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Surgical anatomy of the thyroid gland
Authors: Melanie L Richards, MD, MHPE, Tracy S Wang, MD, MPH, Julie Ann Sosa, MD, MA
Section Editor: Sally E Carty, MD, FACS
Deputy Editor: Wenliang Chen, MD, PhD
All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Feb 2017. | This topic last updated: Sep 02, 2015.
INTRODUCTION — Emil Theodor Kocher and Theodor Billroth pioneered the surgical management of
thyroid disease in the late 1800s. Their surgical techniques, knowledge of thyroid physiology, and antisepsis
practices transitioned a life-threatening operation to one with acceptable morbidity. Meticulous technique,
combined with an understanding of thyroid embryology and anatomy, is the foundation of the surgical
management today. A thorough understanding of thyroid anatomy is central to the performance of safe
thyroid surgery [1].
Thyroid anatomy is discussed here. The indications for thyroidectomy and surgical techniques are discussed
elsewhere. (See "Surgical management of hyperthyroidism" and "Differentiated thyroid cancer: Surgical
treatment" and "Initial thyroidectomy".)
FUNCTION — Thyroid hormones, thyroxine (T4), and 3,5,3'-triiodothyronine (T3), are critical determinants of
brain and somatic development in infants and of metabolic activity in adults; they also affect the function of
virtually every organ system. Thyroid hormone biosynthesis and secretion are maintained within narrow limits
by a regulatory mechanism that is sensitive to small changes in circulating hormone concentrations.
The processes of thyroid hormone synthesis, transport, and metabolism, and the regulation of thyroid
secretion and actions of thyroid hormone are discussed elsewhere. (See "Thyroid hormone synthesis and
physiology" and "Thyroid hormone action".)
SIZE AND LOCATION — The thyroid gland weighs 10 to 20 grams in normal adults [2]. Thyroid volume
measured by ultrasonography (US) is slightly greater in men than women, increases with age and body
weight, and decreases with increasing iodine intake [3]. The thyroid is one of the most vascular organs in the
body. Thus, US measurements of thyroid volume and even nodule size can differ markedly from the size after
devascularization and resection.
The normal thyroid gland is immediately caudal to the larynx and encircles the anterolateral portion of the
trachea (figure 1 and figure 2) [1]. The thyroid is bordered by the trachea and esophagus medially and the
carotid sheath laterally. The sternocleidomastoid muscle and the three strap muscles (sternohyoid,
sternothyroid, and the superior belly of the omohyoid) border the thyroid gland anteriorly and laterally (figure
3). There are many anatomic variations in thyroid gland shape and extent. Conditions such as thyroiditis,
malignancy, goiter, substernal goiter, hypothyroidism, prior cervical surgery, and prior radioiodine ablation can
significantly distort, enlarge, or shrink the thyroid gland and/or obscure its anatomic borders.
Thyroid lobes — The thyroid has two parts or lobes that are connected by the thyroid isthmus, a narrow
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band of thyroid tissue. The thyroid lobes extend from the isthmus superiorly to the mid-thyroid cartilage and
laterally to the common carotid arteries. The lobes have superior and inferior poles. The thyroid lobes can be
flat or globular, but always have a three-dimensional shape as they curve around the trachea posteriorly.
Thyroid isthmus — The thyroid isthmus is usually a narrow band of thyroid tissue overlying the second and
third tracheal rings and connecting the two lobes of the thyroid. The thyroid isthmus can be wide, long or
even absent, and may have a pyramidal lobe.
Pyramidal lobe — The pyramidal lobe extends superiorly from the isthmus and can reach the level of the
hyoid bone. A fibrous tract, which is the obliterated thyroglossal duct, extends from the pyramidal lobe to the
hyoid bone and may harbor a thyroglossal duct cyst. (See "Thyroglossal duct cysts and ectopic thyroid".)
The pyramidal lobe can be long, short and stubby, bifid, or absent. A bifid lobe occurs as paired structures
just to the right and left of the midline. A cadaver study showed that a pyramidal lobe was found in 55 percent
of individuals (32/58), and was found more frequently in men than in women [4].
The identification and resection of a pyramidal lobe is an important step in assuring that a total or near total
thyroidectomy has been completed adequately. Therefore the anterior cervical region requires careful
examination during a total thyroidectomy to avoid leaving residual thyroid tissue.
Tubercle of Zuckerkandl — The tubercle of Zuckerkandl, a pyramidal extension of the thyroid gland, is
located on the posterior aspect of each thyroid lobe [5]. The recurrent laryngeal nerve (RLN) usually
traverses the posterior aspect of the tubercle, which can help the surgeon find and identify the nerve. The
tubercle of Zuckerkandl should be carefully elevated and rotated medially to identify the nerve as it courses
posterior to the tubercle.
Occasionally the tubercle tissue passes behind (deep) to the RLN as it enters the larynx, in effect tethering
this portion of the thyroid gland to the trachea. The surgeon should look for this anatomic situation and
preserve the nerve throughout its course to avoid inadvertent division of the nerve (figure 4) [6].
Ectopic thyroid tissue — Abnormalities in development during embryogenesis may result in ectopic thyroid
tissue [7]. Lingual thyroid tissue along the path of the thyroglossal duct is the most common site of thyroid
ectopy. (See "Thyroglossal duct cysts and ectopic thyroid".)
Ectopic thyroid tissue can be benign or malignant [8]. Malignant transformation of ectopic thyroid tissue is
rare. However, if thyroid tissue is found in the lateral cervical lymph nodes (lateral aberrant thyroid), a
metastasis of a malignant thyroid tumor should be excluded.
EMBRYOLOGY — Thyroid development is detectable in the third week of gestation. The thyroid is primarily
derived from the endoderm. The ventral portion of the fourth pharyngeal pouch will develop into the lateral
thyroid lobes (figure 5).
The pyramidal lobe, present in up to 55 percent of patients, originates from the migration of the thyroglossal
duct that descends from the pharynx at the foramen cecum of the tongue and attaches to the thyroid isthmus
[4,9]. The thyroglossal duct is usually obliterated after its descent. If it remains patent, the patient may
develop a thyroglossal duct cyst. (See "Thyroglossal duct cysts and ectopic thyroid".)
The ultimobranchial bodies (transient embryonic structures) consist of neural crest cells from the fourth and
fifth branchial pouches, which migrate to the upper third of the thyroid lobes. The neuroendocrine

parafollicular cells (C cells), derived from the ultimobranchial bodies, produce calcitonin. The ultimobranchial
bodies fuse with the posterior lobes of the thyroid. C cells make up only about 0.1 percent of the thyroid mass
and are concentrated in the upper thyroid lobes. Multicentric hyperplasia of the parafollicular C cells is a
precursor lesion of medullary thyroid cancer and a hallmark of multiple endocrine neoplasia type 2 (MEN2).
(See "Medullary thyroid cancer: Clinical manifestations, diagnosis, and staging" and "Clinical manifestations
and diagnosis of multiple endocrine neoplasia type 2".)
BLOOD SUPPLY — The arterial blood supply to the thyroid gland is primarily from the right and left superior
and inferior thyroid arteries, derived from the external carotid arteries and thyrocervical trunk, respectively.
The venous drainage consists of the superior, middle, and inferior thyroid veins that drain into the internal
jugular vein and innominate vein (figure 6).
NERVE SUPPLY — It is critical that the superior and recurrent laryngeal nerves be routinely identified and
protected in thyroid surgery to reduce the risk of injury (figure 7).
The surgeon may use a number of different techniques to aid in the identification of the nerves and potential
variations. These include visual recognition, the use of anatomic landmarks, palpation, and intraoperative
nerve monitoring (figure 8).
Visualization of the entire course of the nerves in the central compartment identifies multiple branches when
they occur. It also reduces the chance of inadvertently ligating a nerve when it is more redundant or takes a
more superior course prior to insertion into the trachea. The dissection along the nerves should be conducted
in a manner to reduce the risk of thermal or traction injury.
Intraoperative nerve monitoring can be used as an adjunct to anatomic identification. The dissection should
still continue until the nerve is visible because the nerve monitor may provide a false signal when it is in close
proximity, but not directly on, the nerve. (See "Initial thyroidectomy", section on 'Intraoperative nerve
Superior thyroid artery — The superior thyroid artery is the first branch off the external carotid artery. It
extends inferiorly to the superior pole of the thyroid lobe. In addition to supplying the thyroid, the superior
thyroid artery is the primary blood supply to approximately 15 percent of superior parathyroid glands.
The superior thyroid artery is a landmark for identification of the superior laryngeal nerve, which courses
with the artery until approximately 1 cm from the superior thyroid pole [10].
●
Inferior thyroid artery — The inferior thyroid artery is a branch of the thyrocervical trunk which arises from
the subclavian artery. The inferior thyroid artery courses posterior to the carotid artery to enter the lateral
thyroid. The point of entry can extend from superior to inferior thyroid poles. The inferior thyroid artery
also supplies the inferior parathyroid glands and approximately 85 percent of superior parathyroid
glands.
The RLN may course anterior or posterior to the inferior thyroid artery. In some cases, the RLN may
branch into both an anterior and posterior position.
●
Thyroidea ima artery — A thyroidea ima artery is found in approximately 3 percent of individuals and
arises from the aortic arch or innominate artery and courses to the inferior portion of the isthmus or
inferior thyroid poles [1]. Surgical control of the thyroidea ima artery is essential during thyroidectomy.
The thyroidea ima artery can be quite enlarged in patients with thyroid disease such as goiter or
hyperthyroidism.
●

monitoring'.)
Superior laryngeal nerves — The right and left superior laryngeal nerves originate from the right and left
vagus nerves as they exit the base of the skull [11]. The superior laryngeal nerve courses with the superior
thyroid artery until approximately 1 cm before the artery enters the capsule of the superior pole of the thyroid.
Injury to the superior laryngeal nerve during surgery can be minimized by dissecting the superior thyroid
vessels at the level of the thyroid capsule. Maintaining hemostasis is critical because the control of bleeding
from the superior thyroid vessels with hemostats may put the superior laryngeal nerve at risk.
The superior laryngeal nerve consists of two primary branches:
External branch — The external branch of the superior laryngeal nerve is primarily motor in function [10].
It is the external branch that innervates the inferior constrictor and cricothyroid muscles.
The external branch travels with the superior thyroid artery until approximately 1 cm before the artery enters
the superior thyroid pole. The external branch then divides into branches that enter the lateral inferior
pharyngeal constrictor muscle and the cricothyroid muscle. A few smaller branches may be seen entering the
superior thyroid.
The proximity of the nerve to the branches of the superior thyroid artery make it vulnerable to damage during
dissection; rates of injury are as high as 30 percent [12,13]. Care must be taken during the dissection of the
superior thyroid vessels to prevent inadvertent injury to the superior laryngeal nerve by staying as close as
possible to the thyroid capsule.
Internal branch — The internal branch of the superior laryngeal nerve is sensory to the larynx. The
internal branch enters the larynx through the thyrohyoid membrane superior to the external branch.
Recurrent laryngeal nerve — The recurrent laryngeal nerve (RLN) provides both sensory and motor
function to the larynx. This nerve is sensory to the subglottic region and innervates all muscles to the larynx
except the cricothyroid muscle. The RLN provides motor function for both vocal cord abduction and
adduction.
The RLN is associated with the inferior thyroid artery at approximately the junction of the lower and middle
thirds of the thyroid gland. On the left, the RLN ascends in the tracheoesophageal groove and crosses deep
to the inferior thyroid artery; on the right, the RLN crosses more obliquely and is oriented more laterally than
caudally. While the nerve most often crosses deep to the inferior thyroid artery, documented variations
include passing anterior to the artery as well as passing between branches of the inferior thyroid artery [14].
The RLN also may bifurcate or trifurcate prior to insertion in the cricothyroid muscle. The motor function for
adduction and abduction is located in the anterior branches of the RLN [15].
Palpation of the tracheoesophageal groove and the junction with the inferior edge of the thyroid cartilage
identifies the approximate location of RLN insertion into the trachea. The nerve itself may also be palpated in
the tracheoesophageal groove.
Right recurrent laryngeal nerve — The right RLN originates from the right vagus nerve at the level of the
subclavian artery. It courses posterior to the subclavian artery, taking a transverse course as it travels
superiorly towards the lateral trachea and into the tracheoesophageal groove. It courses through the ligament
of Berry and enters the larynx through the first tracheal ring, inferior to the cricothyroid muscle. It is common

to see several branches of the right RLN as it approaches the trachea. The most anterior branch of the right
RLN is the crucial motor branch, but all branches should be preserved [16].
Left recurrent laryngeal nerve — The left RLN originates from the left vagus nerve at the level of the
aortic arch. It courses posterior to the aorta at the ligamentum arteriosum, taking a direct superior course
toward the tracheoesophageal groove before entering the larynx in a similar fashion to the right laryngeal
nerve. The left RLN thus courses more directly superiorly than the right nerve, and enters the
tracheoesophageal groove at a level lower than the right RLN which takes a more transverse course.
Non-recurrent laryngeal nerves — A non-recurrent RLN may be present in nearly 1 percent of patients.
When present, the nerve will course directly from the vagus nerve to the trachea.
Rarely, the right inferior laryngeal nerve may not recur and instead crosses transversely from the vagus nerve
and behind the common carotid artery; in almost all instances, it enters the larynx at the usual level. Non-
recurrence of the inferior laryngeal nerve results from a vascular anomaly during embryonic development of
the aortic arches in which the fourth vascular arch and right dorsal aorta involute, causing the aberrant
development of arterial structures on the right, including the lack of an innominate artery and the passage of
the subclavian artery behind the esophagus [17,18].
A non-recurrent left inferior laryngeal nerve would require a right aortic arch associated with situs inversus
and is exceedingly rare.
Nerve injury — Nerve injury can result from the disease process, surgery, or airway access for anesthesia.
Injury to the superior laryngeal nerve results in voice weakness or fatigue as well as changes to both voice
quality and pitch [19].
Injury to the recurrent laryngeal nerve (RLN) may result in paresis or paralysis of the true vocal cord to a
paramedian or lateral position. Intrinsic muscles of the larynx, aside from the cricothyroid muscle, can be
impaired and the patient may have swallowing dysfunction with an aspiration risk. A bilateral injury to the RLN
may necessitate a tracheostomy. These are discussed in detail elsewhere. (See "Initial thyroidectomy".)
LYMPHATIC DRAINAGE — The neck is divided into compartments based on patterns of lymphatic drainage
(figure 9 and figure 10). The central compartment (level VI) is the primary lymphatic drainage region for the
thyroid gland. The central compartment is bounded superiorly by the hyoid bone, laterally by the common
carotid arteries, and inferiorly by the innominate artery just caudal to the suprasternal notch [20].
The lateral neck includes levels II through V. Level II is located between the angle of the jaw and base of the
skull to the hyoid bone. Level III is from the hyoid bone to the cricoid cartilage. Level IV is from the omohyoid
muscle to the clavicle. Level V is the posterior triangle that is bounded by the sternocleidomastoid muscle,
trapezius muscle, and clavicle. Superior mediastinal nodes are the Level VII nodes
PARATHYROID GLANDS — The parathyroid glands are in close approximation with the thyroid gland and
function independent of the thyroid gland. Identification of the superior and inferior parathyroid glands allows
the surgeon to delineate the course of the RLN which lies anterior to the superior parathyroid gland and
posterior to the inferior parathyroid gland.
The parathyroid glands are discussed in detail separately. (See "Surgical anatomy of the parathyroid
glands".)

SUMMARY AND RECOMMENDATIONS
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REFERENCES
1. Bliss RD, Gauger PG, Delbridge LW. Surgeon's approach to the thyroid gland: surgical anatomy and the
importance of technique. World J Surg 2000; 24:891.
2. Pankow BG, Michalak J, McGee MK. Adult human thyroid weight. Health Phys 1985; 49:1097.
3. Hegedüs L. Thyroid size determined by ultrasound. Influence of physiological factors and non-thyroidal
disease. Dan Med Bull 1990; 37:249.
4. Braun EM, Windisch G, Wolf G, et al. The pyramidal lobe: clinical anatomy and its importance in thyroid
surgery. Surg Radiol Anat 2007; 29:21.
5. Pelizzo MR, Toniato A, Gemo G. Zuckerkandl's tuberculum: an arrow pointing to the recurrent laryngeal
A thorough understanding of thyroid anatomy is central to the performance of safe thyroid surgery. (See
'Introduction' above.)
●
The normal thyroid gland is immediately caudal to the larynx and encircles the anterolateral portion of
the trachea and is bordered by the trachea and esophagus medially, the carotid sheath laterally, and the
sternocleidomastoid, sternohyoid, and sternothyroid muscles anteriorly and laterally. (See 'Size and
location' above.)
●
The tubercle of Zuckerkandl is located on the posterior aspect of each thyroid lobe. The recurrent
laryngeal nerve usually traverses the posterior aspect of the tubercle, which can help the surgeon find
and identify the nerve. (See 'Tubercle of Zuckerkandl' above.)
●
The arterial blood supply to the thyroid gland is primarily from the right and left superior and inferior
thyroid arteries, derived from the external carotid arteries and thyrocervical trunk, respectively. The
venous drainage consists of the superior, middle, and inferior thyroid veins that drain into the internal
jugular vein and innominate vein. (See 'Blood supply' above.)
●
The surgeon may use a number of different techniques to aid in the identification of the nerves. These
can include direct visualization, the use of anatomic landmarks, palpation, and intraoperative nerve
monitoring. (See 'Nerve supply' above.)
●
The superior laryngeal nerve has an external and internal branch. The external branch is primarily motor
in function and innervates the inferior constrictor and cricothyroid muscles. The internal branch is
sensory in function to the larynx. (See 'Superior laryngeal nerves' above.)
●
The recurrent laryngeal nerve (RLN) provides both sensory and motor function to the larynx. Injury to the
RLN may result in paresis or paralysis of the true vocal cord to a paramedian or lateral position. Intrinsic
muscles of the larynx, aside from the cricothyroid muscle, can be impaired and the patient may have
swallowing dysfunction with an aspiration risk. (See 'Nerve injury' above.)
●
The primary lymphatic drainage region for the thyroid gland is the central compartment of the neck. (See
'Lymphatic drainage' above.)
●

nerve (constant anatomical landmark). J Am Coll Surg 1998; 187:333.
6. Reeve, TS, Delbridge, L. The tubercle of Zuckerkandl: a guide to thyroid and parathyroid surgery. Aust
New Zealand Journal Surgery 1998; 68:59.
7. Batsakis JG, El-Naggar AK, Luna MA. Thyroid gland ectopias. Ann Otol Rhinol Laryngol 1996; 105:996.
8. Kousta E, Konstantinidis K, Michalakis C, et al. Ectopic thyroid tissue in the lower neck with a coexisting
normally located multinodular goiter and brief literature review. Hormones (Athens) 2005; 4:231.
9. Allard RH. The thyroglossal cyst. Head Neck Surg 1982; 5:134.
10. Cernea CR, Ferraz AR, Nishio S, et al. Surgical anatomy of the external branch of the superior
laryngeal nerve. Head Neck 1992; 14:380.
11. Droulias C, Tzinas S, Harlaftis N, et al. The superior laryngeal nerve. Am Surg 1976; 42:635.
12. Lifante JC, McGill J, Murry T, et al. A prospective, randomized trial of nerve monitoring of the external
branch of the superior laryngeal nerve during thyroidectomy under local/regional anesthesia and IV
sedation. Surgery 2009; 146:1167.
13. Morton RP, Whitfield P, Al-Ali S. Anatomical and surgical considerations of the external branch of the
superior laryngeal nerve: a systematic review. Clin Otolaryngol 2006; 31:368.
14. Makay O, Icoz G, Yilmaz M, et al. The recurrent laryngeal nerve and the inferior thyroid artery--
anatomical variations during surgery. Langenbecks Arch Surg 2008; 393:681.
15. Serpell JW, Yeung MJ, Grodski S. The motor fibers of the recurrent laryngeal nerve are located in the
anterior extralaryngeal branch. Ann Surg 2009; 249:648.
16. Myssiorek D. Recurrent laryngeal nerve paralysis: anatomy and etiology. Otolaryngol Clin North Am
2004; 37:25.
17. Henry JF, Audiffret J, Denizot A, Plan M. The nonrecurrent inferior laryngeal nerve: review of 33 cases,
including two on the left side. Surgery 1988; 104:977.
18. Pettiford J, Erasmus J, Grubbs EG, Perrier ND. Dysphagia lucoria: consideration for the endocrine
surgeon. Surgery 2010; 147:890.
19. Teitelbaum BJ, Wenig BL. Superior laryngeal nerve injury from thyroid surgery. Head Neck 1995; 17:36.
20. American Thyroid Association Surgery Working Group, American Association of Endocrine Surgeons,,
American Academy of Otolaryngology-Head and Neck Surgery, et al. Consensus statement on the
terminology and classification of central neck dissection for thyroid cancer. Thyroid 2009; 19:1153.
Topic 2154 Version 15.0

GRAPHICS
Thyroid and parathyroid glands
The thyroid is a butterfly-shaped gland in the middle of the neck. It sits just below the
larynx (voice box). The thyroid makes two hormones, called T3 and T4, which control
how the body uses and stores energy. The parathyroid glands are four small glands
behind the thyroid. They make a hormone called parathyroid hormone, which helps
control the amount of calcium in the blood.
T3: triiodothyronine; T4: thyroxine.
Graphic 66834 Version 8.0

Anatomy of the cricothyroid membrane
* The cricothyroid muscle is bilateral and depicted on one side for illustrative purposes.

Página 10 de 19https://www.uptodate.com/contents/surgical-anatomy-of-the-thyroi…/print?source=search_result&search=tiroides&selectedTitle=8~150
Thyroid anatomy
Dissection of the anterior neck. Anterior view. The fascia has been removed and the muscles on the left
side have been reflected to show the hyoid bone, thyroid gland, and structures related to the carotid
sheath (carotid artery, internal jugular vein [IJV], vagus nerve [CN X], and deep cervical lymph nodes).
Reproduced with permission from: Moore KL, Dalley AF. Clinical Oriented Anatomy, Fourth Edition. Baltimore:
Lippincott Williams & Wilkins, 1999. Copyright © 1999 Lippincott Williams & Wilkins.

Recurrent laryngeal nerve variation
The uncommon, but high-risk anatomic variation where the recurrent laryngeal
nerve (RLN) courses lateral to the tubercle of Zuckerkandl, which is often enlarged.
The nerve is encountered much earlier in the dissection required for thyroidectomy
and is at risk of being misidentified as a vascular structure.
Reproduced with permission from: Mulholland MW, Maier RV, et al. Greenfield's Surgery:
Scientific Principles And Practice, Fourth Edition. Philadelphia: Lippincott Williams & Wilkins,
2006. Copyright © 2006 Lippincott Williams & Wilkins.

Coronal views of pharyngeal arch transformations
The first pouch hardly changes (A). It remains as a thin barrier between outside and inside - the
tympanic membrane of the ear. On the inner side is the auditory tube, which is open to the throat, and
on the outer side is the ear canal. The remaining clefts smooth over as a result of expansion and
descent of the second arch, leaving the possibility of a trapped cyst or fistula in the connective tissue of
the neck (B). The second pouch harbors a condensation of lymphatic tissue - the future tonsil (C).
Parathyroid glands and critical immunologic tissue (the thymus gland) develop from involutions of the
third and fourth pouches. From the midline of the ventral pharynx, the thyroid gland originates from the
lining of the foramen cecum and descends external to the gut tube (C).
Adapted with permission from: Sadler TW. Langman's Medical Embryology, 10th Edition. Baltimore: Lippincott
Williams & Wilkins, 2006. Copyright © 2006 Lippincott Williams & Wilkins.

Thyroid gland blood supply
Overall anatomic relationships of the thyroid and surrounding structures.
Note the course of the inferior thyroid artery, behind and perpendicular to
the carotid artery. The superior thyroid artery and external branch of the
superior laryngeal nerve run in close approximation.
Reproduced with permission from: Surgical Anatomy of the Thyroid, Parathyroid,
and Adrenal Glands. In: Mastery of Surgery, Fischer JE, Bland KI, Callery MP (Eds),
Lippincott Williams & Wilkins, Philadelphia 2006. Copyright © 2006 Lippincott
Williams & Wilkins. www.lww.com.

Nerve supply of the thyroid gland
It is critical that the superior and recurrent laryngeal nerves be routinely identified and
protected in thyroid surgery to reduce the risk of injury.

Variations in nerve supply of the thyroid gland
(A) The external branch of the superior laryngeal nerve innervates the inferior constrictor
and cricothyroid muscles. The external branch travels with the superior thyroid artery until
approximately 1 cm before the artery enters the superior thyroid pole and then divides into
branches that enter the lateral inferior pharyngeal constrictor muscle and the cricothyroid
muscle. A few smaller branches may be seen entering the superior thyroid.
(B) The recurrent laryngeal nerve (RLN) is associated with the inferior thyroid artery at
approximately the junction of the lower and middle thirds of the thyroid gland. On the left,
the RLN ascends in the tracheoesophageal groove and crosses deep to the inferior thyroid
artery; on the right, the RLN crosses more obliquely and is oriented more laterally than
caudally.
While the nerve most often crosses deep to the inferior thyroid artery, documented
variations include passing anterior to the artery as well as passing between branches of the

inferior thyroid artery. Another variation of the nerve is the nonrecurrent laryngeal nerve, in
which the laryngeal nerve branches directly from the vagus nerve. This variation occurs
more commonly on the right side.
(A) Adapted from: Morton RP, Whitfield Al-Ali S. Anatomical and surgical considerations of the
external branch of the superior laryngeal nerve: a systematic review. Clin Otolaryngol 2006;
31:368-374.
(B) Adapted from: Makay O, Icoz G, Yilmaz M, Akyildiz M, Yetkin E. The recurrent laryngeal nerve
and the inferior thyroid artery-anatomical variations during surgery. Langenbecks Arch Surg 2008;
393:681.

Lymph node levels of the neck
Level I, submental (IA) and submandibular (IB); level II, upper internal jugular
nodes; level III, middle jugular nodes; level IV, low jugular nodes; level V, posterior
triangle nodes; level VI, central compartment; level VII, superior mediastinal nodes.
Adapted from: American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original
source for this material is the AJCC Cancer Staging Manual, Seventh Edition (2010)
published by Springer New York, Inc.

Lymph nodes of the head and neck
This drawing schematically depicts the major lymph nodes in the head and neck area that are
likely to be enlarged on physical examination in patients with various local or systemic diseases.
The major nodal groups are shown here in bold, with the areas draining into these nodal groups
noted when appropriate. While enlargement of both the left and right supraclavicular lymph
nodes may reflect disease in the thorax, left supraclavicular nodal enlargement, because of its
drainage pattern, may also reflect the presence of abdominal involvement (ie, Virchow's node).

Contributor Disclosures
Melanie L Richards, MD, MHPE Nothing to disclose Tracy S Wang, MD, MPH Nothing to disclose Julie
Ann Sosa, MD, MA Consultant/Advisory Boards: NovoNordisk; Eli Lilly; GlaxoSmithKline; Astra Zeneca
[Data Monitoring Committee, Medullary Thyroid Cancer Consortium Registry]. Sally E Carty, MD,
FACS Nothing to disclose Wenliang Chen, MD, PhD Nothing to disclose
Contributor disclosures are reviewed for conﬂicts of interest by the editorial group. When found, these are
addressed by vetting through a multi-level review process, and through requirements for references to be
provided to support the content. Appropriately referenced content is required of all authors and must
conform to UpToDate standards of evidence.
Conﬂict of interest policy

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