The scalp refers to the skin layers and subcutaneous tissue that cover the cranium and is comprised of five layers: skin, dense connective tissue, epicranial aponeurosis, loose areolar connective tissue, and the periosteum. The first three layers move as one unit as they are tightly bound together. The veins of the scalp are present within the dense connective tissue, which also contains nerves and arteries, and the loose areolar connective tissue, which also contains emissary veins that connect to the diploic veins of the skull and the intracranial venous sinuses. 

The venous drainage of the scalp divides into superficial and deep. The superficial veins of the scalp, starting anteriorly and moving posteriorly, are the supratrochlear and supraorbital veins, respectively, the superficial temporal veins and its branches, the posterior auricular vein, and the occipital vein and its branches. The deep venous drainage is via the pterygoid venous plexus.

Venous anatomy starts with a thick outer layer of connective tissue called the tunica externa or adventitia, a middle layer of smooth muscle called the tunica media, and an interior layer of endothelial cells called the tunica intima. As veins do not function like arteries in a primarily contractile manner and are not subject to the same kind of high pressures to which arteries are exposed, the smooth muscle layer of veins is less muscular than arteries. Veins also contain valves to prevent backflow.[1]

The veins of the scalp serve to drain the deoxygenated blood from the scalp muscles and back to the right heart via the internal and external jugular veins and the superior vena cava. As previously mentioned, there are also the valveless emissary veins that connect the superficial veins to intracranial venous sinuses and diploic veins of the skull.

The scalp veins are derived from the mesoderm of the first and second branchial arches, embryologic structures that form between the fourth and seventh week of gestation. The branchial arches go on to form the blood vessels, bone, cartilage, and muscles of the face, among other structures.[2] The muscles that these veins drain also derive from the first and second branchial arches. Second branchial arch anomalies account for the majority (95%) of branchial arch anomalies, with first branchial arch anomalies accounting for only 1 to 4% of cases.[3]

We will describe the blood supply and lymphatics of the scalp veins starting with the superficial components anteriorly and moving posteriorly, beginning with the supratrochlear vein.

The supratrochlear vein originates on the forehead where it drains the superficial muscles and skin of the forehead and the front of the scalp supplied by the supratrochlear artery into the angular vein; there is no associated lymph tissue.

The supraorbital vein originates on the forehead and its anastomosis with the frontal branch of the superficial temporal vein and serves to drain the area of forehead, eyebrow, and upper eyelid supplied by the supraorbital artery that anastomoses with the frontal branch of the superficial temporal vein. The vein travels caudally over the frontal bone and superficial to the frontalis muscle before splitting to joining the supratrochlear vein inferiorly and the superior ophthalmic vein medially; it also has no associated lymph tissue.

The superficial temporal vein has frontal and parietal branches, serving to drain the superficial muscles and skin of the temporal region. It originates from a venous plexus on the side of the head and travels laterally from the temporal region over the zygomatic arch and entering the parotid gland to become the retromandibular vein where it joins the transverse facial vein. The retromandibular vein then drains into the internal jugular vein via its anterior branch, and the external jugular vein via its posterior branch. The frontal branch also connects to a parietal emissary vein that runs from the side of the head to the top of the head where it pierces the cranium and communicates with the superior sagittal sinus. The parietal branch anastomoses with the occipital vein. The parotid and auricular lymph vessels that are located both anteriorly and posteriorly of the superficial temporal vein and artery, and the superficial parotid and preauricular lymph nodes located posteriorly, drain the area supplied by the branches of the superficial temporal artery.

The posterior auricular vein assists with the draining of the muscles and skin of the scalp. It originates from small vessels behind the ear superficial to the temporal fascia and anastomoses with the occipital vein superiorly. It runs just behind the ear where it then confluences with the occipital and deep cervical veins, then receives blood from the posterior branch of the retromandibular vein before turning into the external jugular vein. The posterior auricular vein runs alongside the posterior auricular artery, which originates from the external carotid artery. It is surrounded anteriorly by the mastoid lymph nodes that drain into the parotid and auricular lymph vessels and posteriorly from sternocleidomastoid lymph nodes that drain into the occipital lymph vessels. These lymph vessels then drain into the jugular lymph vessels.

The occipital vein originates from small vessels on the posterior aspect of the scalp and drains the superficial muscles and skin of the occipital region. It is superficial to the occipital fascia and the occipital artery and anastomoses laterally with the parietal branch of the superficial temporal vein and inferolateral to the posterior auricular vein. It then runs into the inferior portion of the posterior auricular vein where it becomes the external jugular vein. The occipital vein also has an anastomosis with the intracranial confluence of the sinuses via the occipital emissary vein. The occipital lymph nodes and vessels drain lymph from this area and drain into the jugulodigastric lymph node, which drains into the jugular lymph vessels.

The venous drainage of the deep scalp layers is via the pterygoid venous plexus, an extensive plexus of veins located between the lateral pterygoid and temporalis muscles, draining into the maxillary vein. It receives branches corresponding with the branches of the maxillary artery. These veins include:

• Alveolar
• Buccinator
• Deep temporal (anterior and posterior)
• Infraorbital
• Masseteric
• Middle meningeal
• Pterygoid
• Sphenopalatine

The pterygoid venous plexus also receives blood from some branches of the palatine veins and contains a communicating vein that travels through the inferior orbital fissure to connect the ophthalmic vein to the cavernous sinus.

Again, working our way anteriorly to posteriorly, we will list the nerves that are present near the scalp veins.

The supratrochlear nerve is located medially of the supratrochlear vein, whereas the medial branch of the supraorbital nerve is just deep to the supratrochlear vein.

The lateral branch of the supraorbital nerve is just medial and deep to the supraorbital vein.

The temporal branches of the facial nerve are located between the zygomatic orbital vein (a non-scalp vein) inferiorly, and the frontal branch of the superficial temporal vein superiorly and posteriorly.

The auriculotemporal nerve runs just anterior and deep to the superficial temporal artery and vein.

The posterior auricular artery and vein are sandwiched between the posterior auricular nerve anteriorly and the great auricular nerve just deep and posteroinferiorly.

Sandwiching the occipital artery and vein are the lesser and greater occipital nerve branches, superficially and anteriorly, and posteriorly, respectively.