Thyroid & Parathyroid Flashcards
Colloid is composed of…..stained by…..
Thyroglobin
PAS +ve
Explain how LM features of thyroid follicles reflect its function
In normal functioning follicle, the follicular cells are cuboidal with clear cell boundaries
In hyperactive follicle, they are columnar the size of follicle is smaller with little amount of colloid
In hypoactive follicle, they are flattened cells due to distension of the follicle with large amount of colloid
Describe EM appearance of follicular cells
Have apical junctional complex & luminal microvilli
Have lysosomes, mitochondria, phagosomes, endocytic vesicles.
Characters of protein secreting cells: well-developed rER & golgi apparatus, apical small secretiry vesicles
Describe site of C cells
Between BM & follicular cells they do not reach lumen of the follicle
Describe synthesis of thyroglobin
Glycoprotein is formed by rER & golgi apparatus then exoctosed into follicular lumen. Iodide is picked up by active transport by follicular cells and pupmed into lumen to be oxidized to iodine by thyroperoxidase on microvilli. It then binds thyroglobin to form iodinated thyroglobin.
Describe the release of thyroid hormones
Under effect of TSH follicular cells pick up thyrogobin which enters lysosomes to be cleaved into T3 & T4 which diffuse to blood capillaries
Descrube effect of TSH on thyroid glands
- Hypertrophy & hyperplasia of follicular cells
- Accelerates rate of synthesis, exocytosis & iodination of thyroglobin
- Accelerates endocytosis, intracellular breakdown of colloid resulting in increased production of thyroid hormones
Parathyroid gland cells are……..
Chief cells & oxyphil cells
PTH stimulates release of…..from……
Osteoclast stimulating factor
Osteoblasts
Describe effect of PTH on kidney & gut
-Promotes Ca++ reabsorption by the distal convoluted tubules & dec phosphate reabsorption by proximal convoluted tubules
-Promotes Ca++ absorption
Oxyphil cells are stained…..due to…..
Acidophilic
Abundant mitochondria
