Endocrine System Function PDF

Endocrine system - function Overall function of the endocrine system is to maintain homeostasis Chemical messages –hormones, enable cells to communicate and achieve homeostasis Homeostasis : to maintain a stable internal state for optimal functioning Endocrine system...

Endocrine system - function Overall function of the endocrine system is to maintain homeostasis Chemical messages –hormones, enable cells to communicate and achieve homeostasis Homeostasis : to maintain a stable internal state for optimal functioning Endocrine system -function Short term Blood pressure pH Respiration Long term Growth Reproduction Metabolism Hormones A hormone is released in response to a stimulus/signal The action of the hormone restores equilibrium directly or indirectly Hormones  Endocrine system Endocrine system Hypothalamic-pituitary axis Considered the central regulatory component of the endocrine system Hypothalamus is sensitive to neural and hormonal stimuli The hypothalamus integrates these stimuli and sends signals to the pituitary Hypothalamus  Location: the base of the forebrain ( diencephalon) Structure: pituitary stalk which is continuous with the posterior pituitary gland. Functions: receives inputs from the circulation (temp , BM, hormones ) and neuronal inputs (autonomic and emotional). Based on these inputs hormones are secreted, which target the anterior or posterior pituitary. Blood supply: superior hypophyseal artery , hypophyseal portal vessels to the anterior  pituitary (high hormones concentration), drained by the cavernous sinus Anterior Pituitary Location – lies in the sella turnica. The optic chiasma lies directly superior (pituitary gland tumours can cause visual changes due to compression) Function – release hormones after receiving stimulus from hypothalamus. Hormones act on other endocrine organs. Blood supply – superior  hypophyseal artery, hypophyseal portal vessels from the hypothalamus , drained by the cavernous sinus (hormones enter circulation) Posterior pituitary Location – posterior to anterior pituitary Structure – connected to the hypothalamus by the pituitary stalk Function – release ADH (acts on the collecting ducts of the kidney) and oxytocin Blood supply – inferior hypophyseal artery. Drained by  the cavernous sinus (hormones enter circulation ) Example Thyroid gland Location - anterior to the trachea on the lower aspect of the neck Structure - butterfly shaped, two lobes 5cm long , connected by the isthmus. Attached to the trachea. (when patient swallows the thyroid gland moves upwards) Function – releases calcitonin (calcium homeostasis), T3 and T4  which regulate the metabolism of most of the cells. Iodine store (iodine is needed to make thyroid hormones) thyroglobin store( used for thyroid hormone synthesis Regulated by – the anterior pituitary gland (TSH) Blood supply - superior and inferior thyroid arteries (thyroid ima artery supplying the isthmus in some people), drained by the superior and middle thyroid vein, into the internal jugular vein and the inferior thyroid veins into the brachiocephalic vein.  Disorders of the thyroid Parathyroid Located – one pair on the posterior surface of each lobe of the thyroid gland(total 4) (number can vary 2-6) Structure – 5mm in diameter , chief cells, oxyphil cells and adipocytes Function - calcium and phosphate homeostasis Regulated by – negative feedback  , calcium levels Blood supply – inferior thyroid arteries Adrenal glands Location -Paired retroperitoneal glands situated over the superior pole of each kidney Structure- Right gland is pyramidal in shape, contrasting with the semi-lunar shape of left gland. Separated into medulla and cortex Function- Secrete steroid and cat  echolamine hormones directly into blood Regulated by – adrenal cortex – pituitary gland (ACTH) ,adrenal medulla –sympathetic nervous system Blood supply  Pancreas Location – retroperiotoneal gland , posterior and inferior to the stomach Structure – islets of langerhans, containing 4 types of cells Function – endocrine and exocrine function Blood supply – body and the tail are supplied by branches of the splenic artery. The uncinate and head are supplied by the creaticoduodenal artery.