The major arterial supply to the abdomen and pelvis is provided by the dorsal aorta. This arterial trunk leaves the left ventricle of the heart and bends towards the diaphragm.
The right subclavian artery and the brachiocephalic trunk branch off the aorta in a cranial direction, and the aorta bends caudally. The brachiocephalic trunk gives rise to the right subclavian artery and the two common carotid arteries.
The aorta lies dorsally in the thorax, just ventral to the thoracic vertebrae, and passes caudally to the diaphragm. The aorta perforates the diaphragm at the aortic hiatus, a fibrous ring located dorsally immediately ventral to the L3/L4 vertebrae. The aortic hiatus lies between the left and right crura of the diaphragm. The hiatus is further reinforced by the sublumbar muscles (e.g. psoas muscles).The diaphragm is also perforated by the oesophageal hiatus and the caudal caval foramen. The former is located between the crura but further away from the tendinous origins and is not supported by the sublumbar muscles. The oesophageal hiatus is reinforced by collagen fibres and must be capable of expansion to allow swallowing; nevertheless, this is a weak point with the risk of herniation. The caudal caval foramen is further ventral, perforating the tendinous centre of the diaphragm.
The abdominal aorta is displaced slightly to the left by the caudal vena cava and lies along the roof of the abdomen in a furrow between the left and right psoas muscles. The abdominal aorta ends caudally at the level of the last lumbar vertebra, where it divides into the pair of external iliac arteries.
Between the diaphragm and the caudal bifurcation the abdominal aorta gives origin to a succession of both paired and midline arterial branches.
8.1