Identify the parts labelled A-C in the image given below. Use the hints given below the image for correct identification.
A - cells that form the thyroid follicles
B - cells that secrete calcitonin
C - contains thyroglobulin
In the diagram given above, A represents the cuboidal cells that form follicles, B - are the C cells or parafollicular cells that secrete calcitonin and C - represents the colloid which is formed of thyroglobulin.
If you dissect a slice of the thyroid gland and put it under a microscope you’ll find circular arrangements of cuboidal cells, forming follicles. These follicles are filled with a homogeneous substance called colloid. This colloid is secreted by the cuboidal cells. In between these follicles is loose connective tissue called stroma that holds them together. This stroma is dotted with specialised cells called parafollicular or C cells that secrete a hormone called calcitonin. The colloid contains a glycoprotein thyroglobulin that serves as a precursor of thyroid hormones.