THE BRACHIAL OR HUMERAL ARTERY. 



465 



BRACHIAL OR HUMERAL ARTERY 

 (arteria brachialis, humeraria. Germ, die Ar- 

 marterie.) This artery is the continuation of 

 the trunk of the axillary. It commences at the 

 inferior margin of the tendons of the teres ma- 

 jor and latissimus dorsi, whence it extends to 

 about an inch below the bend of the elbow, 

 where it usually divides into the radial and 

 ulnar arteries ; but not unfrequently this divi- 

 sion takes place high in the arm. 



The brachial artery lies on the internal side 

 of the arm above, but in its course downwards 

 it gradually advances in an oblique direction 

 until it gets completely to the anterior surface 

 of the limb, where it is found situated nearly 

 midway between the condyles of the humerus 

 in front of the elbow joint ; it is superficial in 

 the whole line of its course, in every part of 

 which its pulsations can easily be felt, and 

 sometimes, in the arms of thin persons, are 

 distinctly visible. 



Relations. Anteriorly the brachial artery 

 is overlapped, for about its upper fourth, by the 

 coraco-brachialis muscle and the median nerve; 

 for the greater part of its course down the arm 

 it is covered by the brachial aponeurosis, to 

 which is added, where it crosses the elbow, the 

 falciform expansion sent off from the tendon of 

 the biceps to the internal condyle : the median 

 basilic vein also lies in front of it opposite the 

 bend of the elbow. Posteriorly, for about a 

 third of its length from its commencement it 

 lies in front of the triceps, from which it is se- 

 parated by a quantity of loose cellular tissue 

 which envelopes the musculo-spiral nerve ; in 

 its inferior two-thirds it rests on the brachiseus 

 anticus. Internally it is covered by the bra- 

 chial aponeurosis at its superior part, where the 

 ulnar nerve is also in contact with it. The me- 

 dian nerve which crosses it, sometimes super- 

 ficially, and at other times passing more deeply, 

 in the middle of the arm gets to its internal 

 side, and continues to hold this relation to it in 

 the remainder of its course. Externally it lies 

 at first on the internal side of the humerus, from 

 which it is separated as it descends by the thin 

 muscular expansion in which the coraco-brachi- 

 alis terminates at the lower part of its insertion ; 

 in the remainder of its course the inner edge of 

 the biceps bounds it. The fleshy belly of this 

 muscle also partially covers it in front, a little 

 below the middle of the arm. At the bend of 

 the elbow, the relations of the brachial artery 

 become more numerous and complicated ; here 

 it inclines obliquely outwards and backwards, 

 and sinks into a space which is bounded on the 

 inner side by the origins of the pronator and 

 flexor muscles of the forearm, and on the out- 

 side by those of the supinators and extensors, 

 the floor of which space is formed by the bra- 

 chiaeus anticus muscle, from which the artery is 

 separated by a layer of adipose cellular mem- 

 brane. The artery is accompanied in its passage 

 into this space by the tendon of the biceps and 

 the median nerve, the former being situated to 

 its radial side, the latter to its ulnar ; and it is 

 at the bottom of this space, opposite the coro- 

 noid process of the ulna, that the subdivision 

 of the artery into radial and ulnar usually takes 



VOL. I. 



place. As it enters the space the artery is 

 crossed by the semilunar fascia of the biceps, by 

 which it is separated from the internal cutaneous 

 nerve and median basilic vein. (For further par- 

 ticulars on this stage of the artery, see ELBOW, 

 REGION OF THE.) 



Two venae comites accompany the brachial 

 artery : they are included in its sheath, and lie 

 one on either side of it, often communicating 

 by several transverse branches which cross the 

 artery in front. 



So superficial is the position of this artery 

 from its origin till it enters the region of the 

 bend of the elbow, that it may be exposed during 

 life in any part of its course with facility, and, 

 if the operator use only common caution, with 

 safety. In all this course the artery may be felt, 

 and in the upper third the operator may avail 

 himself of the inner side of the coraco-brachialis 

 muscle as a guide, and in the middle third, of 

 the inner edge of the belly of the biceps. In 

 both situations the operator has to avoid in- 

 juring the cutaneous nerves, and the median 

 and ulnar nerves, as well as the basilic vein, 

 which sometimes passes up as high as the 

 axilla. He should also bear in mind the po- 

 sition of the inferior profunda artery, which 

 is sometimes of a large size; and from its 

 direction, as well as its relation to the ulnar 

 nerve, presents a considerable resemblance to 

 the brachial trunk. 



Branches. The brachial artery furnishes a 

 variable number of branches from its external 

 side, none of which is of sufficient importance 

 to be distinguished by a name ; they are dis- 

 tributed to the os humeri, the deltoid, coraco- 

 brachialis, biceps, and brachiseus anticus muscles, 

 and to the integuments. From its internal side, 

 however, there usually arise, in addition to 

 several small twigs sent to the triceps, teres 

 major, latissimus dorsi, and the integuments, 

 three branches of more considerable size, and 

 which derive their principal importance from 

 being the leading channels of anastomosis be- 

 tween the brachial trunk and the arteries of the 

 forearm. These are, 1, the superior profunda, 

 2, the inferior profunda, 3, the anastomotica 

 magna.* 



1. The superior prof unda (profunda humeri, 

 Haller and Scemm. collateral externe, Boyer, 

 grand musculaire du bras, Chauss.) arises from 

 the posterior side of the brachial artery, close to 

 the border of the axilla. It sometimes comes 

 from the axillary artery by a trunk common to 

 it and the posterior circumflex, and occasionally 

 it arises from the subscapular. Immediately 

 after its origin the profunda superior gives 

 several branches to the coraco-brachialis, triceps, 

 latissimus dorsi, teres major, and deltoid mus- 

 cles. Some of these latter, ascending towards 

 the acromion process of the scapula, anastomose 

 with the thoracica acromialis, supra-scapular and 

 posterior circumflex ; while the branches sent 

 to the latissimus dorsi and teres major anas- 

 tomose with the subscapular artery. The supe- 



* Sometimes the subscapnlar, and one or both 

 of the circumflex arteries, derive their origin from 

 the brachial. 



2 II 



