NECK MUSCLES: CLASSIFICATION AND FUNCTIONS - ANATOMY AND PHYSIOLOGY - 2025

The neck muscles are a series of structures responsible not only for joining the head with the rest of the body, but also for providing the wide range of movements that it is capable of without injuring the delicate structures that run through the neck.

Of all the anatomical areas, the neck is the one with the highest proportion of muscles per surface area, something logical considering that these muscles should keep the weight of the head in place, provide mobility and protect vascular and nervous structures, as well as the digestive and upper airways.

A comprehensive analysis of all the muscles of the neck is the subject of a complete volume of a treatise on anatomy. Their large number, innervation details and complementary functions make these muscles such a complex subject that in the medical area there are surgeons dedicated exclusively to head and neck surgery.

Therefore, in this post we will try to give an overview of their distribution, the most common muscles will be mentioned and a brief description of the function of the most important muscles of the neck will be made.

Classification and functions

All neck muscles are long, lean muscles that act in synergistic, agonal, and antagonistic groups to achieve the full range of head movements.

The muscles of the neck can be divided into two large groups: the muscles of the anterior region (in front of the vertebral bodies) and the muscles of the posterior region (or muscles of the neck), which are located behind the vertebrae in relation to the vertebral processes.

In turn, the muscles of the anterior region are divided into several subgroups according to their location and depth:

- Medium deep group (in direct relationship with the vertebral bodies).

- Deep lateral group.

- Infrahyoid muscles (anterior midline).

- Suprahyoid muscles (anterior midline).

- Group of anterolateral muscles.

- Supraaponeurotic muscles (the most superficial).

The superficial anterior muscles form several triangles, the detailed knowledge of which is vital for the trauma surgeon, since the severity of the injuries can be estimated depending on the affected triangle.

Muscles of the anterior region

These are very powerful muscles and their function is to literally hold the head attached to the neck; In addition, they allow flexion-extension movements of the cervical spine (tilt the head forward and backward), lateral tilt and rotation.

In addition, they sometimes function as accessory muscles of respiration, as in the case of scalenes when they take their fixed point on the cervical vertebrae and their mobile point on their costal insertion.

Medium deep group

They are the deepest muscles of the neck and are directly related to the vertebral bodies, resting on their anterior face. In front of these, the esophagus and trachea, in addition to the great vessels of the neck, run from back to front.

This group is made up of three main muscles: length of the neck, rectus anterior minor, and rectus anterior major, all of them flexors of the cervical spine (they tilt the head forward).

Lateral deep group

They are directly related to the transverse processes of the cervical vertebrae and form what could be considered the lateral wall of the neck.

Its function is to tilt the head to the side (the right muscles tilt the head to the right and vice versa), although if they take their fixed point in the vertebrae, the scalene muscles can function as accessories for breathing.

To this group belong: scalene muscles (three on each side), intertransverse of the neck and lateral rectus.

Infrahyoid muscles

They are more superficial than the previous ones, are located in the midline of the anterior face of the neck and run from the hyoid bone to its insertions in the sternum.

All the infrahyoid muscles work synergistically to pull down and lower the hyoid bone, so that it becomes a firm foothold for the suprahyoid group whose role is to help open the mouth and swallow.

The muscles of this group are divided into two planes, a deep plane where the sternothyroid and thyrohyoid muscles are located, while the superficial plane includes the sternocleidohyoid and omohyoid muscles.

Suprahyoid muscles

They are a group of muscles that form the floor of the mouth and their main function is the mouth opening, taking as a fixed point their insertions in the hyoid bone.

These muscles are divided into three planes: a deep one consisting of the geniohyoid muscle, a middle one where the mylohyoid is located, and a superficial one that includes the digastric and stylohyoid muscles.

Anterolateral group

In this group is the largest and most known muscle of the neck: the sternocleidomastoid. This large and powerful muscle takes its upper attachment on the mastoid process and its lower attachment on the sternal manubrium and clavicle.

When the sternocleidomastoids on both sides contract simultaneously, they help to flex the head, while when they do so unilaterally they rotate the head to the opposite side; that is, the contraction of the right sternocleidomastoid rotates the head to the left and vice versa.

When it takes its fixed point in the mastoid and they contract simultaneously, the sternocleidomastoids like the scalenes become accessory muscles of respiration.

Supraponeurotic muscles

This group is made up of a single muscle known as the platysma or cutaneous neck muscle.

It is the only muscle in the neck that does not take muscle insertions, its function being to "cover" the rest of the structures as a sheath. It is inserted in the deep planes in the cervical fascia and in the superficial planes directly in the skin from which a thin layer of fat separates it.

Muscles of the posterior region

They are very powerful muscles, as they support the weight of the head. They are arranged in four planes from depth to surface:

- Deep plane.

- Plan of the complexes.

- Plane of the splenium and angular.

- Trapeze.

Deep plane

It is in direct contact with the skull and the processes of the cervical vertebrae and includes the posterior rectus minor, rectus posterior major, oblique major, oblique minor, transverse spinous and interspinous.

These are all flat, short, and very powerful muscles with a fairly limited range of motion.

Plan of the complexes

They are long muscles that overlap each other forming layers, taking in turn multiple proximal and distal insertions; in this group are the major complex, minor complex, transverse of the neck and the cervical portion of the lumbar sacral muscle.

Plan of the splenios

They are the most superficial of the muscles in the posterior neck region (as the trapezius plane extends beyond the cervical region) and include two muscles that completely cover the deeper planes: the splenium and the angular.

The function of the splenius is to extend the neck (when the splenios on each side do it simultaneously) or to tilt the head to the side, when they contract unilaterally.

For its part, the angular raises the angle of the scapula when it takes its fixed point on the neck and tilts the head to its side when the fixed point is the scapular insertion.

Trapeze

The trapezius is the largest and most extensive muscle in the dorsal region, covering the back and neck. It has multiple inserts on the spine, shoulder girdle and neck.

Depending on where it takes its fixed point, its action will be reflected in movements of the scapula, shoulder or head.

When it takes its fixed point at the shoulder girdle, the trapezius tilts the head to the same side it was contracted and aids in rotational movements.

References

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