Intro to the Endocrine System (Jahn).pdf

Into to the Endocrine System Stephan C. Jahn, Ph.D. Overview of the Endocrine System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pineal gland...

Into to the Endocrine System Stephan C. Jahn, Ph.D. Overview of the Endocrine System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pineal gland Hypothalamus Pituitary gland Thyroid gland Thymus Adrenal gland Pancreas Parathyroid glands Trachea Posterior view Gonads: Ovary (female) Testis (male) Figure 17.1 17-2 Hypothalamus 17-3 Anatomy The pituitary gland is suspended from hypothalamus by a stalk—infundibulum Location and size  Housed in sella tursica of sphenoid bone  Size and shape of kidney bean Composed of two structures with independent origins and separate functions  Anteriorpituitary  Posterior pituitary 17-4 Anatomy 17-5 Hypothalamic Hormones Eight hormones produced in hypothalamus  Six regulate the anterior pituitary  Two are released into capillaries in the posterior pituitary Six releasing and inhibiting hormones stimulate or inhibit the anterior pituitary  TRH, CRH, GnRH, and GHRH are releasing hormones that promote anterior pituitary secretion  PIH inhibits secretion of prolactin  Somatostatin inhibits secretion by the anterior pituitary 17-6 Hypothalamic Hormones Two other hypothalamic hormones are  Oxytocin (OT)  Antidiuretic hormone (ADH)  Both stored and released by posterior pituitary  Paraventricular nuclei of hypothalamus produce OT  Supraoptic nuclei produce ADH 17-7 The Pineal Gland Pineal gland—attached to the posterior end of corpus callosum After age 7, it undergoes involution (shrinkage)  Down 75% by end of puberty  Tiny mass of shrunken tissue in adults May synchronize physiological function with 24-hour circadian rhythms of daylight and darkness  Synthesizes melatonin from serotonin during the night Fluctuates seasonally with changes in day length 17-8  The Thymus Thymus plays a role in three systems: endocrine, lymphatic, immune Bilobed gland in the mediastinum superior to the heart  Goes through involution after puberty Site of maturation of T cells important in immune defense Secretes hormones (thymopoietin, thymosin, and thymulin) that stimulate development of other lymphatic organs and activity of T lymphocytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thyroid Trachea Thymus Lung Heart Diaphragm Liver (a) Newborn (b) Adult Figure 17.8a,b 17-9 The Adrenal Glands Figure 17.11 Adrenal cortex  Mineralocorticoids & glucocorticoids Adrenal medulla  Epinephrine & norepinephrine 17-10  Other Tissues and Organs Skin  Keratinocytes convert a cholesterol-like steroid into cholecalciferol using UV from sun Liver—involved in the production of at least five hormones  Converts cholecalciferol into calcidiol  Secretes angiotensinogen (a prohormone) Precursor of angiotensin II (a regulator of blood pressure)  Secretes 15% of erythropoietin (stimulates bone marrow)  Hepcidin: promotes intestinal absorption of iron  Source of IGF-I that controls action of growth hormone 17-11  Other Tissues and Organs Kidneys—play role in production of three hormones  Convert calcidiol to calcitriol, the active form of vitamin D Increases Ca2+ absorption by intestine and inhibits loss in the urine  Secrete renin that converts angiotensinogen to angiotensin I  Produces 85% of erythropoietin Stimulates bone marrow to produce RBCs 17-12  Other Tissues and Organs Heart  Atrialmuscle secretes two natriuretic peptides in response to an increase in blood pressure  These decrease blood volume and blood pressure by increasing Na+ and H2O output by kidneys and oppose action of angiotensin II  Lowers blood pressure Stomach and small intestine secrete at least 10 enteric hormones  Coordinatedigestive motility and glandular secretion  Cholecystokinin, gastrin, ghrelin, and peptide YY (PYY) 17-13  Other Tissues and Organs Adipose tissue secretes leptin  Slows appetite Osseous tissue—osteocalcin secreted by osteoblasts  Increases insulin production and sensitivity Placenta  Secretes estrogen, progesterone, and others Regulate pregnancy, stimulate development of fetus and mammary glands 17-14  Hormone Chemistry Three chemical classes: steroids, monoamines, and peptides  Steroids Derived from cholesterol Sex steroids (such as estrogen) from gonads and corticosteroids (such as cortisol) from adrenals  Monoamines (biogenic amines) Made from amino acids Catecholamines (dopamine, epinephrine, norepinephrine), melatonin, thyroid hormone Figure 17.14a,b 17-15 Hormone Chemistry  Peptides and glycoproteins Created from chains of amino acids Examples include hormones from both lobes of the pituitary, and the hypothalamus Insulin is a large peptide hormone Figure 17.14c 17-16