image

Position of the thyroid gland:

  • Infront of the neck
  • In the midline
  • Infront of the trachea
  • Extends up to the thyroid cartilage

Parts of the thyroid gland:

  • 2 lobes
  • Connected by an isthmus
    • infront of the 2nd & 3rd tracheal ring
  • Pyramidal lobe
    • left end of isthmus

Capsules:

  • True capsule (thickening of the connecting tissue)
  • False capsule (pretracheal fascia)

Important relations:

Anterior:

Strap muscles

  • strenohyoid muscle
  • sternothyroid muscle

In surgery, retracting these muscles will expose the thyroid gland

image

Posterior:

  • trachea
    • enlargement of thyroid gland can compress trachea and cause difficulty in breathing
  • oesophagus

Posterolateral:

  • Carotid artery
  • Internal jugular vein

Embedded inside the gland:

  • 2 pairs of parathyroid gland

image

Nerves:

Recurrent laryngeal nerve

  • Runs in the tracheoesophageal groove
  • Passes in between the branches of the inferior thyroid artery
    • During surgery, inferior thyroid artery will be clamped. RLN can be accidentally damaged as well.
      • 1 side damage: Husky voice
      • Both side damage: No voice & Stridor

Venous drainage

image

  • Superior thyroid vein
    • drains into internal jugular vein
  • Middle thyroid vein
    • drains into internal jugular vein
  • Inferior thyroid vein
    • drains into brachiocephalic vein

Lymphatic drainage

  • Pretracheal lymph node
  • Paratracheal lymph node
  • Deep cervical lymph node

Papillary carcinoma spread thru lymph node

Microscopic arrangement of the thyroid gland

image

  • Arranged as follicles
  • lined by cuboidal epithelium
  • cells secrete thyroxine
    • binds to globulin & stored as thyroglobulin (colloid)
  • in between follicles
    • parafollicular cells (secrete calcitonin)
    • medullary carcinoma arise from here

Development of thyroid gland (embryology)

image

Migration of thyroid:

Thyroid gland develops as an outgrowth from the foetal pharynx & decends to the neck region.

 

Abnormalities:

  • Thyroglossal fistula
    • a tract can persist
  • Throglossal cyst
    • part of the tract can persist
  • Ectopic thyroid
    • thyroid tissue remain along the tract

 

 

 

3 COMMENTS

LEAVE A REPLY

Please enter your comment!
Please enter your name here