W3 Thyroid Hormone Flashcards
the thyroid gland is divided into clusters of what?
clusters of follicles by connective tissue
what does a thyroid follicle consist of?
a thin layer of epithelial cells and colloid
what is colloid?
proteinaceous material, contains thyroglobulin which is a source of thyroid hormone
what is the thin layer of epithelial cells in thyroid follicles for?
responsible for synthesis of thyroid hormones
what type of epithelium surrounds the follicles?
cuboidal
where can you find thyroid parafollicular cells?
scattered within the follicle lining
what do parafollicular cells secrete?
calcitonin
what colour will colloid appear in histology?
pink
all the steps involved in the synthesis of thyroid hormone take place where?
in the colloid
where are T4 and T3 produced?
in the colloid
TSH stimulation increases iodide uptake causing what?
iodination of thyroglobulin
where is thyroglobulin stored?
in thyroid follicles
what difference in histological appearance occurs in active vs inactive thyroid follicles?
active has a pale edge (appears white), inactive does not have this
epithelial cell ingest colloid by what?
endocytosis
once colloid has been ingested by epithelial cells what happens in order to release free thyroid hormones?
colloid-laden endosomes fuse with lysosomes containing hydrolytic enzymes that digest thyroglobulin, freeing thyroid hormones
