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Thyroid Gland, Parathyroid gland Adrenal Gland, 1 Thyroid Gland - anterior portion of the neck -thyroxine (T4) and tri-iodothyronine (T3) - calcitonin - TSH from the pituitary stimulates T4 and T3 release 2 Thyroid Gland T4 stored as thyroglobulin in the lumen of follicles Follicles are surrounded by basal lamina, reticular fibers, capillary plexus Follicular cells synthesize T3 and T4. Parafollicular cells synthesize calcitonin 3 Thyroid hormone synthesis - rER synthesizes thyroglobulin Glycosylated on rER and Golgi apparatus Thyroglobulin released by exocytosis into follicular lumen - basolateral mb has iodide pump Cytosolic oxidation by thyroid peroxidase Oxidized iodide enters colloid Iodinates tyrosine residues 4 Release of T3 and T4 TSH released from basophils of the anterior pituitary. Filopodia form on the apical mb Endocytosis of colloid Colloid vesicles fuse with endosomes proteases release T3 and T4 precursers from thyroglobulin iodotyrosine dehaloginase release extra iodides T3 and T4 diffuse into capillaries 5 Parathyroid gland - located on the posterior surface of the thyroid gland - surrounded by CT capsule - clusters of endocrine cells, and bv - slightly acidophilic chief cells that secrete Parathyroid hormone (a polypeptide) - Parathyroid hormone help to regulate levels of extracellular calcium by raising levels if they drop 6 Parathyroid hormone - acts on the kidney to increase calcium re-absorption by the tubules - acts on osteoblasts to stimulate osteoclast-stimulating factor 7 Adrenal Gland: - superior pole of the kidneys - cortex and medulla Cortex - corticosteroids released following stimulation by ACTH from the anterior pituitary Medulla - epinephrine and norepinephrine released following stimulation by sympathetic innervation 8 Adrenal Cortex: parenchymal cells organized into three zones zona glomerulosa -mineralocorticoids zona fasciculata -glucocorticoids zona reticularis - androgens 9 Adrenal Cortex Parenchymal cells: -lots of sER, lipids Zona Glomerulosa - (aldosterone) -small columnar cells arranged in cords and clusters Zona Fasciculata - (cortisone) - largest layer - columns of parenchymal cells Zona Reticularis - cords of acidophilic cells - secrete mainly weak androgens 10 Adrenal Medulla - develops from neural crest cells - fibers of sympathetic pre ganglionic cells are cholinergic Chromaffin cells - secrete the catecholamines epinephrine and norepinephrine - stain with chromaffin salts - dense core vesicles contain catecholamines - some vesicles contain enkaphalins 11