thyroid gland anatomy

1. DR. TANYA RASHID
ANATOMY DEPT

2. THYROID GLAND
 The thyroid gland is a butterfly shaped, unpaired gland.
 It is an endocrine structure which releases hormones
that control metabolism the way your body uses.
 It is a vascular organ that is surrounded by the sheath
derived from the pretracheal layer of deep fascia, which
attaches the gland to the larynx and trachea.
THYROID
GLAND

3. LOCATION AND DESCRIPTION
 The thyroid gland is extending from C5 to T1 vertebrae,
below the prominence of thyroid cartilage of larynx
sometimes called as the Adam's apple.
 The thyroid gland has two lobes that lie on either side of
trachea, and is usually connected by a strip of thyroid
tissue known as an isthmus crossing the anterior surface of
second, third and fourth tracheal rings.
 A pyramidal lobe is often present, projecting upwards from
the isthmus, towards the left of midline.
Adam’s
apple

4. ANATOMICAL RELATIONS OF THE LOBES
ANTEROLATERAL POSTEROLATERAL MEDIAL
• Sternothyroid
• Superior belly of omohyoid
• Sternohyoid
• Anterior border of
sternocleidomastoid
Carotid sheath containing:
• Common carotid artery
• Internal jugular vein
• Vagus nerve
• Larynx
• Trachea
• Pharynx
• Oesophagus
• External laryngeal nerve
• Recurrent laryngeal nerve
The rounded posterior border of each lobe is related posteriorly to
the superior and inferior parathyroid gland and the anastomosis
between superior and inferior thyroid arteries.

5. RELATIONS OF THE LOBES

6. REATIONS OF THE ISTHMUS
 ANTERIORLY:
• The sternothyroids, sternohyoids,
anterior jugular vein, fascia and skin
 POSTERIORLY:
• The second, third and fourth rings of
the trachea.
• the terminal branches of the superior
thyroid arteries anastomose along its
upper border.

7. BLOOD SUPPLY
TWO MAIN ARTERIES:
Superior thyroid arteries
Inferior thyroid arteries
SUPERIOR THYROID ARTERY: First branch of the external carotid artery, supplying
superior and anterior portion of each lobe.
INFERIOR THYROID ARTERY: Branch of the thyrocervical trunk, supplying the
posteroinferior aspect of the gland.
THYROID IMAARTERY: arises from the brachiocephalic trunk of the arch of aorta,
supplying the thyroid gland and trachea and also in some cases parathyroid gland.
These are paired arteries arising on both left and right sides of the gland

8. VENOUS DRAINAGE
Venous drainage is carried out by:
 Superior
 Middle
 Inferior
The superior and middle veins drain into the internal jugular
veins, whereas the inferior drains into the brachiocephalic vein.
Thyroid veins, forming a venous plexus

9. INNERVATION
 The gland is innervated by
the parasympathetic nerve
fibers arising from the
Superior laryngeal nerve and
the Recurrent laryngeal
nerve.
 The sympathetic nerve fibers
from the superior, middle
and inferior cervical ganglia
of the sympathetic trunk.

10. LYMPHATIC DRAINAGE
The lymphatic of the gland drains into:
 Prelaryngeal lymph nodes (infront of cricothyroid membrane)
 Pretracheal lymph nodes (infront of trachea)
 Paratracheal lymph nodes (alongside the trachea)
 Superior & inferior deep cervical lymph nodes (along the
internal jugular vein)
PRELARYNGEAL NODES
PRETRACHEAL NODES
PARATRACHEAL NODES
SUPERIOR DEEP CERVICAL NODES
INFERIOR DEEP CERVICAL NODES

11. FUNCTIONS OF THE THYROID GLAND

12. FUNCTIONS OF THYROID GLAND
TRIIODOTHYRONINE (T3) THYROXINE (T4) CALCITONIN (CT)
• It helps control basal metabolic rate,
which is the least amount of energy
needed to keep the body functioning
while at rest.
• T3 also controls body temperature,
glucose production, heart rate, blood
pressure, and brain and lung
development before birth and in early
childhood.
• T3 works with other hormones to
promote growth of long bones.
• Thyroxine (T4) is the main hormone
produced by the thyroid.
• Some of the T4 made is changed into
T3, which is a more active hormone.
• T4 controls heart function,
metabolism, bone and muscle health
and brain development.
Calcitonin (CT) helps control the amount
of calcium and phosphate in the blood.
It does this in three ways:
• by altering the rate at which bones are
broken down and reformed
• by signaling the kidneys to pass more
calcium into urine
• by signaling the parathyroid gland to
make more parathyroid hormone

13. CLINICAL RELEVANCE
Common problems and disorders of the thyroid gland:
 Thyroid nodules
 Grave’s disease
 Hyperthyroidism
 Hypothyroidism
 Damage to recurrent laryngeal nerve

14. THYROID NODULES
 A thyroid nodule is a lump that can develop in thyroid gland.
 It can be solid or filled with fluid.
 There can be a single nodule or a cluster of nodules.
 Thyroid nodules are relatively common and rarely cancerous.
SYMPTOMS:
 an enlarged thyroid gland, known as a goiter
 pain at the base of your neck
 swallowing difficulties
 breathing difficulties
 hoarse voice

15. GRAVE’S DISEASE
Graves’ disease is a type of autoimmune problem that causes the thyroid
gland to produce too much thyroid hormone, which is called hyperthyroidism.
SYMPTOMS:
 Weight loss—despite increased appetite
 Anxiety, restlessness, tremors, irritability, difficulty sleeping (insomnia)
 Heat intolerance, sweating
 Chest pain, palpitations
 Shortness of breath, difficulty breathing
 Goiter (if grave’s disease goes untreated)
normal
enlarged

16. HYPERTHYROIDISM an overactive thyroid (when it produces too much thyroid hormone)
HYPOTHYROIDISM an underactive thyroid (when it does not produce enough).

17. RECURRENT LARYNGEAL NERVE
 The two recurrent laryngeal nerves on each side, is a branch of the Vagus nerve.
 They pass underneath the thyroid gland to innervate the larynx.
 During surgery of the thyroid gland, care must be taken not to ligate or damage the
recurrent laryngeal nerve
Injury to the recurrent laryngeal nerves can result in:
 A weakened voice (hoarseness) or loss of voice (aphonia)
 Injury to the nerve may paralyze the posterior cricoarytenoid muscle on the same side.