Thyroid, Parathyroid, and Adrenal glands Flashcards
Follicle
Structural and functional unit of the thyroid gland. They contain colloid and are surround by a thin layer of cuboidal cells. They are encapsulated w/ septa projecting towards the inside
Follicular cells
Cuboidal shaped. Foramen cecum is the origin starting point.
Parafollicular cells (C cells)
Produces calcitonin, stains light. Derived from neural crest cells
T3 (triiodothyronine) and T4 (thyroxine)
They increase the basal metabolic rate which increase the number of mitochondria. T3 is more active than T4. T4 is more abundant
Calcitonin
Released by C cells. Decreases blood calcium levels by inhibiting bone resorption by osteoclast
Iodide pumps (transporters)
Located within follicular cells. They concentrate iodide in the thyroid gland in order to produce T3 and T4
Radioactive iodine scan
After injection of radioactive iodide, 40% is in the thyroid gland within 10 minutes
Thyroglobulin
main protein in the thyroid, necessary for thyroid hormone production
Pendrin
anion transporter that transports oxidized iodine into the colloid
Thyroid peroxidase
Oxidizes iodine in follicular cells and iodizes thyroglobulin on its Tyr residues to produce T3 and T4
Hyperactive
Columnar with many resorption vesicles
Thyroid gland
Endocrine gland in neck that secretes thyroid hormones into blood (fenestrated capillaries) that control metabolism, growth, and maturation. Correctly placed in body at 7th week.
Chief (principal) cells
Produce PTH in parathyroid glands. Small, numerous, and arrange themselves in cords
Oxyphil cells
Located in parathyroid glands. Contain eosinophilic cells w/ abundant mitochondria. Their number increases w/ age
Adrenal cortex
Outside layer of adrenal glands, yellowish. Mesoderm origin. Produces steroid hormones
Adrenal medulla
Secretes 80% epinephrine and 20% norepinephrine in response to sympathetic stimulation. Located in the central layer of adrenal glands, redish/brown. Develops from the neural crest cells derived from ectoderm. Vascularized
Layers of the adrenal cortex
zona glomerulosa (ZG) -> zona fasciculata (ZF) -> zona reticularis (ZR)
Zona glomerulosa
secretes aldosterone which stimulates Na+ reabsorption in the kidney. Columnar, round clusters/cords.
Zona fasciculata
secretes cortisol to increase blood glucose. Cells arranged in strait cords. Contains abundant lipid droplets. Fenestrated capillaries. Vesicular cristae
Zona reticularis
Secretes androgens (catecholamines) for masculinization. Irregular cords. Few lipid droplets
Dual blood supply
The adrenal medulla contains arterial blood via medullary arteries and venous blood via cortical veins
Short term stress response
heartbeat and blood pressure increase. Blood glucose level increases. Muscles become energized
Glucocorticoids
Steroid hormones produced in the adrenal gland for long term stress response. Protein and fat metabolism instead of glucose breakdown. Reduction of inflammation, immune cells are suppressed.
Mineralocorticoids
Steroid hormones produced in the adrenal gland for long term stress response. Sodium ions and water are reabsorbed by the kidney. Blood volume and pressure increases.
Isthmus
Join the 2 lobes of the thyroid gland
Thyrotropin releasing hormone (TRH)
Released by hypothalamus to stimulate anterior pituitary to release thyrotropin
Thyrotropin (TSH)
Stimulates the thyroid gland to produce and release T3/T4
Hypoactive
Squamous with increased colloid and follicular space. Few resorption vesicles
Parathyroid hormone
Increases blood calcium levels. Stimulates osteoblast
Adrenal medullary cells
specialized postganglionic sympathetic neurons.
Vesicular cristae
Exhibited by adrenalcortical mitochondria
Lamelliform
Exhibited by endothelial mitochondria
