Innervation of stretch receptors in the extra-thoracic trachea.

We have studied the innervation of the stretch receptors in the extra-thoracic trachea by recording their unitary action potentials from the vagus nerve in the neck before and after blocking the nervous conduction in the recurrent laryngeal nerves (RLNs). On the left side all the receptors had their activity going through the ipsilateral RLN:78% of the stretch receptors had their fibres joining the RLN in the neck whilst the remaining receptors join this nerve within the thorax. These latter receptors were located mainly in the lower extra-thoracic trachea. On the right side only 45% of the receptors were found to follow the right RLN whilst the others reach the vagus nerve through a different pathway. These latter receptors were located in the lower part of the extra-thoracic trachea. Therefore sectioning both the RLNs would interrupt about 3/4 of the fibres coming from the extra-thoracic trachea if done just before their entrance into the main vagus nerves. When the section is done exclusively outside the thorax, at the level of the thoracic inlet, the de-afferentation would be about 60% of the total supply.