The Cell bodies of the cervical sympathetic trunk come from the THORACIC (T1-T5) spinal cord. They synapse in 1 of 3 ganglia, superior, middle and inferior to provide the sole sympathetic supply for the head and neck.
The cell bodies of the ganglia are in the intermediolateral nucleus of the lateral grey column (often textbooks say the lateral horn).
The specific spinal level for the cell bodies of the cervical sympathetic ganglia is T1-T5 (there IS no direct - white rami - cervical outflow! Remember the outflow of sympathetic nerves is thoracolumbar - so the fibres come form the upper thoracic vertebrae and must then course UP the sympathetic chain to get to the ganglia.
The axons leave the thoracic spinal cord through the anterior root.
They then join the anterior rami of the spinal nerves.
Almost immediately, myelinated fibres (hence WHITE rami, mylin makes them look white) leave the ant. rami of the spinal nerves to join the sympathetic trunk.
Lateral horn -> anterior root> anterior rami spinal nerve ->white rami-> sympathetic trunk
These fibres are so far all pre-ganglionic. The cervical sympathetic fibres don't synapse until they have ascended all the way to the cervical ganglia - of which their are 3.
The cervical chain and its 3 ganglia are paravertebral. When it ascends from the thorax it crosses the first rib at its neck, medial to the highest intercostal vein.
It lies on the prevertebral fascia, which is covering the longus colli muscle.
The chain is just behind, posterior to, the carotid sheath,and just medial to the vagus nerve (the nerve in the sheath).
It then runs alll the way up to terminate as the superior cervical ganglion (at around C2-3).
In the developing embryo there is a ganglia for each of the cervical nerves - 1 for c1, 1 for c2 etc.
The reason there is only 3 ganglia and not 8 then, is because as the embryo develops they merge.
The upper four, c1-c4, become the Superior cervical ganglia.
The middle 2, c5-c6 become the middle.
The lower 2, c7-c8, become the inferior.
This explains 2 things - why the superior cervical ganglion is the biggest, and it explains the somatic branches:
each ganglion sends fibres from it (grey ramus because not myelinated) to the cervical spinal nerves.
Just like their formation, the superior sends grey rami to c1-4, the middle to c5-6 and the lower to c7-8 spinal nerves.
Often, the inferior ganglia is merged with the t1 ganglion to form the stellate ganglion or cervicothoracicganglion
The ansa subclavia is a branch of the trunk that connects the middle and inferior ganglia by passing anterior to the subclavian artery.
-lies in front of atlas and axis
- gives branches to external and internal carotid and hence supplies sympathetics to all viscera along their path (pterygopalatine, otic, submandibular ganglion, muscles of the eye, levator palpebrae superioris). Also supplies branches to the pharyngeal plexus.
Located at c6. Subclavian and inferior thyroid arteries - thus lower larynx, trachea, esophagus, hypopharynx.
Located at C7 (sometimes a little lower if merged as stellate ganglion) - supplies vertebral artery.