The submental triangle has its base at the body of the hyoid bone and its apex at the chin. The anterior bellies of both digastric muscles form the side pleura of the triangle. The mylohyoid muscles form its floor. The contents of the triangle are the submental lymph nodes, some small veins that unite to form the anterior jugular vein, and the terminal part of the submental artery as it turns to ascend to the chin.

The submandibular triangle (digastric triangle) is bounded superiorly by the border of the mandible and the line extending from its angle to the mastoid process, posteriorly by the posterior belly of the digastric and the stylohyoid muscle, and anteriorly by the anterior belly of the digastric muscle. The mylohyoid, hyoglossus, and constrictor pharyngis muscles form the floor of the submandibular triangle.

The structures that are of interest in flap surgery when dissecting in a subplatysmal plane in the area of the submandibular triangle are the facial vein, the facial artery as it curves around the mandibular border to enter the face, the submental artery, and the cervical and marginal branches of the facial nerve.

The boundaries of the carotid triangle are superiorly the posterior belly of the digastric and the stylohyoid muscles, anteriorly the superior belly of the omohyoid muscle, and posteriorly the anterior border of the sternocleidomastoid muscle. The inferior and middle pharyngeal muscles form the floor of the triangle. When removing the platysma, a part of the external and the anterior jugular veins and cutaneous cervical branches appear in the superficial level of the triangle.

The borders of the muscular or visceral triangle of the neck are the midline of the neck anteriorly, the superior belly of omohyoid muscle superiorly, and the anterior margin of the sternocleidomastoid inferiorly. It contains the muscles of the neck: sternohyoid, superior belly of omohyoid, sternothyroid, and thyrohyoid. The first two form the superficial layer of these muscles.

The occipital triangle is the upper and larger part of the posterior triangle. Its floor is formed from the top down by the semispinalis capitis at the apex, the splenius capitis, the lavatory scapulae, the scalenus posterior, and the scalenus medius muscles.

The platysma covers the lower part of the triangle in a various degree.

The important surface structures found at this triangle are the branches of the cervical plexus as they radiate emerging from the posterior border of the sternocleidomastoid muscle and the spinal accessory nerve as it emerges slightly superiorly and runs obliquely, crossing the triangle in its middle to reach the trapezius. All of these neural branches emerge from the posterior border of the sternocleidomastoid within 2 cm above or below a point termed Erb’s point. Erb’s point is located at the posterior border of the sternocleidomastoid muscle approximately in the mid of its mastoid and sternoclavicular attachments and serves as an important landmark. Identifying this point is useful not only in locating the emerging point of the mentioned nerves so as to protect them during surgery but also in blocking the cutaneous nerves of the cervical plexus by gaining anesthesia of almost the bigger part of the neck skin.

The supraclavicular triangle (omoclavicular triangle) is the lower and smaller part of the posterior triangle with a variable size that depends on the outspread of the clavicular attachments of the sternocleidomastoid and trapezius muscles. The first rib, the scalenus medius, and a part of the scalenus anterior and the first slip of the serratus anterior muscle form its floor. The triangle is covered almost fully by the platysma and in the superficial level is crossed by the supraclavicular nerves and the external jugular vein as it descends across the posterior edge of the sternocleidomastoid.

The facial artery arises from the external carotid artery, as one of its anterior branches, at the carotid triangle (Fig. 8.7). It usually ends at the inner canthus as angular artery and anastomoses with the dorsal nasal artery (see Chap. 4). For descriptive purposes, this long course is divided in a cervical and a facial part according to the area where the vessels run.

The facial artery arises as an anterior branch of the carotid artery immediately above the greater horn of the hyoid bone and above the lingual artery (Fig. 8.7). It lies beneath the platysma and the hypoglossal nerve often runs above it. Its diameter ranges from 1.7 to 3.6 mm (mean 2.6 mm) (Zhao et al. 2000). In about 20 % of the cases, the facial and the lingual arteries arise with a common trunk from the external carotid artery (Shima et al. 1998).

The facial artery after its origin runs upward and forward, deep to the stylohyoid and the posterior belly of the digastric. Above the stylohyoid, it turns down and forward between the medial pterygoid muscle and the posterior aspect of the submandibular gland. As it reaches the lower border of the mandible, it curves around it, just in front of the anterior edge of the masseter muscle; pierces the deep fascia, lying immediately deep to platysma; and enters the face, continuing as the facial part, running toward the alar base, and giving off its branches to the face (see Chap. 5). At the point where the artery crosses the mandible, it lies very superficial, and its pulsation is most palpable. The facial artery, with its accompanying vein, crosses deep the mandibular branch of the facial nerve.

In the neck, the facial artery gives off the ascending palatine, the tonsillar, the glandular, and the submental arteries. The ascending palatine artery arises close to the origin of the facial artery, runs up between styloglossus and stylopharyngeus to the side of the pharynx, and ascends along it, between the superior constrictor of the pharynx and the medial pterygoid toward the skull base. Its branches supply the soft palate, the tonsils, and the auditory tube and anastomose with its opposite fellow, the greater palatine branch of the maxillary artery and the tonsillar and the ascending pharyngeal arteries.

The tonsillar artery ascends between medial pterygoid and styloglossus and after penetrating the superior constrictor of the pharynx enters the tonsil. It supplies the tonsil and the root of the tongue. The glandular branches are 3–4 and supply the submandibular salivary gland, lymph nodes, and a small area of overlying skin as cutaneous perforators.

The submental artery constitutes the largest cervical branch of the facial artery. It branches off at a point deep to the submandibular gland or at its superior edge as the facial artery separates from the submandibular gland. The artery originates in a point of 5–7 mm from the border of the mandible (Martin et al. 1993; Magden et al. 2004). At its origin, the mean diameter of the artery has been reported ranging between 1 and 2 mm (Martin et al. 1993; Faltaous and Yetman 1996; Pinar et al. 2005a, b).

It runs forward on the surface of the mylohyoid below the border of the mandibular body. As it reaches the anterior belly of the digastric muscle, it continues running either deep to it in 70 % or superficial to it in 30 % of the cases (Faltaous and Yetman 1996). At the symphysis of the mandible, it turns around the lower border of the mandible body, enters the chin, and divides into a superficial branch and deep branch, which anastomose with the inferior labial and mental arteries, supplying the chin and the lower lip (see Chap. 6).

During its course in the submandibular triangle, the artery gives off numerous small branches to the submandibular and sublingual glands and to the adjacent muscles and platysma. It also gives off perforating cutaneous branches in a number of 1–4 (Curran et al. 1997; Kim et al. 2002a, b) (Fig. 8.8). These branches pierce the platysma, supply the skin over the submental triangle, and anastomose with their contralaterals, providing a strong arterial pedicle for designing flaps in the submental region. Moreover, the submental artery anastomoses with the mental, the inferior labial, and the sublingual arteries, a network that is of great importance to the blood supply of platysma muscle and the superiorly based platysma flap (Lasjaunias et al. 1979).

The superior thyroid artery is described as the first branch of the external carotid artery. It arises beneath the anterior border of the sternocleidomastoid muscle just below the level of the greater horn of the hyoid bone (Fig. 8.9). In relation to the carotid bifurcation, it arises in 65 % of the cases at the same level or above it. In 35 % of the cases, it arises below the level of bifurcation from the common carotid artery (Ozgur et al. 2009).

It courses inferiorly and medially, to the apex of the lobe of the thyroid gland. In its course in the carotid triangle, the superior thyroid artery lies only beneath the skin and the platysma. As it descends, it then passes beneath the omohyoid and sternothyroid muscles with the external laryngeal nerve usually lying medially to it. The superior thyroid artery ends at the thyroid gland where it divides into the anterior, isthmal, posterior, and lateral thyroid final branches.

Through its course, the superior thyroid artery gives off the following branches: the infrahyoid artery, the superior laryngeal artery, the sternocleidomastoid artery, the cricothyroid artery, and the final thyroid branches. The branches of the superior thyroid artery that contribute to the neck skin supply are the infrahyoid and the sternocleidomastoid arteries.

This is a small branch running along the lower border of the hyoid bone and supplies the superior portion of the infrahyoid strap muscles and the overlying part of the skin.

The sternocleidomastoid branch arises from the superior thyroid artery in about 80–85 % of the cases, while in the remainder it originates directly from the external carotid artery (Hu et al. 2006; Ozgur et al. 2009). When it originates from the superior thyroid artery, this occurs approximately 0.5–1 cm from the origin of the superior thyroid artery (Hurwitz et al. 1983). It courses downward and laterally across the carotid sheath and at the medial margin of the middle portion of the sternocleidomastoid muscle enters the muscle on its deep surface. The precise point where the sternocleidomastoid artery enters the muscle is situated in a distance of 3 cm away from the origin of the superior thyroid artery (Hu et al. 2006). Small perforators perforate the mid-third of the sternocleidomastoid muscle and supply the overlying platysma and skin. In the same area, a mostly constant direct cutaneous perforator has been found to emerge at the anterior border of the sternocleidomastoid muscle in its midportion (Fig. 8.10). This branch travels initially below the platysma, and after piercing it courses subcutaneously to the midline adjoining its contralateral supplying a large area of the anterior neck skin (Hurwitz et al. 1983; Wilson et al. 2012). Recently, Wilson et al. (2012) raised long perforator flaps that extended even beyond the midline, pedicled on just one of these cutaneous perforators.

The infrahyoid artery anastomoses with its contralateral in the midline. Anastomoses between the muscular branches of the superior thyroid artery and the muscular branches of the inferior thyroid artery (which supplies the inferior portion of these muscles) are formed passing through the entire musculature (Eliachar et al. 1984).

The occipital artery (see Chap. 2) contributes to the vascular supply of the upper part of the neck by two small branches, the lower and the upper sternocleidomastoid branches (Fig. 8.11).

The occipital artery branches from the posterior aspect of the external carotid artery about 2 cm from its origin and opposite to the origin of the facial artery. It courses up and back deep to the posterior belly of the digastric muscle and in front of the internal carotid artery, the internal jugular vein, and the vagus, the hypoglossal, and the accessory nerves. Running to the occipital area, it passes in the occipital groove and the medial aspect of the mastoid process deep to the attachments of the sternocleidomastoid muscle. At this part, it gives off the lower and the upper sternocleidomastoid branches.

The lower sternocleidomastoid branch arises from the starting point of the occipital artery, courses posteroinferiorly over the hypoglossal nerve, and enters the sternocleidomastoid muscle. The upper sternocleidomastoid branch arises from the occipital artery, after a short distance from the previous one, immediately after it crosses the accessory nerve. This branch runs in a same posteroinferiorly course in company with the accessory nerve entering the deep surface of the sternocleidomastoid muscle. Musculocutaneous perforators of both of the branches supply the upper third of the sternocleidomastoid muscle and a quite large area of the upper neck skin.

The posterior auricular artery supplies the digastric and the stylohyoid muscles as well as the parotid gland. The artery gives off small branches to the neck that contribute to the vascularization of the uppermost part of the sternocleidomastoid and the overlying skin (Fig. 8.11).

The inferior thyroid artery is usually branched from the thyrocervical trunk of the subclavian artery (Fig. 8.12). It ascends anterior to the medial border of the scalenus anterior muscle. At the level below the sixth cervical transverse process, it turns medially situated between the vertebral vessels and the carotid sheath. Finally, it descends to the lower border of the thyroid gland, lying on the longus colli muscle and coming in a variable relation to the recurrent laryngeal nerve (Tang et al. 2012).

The inferior thyroid artery gives off the inferior laryngeal artery, the ascending cervical artery, and pharyngeal, tracheal, esophageal, thyroid, and muscular branches. The inferior laryngeal artery runs upward on the trachea accompanied by the recurrent laryngeal nerve and enters the larynx supplying the laryngeal muscles and its mucous membrane. The ascending cervical artery arises at the point where the inferior thyroid artery turns medially to run behind the carotid sheath. It runs upward on the anterior tubercles of the transverse processes of the cervical vertebrae situated between the scalenus anterior and longus capitis muscles. It supplies the neighboring neck muscles and gives off spinal branches into the vertebral canal. The artery anastomoses with the deep cervical, occipital, and ascending pharyngeal arteries.

The pharyngeal, tracheal, and esophageal branches supply the lower part of the pharynx, the trachea, and the esophagus. The thyroid branches supply the thyroid and parathyroid glands and anastomose with the superior thyroid artery glandular branches.