Thyroid gland



Thyroid explanatory video

The thyroid mass is divided into various lobules and the follicle cells, which are the most numerous are disposed around a central eosinophilic follicle in which thyroxin is released.

The follicular cells are responsible for the elaboration of two hormones

1. Thyroxine (tetra iodothyronine- T4)

2.   Tri-iodothyronine T3,

The follicular cells elaborate these hormones by chemical activity in their apical region. Thyroglobulin is produced from the endoplasmic reticulum of the thyroid follicular cells and packaged in the Golgi apparatus. It is then passed through the apex of the follicular cell into the follicular space. In the follicle it combines with iodine to form a complex that becomes the colloid in the follicle. This colloid is reabsorbed into the follicular cells and then processed through activity of enzymes to form T3 (tri-iodothyronine) and T4 (thyroxine). T3 and T4 are they are released into the blood stream where they are bound to albumin in the blood and this time they can be assayed as plasma bound iodine (PBI).   Before they reach the tissues where they act, the albumin is again released from the hormones.   The hormones then freely enter into tissue cells where thyroxin is converted into active component known as tri-iodothyronine (T3).

Thyroxin and tri-iodothyronine are produced in concentration ratio of 3:1.

Parafollicular or C cells are found its junction of the follicles. They are large light staining cells which belong to the APUD system of the body. They elaborate calcitonin and katacalcin which are responsible for lowering blood calcium and act in opposition to parathormone.

Masked metachromasia to toluidine blue. Roll over mouse to demonstrate. Metachromatic cells are APUD cells






Click here for practical, scan or tissue diagnosis  gross  embryology
histophysiology  histochemistry  histopathology  histopharmacology

  Electronic School of Medicine
Creator: Oluwole Ogunranti


Thyroid gland microscope video    Double click for full screen


PAS-Alcian blue reactions in thyroid gland. C cells are alcianophilic APUD cells
Roll over mouse





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