the complex anatomy of the neck; clinically oriented

the anatomy of the normally overcrowded human neck

1. A natomy of the neck C.O.A 208 Session; 5 th session/ 2 nd semester; pages; 668-678 References; C.O.A By Richard Snell & Frank Netters atlas

2. Outline Overview ; Borders and Boundaries Surface anatomy Components/ contents Fascia of the neck / layers (cervical fascia) Neck triangles Bony and muscular content Hollow organs in the neck / tubes Neurovascular contents; arteries, veins, lymphatic vessels and nerves Solid viscera in the neck; thyroid and parathyroid glands Clinical relevance; cervical lymphadenopathy / radical neck surgery/ neck lumps

3. Borders and boundaries The borders of the neck are formed by; Superiorly; the lower edge of the mandible, temporal bone zygomatic process, external occipital protuberance. Inferiorly; the manubrium sterni , clavicle, acromio-clavicular joint and the 7th cervical vertebra spinous process AKA ; root of the neck/ thoracic inlet.

4. Surface anatomy

5. Cervical Fascia Superficial Cervical Fascia; The  superficial cervical fascia  lies between the dermis and the deep cervical fascia . It contains numerous structures: Neurovascular supply to the skin, Superficial veins (e.g. the external jugular vein), Superficial lymph nodes, Fat and the Platysma muscle. Platysma The   platysma  is a broad superficial muscle which lies anteriorly in the neck ( The superficial cervical fascia blends with the ‘paper thin’ platysma muscle) . It originate from the fascia of the  pectoralis major and deltoid. The fibres from the two heads cross the clavicle, and meet in the midline, fusing with the muscles of the face. Superiorly, the platysma inserts into the inferior border of the  mandible . Innervation to the platysma is via the cervical branch of the  facial nerve .

6. The  deep cervical fascia  lies, as its name suggests, ‘deep’ to the superficial fascia and platysma muscle.  This fascia is organized into several layers. These layers act like a shirt collar, supporting the structures and vessels of the neck. The layers of the deep cervical fascia ( superficial to deep): Investing Layer The  investing layer  is the most superficial of the deep cervical fascia. It surrounds all the structures in the neck. Where it meets the trapezius and  sternocleidomastoid  muscles, it splits into two, completely surrounding them. The investing fascia can be thought of as a tube; with superior, inferior, anterior and posterior attachments: Superior  – attaches to the external occipital protuberance and the superior nuchal line of the skull. Anteriorly  – attaches to the hyoid bone. Inferiorly  – attaches to the spine and acromion of the scapula, the clavicle, and the manubrium of the sternum. Posterior  – attaches along the nuchal ligament of the vertebral column

7. Pretracheal Layer The  pretracheal layer  of fascia is situated in the anterior neck. It spans between the hyoid bone superiorly and the thorax inferiorly (where it fuses with the pericardium). The trachea,  oesophagus ,  thyroid gland  and  infrahyoid  muscles are enclosed by the pretracheal fascia. Anatomically, it can be divided into two parts: Muscular part  – encloses the infrahyoid muscles. Visceral part  – encloses the thyroid gland, trachea and oesophagus .

8. Prevertebral Layer 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: Superior attachment  – base of the skull. Anterior attachment  – transverse processes and vertebral bodies of the vertebral column. Posterior attachment  – along the nuchal ligament of the vertebral column Inferior attachment  – fusion with the endothoracic fascia of the ribcage. The anterolateral portion of prevertebral fascia forms the floor of the  posterior triangle  of the neck. It also surrounds the  brachial plexus  as it leaves the neck and subclavian artery as it passes through the lower neck region – in doing so, it forms the  axillary sheath .

9. Neurovascular bundles in the neck

10. The neck is supplied by arteries other than the carotids. The right and left  subclavian  arteries give rise to the thyrocervical trunk. From this trunk, several vessels arise, which go on to supply the neck. The ascending cervical artery arises from the inferior thyroid artery, as it turns medially in the neck.

11. Bony support/ compartment of the neck

12. Hollow organs in the neck! Trachea Esophagus The larynx is also in the neck, above the windpipe (trachea) and in front of the (esophagus).   Hypo-pharynx………. upcoming sessions

13. Clinical relevance Carotid Sinus Hypersensitivity The  carotid sinus   contains specialized sensory cells known as baroreceptors. These cells detect stretch as a measure of blood pressure. The glossopharyngeal nerve feeds this information to the brain, and this is used to regulate blood pressure. In some individuals, the baroreceptors are  hypersensitive  to stretch. The brain becomes under-perfused and  syncope  results. In such patients, checking the pulse at the carotid triangle is not advised.

14. Cervical lymphadenopathy is most commonly localized to inflammatory processes in the neck or nearby areas. For instance, throat infection, the common cold, dental decay, ear infection, bronchitis, conjunctivitis, and infections of the salivary glands are all causative factors.

15. Neck pain, or cervicalgia , can last from days to years, depending on the cause. Common causes include physical strain, poor posture, mental stress, osteoarthritis, spinal stenosis, herniated disk, pinched nerve, tumors and other health conditions.

16. Radical neck dissection All the tissue on the side of the neck from the jawbone to the collarbone is removed. The muscle, nerve, salivary gland, and major blood vessel in this area are all removed.

17. Fascial Spaces of the Neck The neck fascia  compartmentalizes  structures within the neck. These layers of tough fascia can limit the spread of infection (for example, a superficial skin abscess may be prevented from spreading deeper into the neck by the investing fascia). However, infections that reach the  potential spaces  between the neck fascia have a well-defined spread: Retropharyngeal space  – located between the buccopharyngeal fascia (posterior aspect of the visceral pretracheal fascia) and the prevertebral fascia. Extends from the base of the skull to the posterior mediastinum. Visceral space  – enclosed by the visceral pretracheal fascia. Extends from the hyoid bone to the superior mediastinum.

18. End