| Common carotid artery | |
|---|---|
 The common carotid artery arises directly from theaorta on the left and as a branch of thebrachiocephalic trunk on the right. | |
 The common carotid artery and its main branches | |
| Details | |
| Precursor | Aortic arch 3 |
| Source | Aortic arch,brachiocephalic artery |
| Branches | Internal carotid artery,external carotid artery |
| Vein | Internal jugular vein |
| Supplies | Head and neck |
| Identifiers | |
| Latin | arteria carotis communis |
| MeSH | D017536 |
| TA98 | A12.2.04.006 |
| TA2 | 4366 |
| FMA | 3939 |
| Anatomical terminology | |
In anatomy, the left and rightcommon carotid arteries (carotids) (English:/kəˈrɒtɪd/[1][2]) arearteries that supply the head and neck withoxygenated blood; they divide in the neck to form theexternal andinternal carotid arteries.[3][4]
The common carotid arteries are present on the left and right sides of the body. These arteries originate from different arteries but follow symmetrical courses. The right common carotid originates in the neck from thebrachiocephalic trunk; the left from theaortic arch in the thorax. These split into the external and internal carotid arteries at the upper border of thethyroid cartilage, at around the level of thefourth cervical vertebra.
The left common carotid artery can be thought of as having two parts: a thoracic (chest) part and a cervical (neck) part.[5] The right common carotid originates in or close to the neck and contains only a small thoracic portion. There are studies in the bioengineering literature that have looked into characterizing the geometric structure of the common carotid artery from both qualitative and mathematical (quantitative) standpoints.[4]
The average diameters of the common carotids in adult males and females are 6.5 mm and 6.1 mm respectively.[6]
Only the left common carotid artery has a substantial presence in the thorax. It originates directly from the aortic arch, and travels upward through the superiormediastinum to the level of the leftsternoclavicular joint.[citation needed]
During the thoracic part of its course, the left common carotid artery is related to the following structures:In front, it is separated from themanubrium of thesternum by thesternohyoid andsternothyroid muscles, the anterior portions of the leftpleura andlung, the leftbrachiocephalic vein, and the remains of thethymus; behind, it lies on thetrachea,esophagus, leftrecurrent laryngeal nerve, andthoracic duct.
To its right side, below is the brachiocephalic trunk, and above, the trachea, theinferior thyroid veins, and the remains of the thymus; to its left side are the leftvagus andphrenic nerves, left pleura, and lung. The leftsubclavian artery is posterior and slightly lateral to it.
The cervical portions of the common carotids resemble each other so closely that one description will apply to both.[citation needed]
Each vessel passes obliquely upward, from behind the sternoclavicular joint to the level of the upper border of the thyroid cartilage, where it divides.
At the lower neck, the two common carotid arteries are separated from each other by a very narrow interval which contains the trachea; but at the upper part, thethyroid gland, thelarynx andpharynx separate the two arteries.
The common carotid artery is contained in a sheath known as thecarotid sheath, which is derived from thedeep cervical fascia and encloses also theinternal jugular vein andvagus nerve, the vein lying lateral to the artery, and the nerve between the artery and vein, on a plane posterior to both. On opening the sheath, each of these three structures is seen to have a separate fibrous cover.
At approximately the level of the fourthcervical vertebra, the common carotid artery splits ("bifurcates" in literature) into aninternal carotid artery (ICA) and anexternal carotid artery (ECA). While both branches travel upward, the internal carotid takes a deeper (more internal) path, eventually travelling up into the skull to supply thebrain. The external carotid artery travels more closely to the surface, and sends off numerous branches that supply the neck and face.
At the lower part of the neck, the common carotid artery is very deeply seated, being covered by theintegument,superficial fascia, theplatysma muscle,deep cervical fascia, thesternocleidomastoid muscle, thesternohyoid,sternothyroid, and theomohyoid; in the upper part of its course it is more superficial, being covered merely by the integument, the superficial fascia, the platysma, deep cervical fascia, and medial margin of the sternocleidomastoid.
When the sternocleidomastoid muscle is drawn backward, the artery is seen to be contained in a triangular space known as thecarotid triangle. This space is bounded behind by thesternocleidomastoid, above by thestylohyoid and the posterior belly of thedigastric muscle, and below by the superior belly of theomohyoid.
This part of the artery is crossed obliquely, from its medial to its lateral side, by the sternocleidomastoid branch of thesuperior thyroid artery; it is also crossed by thesuperior andmiddle thyroid veins (which end in theinternal jugular vein); descending in front of its sheath is the descending branch of thehypoglossal nerve, this filament being joined by one or two branches from thecervical nerves, which cross the vessel obliquely.
Sometimes the descending branch of the hypoglossal nerve is contained within the sheath.
Thesuperior thyroid vein crosses the artery near its termination, and themiddle thyroid vein a little below the level of thecricoid cartilage; theanterior jugular vein crosses the artery just above theclavicle, but is separated from it by thesternohyoid andsternothyroid.
Behind, the artery is separated from the transverse processes of the cervical vertebrae by thelongus colli andlongus capitis muscles, thesympathetic trunk being interposed between it and the muscles. Theinferior thyroid artery crosses behind the lower part of the vessel.
Medially, it is in relation with the esophagus, trachea, and thyroid gland (which overlaps it), the inferior thyroid artery andrecurrent laryngeal nerve being interposed; higher up, with the larynx and pharynx. Lateral to the artery, inside thecarotid sheath with the common carotid, are theinternal jugular vein andvagus nerve.
At the lower part of the neck, on the right side of the body, the rightrecurrent laryngeal nerve crosses obliquely behind the artery; the rightinternal jugular vein diverges from the artery. On the left side, however, the left internal jugular vein approaches and often overlaps the lower part of the artery.
Behind the angle of bifurcation of the common carotid artery is a reddish-brown oval body known as thecarotid body. It is similar in structure to thecoccygeal body which is situated on themedian sacral artery.
The relations of the cervical region of the common carotid artery may be discussed in two points:
The chief communications outside the skull take place between the superior and inferior thyroid arteries, and thedeep cervical artery and the descending branch of theoccipital artery; thevertebral artery takes the place of theinternal carotid artery within the cranium.
The right common carotid may rise above the level of the upper border of thesternoclavicular joint; this variation occurs in about 12 percent of cases.
In other cases, the artery on the right side may arise as a separate branch from the arch of the aorta, or in conjunction with the left carotid.
The left common carotid varies in its origin more than the right.
In the majority of abnormal cases it arises with thebrachiocephalic trunk; if that artery is absent, the two carotids arise usually by a single trunk.
It is rarely joined with the leftsubclavian artery, except in cases of transposition of theaortic arch.
In the majority of abnormal cases, the bifurcation occurs higher than usual, the artery dividing opposite or even above thehyoid bone; more rarely, it occurs below, opposite the middle of the larynx, or the lower border of thecricoid cartilage. In at least one reported case, the artery was only 4 cm in length and divided at the root of the neck.
Very rarely, the common carotid artery ascends in the neck without any subdivision, either the external or the internal carotid being absent; and in a few cases the common carotid has itself been found to be absent, the external and internal carotids arising directly from the arch of the aorta.
This peculiarity existed on both sides in some instances, on one side in others.
The common carotid usually gives off no branch previous to its bifurcation, but it occasionally gives origin to thesuperior thyroid artery or its laryngeal branch, theascending pharyngeal artery, theinferior thyroid artery, or, more rarely, thevertebral artery.
The condition and health of the common carotid arteries is usually evaluated usingDoppler ultrasound,CT angiography orphase contrast magnetic resonance imaging (PC-MRI).
Typically, blood flow velocities in the common carotid artery are measured as peak systolic velocity (PSV) and end diastolic velocity (EDV).
In a study of normative men aged 20-29 years, the average PSV was 115 cm/sec and EDV was 32 cm/sec. In men 80 years and older, the average PSV was 88 cm/sec and EDV was 17 cm/sec.[7]
The common carotid artery is often used in measuring thepulse,[3] especially in patients who are inshock and who lack a detectable pulse in the more peripheral arteries of the body. The pulse is taken by palpating the artery just deep to the anterior border of the sternocleidomastoid muscle at the level of the superior border of the thyroid cartilage.
Presence of a carotid pulse has been estimated to indicate a systolicblood pressure of more than 40 mmHg, as given by the 50% percentile.[8]
Carotidynia is a syndrome marked by soreness of the carotid artery near the bifurcation.
Carotid stenosis may occur in patients withatherosclerosis.
Theintima-media thickness of the carotid artery wall is a marker of subclinical atherosclerosis and it increases with age and with long-term exposure toparticulateair pollution.[9]
