Thyroid gland integrated lecture Dr.N.Mugunthan. Professor of Anatomy, Sree Mookambika Institute of Medical Sciences, Kulasekharam, Tamil Nadu

1. By
Dr.N.Mugunthan.MS,DNB,MNAMS,PhD,
Professor of Anatomy,
SMIMS.

2. Learning objectives
Development & its associated anomalies
Situation & extent
Coverings
Relations
Blood supply
Lymphatic drainage
Nerve supply
Histology
© Dr.N.Mugunthan

3. Thyroid gland
1. Congenital anomalies?
2. Why does it moves with deglutition?
3. Arteries supplying thyroid gland?
4. Structures accompanying the arteries?
5. How does it differs from other endocrine gland?
© Dr.N.Mugunthan

4. Development of thyroid gland
1. Median thyroid
diverticulum – endodermal
thyroid diverticulum
• Foramen caecum
• Thyroglossal duct (infront
of hyoid bone)
• Isthmus & upper half of
lateral lobes
2. Lateral thyroid rudiment –
caudal pharyngeal complex
• Lower half of lateral lobes
© Dr.N.Mugunthan

5. Congenital anomalies of
thyroid:
a. Agenesis
b. One lobe absent
c. Thyroglossal cyst
d. Thyroglossal fistula
e. Lingual thyroid
f. Retrosternal thyroid
g. Ectopic thyroid –lingual
/ sublingual
h. Accessory thyroid –on
thymus/arise from
thyroglossal duct
Developmental anomalies
© Dr.N.Mugunthan

6. Situation & extent
Front & sides of neck
Deep to the floor of
muscular triangle
Opp. C5,C6,C7 & T1
Extent:
Each lobe – middle of
thyroid cartilage to 5th
tracheal ring
Isthmus – 2nd,3rd & 4th
tracheal ring
© Dr.N.Mugunthan

7. Coverings
2 capsule:
1. Outer false capsule –
(splitting of pretracheal
fascia)
Thick on inner (medial)
surface of gland – forms
suspensory lig.of Berry
Suspensory lig.of Berry
connects the lobe with
cricoid cartilage
© Dr.N.Mugunthan

8. Thyroid gland moves with deglutition
Attachment of
pretracheal fascia (form
false capsule) to body of
hyoid bone
Suspensory lig.of Berry
connects the lobe with
cricoid cartilage
© Dr.N.Mugunthan

9. 2. Inner true capsule –
condensation of fibrous
stroma of gland
Deep to true capsule –
dense capillary plexus.
During thyroidectomy –
remove the gland with
capsule [plane of cleavage
between true & false
capsule]
Coverings cont…..
© Dr.N.Mugunthan

10. Relations of lateral lobe
Apex:
Oblique line of thyroid
cartilage
Sandwiched between
inferior constrictor &
sternothyroid
Thyroid enlargement
cannot extend above
Related to sup.thyroid
artery & ext.laryngeal
nerve
© Dr.N.Mugunthan

11. Base
Extends 5th or 6th tracheal
ring (T1)
Related to inf.thyroid artery
& recurrent laryngeal nerve
© Dr.N.Mugunthan

12. Anterolateral (superficial) surface
Overlapped by
infrahyoid muscles
( Within outwards )
o Sternothyroid
o Sternohyoid
o Superior belly of
omohyoid
o Sternomastoid (partly)
© Dr.N.Mugunthan

13. Anterolateral (superficial) surface
Overlapped by
infrahyoid muscles
( Within outwards )
o Sternothyroid
o Sternohyoid
o Superior belly of
omohyoid
o Sternomastoid (partly)
© Dr.N.Mugunthan

14. Anterolateral (superficial) surface
Overlapped by
infrahyoid muscles
( Within outwards )
o Sternothyroid
o Sternohyoid
o Superior belly of
omohyoid
o Sternomastoid (partly)
© Dr.N.Mugunthan

15. Anterolateral (superficial) surface
Overlapped by
infrahyoid muscles
( Within outwards )
o Sternothyroid
o Sternohyoid
o Superior belly of
omohyoid
o Sternomastoid (partly)
© Dr.N.Mugunthan

16. Anterolateral (superficial) surface
Overlapped by
infrahyoid muscles
( Within outwards )
o Sternothyroid
o Sternohyoid
o Superior belly of
omohyoid
o Sternomastoid (partly)
© Dr.N.Mugunthan

17. Medial (deep) surface
Related to -
2 tubes, 2 nerves & 2
muscles
2 tubes – larynx &trachea ,
pharynx & oesophagus
2 nerves- external &
recurrent laryngeal nerves
2 muscles-cricothyroid &
inferior constrictor
© Dr.N.Mugunthan

18. Carcinoma of thyroid
symptoms ( due to
compression)
Larynx/trachea – dyspnoea
Pharynx/oesophagus –
dysphagia
Involvement of external &
recurrent laryngeal nerve –
hoarseness of voice
Medial (deep) surface cont…
© Dr.N.Mugunthan

19. Posterolateral surface
Related to carotid sheath
& its contents
Ansa cervicalis infront of
carotid sheath
Carotid sheath
Contents:
1. CCA
2. IJV
3. Vagus nerve
Sympathetic chain behind
the sheath © Dr.N.Mugunthan

20. Anterior border
Related to anterior
branch of superior
thyroid artery
© Dr.N.Mugunthan

21. Posterior border
 Anastomosis of sup. & inf.
thyroid arteries
 Parathyroid glands (sup. &
inf.)
[Sup. Parathyroid at the level
of C6 (cricoid)
Inf. Parathyroid at lower pole
of gland]
 On left side thoracic duct
(lower part)
© Dr.N.Mugunthan

22. Isthmus - Anterior surface
Skin
Superficial fascia &
ant.jugular vein
Investing layer of deep
cervical fascia
Sternothyroid &
sternohyoid
© Dr.N.Mugunthan

23. Posterior surface
2nd,3rd & 4th tracheal
rings
© Dr.N.Mugunthan

24. Superior border
Anastomosis between 2
sup.thyroid arteries
Pyramidal lobe
(occasionally from isthmus)
Levator glanduli thyroidae
– fibromuscular band
Extend from hyoid bone to
isthmus or pyramidal lobe
© Dr.N.Mugunthan

25. Inferior border
Inferior thyroid veins
Arteria thyroidea ima
(if present)
© Dr.N.Mugunthan

26. Blood supply
Arterial supply:
1. Sup. Thyroid artery (from
ext.carotid artery)
Accompanied by external
laryngeal nerve
Ligate the artery close to
gland to avoid injury to this
nerve
(nerve is more intimately
related to artery a little away
from gland)
© Dr.N.Mugunthan

27. Arterial supply cont….
2. Inferior thyroid artery
(from thyrocervical trunk)
Accompanied by recurrent
laryngeal nerve
Ligate the artery away
from the gland to avoid
injury to this nerve
(recurrent laryngeal nerve
cross infront of inf.thyroid
artery close to gland)
© Dr.N.Mugunthan

28. 3. Arteria thyroidea ima –
occasionally (from arch
of aorta or
brachiocephalic trunk)
4. Numerous accessory
thyroid arteries ( from
tracheal & oesophageal
branches)
Arterial supply cont….
© Dr.N.Mugunthan

29. Superior & inferior thyroid artery
© Dr.N.Mugunthan

30. Venous drainage
Veins do not accompany
the arteries
 Arise from venous plexus
deep to true capsule
1. Sup.thyroid vein
2. Middle thyroid vein
3. A bunch of inf.thyroid
vein
4. Occasionally fourth
thyroid vein (kocher’s
vein)
© Dr.N.Mugunthan

31. Lymphatic drainage
Upper lateral portion –
upper deep cervical nodes
Lower lateral portion –
lower deep cervical nodes
Upper medial portion –
prelaryngeal nodes
Lower medial portion –
pretracheal nodes
© Dr.N.Mugunthan

32. Nerve supply
1. Sympathetic nerves
2. Parasympathetic nerves
Sympathetic nerves:
From sup.,middle &
inf.cervical ganglion
Vasomotor supply
Parasympathetic nerves:
From vagus & recurrent
laryngeal nerves
© Dr.N.Mugunthan

33. Microstructure
• 20–30 million thyroid
follicles
• Lined with simple
cuboidal epithelium
• Filled with gelatinous
substance – colloid
• Huge quantity
• Extracellular
• Parafollicular or C cell
© Dr.N.Mugunthan

34. Thyroid follicle
© Dr.N.Mugunthan

35. Thyroid gland
1. Congenital anomalies?
2. Why does it moves with deglutition?
3. Arteries supplying thyroid gland?
4. Structures accompanying the arteries?
5. How does it differs from other endocrine gland?
© Dr.N.Mugunthan

36. During thyroidectomy –
Ligate the sup.thyroid
artery close to apex of
gland to avoid injury to
ext.laryngeal nerve
Ligate the inf.thyroid artery
away from base of gland to
avoid injury to recurrent
laryngeal nerve
Take home message -01
© Dr.N.Mugunthan

37. To release the gland
divide the suspensory
lig.of Berry
while cutting avoid injury
to recurrent laryngeal
nerve (related post. to lig
of Berry)
Look for arteria thyroidea
ima
Look for Kocher’s vein
(4th vein)
Take home message -02
© Dr.N.Mugunthan

38. Surgical Anatomy
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