Fascia and spaces of the neck

Definitions & Key takeaways

Fascia is a type of connective tissue that surrounds and supports the muscles, organs, and other tissues of the body. It comprises collagen and elastin proteins, and has a very important role in protecting the body against injuries. The neck has superficial fascia which is just beneath the skin, and deep fascia which is deeper, and surrounds muscles and neck structures, organizing them into compartments.

The spaces of the neck are the areas where the fascia is thin and flexible. This allows for greater movement and flexibility in the neck region, and can help predict the mechanism of spread of infections in surrounding tissues.

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Introduction0:00–0:56

The structures found in the neck are surrounded by a layer of subcutaneous tissue called the superficial fascia, while there are also layers of deep cervical fascia which distribute the structures in the neck into different compartments.
These fascial layers create different anatomical spaces in the neck, and dictate where an infection may spread if it starts in one of these compartments.
So, let’s take a look at the different fascia layers of the neck. You can think of fascia as a pair of thin stockings made of connective tissue that support and bind together different parts of the body, including the neck.
Now, the neck actually has two pairs of stockings on top of each other: the superficial fascia, which sits right underneath our skin, and the deep fascia, which is deep to or beneath the superficial fascia, and it surrounds muscles and viscera organizing them into compartments.
Ok, so the superficial cervical fascia or the cervical subcutaneous tissue is a layer of fatty connective tissue that lies between the skin and the most superficial layer of deep cervical fascia.

Superficial fascia0:56–2:45

This fascia is usually thinner than in other regions, especially anteriorly, and it contains cutaneous nerves, blood and lymphatic vessels, superficial lymph nodes and variable amounts of fat.
Anterolaterally, it contains the platysma, which is a thin sheet of muscle that covers the anterolateral portion of the neck.
Inferiorly, the platysma attaches to the deep fascia that covers the superior parts of pectoralis major and deltoid muscles, with its fibers moving superomedially over the clavicle and attaching superiorly to the inferior border of the mandible, and skin and subcutaneous tissues of the lower face.
The anterior borders of the two platysma muscles join together over the chin and blend with the facial muscles but inferiorly, the fibers remain separated, leaving a gap anterior to the larynx and trachea.
Deep to the platysma, there are the main cutaneous nerves of the neck and the external jugular vein, which descends from the angle of the mandible to the middle of the clavicle.
The platysma is supplied by the cervical branch of the facial nerve, or cranial nerve VII, and it’s involved in facial expression.
Acting from its superior attachment, it tenses the skin producing vertical skin ridges and releasing pressure on the superficial veins.
This action is often used when people shave their necks or ease a tight collar. Acting from its inferior attachment, it depresses the lower jaw and it also draws down the lower lip and angle of the mouth in the expression of sadness and fright.
Moving on, the deep cervical fascia consists of three fascial layers or sheaths called the investing, pretracheal and prevertebral fascia which serve to support the cervical viscera, muscles, vessels and lymph nodes.

Deep fascia2:45–7:23

The deep cervical fascia also wraps around the common carotid arteries, internal jugular veins and vagus nerves to form the carotid sheath.
These fascial layers form natural cleavage planes through which tissues may be separated during surgery and they limit the spread of abscesses that can result from infections.
Also, they allow the structures in the neck to move and pass over one another without difficulty, such as when swallowing or turning the head and neck.
Ok so, let’s begin with the investing layer of the deep cervical fascia which is the most superficial deep fascial layer.
This layer surrounds the entire neck deep to the skin and subcutaneous tissue, investing the trapezius and sternocleidomastoid (SCM) muscles.
Superiorly, it attaches to the superior nuchal lines of the occipital bone, to the mastoid processes of the temporal bones, the zygomatic arches, the inferior border of the mandible, the hyoid bone and the spinous processes of the cervical vertebrae.
Just inferior to its attachment to the mandible, the investing layer splits to enclose the submandibular gland and posterior to the mandible, it splits to form the fibrous capsule of the parotid gland, both of which are salivary glands.
Inferiorly, the investing layer attaches to the manubrium of the sternum, clavicles and acromions, and spines of the scapulae.
Posteriorly, the investing layer continues with the periosteum that covers the C7 spinous process and with the nuchal ligament, which is a triangular membrane that forms a median septum between the muscles of the two sides of the neck.
Inferiorly between the sternal heads of the sternocleidomastoid muscle and just superior to the manubrium, the investing layer remains divided into two layers to enclose the SCM: one layer attaches to the anterior and the other to the posterior surface of the manubrium to form a space called the suprasternal space.
Here, the inferior ends of the anterior jugular veins, the jugular venous arch, fat and a few deep lymph nodes can be found.
Now, let’s move on to the pretracheal layer of deep cervical fascia which is located in the anterior part of the neck and extends from the hyoid bone into the thorax where it blends with the fibrous pericardium that covers the heart.
This layer has two parts: a thin muscular part that encloses the infrahyoid muscles, and a visceral part that encloses the thyroid gland, trachea and esophagus.
The visceral part extends posteriorly and superiorly to blend with the buccopharyngeal fascia of the pharynx. Laterally, the pretracheal layer blends with the carotid sheath.
Superior to the hyoid, the pretracheal layer forms a pulley or trochlea through which passes the intermediate tendon of the digastric muscle, suspending the hyoid.
Inferiorly, the pretracheal layer communicates freely with the mediastinum of the thorax. If an infection between the muscular part of the pretracheal fascia and the visceral part of the pretracheal fascia were to arise, then it could spread anterior to the pericardium into the thoracic cavity.
Next, the prevertebral layer of the deep cervical fascia forms a tubular sheath for the vertebral column and the muscles associated with it such as longus colli and longus capitis anteriorly, the scalenes laterally and the deep cervical muscles posteriorly.
The cervical part of the sympathetic trunk is also embedded in the prevertebral fascial layer. The prevertebral layer is fixed superiorly to the cranial base and inferiorly it ends by blending with the endothoracic fascia and fusing with the anterior longitudinal ligament centrally at approximately the T3 vertebra.
Laterally, the prevertebral fascia extends as the axillary sheath which surrounds the axillary vessels and brachial plexus.

Quiz7:23–7:36

Time for a break! Let’s pause and see if you can identify the superficial cervical fascia as well as the deep cervical fascia with all its layers.

Carotid sheath and retropharyngeal space7:36–9:34

Alright, now, just a few words on the carotid sheath and the retropharyngeal space, which are important spaces located in the neck.
The carotid sheath is a tube of fascia that extends from the cranial base to the root of the neck and contains the common and internal carotid arteries, internal jugular vein, vagus nerve, some deep cervical lymph nodes, carotid sinus nerve, and sympathetic nerve fibers.
This sheath blends anteriorly with the investing and pretracheal layers of deep cervical fascia and posteriorly with the prevertebral layer of deep cervical fascia.
Along with the pretracheal fascia, the carotid sheath communicates freely with the mediastinum inferiorly. Finally, the retropharyngeal space is the largest interfascial space in the neck.
It is a potential space, consisting of loose connective tissue between the visceral part of the prevertebral fascia and the buccopharyngeal fascia surrounding the pharynx superficially, and it allows the pharynx, esophagus, larynx and trachea to move relative to the vertebral column during swallowing.
The retropharyngeal space is closed by the cranial base superiorly and by the carotid sheath laterally but remains open inferiorly communicating with the thorax in the superior mediastinum.
The retropharyngeal space is further divided into a true retropharyngeal space and danger space by a thin sheath of fascia called the alar fascia which attaches along the midline of the buccopharyngeal fascia from the cranium to the level of C7, extending laterally to the carotid sheaths.
The true retropharyngeal space is located anterior to the danger space and extends from the base of the skull to where the alar fascia fuses with the buccopharyngeal fascia.
The danger space extends more inferiorly communicating with the posterior mediastinum until the level of the diaphragm. Alright, as a quick recap… The neck has two pairs of stockings on top of each other: the superficial fascia, which sits right underneath our skin, and the deep fascia, which is deep to or beneath the superficial fascia, and it surrounds muscles and viscera organizing them into compartments.

Review9:34–11:23

The superficial cervical fascia or the cervical subcutaneous tissue is a layer of fatty connective tissue which contains cutaneous nerves, blood and lymphatic vessels, superficial lymph nodes and variable amounts of fat and anterolaterally it contains the platysma which is a thin sheet of muscle involved in facial expression.
The deep cervical fascia supports the cervical viscera, muscles, vessels and lymph nodes and consists of three fascial layers or sheaths: investing, pretracheal and prevertebral and also wraps around the common carotid arteries, internal jugular veins and vagus nerves to form the carotid sheath.
The investing layer encloses the trapezius muscle, sternocleidomastoid muscle, and the submandibular and parotid glands.
The pretracheal layer encloses the infrahyoid muscles, thyroid gland, trachea and esophagus and the prevertebral layer encloses the vertebral column and its associated muscles.
The pretracheal fascia and the carotid sheath freely communicate with the mediastinum inferiorly, and the space between the muscular and the visceral layers of pretracheal fascia communicates with the thoracic cavity anterior to the pericardium.There is also the retropharyngeal space found between the visceral part of the prevertebral fascia and the buccopharyngeal fascia, with part of this space communicating with