case 9 - teach me physiology Flashcards
describe the anatomy of the thyroid gland
it is a ductless alveolar gland found in the anterior neck, just below the laryngeal prominence (Adam’s Apple). it is roughly butterfly shaped with two lobes wrapping around the trachea and connected in the middle by an isthmus. the thyroid gland is not usually palpable.
what supplies the thyroid gland
it is supplied by the superior and inferior thyroid arteries, drained via superior, middle and inferior thyroid veins, and has a rich lymphatic system
what is the function of the thyroid gland
is to produce and store thyroid hromones.
what are thyroid epithelial that form follicles filled with
colloid - a protein-rick reservoir of the materials needed for thyroid hormone production. these follicles range in size and the epithelium may be simple or columnar
where can the parafollicular cells be found
in the spaces between the follicles
what do parafollicular cells do
secrete calcitonin, which is involved in the regulation of calcium metabolism in the body
what is the function of the thyroid
the thyroid gland is one of the main regulators of metabolism.
how do T3 and T4 act
typically act via nuclear receptors in target tissues and initiate a variety of metabolic pathways.
what happens if there are high levels of them
they typically cause these processes to occur faster or more frequently
what metabolic processes increase by thyroid hormones
Basal Metabolic Rate
Gluconeogenesis
Glycogenolysis
Protein synthesis
Lipogenesis
Thermogenesis
how is this achieved
increase number and size of the mitochondria within cells, increasing Na-K pump activity and increasing the presence of beta-adrenergic receptors in tissues such as cardiac muslce
what is the pneumonic to remember thyroid hormone synthesis
ATE ICE
what are the six steps
active transport
thyroglobulin
exocytosis
iodination
coupling
endocytosis
what is the active transport step
Active transport of Iodide into the follicular cell via the Sodium-Iodide Symporter (NIS). This is actually secondary active transport, and the sodium gradient driving it is maintained by a Sodium-Potassium ATPase.
what is the thyroglobulin step
Thyroglobulin (Tg), a large protein rich in Tyrosine, is formed in follicular ribosomes and placed into secretory vesicles.