The document discusses the anatomy of the thyroid and parathyroid glands. It describes the embryology and development of each gland. The thyroid gland normally has two lobes connected by an isthmus and is located in the lower front of the neck. The parathyroid glands usually number four and are often found near the thyroid gland or thymus. The document outlines the blood supply, drainage, innervation and relations to surrounding structures for each gland.

1. The tie
of wind
pipe!

2. ANATOMY OF THYROID
AND PARATHYROID GLAND.
Presenter : Dr Zenebe Teklu
April 2015

3. Outline
 History
 Embryology of thyroid gland
 Anatomy of thyroid gland
 Embryology of parathyroid gland
 Anatomy of parathyroid gland

4. History
 Greek thyreoeides, shield-shaped(1656).
 Classified as a ductless gland (1776)

5. Embryology
 Out pouching of primitive foregut(3rd wk)
 Foramen cecum
 Medial thyroid anlage
 Descends anterior to structures that form the
hyoid bone and larynx.
 Thyroglossal duct
 Ultimobranchial bodies(5th wk)

9. Clinical relevance
 Thyroglosal cyst
 Thyroglosal duct start to obliterate at 5th wk and
disappears by 8th wk.
 Rarely it may persist in whole or in part
 It may occur anywhere along the migratory path
of the thyroid although 80% are found in
juxtaposition to the hyoid bone.
 Sinuses result from infection of the cyst
secondary to spontaneous or surgical drainage of
the cyst
 Sistrunk operation

10. Cont…
 Lingual thyroid
 Failure of the median thyroid anlage to descend
normally
 may be the only thyroid tissue present
 Intervention becomes necessary for obstructive
symptoms such as choking, dysphagia, airway
obstruction, or hemorrhage

11. Anatomy
 Brown, firm, 15-20 g,
 Two lateral lobe connected by median ismuth
 Located anteriorly in the neck at the level of
the C5 -T1 vertebrae.
 Extends superiorly up to mid thyroid cartilage
 Lie adjacent to the carotid sheaths and
sternocleidomastoid muscles laterally.
 Posterior to the strap (sternothyroid and
sternohyoid) muscles.

13. Cont…

14. Cont..
 Encircles about 75% of the diameter of the
junction of the larynx and the upper trachea.
 A thin layer of connective tissue(part of deep
cervical facia) surrounds the thyroid in normal
anatomic position.
 This tissue is part of the fascial layer, which
invests the trachea(pretracheal facia).

16. Cont..
 The true capsule of the thyroid is a thin,
densely adherent fibrous layer that sends out
septa that invaginate into the gland, forming
pseudolobules.
 The thyroid capsule is condensed into the
posterior suspensory or Berry's ligament near
the cricoid cartilage and upper tracheal rings.

18. Sonography

19. Blood supply
 Superior thyroid artery
 Inferior thyroid artery
 Thyroid ima (1-4%)

22. Venous drainage
 Superior thyroid vein
 Middle thyroid vein
 Inferior thyroid vein

24. Nerves
 RLN

27. Relation to trachea and esophagus

28. Relation to ITA

29. Cont..
 It may branch in its coarse

30. Cont..
• Tubercle of Zuckerkandl

31. Cont..
• Are closely approximated to the ligament of
Berry. May traverse the ligament in 25% of
individuals.

33. Cont..
• Non recurrent right RLN 0.5-1%
• Left (rare)

34. Cont..
• Innervate all intrinsic muscle of larynx except
cricothyroid muscle(SLN) .
• Injury to one RLN : paralysis of ipsilateral vocal
cord(paramedian or abducted)
• Bilateral RLN injury: airway obstruction, loss of
voice

35. Cont..
• SLN

36. Cont..
• Cernea and et.al classification.
• The type 2a variant( 20%) places the nerve at
a greater risk of injury.

38. Cont..
• The superior pole vessels should not be
ligated en masse, but should be individually
divided, low on the thyroid gland and
dissected lateral to the cricothyroid muscle.
• 20% at risk of injury.
• Difficulty "hitting high notes," projecting the
voice, and voice fatigue during prolonged
speech.

39. Cont..
• Sympathetic- the superior and middle cervical
sympathetic ganglia(enter gland with vessel).
• Parasympathetic- from vagus

40. Lymphatic system
• The thyroid gland is endowed with an extensive
network of lymphatics.
• Intraglandular lymphatic vessels connect both
thyroid lobes through the isthmus and also drain
to perithyroidal structures and lymph nodes.
• Regional lymph nodes include pretracheal,
paratracheal, perithyroidal, RLN, superior
mediastinal, retropharyngeal, esophageal, and
upper, middle, and lower jugular chain nodes.

41. Cont..
• These lymph nodes can be classified into seven
levels .
• The central compartment includes nodes located
in the area between the two carotid sheaths,
whereas nodes lateral to the vessels are present
in the lateral compartment.
• Thyroid cancers may metastasize to any of these
regions, although metastases to submaxillary
nodes (level I) are rare (<1%).
• There also can be "skip" metastases to nodes in
the ipsilateral neck.

43. Parathyroid

44. Embryology

45. Cont..
• The position of normal superior parathyroid
glands is more consistent.
• 80% of these glands being found near the
posterior aspect of the upper and middle
thyroid lobes, at the level of the cricoid
cartilage.
• As the embryo matures, the thymus and
inferior parathyroids migrate together
caudally in the neck

46. Cont..
• Approximately 15% of inferior glands are
found in the thymus.
• Inferior glands - more variable position due to
their longer migratory path.
• Undescended inferior glands may be found
near the skull base, angle of the mandible, or
superior to the upper parathyroid glands
along with an undescended thymus.
• Intrathyroidal glands is about 2%.

48. Anatomy
• 7 mm in size , weigh 40-50 mg each
• Four in number (84%), supernumerary (13%),
less than four (3%)
• The superior glands - within 1 cm of the entry
point for the RLN into the ligament of Berry
and the cricoid cartilage and usually 1 to 2
cm cranial to the junction of RLN with the ITA.
.

49. Cont..
• The most common location for inferior glands is
within a distance of 1 cm from a point centered
where the inferior thyroid artery and RLN cross.

51. Cont
• Gray and semitransparent in newborns but
appear golden yellow to light brown in adults.
• Parathyroid color depends on cellularity, fat
content, and vascularity.
• Moreover, they often are embedded in and
sometimes difficult to discern from
surrounding fat.
• Usually symmetric : superior- 80%, inferior-
70%

53. Most parathyroid glands (83 percent) are oval, bean shaped
or spherical, but can also be elongated (11 percent).

54. Cont..
• Blood supply: ITA(80%), STA(20%)
• Each parathyroid gland usually has its own
end-artery.
• The parathyroid glands drain ipsilaterally by
the superior, middle, and inferior thyroid
veins.
• The nerve supply of the parathyroid glands is
abundant; it is derived from thyroid branches
of the cervical sympathetic ganglia

56. References