Henry Gray (18251861). Anatomy of the Human Body. 1918.
passes downward in front of them, and the splanchnic nerves also descend in front by the lower arteries. Each artery then divides into an anterior and a posterior ramus.
The Anterior Ramus crosses the corresponding intercostal space obliquely toward the angle of the upper rib, and thence is continued forward in the costal groove. It is placed at first between the pleura and the posterior intercostal membrane, then it pierces this membrane, and lies between it and the Intercostalis externus as far as the angle of the rib; from this onward it runs between the Intercostales externus and internus, and anastomoses in front with the intercostal branch of the internal mammary or musculophrenic. Each artery is accompanied by a vein and a nerve, the former being above and the latter below the artery, except in the upper spaces, where the nerve is at first above the artery. The first aortic intercostal artery anastomoses with the intercostal branch of the costocervical trunk, and may form the chief supply of the second intercostal space. The lower two intercostal arteries are continued anteriorly from the intercostal spaces into the abdominal wall, and anastomose with the subcostal, superior epigastric, and lumbar arteries.
Branches.The anterior rami give off the following branches:
The collateral intercostal branch comes off from the intercostal artery near the angle of the rib, and descends to the upper border of the rib below, along which it courses to anastomose with the intercostal branch of the internal mammary.
Muscular branches are given to the Intercostales and Pectorales and to the Serratus anterior; they anastomose with the highest and lateral thoracic branches of the axillary artery.
The lateral cutaneous branches accompany the lateral cutaneous branches of the thoracic nerves.
Mammary branches are given off by the vessels in the third, fourth, and fifth spaces. They supply the mamma, and increase considerably in size during the period of lactation.
The Posterior Ramus runs backward through a space which is bounded above and below by the necks of the ribs, medially by the body of a vertebra, and laterally by an anterior costotransverse ligament. It gives off a spinal branch which enters the vertebral canal through the intervertebral foramen and is distributed to the medulla spinalis and its membranes and the vertebræ. It then courses over the transverse process with the posterior division of the thoracic nerve, supplies branches to the muscles of the back and cutaneous branches which accompany the corresponding cutaneous branches of the posterior division of the nerve.
The subcostal arteries, so named because they lie below the last ribs, constitute the lowest pair of branches derived from the thoracic aorta, and are in series with the intercostal arteries. Each passes along the lower border of the twelfth rib behind the kidney and in front of the Quadratus lumborum muscle, and is accompanied by the twelfth thoracic nerve. It then pierces the posterior aponeurosis of the Transversus abdominis, and, passing forward between this muscle and the Obliquus internus, anastomoses with the superior epigastric, lower intercostal, and lumbar arteries. Each subcostal artery gives off a posterior branch which has a similar distribution to the posterior ramus of an intercostal artery.
The superior phrenic branches are small and arise from the lower part of the thoracic aorta; they are distributed to the posterior part of the upper surface of the diaphragm, and anastomose with the musculophrenic and pericardiacophrenic arteries.
A small aberrant artery is sometimes found arising from the right side of the thoracic aorta near the origin of the right bronchial. It passes upward and to the right