The brachial artery gives some unnamed branches, which are directed outwards and backwards to the muscles in its immediate neighbourhood, viz., to the coraco-brachialis, biceps, and brachialis anticus; the following, which incline inwards, have received names, and require description.
The superior profunda artery (collateralis magna), [a. profunda brachii,] arises from the inner and back part of the brachial, just below the border of the teres major, and inclines backwards, to reach the interval between the second and third heads of the triceps muscle. It is accompanied by the musculo-spiral nerve, and both, continuing the same oblique direction, enter the spiral groove, which winds round the back of the humerus, passing between it and the triceps, and perforating the external intermuscular septum, to reach the external and anterior aspect of the bone. In the latter situation, the artery lies deeply in the fissure between the brachialis anticus and supinator longus muscles, considerably diminished in size by having given off several branches, and descends to the elbow, where it anastomoses with the recurrent branch of the radial artery. The superior profunda in its first part gives off branches to the deltoid, coraco-brachialis, and triceps; and many to the last-named muscle whilst it is between it and the bone. In this position it also gives one long branch, which descends perpendicularly between the muscle and the bone to the back part of the elbow-joint on its outer side, where it anastomoses with the interosseous recurrent branch, and another which anastomoses on the inner side with the ulnar recurrent, and the anastomotic or inferior profunda.
The most frequent departure from the usual disposition of the superior profunda consists in its giving origin to the posterior circumflex, which is usually a branch of the axillary. Not quite so frequently its own origin is transferred to one of the branches of the axillary; as, for example, to the subscapular, which then also gives off one or both circumflex ; or to the posterior circumflex, which then gives origin to the anterior circumflex, or some other branch. The superior profunda sometimes arises from the axillary artery itself, either alone, or in con- junction with the inferior profunda. Lastly, it is occasionally represented by two, or even three separate branches. It not unfrequently furnishes the inferior profunda.
The nutrient artery of the humerus [a. nutriens humeri] is a very small branch given off by the brachial about the middle of the arm, or by one of its collateral branches. It inclines downwards, enters the oblique canal in the humerus near the insertion of the coraco-brachialis muscle, and is distributed to the medullary membrane.
The inferior profunda artery (collateralis ulnaris prima, [s. superior,]) fig. 242,16 is of small size, and arises from the brachial artery, a little below the middle of the arm. From the point just indicated, the artery is directed to the back part of the inner condyle of the humerus ; to gain this position, it, in the first place, pierces the intermuscular septum, and then lies on the inner surface of the triceps (its third head), giving it branches. In this course the artery lies close to the ulnar nerve, and enters the interval between the olecranon and inner condyle, where it terminates by inosculating with the posterior recurrent branch of the ulnar artery, and with the anastomotic branch.
As already incidentally mentioned in the account of other branches, this artery often arises from the superior profunda, or from the axillary artery in combination with some other branch. It is occasionally altogether wanting. Owing to these frequent changes of condition the inferior profunda has not been recognised by some anatomists.
The anastomotic artery (collateralis ulnaris secunda, [s. inferior, s. a. anastomotica,]), though a small branch, is very constant in its occurrence. Arising from the brachial artery, about two inches above the bend of the arm, it is directed transversely inwards on the brachialis anticus muscle, above the inner condyle of the humerus, and, after perforating the intermuscular septum, turns in the opposite direction outwards behind the humerus, between it and the triceps muscle. In this situation the artery ends by joining with the superior profunda, the two form- ing an arch across the humerus immediately above the olecranon fossa (arcus dorsalis humeri posticus, — Haller).
In front of the humerus the anastomotic artery furnishes a branch which ramifies in the pronator teres, and anastomoses with the anterior ulnar recurrent branch. Behind the inner condyle another offset joins with the posterior ulnar recurrent, and behind the humerus several branches are given to the joint and the muscle. — This anastomotic artery is sometimes much reduced in size, and in that case the inferior profunda takes its place behind the humerus.
A little below the middle of the elbow joint, or opposite the neck of the radius, the brachial artery divides into its two terminal branches —radial and ulnar. Of these the radial artery appears, as far as direction is concerned, the continuation of the parent vessel, but the ulnar is the larger of the two.
From Quain's Anatomy.