Arterial Supply of Scalp and Superficial Temporal Region

The scalp is supplied from front to back by three arteries: supratrochlear, supraorbital, and superficial temporal arteries.
The supratrochlear and supraorbital arteries are branches of the ophthalmic artery, which is a branch of the internal carotid artery.
The superficial temporal artery is a branch of the external carotid artery.
Behind the auricle, the scalp is supplied from front to back by the posterior auricular and occipital (tortuous) arteries, both of which are branches of the external carotid artery.
The scalp has a rich blood supply derived from both the internal and external carotid arteries, with the two systems anastomosing over the temple.

The veins of the scalp accompany the arteries and have similar names.
The supratrochlear and supraorbital veins unite at the medial angle of the eye to form the angular vein, which continues down as the facial vein.
The superficial temporal vein descends in front of the tragus, enters the parotid gland, and joins the maxillary vein to form the retromandibular vein.
The retromandibular vein divides into two divisions: anterior and posterior.
The anterior division of the retromandibular vein unites with the facial vein to form the common facial vein, which drains into the internal jugular vein.
The posterior division of the retromandibular vein unites with the posterior auricular vein to form the external jugular vein, which ultimately drains into the subclavian vein.
The occipital veins terminate in the suboccipital venous plexus.
Emissary veins connect the extracranial veins with the intracranial venous sinuses to equalize the pressure and are valveless.
Examples of emissary veins include the parietal emissary vein, mastoid emissary vein, and others (see Table 1.1).

Diploic veins start from the cancellous bone within the two tables of the skull.
These veins carry newly formed blood cells into the general circulation.
There are four diploic veins on each side: frontal, anterior temporal, posterior temporal, and occipital.
Each diploic vein has a specific drainage pathway (see Fig. 1.17a and Table 1.2).

The anterior part of the scalp drains into the preauricular or parotid lymph nodes, situated on the surface of the parotid gland.
The posterior part of the scalp drains into the posterior auricular or mastoid and occipital lymph nodes.

The scalp and temple are supplied by 10 nerves on each side.
Five nerves (four sensory and one motor) enter the scalp in front of the auricle.
The remaining five nerves (again four sensory and one motor) enter the scalp behind the auricle.

Wounds of the scalp gape when the epicranial aponeurosis is divided transversely.
The scalp is a common site for sebaceous cysts due to the abundance of sebaceous glands.
Wounds of the scalp bleed profusely because the vessels are prevented from retracting by the fibrous fascia.
Bleeding can be arrested by applying pressure at the site of injury by a tight cotton bandage against the bone.
Subcutaneous hemorrhages are never extensive due to the density of fascia, but cause much pain.