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30 Cards in this Set

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Thyroid gland location
anterior neck over cartilaginous rings of the trachea
Thyroid structure
shield shape
right and left lobe connected by isthmus
vascular
thyroid development
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
pyramidal lobe
attached to the isthmus, proximal part of the duct persists (40% of population)
duct remnants in the tongue or anterior neck causing cysts
thyroglossal duct cysts
parenchyma :

follicular cells come from?

parafollicular comes from?
follicular = endoderm of floor of oral cavity

parafollicular= neural crest via ultimobranchial body
Follicle
surrounded by squamos to cuboidal single layer,

colloid is acidophilic and PAS positive
Thyroglobulin
inactive storage form of thyroid H

follicles contain a 3 mo supply
inactive follicle
squamos epithelium
cuboidal=active
follicle cell structure
RER basal end = basophilic

shelf-like cristae in mito
LYSOSOMES
junctional complexes at apical-lateral membranes
capillaries
dense plexus
uptake aa and I-
Thyroglobulin synthesis
Tg is a glycosylated PROTEIN, so need to take up aa


assembly and GLYCOSYLATION in RER and golgi

secreted via exocytosis
what oxidizes I- to I2?
thyroid peroxidase (TPO)
where does iodination of tyr on Tg occur?
near microvilli of apical cell membranes
how is colloid taken up?
endocytosis, see colloid resorption droplets which fuse w/lysosomes
what is the ratio of T4 to T3
20:1
TSH
stimulates resorption of colloid and hydrolysis of Tg
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
calcitonin
-antagonist to parathyroid H
-decreases blood Ca
-helps prevent bone loss during lactation
how does calcitonin decrease blood Ca levels?
suppress bone resoption, increase calcification of osteoid
inhibits osteoclasts
PARATHYROID GLAND
location
produce?
2 pairs superior and inferior

located on posterior surface of thyroid

produce PTH
PTH does?
raises Ca blood levels

activates and stimulates development of osteoclasts

increase Ca uptake in gut and kidney
parathyroid development
superior - endoderm of forth pharyngeal pouch

inferior - endoderm of 3rd pharyngeal pouch
two cell types in parathyroid
chief cells - small pale staining acidophilic produce PTH, granules

Oxyphil cells - LARGER, mito, increase with age
parathyroid microanatomy
CT capsule, cluster or cord cells, adipocytes increase with age
iodine deficiency
low T3 T4, TSH is high, ENLARGEMENT OF THYROID, goiter due to stored colloid
hypothyroidism in infant
not making enough thyroid H

results in cretinism - lethargy mental retardation abnormal bone development
hypothyroidism in adults
not making enough T3 T4

myxedema - edema, low metab lethargy
Graves
hyperthyroidism, too much T3 T4
weight loss
increase heart rate
bulging eyes(exophthalmos)
removal of all four parathyroid glands
death due to tetany - overactive neurological reflexes,spasms of the hands and feet and larynx

due to looow Ca