296 THE HUMAN BODY 



phragm it enters the abdomen and after supplying the parts in 

 and around that cavity with branches, it ends opposite the last 

 lumbar vertebra by dividing into the right and left common iliac 

 arteries, which carry blood to the lower limbs. We have then to 

 consider the branches of the arch of the aorta, and those of the 

 descending aorta, which latter is for convenience described by 

 anatomists as consisting of the thoracic aorta, extending from the 

 end of the arch to the diaphragm, and the abdominal aorta, extend- 

 ing from the diaphragm to the final subdivision of the vessel. 



Branches of the Arch of the Aorta. From this arise first the 

 coronary arteries (crd and crs, Figs. 103 and 104) which spring 

 close to the heart, just above two of the pouches of the semilunar 

 valve, and carry blood into the substance of that organ. The 

 remaining branches of the arch are three in number, and all arise 

 from its convexity. The first is the innominate artery (Ab, Fig. 

 103), which is very short, immediately breaking up into the right 

 subclavian artery, and the right common carotid. Then comes the 

 left common carotid, Cs, and finally the left subclavian, Ssi. 



Each subclavian artery runs out to the arm on its own side and 

 after giving off a vertebral artery (which runs up the neck to the 

 head in the vertebral canal of the transverse processes of the 

 cervical vertebrae), crosses the armpit and takes there the name of 

 the axillary artery. This continues down the arm as the brachial 

 artery, which, giving off branches on its way, runs to the front of 

 the arm, and just below the elbow-joint divides into the radial 

 and ulnar arteries, the lower ends of which are seen at R and U in 

 Fig. 101. These supply the forearm and end in the hand by unit- 

 ing to form an arch, from which branches are given off to the 

 fingers. 



The common carotid arteries pass out of the chest into the neck, 

 along which they ascend on the sides of the windpipe. Opposite 

 the angle of the lower jaw each divides into an internal and exter- 

 nal carotid artery, right or left as the case may be. The external 

 ends mainly in branches for the face, scalp, and salivary glands, 

 one great subdivision of it with a tortuous course, the temporal 

 artery, being often seen in thin persons beating on the side of the 

 brow. The internal carotid artery enters the skull through an 

 aperture in its base and supplies the brain, which it will be re- 

 membered also gets blood through the vertebral arteries. 



