of the neck of the first rib, which is 2.5–5.0 cm above the sternal end of the first rib. A thickening of the fascia—the suprapleural membrane—stretches from the transverse process of the seventh cervical vertebra to the inner margin of the first rib and cov- ers the cervical pleura. This membrane may contain some muscle fibres—the scalenus minimus.
The upper two ribs, the first intercostal space, and the sympathetic trunk lie posterior to the cer- vical pleura. The great vessels of the upper limb and head and neck lie anterior to it. The vertebral artery curves superiorly over the dome of the pleura to reach the vertebral column [Fig. 9.7].
The vertebral bodies, oesophagus, and trachea, and on the left side the thoracic duct and the re- current laryngeal nerve, lie medial to the cervical pleura. The scalenus anterior, subclavian artery,
and the lower trunk of the brachial plexus lie lat- eral to it. Because the subclavian artery lies on the anterior surface of the cervical pleura, its ascending and descending branches—the vertebral artery, in- ferior thyroid artery, and internal thoracic artery—
also lie on the anterior surface. The costocervical trunk and its superior intercostal branch arch over the dome of the pleura from the anterior to the posterior surface.
Vertical neurovascular bundles of the neck
A neurovascular bundle lies on each side of the tra- chea and oesophagus. In the lower part of the neck, the bundle consists of the internal jugular vein laterally, the common carotid artery medially, and the vagus nerve behind and between them.
Above the level of the thyroid cartilage, the neuro- vascular bundle consists of the internal carotid artery, internal jugular vein, glossopharyngeal,
Larynx Pharynx
External carotid A.
1
2
3
4
5
6 7
Internal carotid A.
Ascending cervical A.
Superficial cervical A.
Deep cervical A.
Vertebral A.
Spinal cord Dorsal ramus
cervical N.
Ventral ramus Accessory N.
Vagus N.
Sympathetic trunk Thyroid gland
Fig. 9.10 Diagrammatic transverse section through the neck to show the distribution of nerves (left) and arteries (right). The diagram is constructed from a number of adjacent levels. The part of the accessory nerve shown by an interrupted line is at a still higher level. 1. In- frahyoid muscles. 2. Sternocleidomastoid. 3. Scalenus medius. 4. Levator scapulae. 5. Semispinalis capitis. 6. Splenius capitis. 7. Trapezius.
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Vertical neurovascular bundles of the neck
vagus, spinal accessory, and hypoglossal nerves. The bundle is enclosed in a fascial sheath—
the carotid sheath [see Fig. 5.2; Fig. 9.11]—which extends from the root of the neck to the base of the skull. It lies on the sympathetic trunk, prevertebral fascia, prevertebral muscles, and cervical transverse processes. Parts of this neurovascular bundle have been seen and described in the carotid triangle in Chapter 6.
Dissection 9.5 provides instructions on dissec- tion of the neurovascular structures of the neck.
Before beginning the dissection, identify the car- otid canal, jugular foramen, hypoglossal canal, and foramen magnum on the base of a dried skull, and note the openings of these foramina on its internal aspect [see Fig. 8.7]. The carotid canal lies fur- thest anteriorly and transmits the internal carotid artery. Immediately posterior to it is the jugular foramen which transmits the sigmoid and infe- rior petrosal sinuses and the glossopharyngeal, va- gus, and accessory nerves between the two veins.
The hypoglossal nerve traverses the hypoglossal
DISSECTION 9.5 Neurovascular structures of the neck Objectives
I. To remove the right half of the skull and related structures, so as to gain approach to the cavities of the nose, mouth, pharynx, and larynx from the medial side. II. To expose the superior parts of the internal ca- rotid artery, the internal jugular vein, and the lower four cranial nerves in the upper part of the carotid sheath.
Instructions
1. On the right side, free the greater occipital nerve from the scalp, and turn it inferiorly. Cut through the great auricular, lesser occipital, and transverse nerve of the neck on the sternocleidomastoid.
Leave sufficient nerve on both sides of the cuts to allow the ends to be identified subsequently.
2. In the suboccipital triangle, separate the supe- rior oblique and rectus capitis posterior major and the minor muscles from their bony attach- ments, and remove them. This exposes the pos- terior atlanto-occipital membrane [see Fig. 22.4].
Cut across this membrane close to the skull, but
avoid damage to the vertebral arteries on the posterior arch of the atlas.
3. Detach the longissimus muscle from the skull [see Fig. 7.4].
4. Cut across the sternocleidomastoid 2–3 cm above the clavicle, and turn it superiorly. Clean the deep surface of the sternocleidomastoid as far as the skull, and identify the accessory nerve entering it.
Cut the nerve in the posterior triangle, so that the superior part of the nerve remains with the ster- nocleidomastoid.
5. Pass a finger behind the carotid sheath and phar- ynx, and separate them from the prevertebral fascia and the sympathetic trunk as far superiorly as the superior cervical ganglion. Note how easily the loose fascia behind the pharynx is torn. (In the living, this loose areolar tissue permits the phar- ynx to slide on the vertebral column.)
6. Saw through the mandible in the midline, and continue this cut through the tongue and epiglot- tis with a knife. Cut through the hyoid bone in the Fig. 9.11 Transverse section through the anterior part of the neck at the level of the upper part of the thyroid cartilage.
Infrahyoid Mm.
Thyroid cartilage Piriform recess
Superior thyroid A.
Superior root of ansa cervicalis
Sympathetic trunk
Vertebral A.
Longus colli Scalenus anterior
Sternocleidomastoid Retropharyngeal space Carotid sheath Posterior wall of pharynx
Arytenoid cartilage Vocal fold Median thyrohyoid ligament
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Deep dissection of the neck
midline, and extend the incision inferiorly through the larynx, pharynx, and trachea to the inferior border of the isthmus of the thyroid gland.
7. Cut transversely through the right half of the tra- chea, oesophagus, and neurovascular bundle. (Do not cut the sympathetic trunk, phrenic nerve, and scalenus anterior.)
8. Separate the upper parts of the transected struc- tures from those behind them.
9. Make a mid-sagittal saw cut through the anterior part of the skull up to the foramen magnum. Do not damage the atlas vertebra.
10. Within the skull, detach the dura mater and mem- brana tectoria [see Fig. 22.4] from the anterior mar- gin of the foramen magnum, and turn it inferiorly to expose the alar ligaments and the longitudinal fibres of the cruciate ligament [see Fig. 22.1].
11. Cut across the right alar ligament, and flex the right half of the head on the vertebral column.
Divide the tight posterior part of the capsule of the atlanto-occipital joint. Now lever the occipi- tal condyle out of its articulation, cutting any re- maining parts of the capsule of the joint as they are exposed.
12. Free the vertebral artery and the first cervical nerve from the posterior arch of the atlas, and cut across the artery where it emerges from the transverse process of the atlas. Cut through the rectus capitis lateralis, rectus capitis anterior, lon- gus capitis [see Fig. 10.1], and anterior atlanto- occipital membrane [see Fig. 22.4].
13. Complete the median division of the soft palate and of the posterior pharyngeal wall with a knife.
Gently lift away the right half of the skull and at- tached structures. (Leave the ganglion and sympa- thethic trunk on the vertebral column.)
On the right side:
14. Find the internal laryngeal nerve piercing the thy- rohyoid membrane. Trace it superiorly to the su- perior laryngeal nerve, medial to the external and internal carotid arteries. Trace the superior laryn- geal nerve to the vagus. Above its origin from the vagus, find the pharyngeal branch of the vagus, and trace it between the carotid arteries to the pharynx [see Fig. 6.5; Fig. 9.12].
15. Find the glossopharyngeal, accessory, and hy- poglossal nerves in the upper part of the neu-
rovascular bundle, and trace them distally. The nerves separate inferiorly [Figs. 9.12, 9.13]. The accessory (spinal part) runs postero-inferiorly, either superficial or deep to the internal jugular vein. The glossopharyngeal nerve passes ante- ro-inferiorly with the stylopharyngeus muscle, lateral to the internal carotid artery. The hypo- glossal nerve curves anteriorly, superficial to the internal and external carotid arteries. The vagus descends vertically between the artery and vein in the carotid sheath.
16. When following the glossopharyngeal nerve, identify the stylopharyngeus muscle on which it runs to the pharynx. Trace the muscle to its origin from the styloid process.
17. The stylopharyngeus enters the pharynx be- tween the superior and middle constrictor mus- cles of the pharynx. The upper margin of the middle constrictor can be defined and followed forwards to the hyoid bone [see Fig. 6.5].
18. Trace a branch from the glossopharyngeal and va- gus nerves down between the two carotid arteries to the carotid sinus [Fig. 9.12]. This branch is the carotid sinus nerve and may be followed to the carotid body in the bifurcation of the common carotid artery.
19. Find the branches of the sympathetic ganglion (grey rami communicantes) passing posteriorly to the upper four cervical ventral rami.
20. Trace the occipital artery from the occiput to its origin.
21. Expose the posterior belly of the digastric from behind, and find the hypoglossal nerve hooking round the origin of the occipital artery, superficial to both carotid arteries [Fig. 9.14].
On the left side:
22. Cut through the posterior belly of the digastric, close to its origin. Turn it antero-inferiorly to ex- pose the stylopharyngeus [see Fig. 6.5], but avoid damage to the glossopharyngeal nerve which curves round the lateral aspect of the muscle.
23. Lift the neurovascular bundle from the sympa- thetic trunk, and trace the trunk upwards to the superior cervical ganglion. Attempt to find the branches of the ganglion to the internal carotid artery, the external carotid artery, and the cranial nerves in the bundle.