The document provides information on the anatomy and function of the thyroid gland. It discusses the gross anatomy including coverings, blood supply from arteries like the superior thyroid artery, and venous drainage. It also describes the nerve supply including parasympathetic fibers from the vagus and recurrent laryngeal nerves and sympathetic fibers from cervical ganglia. The lymphatic drainage is to prelaryngeal, jugulodigastric and pretracheal lymph nodes. Key aspects of surgical anatomy are highlighted regarding ligating arteries and removing the gland with its true capsule. The function of producing T3, T4, and calcitonin hormones is summarized. Normal and abnormal thyroid hormone levels are provided to define euthyroidism, hyperthy

1. GROUP MEMBERS:
SUDAKSHINA DAS
DEBALINA BHATTACHARJEE
KOUSIK KARMAKAR
SAYAN BANERJEE
AN APPROACH TO THYROID
SWELLING

2. Gr0ss Anatomy
● Coverings:
 True capsule
 False capsule
 The false capsule is thickened to form ligament of Berry which connects medial surface of the lateral
lobe of the gland with cricoid cartilage. This attachment explains why the thyroid gland moves up and
down with deglutination.
 The space between true and false capsules is occupied by parathyroid glands and trunks of blood
vessels.
● Presenting Parts: The gland consists of:-
 Two lateral lobes.
 An isthmus.
 It forms a H-shaped mass and weighs about 25 gms.
 Each lobe consists of :-
 Apex and a base
 3 surfaces : anterolateral ,medial, posterolateral
 Anterior and posterior borders

3. Blood Supply of Thyroid Gland
● Arterial supply – the gland is
supplied by the following arteries:
1. Superior thyroid artery.
2. Inferior thyroid artery.
3. Arteria thyroidea ima.
4. Numerous accessory thyroid arteries.
● Venous drainage –Veins arise
from venous plexus which lies deep to the
true capsule and are drained by:
1. Superior thyroid vein.
2. Middle thyroid vein.
3. Inferior thyroid veins.
4. Sometimes a forth thyroid vein
(Kocher’s vein) emerges from lower
pole and drains into internal jugular
vein.

4. Nerve Supply
 The parasympathetics are
derived from both vagus and
recurrent laryngeal nerves.
 The postganglionic
sympathetic fibres arise from
superior, middle and inferior
cervical ganglion.

5. Lymphatic Drainage
 Lymphatics form a plexus
around the thyroid follicles.
 The upper group drains into
prelaryngeal and
jugulodigastric lymph nodes .
 The lower group drains into
pretracheal and a group of
lymph nodes along recurrent
laryngeal nerve.

6. Surgical Anatomy
 The thyroid gland is the most vascular endocrine gland.
 During thyroidectomy, the superior thyroid artery is ligated
close to superior pole of thyroid gland to avoid ligation of
external laryngeal nerve as the external laryngeal nerve lies
away from superior thyroid artery.
 The inferior thyroid artery is ligated away from inferior
pole of the gland because the recurrent laryngeal nerve lies
near the inferior thyroid artery in the inferior pole.
 Damage to external laryngeal nerve cause significant voice
alteration. Damage to recurrent laryngeal nerve may cause
loss of phonation.

7. Surgical Anatomy(contd....)
 During thyroidectomy the thyroid gland is removed along
with the true capsule to avoid haemorrhage during
operation as a dense capillary plexus is present deep to the
true capsule of thyroid gland.
 Before thyroidectomy the first vessel that is ligated is the
middle thyroid vein because it is the most prominent and
shortest and vessel.

8. Function of Thyroid Gland
• The hormones of thyroid gland are three in number-
-Thyroxine(T4)
-Triiodothyronine(T3)
-Calcitonin
• Synthesis of thyroid hormones involves the following steps-
1.Iodide trapping.
2.Oxidation.
3.Organification.
4.Coupling.
5.Release of thyroid hormones.

9. FUNCTION OF THYROID GLAND (cont...)

10. Regulation of thyroid hormone secretion
 TRH secreted from
hypothalamus. Rise in TRH
augments secretion of thyroid
hormones by stimulating TSH
secretion from the pituitary.
 TSH secreted from anterior
pituitary, stimulates secretion
of hormone from thyroid.
 Negative feedback is exerted by
circulating T3 and T4
hormones.

11. Normal and abnormal levels of thyroid
hormones
 Serum triiodothyronine (T3)- 1.2-3.1 nmol/litre.
 Serum thyroxine (T4)- 55-150 nmol/litre.
 Free T3 - 3-9 nmol/litre.
 Free T4 -8-6 nmol/litre.
 TSH 0-5 IU/ml of plasma.
 Thyroglobulin – 0.5-50 μg/litre.
EUTHYROIDISM- It is a state of having normal thyroid gland
function.

12. Normal and abnormal levels of thyroid
hormones(Contd...)
HYPERTHYROIDISM - It is a condition that occurs
due to excessive production of thyroid hormones by
the thyroid gland.
HYPOTHYROIDISM – It is a more commoner
disorder of the thyroid gland in which the thyroid
gland does not produce enough thyroid hormone.