In human anatomy, the subclavian arteries are paired major arteries of the upper

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...

, below the

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...

. They receive blood from the

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplies blood to the right arm, with some branches supplying the head and thorax. On the left side of the body, the subclavian comes directly off the

, while on the right side it arises from the relatively short brachiocephalic artery when it bifurcates into the subclavian and the right common carotid artery. The usual branches of the subclavian on both sides of the body are the

vertebral artery The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline ...

, the internal thoracic artery, the thyrocervical trunk, the

costocervical trunk The costocervical trunk arises from the upper and back part of the second part of subclavian artery, behind the scalenus anterior on the right side, and medial to that muscle on the left side. Passing backward, it splits into the deep cervical ...

and the dorsal scapular artery, which may branch off the transverse cervical artery, which is a branch of the thyrocervical trunk. The subclavian becomes the axillary artery at the lateral border of the first

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

Structure

From its origin, the subclavian artery travels laterally, passing between anterior and middle scalene muscles, with the anterior scalene ( scalenus anterior) on its anterior side and the middle scalene (

scalenus medius The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the third to the eight cervical spinal nerves (C3-C8). The anterior and m ...

) on its posterior. This is in contrast to the

subclavian vein The subclavian vein is a paired large vein, one on either side of the body, that is responsible for draining blood from the upper extremities, allowing this blood to return to the heart. The left subclavian vein plays a key role in the absorptio ...

, which travels anterior to the scalenus anterior. As the subclavian artery crosses the lateral border of the

first rib The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a ...

, it becomes the axillary artery. On the right side the subclavian artery arises from the brachiocephalic (innominate) artery behind the right sternoclavicular articulation; on the left side it springs from the arch of the aorta. The two vessels, therefore, in the first part of their course, differ in length, direction, and relation with neighboring structures. The left subclavian artery is around 9 cm long in adults, while the right subclavian artery is around 6 cm long. Both have a width of 9-12 mm.

Parts

In order to facilitate the description, each subclavian artery is divided into three parts: * The first part, also known as the prescalene part, extends from the origin of the vessel to the medial border of the scalenus anterior muscle. * The second part, also known as the scalene part, lies behind the scalenus anterior muscle. * The third part, also known as the postscalene part, extends from the lateral margin of the muscle to the outer border of the first rib, where it becomes the axillary artery. The first portions of the two vessels require separate descriptions; the second and third parts of the two arteries are practically alike.

First part

=Right subclavian artery

= The first part of the right subclavian artery arises from the brachiocephalic trunk, behind the upper part of the right sternoclavicular articulation. It passes upward and lateralward to the medial margin of the scalenus anterior muscle. It ascends a little above the medial part of the

. It is covered, in front, by the integument, superficial fascia, the platysma muscle, deep fascia, the clavicular origin of the sternocleidomastoid muscle, the sternohyoid muscle, and the sternothyroid muscle, and another layer of the

deep fascia Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the ...

. It is crossed by the internal jugular vein and the vertebral vein, by the vagus nerve and the cardiac branches of the vagus and sympathetic, and by the subclavian loop of the sympathetic trunk which forms a ring around the vessel. The anterior jugular vein is directed laterally in front of the artery, but is separated from it by the sternohyoid muscle and the sternothyroid muscle. Below and behind the artery is the

pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips b ...

, which separates it from the apex of the lung. Behind the artery is the sympathetic trunk, the

longus colli muscle The longus colli muscle (Latin for ''long muscle of the neck'') is a muscle of the human body. The longus colli is situated on the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra. It is broad in the m ...

and the first thoracic vertebra (T1). The right recurrent laryngeal nerve winds around the lower and back part of the vessel.

=Left subclavian artery

= The first part of the left subclavian artery arises from the

, behind the

left common carotid artery In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
fourth thoracic vertebra. It ascends in the superior mediastinal cavity to the root of the neck, and then arches lateralward to the medial border of the scalenus anterior muscle. It is in relation, in front, with the vagus nerve, the cardiac nerves, and the phrenic nerves, which lie parallel with it, the left common carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein. It is covered by the sternothyroid muscle, the sternohyoid muscle, and the sternocleidomastoid muscle. Behind, it is in relation with the esophagus, thoracic duct, left recurrent laryngeal nerve, inferior cervical ganglion of the sympathetic trunk, and the longus colli muscle; higher up, however, the esophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. Medial to it are the esophagus, trachea, thoracic duct, and left recurrent laryngeal nerve. Lateral to it are the left pleura and lung.

Second part

The second portion of the subclavian artery lies behind the scalenus anterior muscle and in front of the scalenus medius muscle. It is very short, and forms the highest part of the arch described by the vessel. In front, it is covered by the skin, the superficial fascia, the platysma muscle, the deep cervical fascia, the sternocleidomastoid muscle, and the scalenus anterior muscle. On the right side of the neck, the phrenic nerve is separated from the second part of the artery by the scalenus anterior muscle, while on the left side it crosses the first part of the artery close to the medial edge of the muscle. Behind the artery are the pleura and the scalenus medius muscle. Above the artery is the brachial plexus. Below the artery is the pleura. The subclavian vein lies below and anterior to the artery, separated from it by the scalenus anterior muscle.

Third part

The third portion of the subclavian artery runs downward and lateralward from the lateral margin of the scalenus anterior muscle to the outer border of the first rib, where it becomes the axillary artery. This is the most superficial portion of the vessel, and is contained in the subclavian triangle. It is covered, in front, by the skin, the superficial fascia, the platysma muscle, the supraclavicular nerves, and the deep cervical fascia. The external jugular vein crosses its medial part and receives the transverse scapular, transverse cervical, and anterior jugular veins, which frequently form a plexus in front of the artery. Behind the veins, the nerve to the Subclavius descends in front of the artery. The terminal part of the artery lies behind the clavicle and the Subclavius and is crossed by the transverse scapular vessels. The subclavian vein is in front of and at a slightly lower level than the artery. Behind, it lies on the lowest trunk of the brachial plexus, which intervenes between it and the scalenus medius muscle. Above and to its lateral side are the upper trunks of the brachial plexus and the omohyoid muscle. Below, it rests on the upper surface of the first rib.

Branches

The subclavian arteries give off five major arteries each: the

, the internal thoracic artery, the thyrocervical trunk, the

, and the dorsal scapular artery. Subclavius 1st part

Development

Embryologically, the left subclavian simply arises from the left 7th

intersegmental artery The intersegmental arteries are a set of 30 arteries arising from the embryonic dorsal aorta, with each artery providing blood supply to one somite and its derivatives. Cervical intersegmental arteries The cervical intersegmental arteries merge i ...

, while the right subclavian arises, proximal to distal: # right 4th

# right dorsal aorta # right 7th intersegmental artery Essentially, the 4th aortic arch and dorsal aorta form the aortic arch on the left, but since the right dorsal aorta regresses distal to the right 7th intersegmental artery, on the right they form the proximal portion of the subclavian artery. Since the left subclavian is then a tributary of the left common carotid, they can be thought of as arising from the brachiocephalic trunk.

Variation

The subclavian arteries vary in their origin, their course, and the height to which they rise in the neck. The origin of the right subclavian from the innominate takes place, in some cases, above the sternoclavicular articulation, and occasionally, but less frequently, below that joint. The artery may arise as a separate trunk from the arch of the aorta, and in such cases it may be either the first, second, third, or even the last branch derived from that vessel; in the majority, however, it is the first or last, rarely the second or third. When it is the first branch, it occupies the ordinary position of the innominate artery; when the second or third, it gains its usual position by passing behind the right carotid; and when the last branch, it arises from the left extremity of the arch, and passes obliquely toward the right side, usually behind the trachea, esophagus, and right carotid, sometimes between the esophagus and trachea, to the upper border of the first rib, whence it follows its ordinary course. In very rare instances, this vessel arises from the thoracic aorta, as low down as the fourth thoracic vertebra. Occasionally, it perforates the Scalenus anterior; more rarely it passes in front of that muscle. Sometimes the subclavian vein passes with the artery behind the Scalenus anterior. The artery may ascend as high as 4 cm. above the clavicle, or any intermediate point between this and the upper border of the bone, the right subclavian usually ascending higher than the left. The left subclavian is occasionally joined at its origin with the left common carotid artery, forming a left brachiocephalic trunk. The left subclavian artery is more deeply placed than the right in the first part of its course, and, as a rule, does not reach quite as high a level in the neck. The posterior border of the Sternocleidomastoideus corresponds pretty closely to the lateral border of the Scalenus anterior, so that the third portion of the artery, the part most accessible for operation, lies immediately lateral to the posterior border of the Sternocleidomastoideus. Some authors describe the subclavian artery as arising from the 7th intersegmental artery.

Function

The subclavian arteries carry most of the blood that supplies the arms. It also supplies some blood to the neck and brain.

Clinical significance

Compression of the subclavian artery can cause thoracic outlet syndrome (TOS). The subclavian arteries can be vulnerable to

aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus ( ...

. Subclavian steal syndrome occurs when there is occlusion or stenosis of the subclavian artery at a point before the branching of the

. This can cause blood to flow the wrong way through the vertebral artery into the distal subclavian artery, allowed by the reduced pressure. The subclavian arteries are relatively superficial, and can be seen using

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

. Aberrant right subclavian artery is a condition where the right subclavian artery arises on the

arch of aorta The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins a ...

distal to the left subclavian artery, instead of

brachiocephalic trunk The brachiocephalic artery (or brachiocephalic trunk or innominate artery) is an artery of the mediastinum that supplies blood to the right arm and the head and neck. It is the first branch of the aortic arch. Soon after it emerges, the brachi ...

. This condition occurs in about 0.4 to 1.8% of the general population. The aberrant right subclavian artery than has to cross behind the oesophagus to reach the right side of the body. Majority of those having the condition are asymptomatic, but some may be presented with difficulty in breathing, difficulty in swallowing, grating noise during breathing, and chest pain. This condition has to be ruled out during procedures relating to oesophagus because injury to this artery during the procedure can cause massive bleeding.

Additional images

File:Gray1210.png, Side of neck, showing chief surface markings. File:Mra1.jpg, Magnetic Resonance Angiography; view from the front File:Slide8a.JPG, Right subclavian artery File:PLEXUS BRACHIALIS.jpg, Brachial plexus and subclavian artery

References

External links

* *
Diagram of branches at informatics.jax.org
* {{Authority control Arteries of the head and neck Arteries of the thorax