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30 Cards in this Set
- Front
- Back
Thyroid gland location
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anterior neck over cartilaginous rings of the trachea
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Thyroid structure
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shield shape
right and left lobe connected by isthmus vascular |
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thyroid development
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outgrowth, ventral diverticulum of the floor of the oral cavity
thyroid gland connected to thyroglossal duct connected to foramen caecum of the tongue thyroid migrates caudally toward neck, duct connection is lost leaving behind foramen caecum on the surface of the tongue |
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pyramidal lobe
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attached to the isthmus, proximal part of the duct persists (40% of population)
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duct remnants in the tongue or anterior neck causing cysts
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thyroglossal duct cysts
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parenchyma :
follicular cells come from? parafollicular comes from? |
follicular = endoderm of floor of oral cavity
parafollicular= neural crest via ultimobranchial body |
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Follicle
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surrounded by squamos to cuboidal single layer,
colloid is acidophilic and PAS positive |
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Thyroglobulin
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inactive storage form of thyroid H
follicles contain a 3 mo supply |
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inactive follicle
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squamos epithelium
cuboidal=active |
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follicle cell structure
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RER basal end = basophilic
shelf-like cristae in mito LYSOSOMES junctional complexes at apical-lateral membranes |
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capillaries
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dense plexus
uptake aa and I- |
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Thyroglobulin synthesis
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Tg is a glycosylated PROTEIN, so need to take up aa
assembly and GLYCOSYLATION in RER and golgi secreted via exocytosis |
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what oxidizes I- to I2?
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thyroid peroxidase (TPO)
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where does iodination of tyr on Tg occur?
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near microvilli of apical cell membranes
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how is colloid taken up?
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endocytosis, see colloid resorption droplets which fuse w/lysosomes
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what is the ratio of T4 to T3
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20:1
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TSH
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stimulates resorption of colloid and hydrolysis of Tg
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parafollicular cells
other name location produce? |
C-cells
basement membrane of follicle cells, don't touch colloid calcitonin large-round-pale, contain small e dense granules |
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calcitonin
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-antagonist to parathyroid H
-decreases blood Ca -helps prevent bone loss during lactation |
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how does calcitonin decrease blood Ca levels?
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suppress bone resoption, increase calcification of osteoid
inhibits osteoclasts |
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PARATHYROID GLAND
location produce? |
2 pairs superior and inferior
located on posterior surface of thyroid produce PTH |
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PTH does?
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raises Ca blood levels
activates and stimulates development of osteoclasts increase Ca uptake in gut and kidney |
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parathyroid development
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superior - endoderm of forth pharyngeal pouch
inferior - endoderm of 3rd pharyngeal pouch |
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two cell types in parathyroid
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chief cells - small pale staining acidophilic produce PTH, granules
Oxyphil cells - LARGER, mito, increase with age |
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parathyroid microanatomy
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CT capsule, cluster or cord cells, adipocytes increase with age
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iodine deficiency
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low T3 T4, TSH is high, ENLARGEMENT OF THYROID, goiter due to stored colloid
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hypothyroidism in infant
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not making enough thyroid H
results in cretinism - lethargy mental retardation abnormal bone development |
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hypothyroidism in adults
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not making enough T3 T4
myxedema - edema, low metab lethargy |
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Graves
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hyperthyroidism, too much T3 T4
weight loss increase heart rate bulging eyes(exophthalmos) |
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removal of all four parathyroid glands
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death due to tetany - overactive neurological reflexes,spasms of the hands and feet and larynx
due to looow Ca |