Thyroid gland anatomy

Thyroid gland anatomy

• 1.
  THYROID GLAND Anatomy
• 2.
  THYROID GLAND  Endocrinegland, situated in the lower part of the front and sides of the neck.  Extends : from oblique line of thyroid cartilage to the 5th or 6th tracheal ring.  Lie against C5,C6,C7 & T1.  Consist Right & Left lobes, joined by isthmus.  A 3rd pyramidal lobe may project upwards from the isthmus.  Capsules: two; True & false.  Larger in females than males.  Development: from the endoderm of the floor of primitive oral cavity in the region of the future foramen caecum and ultimobranchial body.
• 3.
  RELATIONS OF THELOBES  The lobes are conical in shape having: • An apex • A base • Three surfaces: Lateral, medial, posterolateral • Two borders: Anterior and posterior  Apex: • directed upwards and slightly laterally.  Base: on level with the 4th or 5th tracheal ring.
• 4.
   • • • • Lateral surface: convexand covered by Sternohyoid Superior belly of omohyoid Sternothyroid Anterior border of sternocleidomastoid
• 5.
   Medial surface: •2 tubes, trachea and oesophagus • 2 muscles,inferior constrictor and cricothyroid • 2 nerves,external laryngeal and recurrent laryngeal
• 6.
   Posterolateral surface:carotid sheath and overlaps common carotid artery.  Anterior border: anterior branch of superior thyroid artery  Posterior border: separates medial and posterior surfaces. • Inferior thyroid artery • Anastomosis between superior and inferior thyroid arteries • Parathyroid glands • On left side thoracic duct
• 7.
  RELATIONS OF ISTHMUS Connects lower parts of the 2 lobes.  Anterior surface: covered by, • Sternothyroid and sternohyoid • Anterior jugular vein • Fascia and skin  Posterior surface: 2nd to 4th tracheal rings.  Upper border: anastomosis between right and left superior thyroid arteries.  Lower border: Inferior thyroid veins.
• 8.
   Blood supply: •Superior and inferior thyroid arteries. • Superior, middle and inferior thyroid veins.  Lymphatic drainage: • Upper & lower deep cervical lymph node • Pretracheal and paratracheal lymph node  Nerve supply: • Middle cervical ganglion • Superior and inferior cervical ganglia
• 9.
  HISTOLOGY  2 typesof cells : • follicular & parafollicular.  The follicular cells secrete T3 & T4.  T3 & T4 binds with glycoproteins to form the thyroglobulin (colloid).  Most of the thyroid follicles are full of stored Thyroglobulin (colloid).  Parafollicular cells/clear (C) cells are found among the follicular cells.  They pale staining cells with a granular cytoplasm.  Unlike follicular cells, they are not exposed to the follicular lumen.  They secrete Calcitonin which help regulating blood calcium levels.
• 10.
  Follicular cells Thyroid: highpower x 45
• 11.
  Parafollicular or Ccells Follicular cells Thyroid gland: high power x 45