What is the thoracic portion of the sympathetic system?

What it is

• The thoracic portion of the sympathetic trunk . consists of a series of ganglia, which usually correspond in number to that of the vertebræ; but, on account of the occasional coalescence of two ganglia, their number is uncertain. The thoracic ganglia rest against the heads of the ribs, and are covered by the costal pleura; the last two, however, are more anterior than the rest, and are placed on the sides of the bodies of the eleventh and twelfth thoracic vertebræ.
• The ganglia are small in size, and of a grayish color. The first, larger than the others, is of an elongated form, and frequently blended with the inferior cervical ganglion. They are connected together by the intervening portions of the trunk. Two rami communicantes, a white and a gray, connect each ganglion with its corresponding spinal nerve. The branches from the upper five ganglia are very small; they supply filaments to the thoracic aorta and its branches.
• Twigs from the second, third, and fourth ganglia enter the posterior pulmonary plexus.