thyroid gland anatomy

1. THYROID GLAND

2. Size & Shape
• One of the largest endocrine
glands.
• Its weight is about 25 grams.
• Its butter-fly shapped organ.

3. Structure
Its formed of the following parts:
• 2 Lateral lobes each lobe is pear-shaped.
Each lobe is pyramidal in shape, with its
apex directed upward and its base
directed downward.
• A narrow median isthmus connecting the
2 lateral lobes.
• A small pyramidal lobe, (28%-55% of
population), It is of conical shape and
extends from the upper part of the
isthmus, up across the thyroid cartilage
to the hyoid bone.

4. Location of the gland
• Its Situated on the anterior side of the
neck, lying against and around
the larynx and trachea, reaching
posteriorly the oesophagus and carotid sheath.
It starts cranially at the oblique line on
the thyroid cartilage (just below the laryngeal
prominence, or 'Adam's Apple'), and extends
inferiorly to approximately the fifth or
sixth tracheal ring.

5. Capsules of the thyroid gland
It has 2 Capsules:
• True Fibrous capsule
enclosing the gland.
• False fascial capsule derived
from the pretrachial
fascia.(Thickend laterally
forming the lat. Ligament of
berry which fixes the gland to the
cricoid cartilage)

6. Relations of the gland
1. Relations of the isthmus.
2. Relations of the lateral lobes.

7. 1. Relations of the isthmus.
The isthmus has 2 surfaces (Ant. & Post.) & 2 borders (Upper & lower)
Anterior Posterior Upper Lower
1. Skin & superficial
fascia.
2. Ant. Jugular veins.
3. Deep fascia.
4. Sternohyoid &
sternothyroid
muscles.
1. Trachea (2nd, 3rd & 4th
rings)
1. Related to the sup.
Anastomotic a.
(between rt & lft sup.
Thyroid aa)
2. The pyramidal lobe
may project upwards
from the isthmus.
1. Give rise to the Rt & Lt
Inf. Thyroid veins.
2. The thyroid ima a.
enters the lower
border.
3. An Inf. Anasomotic a.
runs along the lower
border of the isthmus.

8. Anterior
1. Skin & superficial
fascia.
2. Ant. Jugular veins.
3. Deep fascia.
4. Sternohyoid &
sternothyroid
muscles.

9. Lower
1. Give rise to the Rt & Lt
Inf. Thyroid veins.
2. The thyroid ima a.
enters the lower
border.
3. An Inf. Anasomotic a.
runs along the lower
border of the isthmus.
Upper
1. Related to the sup.
Anastomotic a.
(between rt & lft sup.
Thyroid aa)
2. The pyramidal lobe
may project upwards
from the isthmus.

10. 2. Relations of the lateral lobes.
each lobe has 3 surfaces:
Posterior Medial Anterolateral
1. 2 Parathyroid glands
( sup. & inf. ) embedded
in the post. Surface.
1. 2 arteries:
A- Common Carotid a. (
inside the carotid sheath)
B- Inf. Thyroid a. before it
enters the gland.
1. Its upper part related to:
A- Layrnx (thyroid & cricoid
cartilages & cricothyroid m.)
B- Pharynx (Inf.
Constrictor m.)
C- External laryngeal n.
2. Its lower part is related to:
A- trachea
B- oesophagus
C- Recurrent laryngeal n. in
between
1. Skin, superficial fascia & deep
fascia.
2. Its upper part is crossed by sup.
Belly of omohyoid.
3. Its middle part is covered by
sternohyoid & sternothyroid m.
4. Its lower part is overlapped by
the ant. Border of
sternomastoid.

11. Posterior
1. 2 Parathyroid glands
( sup. & inf. ) embedded
in the post. Surface.
1. 2 arteries:
A- Common Carotid a. (
inside the carotid sheath)
B- Inf. Thyroid a. before it
enters the gland.

12. Medial
1. Its upper part related to:
A- Layrnx (thyroid & cricoid
cartilages & cricothyroid m.)
B- Pharynx (Inf.
Constrictor m.)
C- External laryngeal n.
2. Its lower part is related to:
A- trachea
B- oesophagus
C- Recurrent laryngeal n. in
between

13. Anterolateral
1. Skin, superficial fascia & deep
fascia.
2. Its upper part is crossed by sup.
Belly of omohyoid.
3. Its middle part is covered by
sternohyoid & sternothyroid m.
4. Its lower part is overlapped by
the ant. Border of
sternomastoid.

14. Arterial supply to the gland
• The thyroid is supplied with arterial
blood from the:
1. superior thyroid artery, a branch of
the external carotid artery.
2. inferior thyroid artery, a branch of
the thyrocervical trunk.
3. sometimes by the thyroid ima artery,
branching directly from the subclavian
artery.

15. Venous Drianage
• venous blood is drained via:
1. superior thyroid veins, emerges from
the apex of each lateral lobe,
draining in the internal jugular vein.
2. Midlle thyroid viens, emerges from
the lower part of each lat. Lobe.
3. inferior thyroid veins, emerges from
the isthmus & lower part of the lat.
Lobe. draining via the plexus
thyreoidea impar in the
left brachiocephalic vein.

16. Lymphatic drainage
• The lymphatic of the gland drain into:
1. Prelaryngeal L.Ns, infront of
cricothyroid memb.
2. Pretracheal L.Ns, infront of trachea.
3. Paratracheal L.Ns, alongside the
trachea.
4. Upper & lower deep cervical L.Ns,
along the I.J.V .
5. Brachiocephalic L.Ns.

17. Thank You
Done by:
Dr. Hamzeh Al-Battikhi