Download Thyroid Gland

Thyroid Gland,
Parathyroid gland
Adrenal Gland,
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Thyroid Gland
- anterior portion of the neck
-thyroxine (T4) and tri-iodothyronine (T3)
- calcitonin
- TSH from the pituitary stimulates T4 and
T3 release
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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
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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
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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
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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
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Parathyroid hormone
- acts on the kidney to increase calcium
re-absorption by the tubules
- acts on osteoblasts to stimulate osteoclast-stimulating
factor
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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
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Adrenal Cortex: parenchymal cells organized into
three zones
zona glomerulosa -mineralocorticoids
zona fasciculata -glucocorticoids
zona reticularis - androgens
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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
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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
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