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17 PART 1

17 PART 1. The Endocrine System Pages 522-537. 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. Endocrine Organs.

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17 PART 1

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  1. 17 PART 1 The Endocrine System Pages 522-537

  2. 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

  3. Endocrine Organs • Scattered throughout the body • Pure endocrine organs • Pituitary, pineal, thyroid, parathyroid, and adrenal glands • Organs containing endocrine cells • Pancreas, thymus, gonads, and the hypothalamus • Hypothalamus is a neuroendocrine organ • Produces hormones and has nervous functions • Endocrine cells are of epithelial origin

  4. Location of the Major Endocrine Glands Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 17.1

  5. Hormones • 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—target cells • A hormone can have different effects on different target cells

  6. Control of Hormones Secretion • 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 • Parathyroid monitors calcium • Responds to decline by secreting hormone to reverse decline

  7. Control of Hormones Secretion • Secretion triggered by three major types of stimuli (continued) • 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 • Hypothalamus secretes hormones  stimulates pituitary  stimulates other glands

  8. (a) Humoral stimulus (b) Neural stimulus (c) Hormonal stimulus 1 1 1 Capillary blood contains low concentration of Ca2+, which stimulates… Preganglionic sympathetic fibers stimulate adrenal medulla cells… The hypothalamus secretes hormones that… 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 Adrenal cortex Thyroid gland Gonad (Testis) Medulla of adrenal gland Parathyroid glands PTH Capillary 3 2 2 …secretion of parathyroid hormone (PTH) by parathyroid glands. PTH acts to increase blood Ca2+. …to secrete catecholamines (epinephrine and norepinephrine) …stimulate other endocrine glands to secrete hormones Types of Endocrine Gland Stimuli Figure 17.2

  9. Control of Hormones Secretion • Always controlled by feedback loops • Blood concentration declines below a minimum • More hormone is secreted • Blood concentration exceeds maximum • Hormone production is halted

  10. The Pituitary Gland • 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—has two major divisions • Pars nervosa and infundibular

  11. Figure 17.3 The pituitary gland (hypophysis). Corpuscallosum Thalamus Pineal Hypothalamus Mammillarybody Brain stem Pituitary (hypophysis) Posteriorlobe Anterior lobe Optic chiasma Mammillarybody Median eminenceof hypothalamus Chromophobecells Tuber cinereum Anterior lobe Basophilcells Posterior lobe Pars tuberalis Infundibulum Pars intermedia Pars nervosa Acidophilcells Pars distalis Pituicytes(neuroglia)

  12. http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/histo.htmlhttp://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/histo.html

  13. The Anterior Lobe • The pars distalis—largest division of the anterior lobe • Contains five different endocrine cells • Makes and secretes seven different hormones • Tropic hormones regulate hormone secretion by other glands • Include: thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), FSH, LH

  14. The Anterior Lobe • GH (growth hormone), PRL (prolactin), and MSH (melanocyte-stimulating hormone) • Act directly on non-endocrine target tissues

  15. The Anterior Lobe • Growth hormone (somatotropic 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.

  16. The Anterior Lobe • Thyroid-stimulating hormone • Produced by thyrotropic cells • Signals thyroid gland to secrete thyroid hormone • Adrenocorticotropic hormone • Stimulates the adrenal cortex to secrete hormones that help cope with stress

  17. The Anterior Lobe • Melanocyte-stimulating hormone • In humans, MSH functions in appetite suppression • Gonadotropins—are produced by gonadotropic cells • FSH and LH • In females, FSH and LH stimulate maturation of follicles, secretion of androgen, estrogen & progesterone

  18. The Anterior Lobe • Prolactin—produced by prolactin cells • Targets milk-producing glands in the breast—stimulates milk production • Endocrine cells of the pars distalis • Clustered in spheres and branching cords

  19. Figure 17.3d The pituitary gland (hypophysis). Posteriorlobe Anterior lobe Chromophobecells Basophilcells Acidophilcells Pituicytes(neuroglia)

  20. Hypothalamic Control of Hormone Secretion from the Anterior Lobe • The hypothalamus • 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

  21. Hypothalamic Control of Hormone Secretion from the Anterior Lobe • Releasing hormones • Are secreted like neurotransmitters • Enter a primary capillary plexus • Travel in hypophyseal portal veins to a secondary capillary plexus • From the secondary capillary plexus, hormones secreted by the anterior lobe enter general circulation and travel to target organs

  22. Mammillary body Optic chiasma Median eminence of hypothalamus Tuber cinereum Anterior lobe Posterior lobe Pars tuberalis Pars intermedia Infundibulum Pars distalis Pars nervosa (c)

  23. When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. 1 Hypothalamic neuron cell bodies Hypothalamus Superior hypophyseal artery Hypophyseal portal system Primary capillary plexus Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior lobe. 2 Hypophyseal portal veins Secondary capillary plexus Anterior lobe of pituitary Anterior pituitary hormones are secreted into the secondary capillary plexus. 3 TSH, FSH, LH, ACTH, GH, PRL (a) Relationship between the anterior pituitary and the hypothalamus The Anterior Lobe

  24. The Posterior 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

  25. Hypothalamic neurons synthesize oxytocin and ADH. 1 Hypothalamus Paraventricular nucleus Supraoptic nucleus Oxytocin and ADH are transported along the hypothalamic- hypophyseal tract to the posterior lobe. 2 Optic chiasma Infundibulum (connecting stalk) Inferior hypophyseal artery Hypothalamic- hypophyseal tract 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Axon terminals Oxytocin and ADH are released into the blood when hypothalamic neurons fire. Posterior lobe of pituitary 4 Oxytocin ADH (b) Relationship between the posterior pituitary and the hypothalamus Relationship Between the Posterior Pituitary and Hypothalamus

  26. The Posterior Lobe • Does not make hormones • Stores and releases hormones made in the hypothalamus • Releases two peptide hormones • Antidiuretic hormone (ADH) • Oxytocin

  27. The Posterior Lobe • ADH (vasopressin) • Made in supraoptic nucleus • Targets kidneys to resorb 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

  28. The Thyroid Gland • Located in the anterior neck • Largest pure endocrine gland • Composed of follicles and areolar connective tissue • Produces two hormones • Thyroid hormone (TH) • Calcitonin

  29. Hyoid bone Epiglottis Thyroid cartilage External carotid artery Superior thyroid artery Common carotid artery Inferior thyroid artery Isthmus of thyroid gland Right subclavian artery Left subclavian artery Left lateral lobe of thyroid gland Trachea Aorta (a) Gross anatomy of the thyroid gland, anterior view The Thyroid Gland

  30. Figure 17.5b The thyroid gland. Parafollicular cells(secrete calcitonin) Follicular cells(secrete thyroidhormone) Colloid-filledfollicles Photomicrograph of thyroid glandfollicles (315)

  31. The Parathyroid Glands • Lie on the posterior surface of the thyroid gland • Contain two types of endocrine cells • Chief cells/parathyroid cells • Produce parathyroid hormone (PTH) • Increases blood concentration of Ca2+ • Oxyphil cells • Function unknown

  32. Figure 17.6 The parathyroid glands. Pharynx(posterioraspect) Capillary Parathyroidcells(secreteparathyroidhormone) Thyroidgland Esophagus Oxyphilcells Parathyroidglands Trachea Photomicrographof parathyroidgland embeddedwithin the thyroidgland (2) Illustration ofparathyroid glandsembedded withinthe thyroid gland,posterior view Photomicrograph of parathyroid gland (205)

  33. The Adrenal (Suprarenal) Glands • Pyramid-shaped glands located on the superior surface of each kidney • Two endocrine glands in one • Adrenal medulla—a cluster of neurons • Part of the sympathetic nervous system • Adrenal cortex—forms the bulk of the gland • All adrenal hormones help one cope with danger, terror, or stress

  34. Location of the Major Endocrine Glands Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 17.1

  35. The Adrenal Medulla • Chromaffin cells • 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

  36. Figure 17.7 The adrenal gland, gross and microscopic structure. Hormonessecreted Capsule Zonaglomerulosa Aldosterone Zonafasciculata Adrenalgland Cortex Medulla Cortex Cortisolandandrogens Kidney Zonareticularis Adrenalmedulla Medulla Epinephrineandnorepinephrine Drawing of the histologyof the adrenal cortexand a portion of theadrenal medulla Photomicrograph (120)

  37. Short-term stress More prolonged stress Stress Nerve impulses Hypothalamus CRH (corticotropin- releasing hormone) Spinal cord Corticotroph cells of anterior pituitary Preganglionic sympathetic fibers To target in blood Adrenal cortex (secretes steroid hormones) Adrenal medulla (secretes amino acid– based hormones) ACTH Catecholamines (epinephrine and norepinephrine) Mineralocorticoids Glucocorticoids Short-term stress response Long-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 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 Stress and the Adrenal Gland Figure 17.8

  38. The Adrenal Cortex • Secretes lipid-based steroid hormones • Cortex is composed of three layers (zones) • 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

  39. Figure 17.7 The adrenal gland, gross and microscopic structure. Hormonessecreted Capsule Zonaglomerulosa Aldosterone Zonafasciculata Adrenalgland Cortex Medulla Cortex Cortisolandandrogens Kidney Zonareticularis Adrenalmedulla Medulla Epinephrineandnorepinephrine Drawing of the histologyof the adrenal cortexand a portion of theadrenal medulla Photomicrograph (120)

  40. The Adrenal Cortex • Hormones are corticosteroids • Adrenal corticosteroids are of two main classes • Mineralocorticoids • Glucocorticoids

  41. Mineralocorticoids • Aldosterone—secreted by the zona glomerulosa • Secreted in response to decline in blood volume or blood pressure • Is the terminal hormone of the renin-angiotensin mechanism

  42. Glucocorticoids • Cortisol is the main type • Secreted by zona fasciculata and zona reticularis • Helps the body deal with stressful situations

  43. Short-term stress More prolonged stress Stress Nerve impulses Hypothalamus CRH (corticotropin- releasing hormone) Spinal cord Corticotroph cells of anterior pituitary Preganglionic sympathetic fibers To target in blood Adrenal cortex (secretes steroid hormones) Adrenal medulla (secretes amino acid– based hormones) ACTH Catecholamines (epinephrine and norepinephrine) Mineralocorticoids Glucocorticoids Short-term stress response Long-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 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 Stress and the Adrenal Gland Figure 17.8

  44. The Pineal Gland • Located on the roof of the diencephalon • Shaped like a pine cone • Pinealocytes secrete melatonin • A hormone that regulates circadian rhythms • “Pineal sand” is radiopaque • Used as a landmark to identify other brain structures in X rays

  45. Corpus callosum Thalamus Pineal Hypothalamus Mammillary body Brain stem Pituitary (hypophysis) (b)

  46. The Pancreas • Located in the posterior abdominal wall • Contains endocrine and exocrine cells • Exocrine cells • Acinar cells—secrete digestive enzymes • Endocrine cells • Pancreatic islets—islets of Langerhans • About one million islets—scattered throughout the pancreas

  47. The Pancreas • Main endocrine cell types • Alpha cells ( cells)—secrete glucagon • Signals liver to release glucose from glycogen • Raises blood sugar • Beta cells ( 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

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