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 Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the ci ...

; they divide in the neck to form the external and

internal carotid arteries The internal carotid artery (Latin: arteria carotis interna) is an artery in the neck which supplies the anterior circulation of the brain. In human anatomy, the internal and external carotids arise from the common carotid arteries, where these b ...

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 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 ...

; the left 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 a ...

in the thorax. These split into the external and internal carotid arteries at the upper border of the

thyroid cartilage The thyroid cartilage is the largest of the nine cartilages that make up the ''laryngeal skeleton'', the cartilage structure in and around the trachea that contains the larynx. It does not completely encircle the larynx (only the cricoid 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. 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 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. Sha ...

of the sternum by the

sternohyoid The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternohy ...

and

sternothyroid The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid. Structure The sternothyroid arises from the ...

muscles, the anterior portions of the left

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 bet ...

and

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

, the left

brachiocephalic vein The left and right brachiocephalic veins (previously called innominate veins) are major veins in the upper chest, formed by the union of each corresponding internal jugular vein and subclavian vein. This is at the level of the sternoclavicular j ...

, 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 Cartilage, 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 ...

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 The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles. There are two recurrent laryngeal nerves, right and le ...

, and

thoracic duct In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the ''left lymphatic duct'', ''alimentary duct'', ''chyliferous duct'', and ''Van Hoorne's canal''. The other duct is the right ...

. To its right side below is the brachiocephalic trunk, and above, the trachea, the

inferior thyroid vein The inferior thyroid veins appear two, frequently three or four, in number, and arise in the venous plexus on the thyroid gland, communicating with the middle and superior thyroid veins. While the superior and middle thyroid veins serve as direct ...

s, and the remains of the thymus; to its left side are the left vagus and

phrenic nerve The phrenic nerve is a mixed motor/sensory nerve which originates from the C3-C5 spinal nerves in the neck. The nerve is important for breathing because it provides exclusive motor control of the diaphragm, the primary muscle of respiration. In ...

s, left pleura, and lung. The left

subclavian artery In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplie ...

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 thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue cal ...

, the

larynx The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...

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 struc ...

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 adipo ...

, which is derived from the

deep cervical fascia The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its a ...

and encloses also the internal jugular vein 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 right ...

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

internal carotid artery The internal carotid artery (Latin: arteria carotis interna) is an artery in the neck which supplies the anterior circulation of the brain. In human anatomy, the internal and external carotids arise from the common carotid arteries, where these b ...

(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 T ...

(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 A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. 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,

superficial fascia A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal orga ...

, the platysma muscle,

, the sternocleidomastoid muscle, the

, 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 The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

, above by the stylohyoid and the posterior belly of the

digastric muscle The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellie ...

, 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 The superior thyroid artery arises from the external carotid artery just below the level of the greater cornu of the hyoid bone and ends in the thyroid gland. Structure From its origin under the anterior border of the sternocleidomastoid the sup ...

; 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 vein The middle thyroid vein ( la, vena thyreoidea media) collects the blood from the lower part of the thyroid gland, and after being joined by some veins from the larynx and trachea, ends in the lower part of the internal jugular vein. Clinical featu ...

s (which end in the internal jugular vein); descending in front of its sheath is the descending branch of the

hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated by ...

, 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

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 tr ...

crosses the artery just above 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 rig ...

, but is separated from it by the

and

. 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 The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and als ...

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

being interposed; higher up, with the larynx and pharynx. Lateral to the artery, inside the

with the common carotid, are the internal jugular vein and

. At the lower part of the neck, on the right side of the body, the right

crosses obliquely behind the artery; the right internal 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 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 qu ...

. 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 The deep cervical artery (Profunda cervicalis) is an artery of the neck. Course It arises, in most cases, from the costocervical trunk, and is analogous to the posterior branch of an aortic intercostal artery: occasionally it is a separate br ...

and the descending branch of the

occipital artery The occipital artery arises from the external carotid artery opposite the facial artery. Its path is below the posterior belly of digastric to the occipital region. This artery supplies blood to the back of the scalp and sternocleidomastoid muscles ...

; the

vertebral artery The vertebral arteries are major arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry o ...

takes the place of the

within the cranium.

Variation

Origin

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

; if that artery is absent, the two carotids arise usually by a single trunk. It is rarely joined with the left

, except in cases of transposition of the

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 vertebr ...

; 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

or its laryngeal branch, the ascending pharyngeal artery, the

, or, more rarely, the

Clinical significance

The common carotid artery is often used in measuring the pulse, especially in patients who are in

shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emerge ...

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 pressure" r ...

of more than 40 mmHg, as given by the 50% percentile.

Carotidynia Carotidynia is a syndrome characterized by unilateral (one-sided) tenderness of the carotid artery, near the bifurcation. It was first described in 1927 by Temple Fay. The most common cause of carotidynia may be migraine, and then it is usually s ...

is a syndrome marked by soreness of the carotid artery near the bifurcation.

Carotid stenosis Carotid artery stenosis is a narrowing or constriction of any part of the carotid arteries, usually caused by atherosclerosis. Signs and symptoms The common carotid artery is the large artery whose pulse can be felt on both sides of the neck unde ...

may occur in patients with atherosclerosis. The

intima-media thickness Intima–media thickness (IMT), also called intimal medial thickness, is a measurement of the thickness of tunica intima and tunica media, the innermost two layers of the wall of an artery. The measurement is usually made by external ultrasound and ...

of the carotid artery wall is a marker of subclinical atherosclerosis, it increases with age and with long-term exposure to particulate

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 types ...

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