Fascia is an intricate internal connective tissue, forming bands or sheets that help support and reinforce the muscles, vessels, and nerves in the body. Within the neck, the layers of the fascia work to provide structural support, as well as serving to compartmentalise the neck structures into two distinct layers – the superficial cervical fascia and the deep cervical fascia.
In this article, we shall further investigate the anatomy of the fascial layers of the neck, looking more closely into their attachments, anatomical relationships, and their associated clinical relevance.
The superficial cervical fascia lies beneath the dermis and above the deep cervical fascia, containing several structures and components. These include the neurovascular supply to the skin, superficial veins (such as the external jugular vein), superficial lymph nodes, fat, and the platysma muscle.
The superficial cervical fascia is connected to a broad, 'paper thin' platysma muscle, located on the anterior side of the neck. This is split into two heads, originating from the fascia of the pectoralis major and deltoid muscles. When it reaches the midline, these two heads fuse together, becoming one with the facial muscles. Superiorly, it inserts into the inferior border of the mandible, being innervated by the cervical branch of the facial nerve.
The deep cervical fascia is situated beneath the superficial fascia and platysma muscle, being organised into several layers. These layers act similarly to a shirt collar, providing support for the vessels of the neck. This article will investigate the layers of the deep cervical fascia in more detail, examining the anatomical components from the superficial to the deep layer.
The investing layer is by far the most superficial of the deep cervical fascia, surrounding all of the structures in the neck. As it meets the trapezius and sternocleidomastoid muscles, it splits into two, completely encircling them. This investing fascial layer can be thought of as a tube-like structure, stretching anatomically superior to the external occipital protuberance and the superior nuchal line of the skull, anteriorly to the hyoid bone, inferiorly to the spine and acromion of the scapula, the clavicle, and the manubrium of the sternum, and posteriorly attaching along the nuchal ligament of the vertebral column.
The pretracheal layer of the deep cervical fascia is located within the anterior neck, spanning from the hyoid bone superiorly, to the thorax inferiorly, where it connects with the pericardium. The trachea, oesophagus, thyroid gland, and infrahyoid muscles are all enclosed by this prethacheal fascia. Anatomically, it can be split into two distinct segments – the muscular component which encloses the infrahyoid muscles, and the visceral component, which encircles the thyroid gland, trachea, and oesophagus. The posterior aspect of this layer is formed by contributions from the buccopharyngeal fascia, which is the fascial covering of the pharynx.
The prevertebral fascia surrounds the vertebral column and its related muscle structures, including the scalene muscles, the prevertebral muscles, and the deep muscles of the back. In terms of its attachments, this layer of fascia stretches superiorly all the way to the base of the skull, anteriorly to the transverse processes and vertebral bodies of the vertebral column, posteriorly to the nuchal ligament of the vertebral column, and inferiorly to where it fuses with the endothoracic fascia of the ribcage. The anterolateral portion of this prevertebral fascia forms the floor of the posterior triangle of the neck.
The neck is an area comprised of several distinct anatomical structures. Located in the neck, and contributing to its physical makeup, are the following: the external jugular vein, superficial lymph nodes, fat, and the platysma muscle. The platysma is a broad, superficial muscle located anteriorly in the neck and is responsible for its unique structure.
The platysma is comprised of two heads, which originate from the fascia of the pectoralis major and deltoid muscles. These two heads cross the clavicle and meet in the midline, fusing with the muscles of the face. The platysma inserts into the inferior border of the mandible superiorly. Innervation of the platysma is provided by the cervical branch of the facial nerve.
Located beneath the superficial fascia and platysma muscle is the deep cervical fascia. There are several layers to this fascia, which act like a shirt collar, supporting the various structures and vessels of the neck. To better understand the make-up of the deep cervical fascia, its layers will be broken down one at a time (superficial to deep).
The investing layer of the deep cervical fascia is the most superficial. It surrounds all of the structures in the neck, and is unique in that it splits into two when it meets with the trapezius and sternocleidomastoid muscles, completely encircling them. The investing fascia can be thought of as a tube, with superior, inferior, anterior, and posterior attachments.
The pretracheal layer of fascia is situated in the anterior portion of the neck and spans between the hyoid bone superiorly and the thorax inferiorly. It encloses the trachea, oesophagus, thyroid gland, and infrahyoid muscles. It can be further divided into two parts: a muscular part that encloses the infrahyoid muscles and a visceral part that encloses the thyroid gland, trachea, and esophagus. The posterior aspect of this visceral fascia is formed by contributions from the buccopharyngeal fascia.
The prevertebral fascia surrounds the vertebral column and its associated muscles: scalene muscles, prevertebral muscles, and the deep muscles of the back. It has attachments along the antero-posterior and supero-inferior axes. These attachments include the base of the skull superiorly, the transverse processes and vertebral bodies of the vertebral column anteriorly, the nuchal ligament of the vertebral column posteriorly, and fusion with the endothoracic fascia of the ribcage inferiorly.
The anterolateral portion of the prevertebral fascia forms the floor of the posterior triangle of the neck. It also surrounds the brachial plexus as it leaves the neck and the subclavian artery as it passes through the lower neck region, forming the axillary sheath.
The carotid sheath is a paired structure on either side of the neck which encloses a neurovascular bundle in the neck. This bundle is comprised of the common carotid artery, the internal jugular vein, the vagus nerve, as well as accompanying cervical lymph nodes. The fascia of the carotid sheath is formed by contributions from the pretracheal, prevertebral, and investing fascia layers. The carotid artery bifurcates within the sheath into the external and internal carotid arteries.
The carotid fascia is organized into a column which runs from the base of the skull to the thoracic mediastinum. This is of clinical importance as it acts as a pathway for the spread of infection.
The neck fascia compartments structures within the neck, and its layers of tough fascia can work to limit the spread of infection. For example, a superficial skin abscess can be prevented from spreading further into the neck by the investing fascia. Infections which breach these spaces, however, have a well-defined spread.
The retropharyngeal space is located between the buccopharyngeal fascia and the prevertebral fascia and extends from the base of the skull to the posterior mediastinum. The visceral space is enclosed by the visceral pretracheal fascia.
The neck is a complex structure that extends from the hyoid bone to the superior mediastinum. It is comprised of several layers, including the skin, superficial fascia, platysma muscle, investing layer of deep cervical fascia, and prevertebral layer of deep cervical fascia. Each of these layers contains vessels, nerves, and muscles, however, they each have different relationships as well as different implications clinically.
The investing layer of deep cervical fascia is comparatively more lax than the other layers and serves as a suitable site for injections as well as the formation of fascial spaces. On the contrary, the prevertebral layer of deep cervical fascia is much denser and heftier, primarily made up of muscles. Its function is to protect the major vessels and nerves that traverse through the neck.
Having a thorough understanding of the anatomy of the neck and the relationships and relevance of its muscles and nerves is of great importance when it comes to effective clinical practice. To that end, the following sections will discuss the anatomy and clinical relevance of the neck in greater detail.
The layers of the neck include the skin, superficial fascia, platysma muscle, investing layer of deep cervical fascia, and prevertebral layer of deep cervical fascia. Let us examine each of these in greater detail.
The neck is comprised of several muscles that are responsible for different movements. These include the Sternomastoid, Scalene, Digastric, Splenius Capitis, Longus Capitis, Rectus Capitis Anterior, and Rectus Capitis Lateralis. Let us examine each of these muscles in more detail.
The neck contains a number of important nerves that are responsible for a variety of functions. These include the ansa cervicalis nerve, the brachial plexus, the glossopharyngeal nerve, the hypoglossal nerve, the vagus nerve, the accessory nerve, and the hypoglossal nerve. Let us examine each of these nerves in more detail.
Understanding the anatomy and clinical relevance of the neck is essential in order to effectively diagnose and manage conditions related to the neck. For instance, a thorough understanding of the fascial layers of the neck will help to ensure that injections are placed accurately and that fascial spaces are formed correctly. Similarly, a comprehensive knowledge of the muscles and nerves of the neck will aid in the differential diagnosis of neck pain and other neck-related disorders. Additionally, being aware of the vascular supply of the neck can help to ensure safe surgery and prevent excessive bleeding and tissue damage.
In conclusion, the anatomy of the neck and its associated muscles, nerves, and vessels are essential for proper diagnosis and management of neck-related conditions. An in-depth knowledge of these structures is necessary in order to effectively practice medicine and provide the best possible care for patients.
