitofrontalis muscle, and the auricular branch of the facial nerve supplies the occipital bellies of the muscle.
Arterial Supply, Venous and Lymphatic Drainage
Arterial supply
The scalp has a rich vascular supply. The blood vessels traverse the connective tissue layer, which receives vascular contribution from the internal and external carotid arteries. The blood vessels anastomose freely in the scalp. From the midline anteriorly, the arteries present as follows: supratrochlear, supraorbital, superficial temporal, posterior auricular, and occipital.
The supratrochlear and supraorbital arteries are 2 branches of the ophthalmic artery, which, in turn, is a branch of the internal carotid artery. These arteries accompany the corresponding nerves.
The superficial temporal artery is a terminal branch of the external carotid artery that ascends in front of the auricle. This artery, which supplies the scalp over the temporal region, travels with the auriculotemporal nerve and divides into anterior and posterior branches.
The posterior auricular artery is a branch of the external carotid artery that ascends posterior to the auricle.
The occipital artery is a branch of the external carotid artery. It is accompanied by the greater occipital nerve.
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