Abdominal Aorta

The Abdominal Aorta extends from the middle of the body of the last dorsal vertebra to the left side of the body of the fourth lumbar vertebra, where it divides into the two common iliac arteries. The bifurcation.is in the intertubercular plane. It lies on the vertebral column, and anteriorly is in contact with the solar plexus, the third part of the duodenum, the mesentery, peritoneum, and coils of small intestine. The pancreas is separated from the aorta by the splenic vein and superior mesenteric artery.

Fig. 57. - The Abdominal Aorta.

Branches

The branches are divided into two sets-visceral

Aorta and parietal - and each set is again divided into paired and unpaired groups, which supply the viscera, the muscles of the trunk and the lower limbs.

The lumbar arteries which supply the muscles of the trunk arise down the sides of the aorta opposite the bodies of the lumbar vertebrae.

Common Carotid Artery

The Common Carotid arteries vary slightly at their commencement; otherwise they are similar in course and distribution.

The Right Common Carotid artery arises from the innominate artery behind the right sterno-clavicular articulation; the left arises direct from the arch of the aorta about an inch below the left sterno-clavicular articulation. They both terminate at the level of the upper border of the thyroid cartilage of the larynx, or the lower border of the third cervical vertebra. They are separated from one another- below by the trachea and oesophagus, above by the pharynx.

The common carotid artery is enclosed in a fibrous sheath with the vagus nerve and internal jugular vein. It lies on scalenus anticus and longus colli muscles below, and rectus capitis anticus major above, and is covered by sterno-mastoid. On its outer side lies the internal jugular vein, which slightly overlaps it below.

Branches

The artery bifurcates at its termination, forming the external and internal carotid arteries.

External Carotid Artery

The External Carotid artery extends from the bifurcation of the common carotid artery to the back of the neck of the mandible, where it terminates by dividing into the superficial temporal and internal maxillary arteries.

Branches

Occipital.

Superficial temporal.

Internal maxillary, and five other branches which supply the face, tongue, pharynx, and larynx.

The Occipital artery runs upwards under the mastoid process to the back of the scalp, and terminates near the inner end of the superior curved line of the occipital bone. By dividing into-branches it supplies the scalp and surrounding structures.

The Superficial Temporal artery commences in the parotid gland and runs straight up, terminating about 2 inches above the zygoma by dividing into branches. It supplies the scalp and surrounding structures.

The Internal Maxillary artery commences in the parotid gland and passes inwards to supply the teeth and structures behind the superior maxilla and mandible.

The Internal Carotid artery commences at the bifurcation of the common carotid and terminates in the brain by dividing into branches. At first it lies on the outer side of the external carotid, but passes behind it and gets to the inner side. It passes up at the back of the parotid gland and reaches the brain by means of the carotid canal in the temporal bone.

The Subclavian arteries also vary slightly at their commencement, the right subclavian artery commencing at the bifurcation of the innominate artery behind the right sterno-clavicular articulation, and the left subclavian artery commencing from the arch of the aorta behind the lower part of the manubrium sterni. The artery arches up over the apex of the lung, and passing between scalenus anticus and medius, it ends at the lower border of the first rib by becoming the axillary artery. The scalenus anticus, in crossing the subclavian artery divides it into three parts-the first part being internal to the muscle, the second behind it, and the third on the external side. The third part of the artery is separated from scalenus medius by the cords of the brachial plexus.

Branches

From the first part:

Vertebral, thyroid axis, internal mammary. From the second part: Superior intercostal.