Endocrine Glands: Histology and Function
Classified in Biology
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Thyroid
Origin: Endodermal derivative, initially from the floor of the pharyngeal gut. It is a solid organ.
Capsule: Connective tissue rich in collagen fibers (fibrosis), surrounding the thyroid tissue.
Stroma: Septa extend inward (including into the parathyroid), containing reticular fibers surrounding the thyroid follicles. It is highly vascularized (by the superior and inferior thyroid arteries) with fenestrated capillaries.
Parenchyma: The gland consists of thousands of thyroid follicles, lined by simple cuboidal epithelium (flat or cylindrical) on a thin basal lamina. The cavity contains thyroid colloid.
Cells:
- Follicular cells: Cuboidal [low height indicates underactivity, high height indicates overactivity (less colloid)].
- Parafollicular cells: