The inferior thyroid artery is an

artery 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 oxygenated blood; the two exceptions are the pu ...

in the

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

. It arises from the

thyrocervical trunk The thyrocervical trunk is an artery of the neck. It is a branch of the subclavian artery. It arises from the first portion of this vessel, between the origin of the subclavian artery and the inner border of the scalenus anterior muscle. It is ...

and passes upward, in front of 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 ...

and

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 ...

. It then turns medially behind 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 ...

and its contents, and also behind the

sympathetic trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system. Structure The sympathetic trunk lies j ...

, the middle cervical ganglion resting upon the vessel. Reaching the lower border of 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 lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

it divides into two branches, which supply the postero-inferior parts of the gland, and

anastomose An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal ...

with 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 su ...

, and with the corresponding artery of the opposite side.

Structure

The branches of the inferior thyroid artery are the inferior laryngeal, the oesophageal, the tracheal, the ascending cervical and the pharyngeal arteries. The inferior laryngeal artery climbs 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 t ...

to the back part of 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 ...

under cover of the inferior pharyngeal constrictor muscle. It is accompanied by the

recurrent 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 ...

, and supplies the muscles and mucous membrane of this part,

anastomosing An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal ...

with the branch from the opposite side, and with the superior laryngeal branch of the

. The tracheal branches of the inferior thyroid artery are distributed on the trachea, and anastomose below with the

bronchial arteries In human anatomy, the bronchial arteries supply the lungs with nutrition and oxygenated blood. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung and are a vital part ...

. The esophageal branches of the inferior thyroid artery supply the

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 t ...

, and anastomose with the esophageal branches of the aorta. The ascending cervical artery is a small branch which arises from the inferior thyroid artery as it passes behind the

; it runs up on the anterior tubercles of the transverse processes of the

cervical vertebrae 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 ...

in the interval between the anterior scalene muscle and the

longus capitis The longus capitis muscle (Latin for ''long muscle of the head'', alternatively rectus capitis anticus major), is broad and thick above, narrow below, and arises by four tendinous slips, from the anterior tubercles of the transverse processes of th ...

. The ascending cervical artery gives twigs to the neck muscles and these anastomose with branches of the

vertebral arteries 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 ...

. One or two spinal branches are sent into the

spinal canal The spinal canal (or vertebral canal or spinal cavity) is the canal that contains the spinal cord within the vertebral column. The spinal canal is formed by the vertebrae through which the spinal cord passes. It is a process of the dorsal body ca ...

, through the

intervertebral foramina The intervertebral foramen (also called neural foramen, and often abbreviated as IV foramen or IVF) is a foramen between two spinal vertebrae. Cervical, thoracic, and lumbar vertebrae all have intervertebral foramina. The foramina, or openi ...

to be distributed to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

and its membranes, and to the bodies of the vertebrae. It then anastomoses with the ascending pharyngeal and

occipital arteries 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 pharyngeal branches of the inferior thyroid artery supply the

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 st ...

. The glandular branches of the inferior thyroid artery are small branches which directly supply the

Clinical significance

The relationship between the

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 ...

and inferior thyroid artery is highly variable. The

passes upward generally behind, but occasionally in front of, the inferior thyroid artery. This makes it vulnerable to injury during surgery that involves ligating the inferior thyroid artery, such as excision of the lower pole of the

. Also as the parathyroid is mainly supplied by inferior thyroid artery accidental ligation during thyroidectomy can cause hypoparathyroidism. The injection of dye into the inferior thyroid artery can be used as an alternate method in identification the recurrent laryngeal nerve.

Additional images

File:Gray1032.png, The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.

References

External links

* () * * - "Larynx: Recurrent Laryngeal Nerve and Inferior Laryngeal Artery" {{Authority control Arteries of the head and neck Thyroid

Structure

Clinical significance

Additional images

See also

References

External links