Arterial Supply of Scalp and Superficial Temporal Region

Arterial Supply of Scalp

• 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.

Venous Drainage

• 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

• 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).

Lymphatic Drainage

• 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.

Nerve Supply

• 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.

Clinical Importance

• 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.