Question

Describe the T. S. of thyroid gland

Sketch and label T.S. of the thyroid gland.

Answer 1

Thyroid gland is externally covered by connective tissue sheath or capsule.
From the capsule, number of septa called trabeculae arise, which divide the thyroid gland into
several lobules. The lobules contain about 3 million thyroid follicles. Each thyroid follicle is oval in shape and varies in size. Larger follicles are present towards periphery, whereas smaller ones are present in the interior. The follicles are surrounded by a connective tissue called interfollicular tissue which contains blood vessels and nerve fibres.Each follicle is lined by a single layer of cuboidal glandular epithelium which rest on a very thin
basement. The follicular cavity or acinus is filled by dense amorphous semisolid substance called colloid, which is thyroglobulin, a precursor of thyroid hormone, thyroxine. Other cells bigger than follicular cells are also present singly or in groups in the connective tissue. 
These are called parafollicular or ‘C’ cells.
They secrete hormone thyrocalcitonin.