Topographic Regions of the Neck
For ease of study in anatomy and clinical practice, the neck is traditionally divided into four key regions (regiones cervicales). This helps to accurately locate superficial and deep structures.
- Anterior cervical region (regio cervicalis anterior)
This space is bounded by strict landmarks:
- The medial boundary runs along the midline of the neck.
- The lateral boundary is formed by the anterior border of the sternocleidomastoid muscle.
- Superiorly, the region is bounded by the inferior border of the mandible.
- Inferiorly, the boundary is the jugular notch of the sternum.
- Sternocleidomastoid region (regio sternocleidomastoidea)
This zone strictly corresponds to the projection of the eponymous muscle. It has crucial clinical significance because the main neurovascular bundle of the neck, including the carotid artery, internal jugular vein, and vagus nerve, runs here.
- Lateral cervical region (regio cervicalis lateralis)
Located posterior to the sternocleidomastoid muscle and anterior to the trapezius. This region contains the subclavian artery and the trunks of the brachial plexus. In its lower part, it features an important landmark — the greater supraclavicular fossa (fossa supraclavicularis major).
- Posterior cervical region (regio cervicalis posterior)
Its outer boundaries are defined by the lateral borders of the trapezius muscle (m. trapezius). This region includes the suboccipital zone and the complex of posterior neck muscles.
Classification of Neck Muscles
The entire muscular mass of the neck (mm. colli) is classically categorized into three large groups depending on their depth:
- Superficial muscles (discussed in this article).
- Intermediate muscles (suprahyoid and infrahyoid groups).
- Deep muscles.
Additionally, there is a functional division into lateral, anterior (median), and deep groups.
Platysma
The platysma is a thin, broad muscular sheet closely fused with the subcutaneous tissue and skin.
- Origin: Muscle fibers originate in the chest region at the level of the 2nd rib, blending into the fascia of the pectoralis major and deltoid muscles.
- Insertion: Ascending upward, the muscle attaches to the inferior border of the mandible and blends into the skin of the angle of the mouth and the lower lip.
- Function: The primary task of the muscle is to tension the skin of the neck, protecting superficial veins from compression. When contracting, it pulls the angle of the mouth inferiorly, which is associated with expressing strong fear or rage.
- Innervation: Supplied by the cervical branch of the facial nerve (ramus colli n. facialis).
- Blood supply: Supplied by the superficial cervical artery (a. cervicalis superficialis) and facial artery (a. facialis).
Sternocleidomastoid Muscle
The sternocleidomastoid muscle (m. sternocleidomastoideus) is the most massive and prominent muscle of the anterolateral surface of the neck.
Attachment points:
- Origin: Has two heads. The sternal head (caput sternale) originates from the anterior surface of the manubrium sterni, while the clavicular head (caput claviculare) originates from the medial third of the clavicle.
- Insertion: The fibers of both heads unite and attach to the mastoid process of the temporal bone (processus mastoideus) and the superior nuchal line (linea nuchae superior) of the occipital bone.
Biomechanics and functions:
- Unilateral contraction: tilts the head toward the same side while rotating the face in the opposite direction.
- Bilateral contraction: flexes the cervical spine, tilts the head backward, and pulls it forward. With a fixed head, the muscle can elevate the thorax, acting as an accessory muscle of respiration.
Innervation and blood supply:
- Innervation: Motor innervation is provided by the accessory nerve (n. accessorius, CN XI) and branches of the cervical plexus at spinal segments C2–C4.
- Blood supply: Provided by three sources: the sternocleidomastoid artery (a. sternocleidomastoidea), superior thyroid artery (a. thyroidea superior), and occipital artery (a. occipitalis).