Fig. 20-5. The ventral ramus of the first thoracic nerve, viewed from below. Note how the upper division of T1 joins C8 and forms the lower trunk of the brachial plexus, which rests on the first rib. Part of the sympathetic trunk is shown. The cervicothoracic ganglion is tightly bound to the first thoracic nerve by rami communicantes, but these lie posteriorly and are hidden. Click for high resolution image.