In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
Merriam-Webster Online Dictionary
'.) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.

Structure

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 the brachiocephalic trunk; the left from the aortic arch in the thorax. These split into the external and internal carotid arteries at the upper border of the thyroid cartilage, at around the level of the

fourth cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sau ...

. The left common carotid artery can be thought of as having two parts: a thoracic (chest) part and a cervical (neck) part. 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. The average diameters of the common carotids in adult males and females are 6.5 mm and 6.1 mm respectively.

In the chest

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 superior

mediastinum The mediastinum (from ) is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esophagu ...

to the level of the left

sternoclavicular joint The sternoclavicular joint or sternoclavicular articulation is a synovial saddle joint between the manubrium of the sternum, and the clavicle, as well as the first rib. The joint possesses a joint capsule, and an articular disk, and is rein ...

. During the thoracic part of its course, the left common carotid artery is related to the following structures: In front, it is separated from the manubrium of the

sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. ...

by the sternohyoid and sternothyroid muscles, the anterior portions of the left pleura and lung, the left brachiocephalic vein, and the remains of the

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

; behind, it lies on the

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from th ...

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

, left recurrent laryngeal nerve, and thoracic duct. To its right side below is the brachiocephalic trunk, and above, the trachea, the inferior thyroid veins, and the remains of the thymus; to its left side are the left vagus and phrenic nerves, left pleura, and lung. The left subclavian artery is posterior and slightly lateral to it.

In the neck

The cervical portions of the common carotids resemble each other so closely that one description will apply to both. 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, the thyroid gland, the larynx and

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its ...

separate the two arteries. The common carotid artery is contained in a sheath known as the

carotid sheath The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adi ...

, which is derived from the deep cervical fascia and encloses also the

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the post ...

and

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and rig ...

, 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 fourth

cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

, the common carotid artery splits (" bifurcates" in literature) into an internal carotid artery (ICA) and an

external carotid artery The external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it splits into the external and internal carotid artery. External carotid artery supplies blood to the face and neck. Structure ...

(ECA). While both branches travel upward, the internal carotid takes a deeper (more internal) path, eventually travelling up into the skull to supply the

brain The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...

. The external carotid artery travels more closely to the surface, and sends off numerous branches that supply the neck and face. Gray507

At the lower part of the neck the common carotid artery is very deeply seated, being covered by the

integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, shell, germ or rind. Etymology The term is derived from ''integumentum'', which is Latin for "a covering". In a transferred, or ...

, superficial fascia, the

platysma The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the neck, and a "bowstring" eff ...

muscle, deep cervical fascia, the sternocleidomastoid muscle, the sternohyoid, sternothyroid, and the

omohyoid The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to th ...

; 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 the carotid triangle. This space is bounded behind by the sternocleidomastoid, above by the stylohyoid and the posterior belly of the digastric muscle, and below by the superior belly of the

. This part of the artery is crossed obliquely, from its medial to its lateral side, by the sternocleidomastoid branch of the superior thyroid artery; it is also crossed by the

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...

and middle thyroid veins (which end in the

); descending in front of its sheath is the descending branch of the hypoglossal nerve, this filament being joined by one or two branches from the cervical nerves, which cross the vessel obliquely. Sometimes the descending branch of the hypoglossal nerve is contained within the sheath. The superior thyroid vein crosses the artery near its termination, and the middle thyroid vein a little below the level of the

cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...

; the

anterior jugular vein The anterior jugular vein is a vein in the neck. Structure The anterior jugular vein lies lateral to the cricothyroid ligament. It begins near the hyoid bone by the confluence of several superficial veins from the submandibular region. Its tri ...

crosses the artery just above the clavicle, but is separated from it by the sternohyoid and sternothyroid. Behind, the artery is separated from the transverse processes of the cervical vertebrae by the longus colli and longus capitis muscles, the sympathetic trunk being interposed between it and the muscles. The inferior 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 and recurrent laryngeal nerve being interposed; higher up, with the larynx and pharynx. Lateral to the artery, inside the

with the common carotid, are the

and

. At the lower part of the neck, on the right side of the body, the right recurrent laryngeal nerve crosses obliquely behind the artery; the right

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 the carotid body. It is similar in structure to the

coccygeal body The coccygeal glomus (coccygeal gland or body; Luschka’s gland) is a vestigial structure placed in front of, or immediately below, the tip of the coccyx. Anatomy It is about 2.5 mm. in diameter and is irregularly oval in shape; several sma ...

which is situated on the

median sacral artery The median sacral artery (or middle sacral artery) is a small artery that arises posterior to the abdominal aorta and superior to its bifurcation. Structure The median sacral artery arises from the abdominal aorta at the level of the bottom qua ...

. The relations of the cervical region of the common carotid artery may be discussed in two points: *Internal relations of organs present inside the carotid sheath *two external relations of carotid sheath

Collateral circulation

The chief communications outside the skull take place between the superior and inferior thyroid arteries, and the deep cervical artery and the descending branch of the occipital artery; 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 ...

takes the place of the internal carotid artery within the cranium.

Variation

Origin

The right common carotid may rise above the level of the upper border of the

; 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 the brachiocephalic trunk; if that artery is absent, the two carotids arise usually by a single trunk. It is rarely joined with the left subclavian artery, except in cases of transposition of the aortic arch.

Point of division

In the majority of abnormal cases, the bifurcation occurs higher than usual, the artery dividing opposite or even above the

hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical verteb ...

; more rarely, it occurs below, opposite the middle of the larynx, or the lower border of the

. 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.

Occasional branches

The common carotid usually gives off no branch previous to its bifurcation, but it occasionally gives origin to the superior thyroid artery or its laryngeal branch, the ascending pharyngeal artery, the inferior thyroid artery, or, more rarely, the

Clinical significance

The common carotid artery is often used in measuring the

pulse In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the ...

, especially in patients who are in shock 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 systolic

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressur ...

of more than 40 mmHg, as given by the 50% percentile. Carotidynia is a syndrome marked by soreness of the carotid artery near the bifurcation. Carotid stenosis may occur in patients with

atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheromatous plaque. At onset there are usually ...

. The intima-media thickness of the carotid artery wall is a marker of subclinical atherosclerosis, it increases with age and with long-term exposure to

particulate Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The t ...

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different type ...

Gallery

File:mra1.jpg, Magnetic Resonance Angiography File:Ao Carotide Nle.JPG, Normal carotidal arteriography File:Slide14b.JPG, Common carotid artery File:Slide13d.JPG, Common carotid artery – right view File:PLEXUS BRACHIALIS.jpg, Brachial plexus and common carotid artery File:Slide1aaa.JPG, Common carotid artery File:Slide11hhh.JPG, Common carotid artery File:Slide4eeee.JPG, Right and left common carotid arteries

References

External links

*
Blood flow numerical simulations in stenosed carotid
{{Authority control Arteries of the head and neck Arteries of the thorax