The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipose tissue immediately beneath the skin.

The deep cervical fascia of the neck includes four parts:

• The investing layer (encloses the SCM and Trapezius)
• The carotid sheath (encloses the vascular region of the neck)
• The pretracheal fascia (encloses the visceral region of the neck)
• The prevertebral fascia (encloses the vertebral region of the neck)

Structure

The carotid sheath is located at the lateral boundary of the retropharyngeal space

Retropharyngeal space

The retropharyngeal space is a space bounded by the buccopharyngeal fascia anteriorly and the alar fascia posteriorly.It includes the retropharyngeal lymph nodes....

 at the level of the oropharynx

Oropharynx

The Oropharynx reaches from the Uvula to the level of the hyoid bone.It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two palatine arches, is the palatine tonsil....

 on each side of the neck and deep to the sternocleidomastoid muscle

Sternocleidomastoid muscle

In human anatomy, the sternocleidomastoid muscle , also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the anterior portion of the neck...

, extending from the base of the skull

Human skull

The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...

 to the first rib and sternum.

Contents

The four major structures contained in the carotid sheath are:

• the common carotid artery
  Common carotid artery
  In human anatomy, the common carotid artery is an artery that supplies the head and neck with oxygenated blood; it divides in the neck to form the external and internal carotid arteries. - Structure :...
  
   as well as the internal carotid artery
• internal jugular vein
  Internal jugular vein
  The two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck.-Path:On both sides and at the base of the brain, the inferior petrosal sinus and the sigmoid sinus join to form the internal jugular vein...
  
  
• the vagus nerve
  Vagus nerve
  The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
  
  (CN X)
• the deep cervical lymph nodes
  Deep cervical lymph nodes
  The deep cervical lymph nodes are a group of cervical lymph nodes found near the internal jugular vein.They can be divided into upper and lower groups, or superior and inferior groups....
  
  .

The carotid artery lies medial to the internal jugular vein, and the vagus nerve is situated posteriorly between the two vessels.

In the upper part, the carotid sheath also contains the glossopharyngeal nerve

Glossopharyngeal nerve

The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...

 (IX), the accessory nerve

Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...

 (XI), and the hypoglossal nerve

Hypoglossal nerve

The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal...

 (XII), which pierce the fascia of the carotid sheath.

The ansa cervicalis

Ansa cervicalis

The ansa cervicalis is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid sheath....

 is embedded in the anterior wall of sheath. It is formed by "descendens hypoglossi" (C1) and "descendens cervicalis" (C2-C3).

Layers

The three major fascial layers in the neck contribute to the carotid sheath: the investing fascia, the pretracheal fascia

Pretracheal fascia

The pretracheal fascia extends medially in front of the carotid vessels, and assists in forming the carotid sheath.It is continued behind the depressor muscles of the hyoid bone, and, after enveloping the thyroid gland, is prolonged in front of the trachea to meet the corresponding layer of the...

, and the prevertebral fascia

Prevertebral fascia

The prevertebral fascia is a fascia in the neck.-Variations:In some literature, the prevertebral fascia also includes the rest of the fascia extending around the vertebral column and enclosing all muscles laterally and posteriorly to it...

Relations

The cervical part of the sympathetic trunk

Sympathetic trunk

The sympathetic trunks are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.-Structure:...

 is embedded in prevertebral fascia

Prevertebral fascia

The prevertebral fascia is a fascia in the neck.-Variations:In some literature, the prevertebral fascia also includes the rest of the fascia extending around the vertebral column and enclosing all muscles laterally and posteriorly to it...

immediately posterior to the sheath.

External links

• Cross section at tufts.edu