The arm includes two muscular components, the anterior one, which contains the coracobrachialis, biceps brachii and brachalis muscles and the posterior comportment, which contains the triceps brachii muscle.
Located within the anterior compartment, the brachial artery constitutes the main arterial supply of the arm. This article will discuss the anatomical relations and variations of the brachial artery as well as talking about its many branches. This will be followed by clinically pathology related to the brachial artery.
As a continuation of the axillary artery, it begins at the inferior border of the teres major tendon and it ends at the level of the neck of the radius about 1cm distal to the elbow joint. At this point, it divides into the ulnar and radial arteries. The brachial artery runs medial to the humerus proximally, before moving more anteriorly to lie between the epicondyles of the humerus.
Relationships of the brachial artery to other structures in the arm can be important in clinical practice. The brachial artery is a superficial vessel and is only covered by the layers of the skin, as well as the superficial and deep fasciae, with a few exceptions:
- The first exception to this is at the cubital fossa, where the bicipital aponeurosis, which is the aponeurosis of the biceps brachii muscle, covers the artery, and separates it from the median cubital vein.
- The second exception is when the median nerve crosses the brachial artery near the distal attachment of the coracobrachialis.
Posteriorly, the brachial artery is separated from the long head of the triceps brachii muscle by the profunda brachii artery and the radial nerve. The attachments of the coracobrachialis and the brachialis muscles, as well as the medial head of the triceps brachii muscle, also lie posterior to the brachial artery.
The median nerve and coracobrachialis muscle lie laterally to the brachial artery at its proximal aspect whereas the medial cutaneous nerve of the forearm and the ulnar nerve lie medially to the artery proximally.
At the distal aspect of the brachial artery, the basilic vein and median nerve lie medially. Two venae comitantes, or accompanying veins, run with the brachial artery, and are connected together by transverse and oblique branches.
Along with many other structures in the human body, the anatomical course of the brachial artery may vary between people:
- The brachial artery may diverge from its usual course along the medial aspect of the biceps and run more medially towards the medial epicondyle of the humerus. In this case, the brachial artery passes posterior to the supracondylar process of the humerus before running through, or posterior to, the pronator teres muscle.
- The brachial artery can also form anastomoses or branches more proximal than usual. In this case, the artery divides into three branches referred to as the ulnar, radial and common interosseus arteries. The radial artery usually arises from the brachial artery more proximally, leaving a common division for the ulnar and common interosseus arteries. Occasionally, the ulnar artery may instead branch off more proximally, which then leaves a common division for the radial and common interosseus arteries.
- Sometimes, small slender arteries connect the brachial artery to the axillary artery and these are referred to as vasa aberrantia.
The brachial artery forms 8 branches including the:
- Profunda brachii artery
- Nutrient artery of the humerus
- Superior ulnar collateral artery
- Middle ulnar collateral artery
- Inferior ulnar collateral (supratrochlear) artery
- Deltoid (ascending) artery
- Radial artery
- Ulnar artery
The middle collateral branch is the larger of the two branches and arises posterior to the humerus before descending posterior to the lateral intermuscular septum to the elbow. Proximally, this branch runs between the brachialis and the lateral head of the triceps brachii. Distally, it runs posterior to the brachioradialis and anterior to the lateral head of the triceps brachii. The middle collateral branch then either remains deep to the fascia or crosses it to become cutaneous before reaching the interosseus recurrent artery posterior to the lateral epicondyle. It gives off five fasciocutaneous perforators, which are small arteries that pass through the fascia between muscles and supply the skin.
The radial collateral branch runs with the radial nerve and crosses the lateral intermuscular septum to descend anteriorly to the lateral epicondyle, between the brachialis and brachioradialis. It then joins the radial recurrent artery and supplies the radial nerve, the brachioradialis and brachialis muscles, as well as some fasciocutaneous perforators.
The nutrient artery arises from the brachial artery around the middle level of the upper arm before entering the nutrient canal, which is essentially a large foramen or hole in the humerus. It enters this canal posterior to the deltoid tuberosity, near the attachment of coracobrachialis.The superior ulnar collateral artery arises from the brachial artery slightly distal to the mid-level of the upper arm but can occasionally arise as a branch of the profunda brachii artery. Along the ulnar nerve, it passes through the medial intermuscular septum into the posterior compartment of the upper arm to supply the medial head of the triceps brachii muscle. It then runs between the medial epicondyle of the humerus and the ulnar epicondyle. Deep to the flexor carpi ulnaris muscle, it joins the inferior collateral artery and the posterior ulnar recurrent artery. Sometimes, a branch anastomoses with the anterior ulnar recurrent artery after it travels anteriorly to the medial epicondyle.
The middle ulnar collateral artery is present in some people to supply the triceps brachii muscle, in which case it arises from the brachial artery between the superior and inferior ulnar collateral arteries and travels anteriorly to the medial epicondyle before anastomosing with the anterior ulnar recurrent artery. Similar to the middle collateral branch of the profunda brachii artery, it gives off some small fasciocutaneous perforators.
The inferior ulnar collateral (supratrochlear) artery arises from the brachial artery about 5cm proximal to the elbow joint. It runs medially between the brachialis muscle and the median nerve before crossing the medial intermuscular septum. It then spirals round the humerus between the bone and the triceps brachii muscle until it anastomoses with the middle collateral branch of the profunda brachii artery to form an arch located proximally to the olecranon fossa, a depression on the posterior aspect of the humerus. Anterior to the brachialis muscle, the inferior ulnar collateral artery divides into a few branches, which either run anteriorly to the medial epicondyle to anastamose with the anterior ulnar recurrent artery or run posteriorly to it to anastomose with the posterior ulnar recurrent artery and superior ulnar collateral artery.
The deltoid artery is a muscular branch of the brachial artery, which lies between the lateral and long heads of the triceps brachii until it reaches the descending branch of the posterior humeral circumflex artery.The radial artery runs deep to the brachioradialis to give off the radial recurrent artery distal to the elbow joint. It runs between the superficial and deep branches of the radial nerve before it passes, in a superior direction, posteriorly to the brachioradialis muscle and anteriorly to the supinator and brachialis muscles. It supplies the brachioradialis, supinator and brachialis muscles as well as the elbow joint, before anastomosing with the radial collateral branch of the profunda brachii artery.
The ulnar artery is the largest of the terminal branches of the brachial artery. Before passing below the pronator teres muscle, it gives off two branches distal to the elbow joint. The first branch is the anterior ulnar recurrent artery, which supplies the brachialis and pronator teres muscles before anastomosing with the inferior ulnar collateral artery at the medial epicondyle. The other branch, the posterior ulnar recurrent artery, joins up with the interosseus recurrent arteries and with the ulnar collateral arteries. The ulnar artery then continues along the forearm to give off more divisions.
The brachial pulse can be felt medial to the biceps brachii muscle by applying pressure to the medial edge of the humerus. More proximally, it can be felt in the depression posterior to the coracobrachialis muscle. More distally, it can be felt medially to the biceps brachii tendon. As the brachial artery runs deep to the bicipital aponeurosis, its pulsation cannot be felt beyond this point.
Blood pressure is a vital sign in clinical practice. Hypertension or high blood pressure is an important risk factor for many diseases including stroke and myocardial infarction. Hypotension or low pressure may be an indicator of blood loss or poor myocardial contractility. Blood pressure is measured with a sphygmomanometer and a stethoscope. The cuff of the sphygmomanometer is placed over the arm and is inflated to a pressure 20-30 mmHg greater than the estimated systolic blood pressure in order to compress the brachial artery. The cuff is then slowly deflated to restore blood flow in the artery. The resulting Korotkoff sounds are amplified using a stethoscope, held over the brachial artery in the cubital fossa, and are used in order to determine the systolic and diastolic blood pressures.
Supracondylar fractures of the humeral shaft are common in children after a fall on the elbow or on an extended hand and may cause posterior displacement of the distal fragment. This proximal bone fragment may injure the brachial artery.
Compression of the brachial artery can be performed to control blood loss in trauma patients and is best carried out proximal to the site of laceration and medial to the humerus. Clamping of the brachial artery distal to where the profunda brachii artery branches off can be carried out without causing tissue damage. This is because the branches arising from the brachial artery will still provide adequate blood flow to the more distal ulnar and radial arteries by forming a collateral circulation around the elbow joint.
Ischaemic compartment syndrome happens as a result of severe injury to the arm, leading to swelling of the soft tissues, raised intracompartmental pressure and associated compression of the surrounding nerves and muscles within the affected compartments. Ischaemia ensues and after 6 hours, necrotic tissue in the muscles is replaced by fibrotic scar tissue. This causes contracture due to permanent shortening of the muscles. This can result in pain, paralysis and paraesthesia.