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PowerPoint® Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham CHAPTER 17 Part 1 The Endocrine System Copyright © 2011 Pearson Education, Inc. Endocrine Organs The Endocrine System: An Overview • A system of ductless glands • Secrete messenger molecules called hormones • Interacts closely with the nervous system • Endocrinology • Study of hormones and endocrine glands Copyright © 2011 Pearson Education, Inc. Location of the Major Endocrine Glands Pineal gland • Scattered throughout the body • Pure endocrine organs are the … Hypothalamus Pituitary gland Thyroid gland • Pituitary, pineal, thyroid, parathyroid, and adrenal glands Parathyroid glands (on dorsal aspect of thyroid gland) Thymus • Organs containing endocrine cells include: • Pancreas, thymus, gonads, and the hypothalamus • Plus other organs secrete hormones (eg., kidney, stomach, intestine) Adrenal glands Pancreas • Hypothalamus is a neuroendocrine organ • Produces hormones and has nervous functions Ovary (female) • Endocrine cells are of epithelial origin Copyright © 2011 Pearson Education, Inc. Hormones Testis (male) Copyright © 2011 Pearson Education, Inc. Figure 17.1 Control of Hormones Secretion • Classes of hormones • Amino acid–based hormones • Steroids—derived from cholesterol • Basic hormone action • Circulate throughout the body in blood vessels • Influences only specific tissues— those with target cells that have receptor molecules for that hormone • A hormone can have different effects on different target cells (depends on the receptor) Copyright © 2011 Pearson Education, Inc. • Secretion triggered by three major types of stimuli: • Humoral—simplest of endocrine control mechanisms • Secretion in direct response to changing ion or nutrient levels in the blood • Example: Parathyroid monitors calcium • Responds to decline by secreting hormone to reverse decline Copyright © 2011 Pearson Education, Inc. 1 Control of Hormones Secretion Types of Endocrine Gland Stimuli • Secretion triggered by three major types of stimuli (continued) 1 Capillary blood contains low concentration of Ca2+, which stimulates… • Neural • Sympathetic nerve fibers stimulate cells in the adrenal medulla • Induces release of epinephrine and norepinephrine • Hormonal • Stimuli received from other glands • Certain hormones signal secretion of other hormones • Example: Hypothalamus secretes hormones stimulates pituitary stimulates other glands (a) Humoral stimulus (b) Neural stimulus 1 Preganglionic sympathetic fibers stimulate adrenal medulla cells… Hormonal stimulus Hypothalamus CNS (spinal cord) Capillary (low Ca2+ in blood) 2 …stimulate the anterior pituitary gland to secrete hormones that… Thyroid gland (posterior view) Parathyroid glands Pituitary gland Preganglionic sympathetic fibers Thyroid gland Adrenal cortex Gonad (Testis) Medulla of adrenal gland Parathyroid glands PTH Capillary 2 …secretion of parathyroid hormone 2 …to secrete catecholamines (PTH) by parathyroid glands. PTH acts to (epinephrine and norepinephrine) increase blood Ca2+. Copyright © 2011 Pearson Education, Inc. (c) 1 The hypothalamus secretes hormones that… 3 …stimulate other endocrine glands to secrete hormones Copyright © 2011 Pearson Education, Inc. Control of Hormone Secretion The Pituitary Gland • Always controlled by feedback loops • Secretes nine major hormones • Attached to the hypothalamus by the infundibulum • Two basic divisions of the pituitary gland • Adenohypophysis (anterior lobe) • Has three major divisions • Pars distalis, pars intermedia, and pars tuberalis • Neurohypophysis (posterior lobe) —has two major divisions • Pars nervosa and infundibular • Blood concentration declines below a minimum --> More hormone is secreted • Blood concentration exceeds maximum --> Hormone production is halted Copyright © 2011 Pearson Education, Inc. Figure 17.2 Copyright © 2011 Pearson Education, Inc. The Pituitary Gland The Anterior Lobe Corpus callosum Thalamus Pineal Hypothalamus Mammillary body Brain stem (b) Acidophil Basophil (a) Optic chiasma Median eminence of hypothalamus Anterior lobe Pars tuberalis Pars intermedia Pars distalis (c) Copyright © 2011 Pearson Education, Inc. Pituitary (hypophysis) Chromophobe cell Mammillary body Tuber cinereum Posterior lobe Infundibulum Pars nervosa Capillary with red blood cells (d) • The pars distalis—largest division of the anterior lobe • Contains five different endocrine cell groups • Makes and secretes seven different hormones • Tropic hormones regulate hormone secretion by other glands • Include: TSH, ACTH, FSH, LH • GH, PRL, and MSH • Act directly on non-endocrine target tissues Spherical cluster of cells Figure 17.3 Copyright © 2011 Pearson Education, Inc. 2 The Anterior Lobe The Anterior Lobe • Growth hormone, GH (somatotropic hormone) • Thyroid-stimulating hormone, TSH • Produced by thyrotropic cells • Signals thyroid gland to secrete thyroid hormone • Produced by somatotropic cells • Stimulates body growth by stimulating increased protein production and growth of epiphyseal plates • Stimulates growth directly and indirectly by the liver’s secretion of insulin-like growth factor-1. • Adrenocorticotropic hormone, ACTH • Stimulates the adrenal cortex to secrete hormones that help cope with stress Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Anterior Lobe The Anterior Lobe • Melanocyte-stimulating hormone, MSH • Prolactin—produced by prolactin cells • In humans, MSH functions in appetite supression • Targets milk-producing glands in the breast— stimulates milk production • Gonadotropins— are produced by gonadotropic cells and affect the gonads • Endocrine cells of the pars distalis • Clustered in spheres and branching cords • Follicle-stimulating hormone, FSH, and luteinizing hormone, LH Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Anterior Lobe Copyright © 2011 Pearson Education, Inc. The Anterior Lobe Table 17.1 Copyright © 2011 Pearson Education, Inc. Table 17.1 3 Hypothalamic Control of Hormone Secretion from the Anterior Lobe Hypothalamic Control of Hormone Secretion from the Anterior Lobe • The hypothalamus • Releasing hormones • Controls secretion of anterior lobe hormones • Exerts control by secreting: • Releasing hormones—prompt anterior lobe to release hormones • Inhibiting hormones—turn off secretion of anterior lobe hormones Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Posterior Lobe The Anterior Lobe Hypothalamic neuron cell bodies Superior hypophyseal artery Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Anterior lobe of pituitary TSH, FSH, LH, ACTH, GH, PRL • Are secreted like neurotransmitters • Enter a primary capillary plexus • Travel in hypophyseal portal veins to a secondary capillary plexus (hypothalamohypophyseal portal system) • From the secondary capillary plexus, hormones secreted by the anterior lobe enter general circulation and travel to target organs Hypothalamus 1 When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. 2 Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior lobe. • Is structurally part of the brain • Its axons make up the hypothalamic– hypophyseal tract • Arises from neuronal cell bodies in the hypothalamus • Supraoptic nucleus • Paraventricular nucleus 3 Anterior pituitary hormones are secreted into the secondary capillary plexus. (a) Relationship between the anterior pituitary and the hypothalamus Copyright © 2011 Pearson Education, Inc. Figure 17.4a The Posterior Lobe • Does not make hormones • Stores and releases hormones made in the hypothalamus • Releases two peptide hormones • Antidiuretic hormone (ADH) [aka, vasopressin] • Oxytocin (OT) Copyright © 2011 Pearson Education, Inc. Relationship Between the Posterior Pituitary and Hypothalamus 1 Hypothalamic neurons synthesize oxytocin and ADH. Paraventricular nucleus Hypothalamus Supraoptic nucleus Optic chiasma Infundibulum (connecting stalk) Hypothalamichypophyseal tract Inferior hypophyseal artery Axon terminals Posterior lobe of pituitary Oxytocin ADH 2 Oxytocin and ADH are transported along the hypothalamichypophyseal tract to the posterior lobe. 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. 4 Oxytocin and ADH are released into the blood when hypothalamic neurons fire. (b) Relationship between the posterior pituitary and the hypothalamus Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 17.4b 4 The Posterior Lobe • ADH (vasopressin) • Made in supraoptic nucleus • Targets kidneys to reabsorb water • Oxytocin • Produced in the paraventricular nucleus • Induces smooth muscle contraction of reproductive organs, ejects milk during breast feeding, and signals contraction of the uterus during childbirth Copyright © 2011 Pearson Education, Inc. Table 17.1 Copyright © 2011 Pearson Education, Inc. The Thyroid Gland The Thyroid Gland Hyoid bone Thyroid cartilage • Located in the anterior neck • Largest pure endocrine gland • Composed of follicles and areolar connective tissue • Produces two hormones Common carotid artery Inferior thyroid artery • Thyroid hormone (TH) • Calcitonin Right subclavian artery Trachea Epiglottis External carotid artery Superior thyroid artery Isthmus of thyroid gland Left subclavian artery Left lateral lobe of thyroid gland Aorta (a) Gross anatomy of the thyroid gland, anterior view Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Thyroid Gland Figure 17.5a The Parathyroid Glands Colloid-filled Follicular cells follicles (secrete thyroid hormone) • Lie on the posterior surface of the thyroid gland • Contain two types of endocrine cells • Chief cells • Produce parathyroid hormone (PTH) • Increases blood concentration of Ca2+ • Oxyphil cells • Function unknown Parafollicular cell (secretes calcitonin) (b) Photomicrograph of thyroid gland follicles (160×) Copyright © 2011 Pearson Education, Inc. Figure 17.5b Copyright © 2011 Pearson Education, Inc. 5 The Parathyroid Glands The Adrenal (Suprarenal) Glands Pharynx (posterior aspect) Thyroid gland Esophagus Parathyroid cells (secrete parathyroid hormone) Oxyphil cells Parathyroid glands Trachea • Pyramid-shaped glands located on the superior surface of each kidney • Supplied by about 60 suprarenal arteries • Nerve supply is almost exclusively sympathetic fibers Capillary (a) Location of parathyroid glands, posterior view (b) Photomicrograph of parathyroid gland tissue (360×) Copyright © 2011 Pearson Education, Inc. Figure 17.6a, b Copyright © 2011 Pearson Education, Inc. The Adrenal (Suprarenal) Glands The Adrenal Medulla • Two endocrine glands in one • Chromaffin cells • Adrenal medulla—a cluster of neurons • Derived from neural crest • Part of the sympathetic nervous system • Adrenal cortex—forms the bulk of the gland • Derived from somatic mesoderm • All adrenal hormones help one cope with danger, terror, or stress Copyright © 2011 Pearson Education, Inc. • Are modified ganglionic sympathetic neurons • Secrete amine hormones epinephrine and norepinephrine • Enhance “fight-or-flight” response • Hormones are stored in secretory vesicles • Are arranged in spherical clusters and some branching cords Copyright © 2011 Pearson Education, Inc. The Adrenal Cortex The Adrenal Cortex • Secretes lipid-based steroid hormones • Cortex is composed of three layers (zones) • Hormones are corticosteroids • Adrenal corticosteroids are of two main classes • Zona glomerulosa—cells arranged in spherical clusters • Zona fasciculata—cells arranged in parallel cords; contains lipid droplets • Zona reticularis—cells arranged in a branching network Copyright © 2011 Pearson Education, Inc. • Mineralocorticoids • Glucocorticoids • Also secretes androgens Copyright © 2011 Pearson Education, Inc. 6 Mineralocorticoids Glucocorticoids • Aldosterone—secreted by the zona glomerulosa • Cortisol is the main type • Secreted by zona fasciculata and zona reticularis • Helps the body deal with stressful situations • Secreted in response to decline in blood volume or blood pressure • Is the terminal hormone of the reninangiotensin mechanism Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Adrenal Gland–Gross and Microscopic Stress and the Adrenal Gland Short-term stress More prolonged stress Stress Hormones secreted Capsule Zona glomerulosa Nerve impulses Hypothalamus Aldosterone CRH (corticotropinreleasing hormone) Zona fasciculata Medulla Cortex Adrenal gland Spinal cord Cortisol and androgens Cortex Zona reticularis Medulla Kidney To target in blood Adrenal medulla (secretes amino acid– based hormones) Adrenal medulla (a)Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla Corticotroph cells of anterior pituitary Preganglionic sympathetic fibers Epinephrine and norepinephrine (b) Photomicrograph (140X) Copyright © 2011 Pearson Education, Inc. Figure 17.7a, b Catecholamines (epinephrine and norepinephrine) Short-term stress response 1.Increased heart rate 2.Increased blood pressure 3.Liver converts glycogen to glucose and releases glucose to blood 4.Dilation of bronchioles 5.Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6.Increased metabolic rate Adrenal cortex (secretes steroid hormones) ACTH Mineralocorticoids Glucocorticoids Long-term stress response 1.Retention of sodium and water by kidneys 2.Increased blood volume and blood pressure 1.Proteins and fats converted to glucose or broken down for energy 2.Increased blood glucose 3.Suppression of immune system Copyright © 2011 Pearson Education, Inc. The Pineal Gland The Pancreas • Located on the roof of the diencephalon • Shaped like a pine cone • “Pineal sand” is radiopaque • Located in the posterior abdominal wall • Contains endocrine and exocrine cells • Used as a landmark to identify other brain structures in X rays • Pinealocytes secrete melatonin • A hormone that regulates circadian rhythms Copyright © 2011 Pearson Education, Inc. Figure 17.8 • Exocrine cells • Acinar cells —secrete digestive enzymes • Endocrine cells • Pancreatic islet cells —islets of Langerhans • About one million islets—scattered throughout the pancreas Copyright © 2011 Pearson Education, Inc. 7 The Pancreas The Pancreas • Main endocrine cell types • Pancreatic islets contain two rare cell types • Alpha cells (α cells)—secrete glucagon • Signals liver to release glucose from glycogen • Raises blood sugar • Beta cells (β cells)—secrete insulin • Signals most body cells to take up glucose from the blood • Promotes storage of glucose as glycogen in liver • Lowers blood sugar Copyright © 2011 Pearson Education, Inc. • Delta (∂) cells • Secrete somatostatin • Inhibits secretion of insulin and glucagon • F (PP) cells • Secrete pancreatic polypeptide • May inhibit exocrine activity of the pancreas Copyright © 2011 Pearson Education, Inc. The Thymus The Gonads • Located in the lower neck and anterior thorax • Important immune organ • Site at which T-lymphocytes arise from precursor cells • Main sources of sex hormones • Testes and ovaries • Male • Interstitial cells secrete androgens • Primarily testosterone • Promotes the formation of sperm • Maintains secondary sex characteristics PLAY Copyright © 2011 Pearson Education, Inc. Male Hormones Copyright © 2011 Pearson Education, Inc. The Gonads Other Endocrine Structures • Female • Endocrine cells occur within • Ovaries • Androgens secreted by the theca folliculi • Converted to estrogen by follicular granulosa cells • Estrogen • Maintains secondary sex characteristics • Progesterone • Prepares the uterus for pregnancy Copyright © 2011 Pearson Education, Inc. • The heart • Atria contain atrial natriuretic peptide (ANP) • The GI tract • Enteroendocrine cells • The placenta • Sustains the fetus and secretes several steroid protein hormones Copyright © 2011 Pearson Education, Inc. 8 Other Endocrine Structures • The kidneys • Cells of the juxtaglomerular apparatus (JGA) secrete renin • Endothelial cells and interstitial connective tissue—secrete erythropoietin • The skin • Modified cholesterol molecules convert to a precursor of vitamin D Copyright © 2011 Pearson Education, Inc. Pituitary Disorders • Gigantism • Hypersecretion of GH in children • Pituitary dwarfism • Hyposecretion of GH • Diabetes insipidus • Pars nervosa does not make enough ADH Copyright © 2011 Pearson Education, Inc. Disorders of the Pancreas: Diabetes Mellitus Diabetes Mellitus • Caused by • Type 2 diabetes • Insufficient secretion of insulin • Resistance of body cells to the effects of insulin • Type 1 diabetes • Develops suddenly, usually before age 15 • T cell–mediated autoimmune response destroys beta cells Copyright © 2011 Pearson Education, Inc. • • • • Adult onset Usually occurs after age 40 Cells have lowered sensitivity to insulin Controlled by dietary changes and regular exercise Copyright © 2011 Pearson Education, Inc. Disorders of the Thyroid Gland Disorders of the Thyroid Gland • Grave’s disease • Myxedema • Most common type of hyperthyroidism • Immune system makes abnormal antibodies • Stimulates the oversecretion of TH by follicle cells • Leads to nervousness, weight loss, sweating, and rapid heart rate Copyright © 2011 Pearson Education, Inc. • Adult hypothyroidism • Antibodies attack and destroy thyroid tissue • Low metabolic rate and weight gain are common symptoms Copyright © 2011 Pearson Education, Inc. 9 Disorders of the Thyroid Gland Thyroid Disorders • Endemic goiter • Due to lack of iodine in the diet • Cretinism • Hypothyroidism in children • Short, disproportionate body, thick tongue, and mental retardation Copyright © 2011 Pearson Education, Inc. Disorders of the Adrenal Cortex Copyright © 2011 Pearson Education, Inc. Figure 17.10 Thyroid Disorders • Cushing’s syndrome • Caused by hypersecretion of glucocorticoid hormones—usually a pituitary tumor • Addison’s disease • Hyposecretory disorder of the adrenal cortex • Deficiencies of both mineralocorticoids and glucocorticoids Copyright © 2011 Pearson Education, Inc. The Endocrine System Throughout Life • Thyroid gland • Forms from a thickening of endoderm on the floor of the pharynx • Parathyroids and the thymus gland • From endoderm lining the pharyngeal pouches Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 17.11 Embryological Origin of Selected Endocrine Organs • Pineal gland • Originates from ependymal cells • Pituitary gland—dual origin • Adenohypophysis originates from the roof of the mouth • Neurohypophysis grows inferiorly from the floor of the brain Copyright © 2011 Pearson Education, Inc. 10 Embryological Origin of Selected Endocrine Organs Embryological Origin of Selected Endocrine Organs Hypophyseal pouch Pharyngeal pouches Future thymus • Adrenal gland—dual origin gland • Adrenal medulla—from neural crest cells of nearby sympathetic trunk ganglia • Adrenal cortex—from mesoderm lining the coelom Brain Future parathyroid glands Hypothalamus (a) Week 5. Thyroid, thymus, and parathyroid glands form from pharyngeal endoderm. Hypophyseal pouch extends superiorly from ectoderm in the roof of the mouth. Neurohypophyseal bud Future thyroid gland Esophagus Lung bud Future mouth Hypophyseal pouch (b) Week 6. Inferior extension of the floor of the diencephalon forms the neurohypophyseal bud. Copyright © 2011 Pearson Education, Inc. Neurohypophyseal bud Anterior Posterior Copyright © 2011 Pearson Education, Inc. Embryological Origin of Selected Endocrine Organs Hypophyseal pouch (c) Week 7. Hypophyseal pouch pinches off the surface ectoderm and is closely associated with the neurohypophyseal bud. Neurohypophyseal bud Third ventricle of brain (d) Week 8. Hypophyseal pouch forms the anterior lobe of pituitary; neurohypophyseal bud forms the posterior lobe. Distinct portions of each differentiate. Anterior lobe Posterior lobe Pars tuberalis Infundibulum Pars distalis Pars nervosa Figure 17.12a, b The Endocrine System Throughout Life • Endocrine organs operate effectively until old age • Anterior pituitary • Increase in connective tissue and lipofuscin • Decrease in vascularization and number of hormonesecreting cells • Adrenal cortex • Normal rates of glucocorticoid secretion continue • Adrenal medulla • No age-related changes in catecholamines Pars intermedia Copyright © 2011 Pearson Education, Inc. Figure 17.12c, d Copyright © 2011 Pearson Education, Inc. The Endocrine System Throughout Life • Thyroid hormones • Decrease slightly with age • Parathyroid glands • Little change with aging • GH, DHEA, and the sex hormones • Marked drops in secretion with age Copyright © 2011 Pearson Education, Inc. 11