HUMAN NECK: ANATOMY - ANATOMY AND PHYSIOLOGY - 2024

The neck or cervical region is the transition between the head and the thorax. Its superficial and deep limits are very well identified anatomical landmarks that allow determining where the head ends, where the neck begins, and where the thorax begins.

The anatomy of the human neck is among the most complex of mammals due to the large number of anatomical elements that come together in a small space, as well as its close anatomical relationships.

In turn, the neck is divided into various compartments by the large muscles that run along it, each one containing structures vital to life.

A detailed study of the anatomy of the neck would require an entire volume of an encyclopedia of anatomy, however in order to understand so many and such complex anatomical relationships it is essential to know the basics, hence an approach to the essential elements will be attempted to achieve understand cervical anatomy.

Neck limits

Olek Remesz (wiki-pl: Orem, commons: Orem)

The neck has superficial and deep limits. The superficial limits are those that can be seen with the naked eye and indicate the structures that mark the "border" between the cervical region (neck) and the adjacent regions (skull and thorax).

Deep limits are those anatomical landmarks that are used when studying images of the inside of the neck (such as CT scans or MRIs), as well as during surgeries to determine exactly where the neck begins and ends.

Since the neck is a kind of cylinder that connects the head to the rest of the body, the cervical region has upper and lower limits.

Superficial limits of the neck

The superficial limits of the neck are part easily identifiable anatomical structures and part imaginary lines that run along or between them.

Starting from the most anterior part of the neck, the upper limit of the neck is given by:

- Lower edge of the mandible (or lower maxilla).

- Posterior border of the ascending branch of the lower jaw.

- An imaginary straight line that goes from the temporo-mandibular joint to the mastoid process.

- A curved line that joins both mastoid processes following the occipital circumference passing through the occiput

Any structure that is above this limit corresponds to the head, while those that are below are part of the neck.

In its lower portion, the superficial limits of the neck are as follows:

- Upper edge of the sternal fork.

- Upper border of both clavicles.

- A straight line that goes from each of the acromio-clavicular joints to C7.

Structures that are above these limits are considered part of the neck, while those that are below them correspond to thoracic structures.

In this way, it is very easy to identify when a lesion or structure is part of the neck and when it is not, although sometimes with very extensive tumor lesions or extensive lesions it is possible that there is involvement of both cervical, thoracic and / or cranial structures.

Deep neck limits

To see these limits it is necessary to have an imaging study such as nuclear magnetic resonance or computerized axial tomography, in order to be able to visualize deep structures that are beyond the skin or, failing that, to perform a surgical dissection.

In this sense, the deep anatomical limits of the neck are extremely important for surgeons when performing interventions in the cervical region, since they allow them to stay within their working area.

The deep upper limit of the neck is given by the base of the skull itself and its anatomical features: pterygoid process, styloid process and mastoid process.

For its part, the deep lower limit is given by an oblique plane that begins at the joint between C7 and T1, passing through the upper edge of the first rib, and ending at the upper edge of the sternal manubrium.

This plane constitutes both the deep lower limit of the neck and the apex of the thorax.

Neck compartments

From a morphological and functional point of view, the neck is divided into three large compartments:

- Anterior cervical compartment or triangle.

- Laterocervical compartment.

- Back compartment or neck.

The limits of these compartments are given mainly by the sternocleidomastoid muscles in front and to the sides, and by the trapezius muscle in the back.

In each of the triangles or cervical compartments are vital structures for life; some of these structures are unique to the neck (such as the larynx or thyroid gland), while others are 'passing through' the neck on their way from the head to the chest or vice versa (for example esophagus, trachea, carotid arteries)

Anterior neck compartment

The anterior compartment of the neck is that delimited by the anterior border of both sternocleidomastoid muscles. The compartment is divided into several triangles, each of which contains both superficial and deep structures.

In the lower triangle, for example, is the thyroid cell, which, as its name implies, is occupied by the thyroid gland.

Posterior to the thyroid and immediately in front of the cervical vertebrae, is what could be called the visceral compartment, a space that in the upper portion of the neck is occupied by the pharynx and larynx, which continue with the esophagus and the trachea respectively.

Both the trachea and esophagus begin in the neck and end in the chest (trachea) and abdomen (esophagus). In its cervical portion, both the trachea and the esophagus are closely related to the recurrent laryngeal nerve, which ascends from the thorax towards the larynx in the space known as the tracheoesophageal groove.

Lateral neck compartment (laterocervical region)

The lateral compartment of the neck begins at the anterior border of the sternocleidomastoid and ends at the anterior border of the trapezius muscle.

In this region are the most important neurovascular elements of the cervical region, partially covered in its lower portion by the sternocleidomastoid muscle itself.

The laterocervical region is divided into several triangles, although in general they all contain part of the same elements: carotid artery, internal jugular vein, and vagus (pneumogastric) nerve; however, the division into triangles or zones makes it possible to identify the relationships of these structures with elements of the cervical region at the time of surgical exploration.

In intimate relationship with the internal jugular vein are the internal jugular lymphatic chains with their different ganglion stations.

In this region there is also a portion of the hypoglossal nerve, which runs perpendicular to the vascular pedicle on its way to the muscles of the base of the tongue.

Back compartment of the neck (nape)

The posterior compartment of the neck corresponds to all the structures that are posterior to the sagittal plane that forms between the anterior border of both trapezius muscles.

It includes all the posterior muscles of the neck, both superficial and deep; the latter posterior to the visceral compartment of the anterior triangle. These muscles are responsible for keeping the head in position and offering the neck all its mobility.

In the nape region there are also the bony structures of the integrated region such as the cervical vertebrae C2-C7, as well as the spinal cord in its cervical portion.

References

1. Tubbs, RS, Rasmussen, M., Loukas, M., Shoja, MM, & Cohen-Gadol, AA (2011). Three nearly forgotten anatomical triangles of the neck: triangles of Beclard, Lesser and Pirogoff and their potential applications in surgical dissection of the neck. Surgical and Radiologic Anatomy, 33 (1), 53-57.
2. Skolnik, EM, Yee, KF, Friedman, M., & Golden, TA (1976). The posterior triangle in radical neck surgery. Archives of Otolaryngology, 102 (1), 1-4.
3. Klem, C. (2012). Head Anatomy and and Neck Ultrasound Correlation. Head & Neck Ultrasound, An Issue of Ultrasound Clinics-E-Book, 7 (2), 161.
4. McMinn, RM, & Ship, AG (1986). Color atlas of head and neck anatomy.
5. Burns, A., & Pattison, GS (1824). Observations on the Surgical Anatomy of the Head and Neck. Wardlaw & Cunninghame.