Endocrine System Presented by: Kaitlin Victor September 24, 2014 1
Endocrinology The endocrine system is in charge of regulating an integrated and organized group of organs that have metabolic control in the body. Secreted molecules, or hormones, act on target cells in distant tissues that act to regulate some aspect of the target tissue. Hormones are often carried to the target by the blood. There are three types of secreted molecules Paracrine Endocrine Autocrine Elsevier s Integrated Physiology, Robert G. Carroll, 13, 157-176. Copyright 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
Endocrinology We will be focusing on endocrine molecules There are several important endocrine tissues that I will focus on today Hypothalamus Pituitary Gland Thyroid Gland Parathyroid Gland Adrenal Gland Ovaries Testes Elsevier s Integrated Physiology, Robert G. Carroll, 13, 157-176. Copyright 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
Hypothalamus The hypothalamus releases hormones that are needed to signal the pituitary gland to release (or not release) a hormone that is needed by the body Secretion from the posterior pituitary is activated by nerve signals that originate in the hypothalamus Secretion from the anterior pituitary is controlled by hormones secreted from the hypothalamus and get to the anterior pituitary through the hypothalamichypophysial portal vessels. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Hypothalamus Hormone Thyrotropin-releasing hormone (TRH) Gonadotropin-releasing hormone (GnRH) Corticotropin-releasing hormone (CRH) Growth hormone-releasing hormone (GHRH) Growth hormone inhibitory hormone (somatostatin) Prolactin-inhibiting hormone (PIH) Function Stimulates secretion of thyroid stimulating hormone Stimulates secretion of follicle stimulating hormone and luteinizing hormone Stimulates secretion of ACTH Stimulates secretion of growth hormone Inhibits secretion of growth hormone Inhibits synthesis and secretion of prolactin Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Hypothalamus A major role of the hypothalamus is the regulation of growth hormone release from the anterior pituitary gland. The two hormones that are responsible for the control of GH are GHRH and somatostatin GRHR is secreted from the ventromedial nucleus of the hypothalamus. The ventromedial nucleus is the portion of the hypothalamus that is sensitive to blood glucose levels. Somatostatin is released from a nearby area of the hypothalamus. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Hypothalamus It appears that most of the control in the secretion of GH is due to GHRH GHRH works by binding to the cell surface of the cells that secrete GH This causes both a short term and long term effect The short term effect is the increase of Ca 2+ transport in to the cell which will activate the secretion of GH The long term effect is the upregulation of genes that increase the synthesis of GH Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Hypothalamus/Hypophysis https://www.inkling.com/read/brs-neuroanatomy-gould-fix-5th/chapter-13/diencephalon-thalamus-and
Pituitary Gland The pituitary gland, or hypophysis, is made up of two embryologically distinct portions Anterior pituitary or adenohypophysis Posterior pituitary or neurohypophysis The anterior pituitary is derived from the Rathke s pouch, which is a part of the phatyngeal epithelium The posterior pituitary is derived from neural tissue from the hypothalamus Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Pituitary Gland The anterior pituitary hormones Hormone Growth hormone Adrenocorticotropin Function Promotes growth of the entire body Controls secretion off adrenocortical hormones Thyroid-stimulating hormone Prolactin Follicle-stimulating hormone Luteinizing hormone Controls rate of secretion of thyroxine and trrodothyronine Promotes mammary gland development and milk production Control growth of ovaries and testes Control growth of ovaries and testes Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Pituitary Gland The posterior pituitary hormone Hormone Function Oxytocin Anti-diuretic hormone (Vasopressin) Helps with the delivery of a baby during pregnancy and let down of milk after suckling Regulates water reabsorption in the kidneys at low levels. At higher levels, effects the arteriole pressure. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Pituitary Gland One of the most interesting hormones produced by the pituitary gland is ADH (Vasopressin) which is released by the posterior pituitary gland. When low levels of ADH is released, the collecting duct and tubules in the kidney become more permeable to water and allows for the reabsorption of the water. ADH causes the increase of camp from adenylate cyclase which causes phosphorylation events on a vesicle. This vesicle then inserts into the apical membrane which is what allows for the reabsorption of the water. Now the concentration of electrolytes is sensed by osmoreceptors in the hypothalamus which then triggers the release of ADH. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Pituitary Gland When higher levels of ADH is released from the posterior pituitary gland, ADH has a different effect At higher levels ADH becomes known as vasopressin. It works to increase atrial blood pressure by constricting arterioles in the body. The intense release of ADH is due to the decrease in blood volume especially if there is a reduction of 15-25%. The atria has stretch receptors that recognize blood volume. If the stretch receptors are not activated, this signals for the intense release of ADH. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 75
Thyroid Gland The thyroid gland is a butterfly shaped organ located below the larynx. It is composed of many closed follicles that are filled with colloid which is made up of thyroglobulin. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 76
Thyroid Gland Hormone T 3 T 4 Calcitonin Function Effect nuclear transcription of genes, increase number and activity of the mitochondria Effect nuclear transcription of genes, increase number and activity of the mitochondria Important for calcium metabolism 93% of the hormone released from the thyroid is T 4 (thyroxine) and 7% is T 3 (triiodothyronine) About half of the thyroxine is converted to triiodothyronine About 99% of T 3 andt 4 are bound to plasma proteins in the blood Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 76
Thyroid Gland
Thyroid Gland Thyroxine and triiodothyronine are the two most important hormones released from the thyroid gland. Thyroxine and triiodothyronine are part of the thyroglobulin molecule and must be cleaved form it to become active To cleave thyroglobulin, the process starts with psuedopod extensions released from the apical surface of thyroid cells that close around portions of the colloid to form pinocytic vesicles. These vesicles enter the apex of the thyroid cell. Lysosomes fuse with the vesicles; within the lysosome multiple proteases digest the thyroglobulin molecules so that active thyroxine and triiodothyronine can be released. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 76
Parathyroid Gland The parathyroid is embryologically distinct from the thyroid gland. There are many genes that are involved in the development of the parathyroid including SHH. The primary goal of the parathyroid is to help regulate Ca 2+ levels. Histology for Pathologists, 4th Edition, Chapter 45 Copyright 2012 Lippincott Williams & Wilkins www.parathyroidglands.com
Parathyroid Gland The parathyroid is one of five organs that regulate Ca 2+ in the body Parathyroid Gland C cells of the thyroid Bones Kidneys GI Tract The hormone within the parathyroid gland is the parathyroid hormone It works through the receptor PTH1R in the proximal tubules in the kidney and in osteoblasts in bone It promotes Ca 2+ reabsorption by the tubules and the reabsorbtion of bones. Histology for Pathologists, 4th Edition, Chapter 45 Copyright 2012 Lippincott Williams & Wilkins
Parathyroid Gland An interesting disease associated with the parathyroid gland is DiGeorge Syndrome which is also known as 22q11.2 deletion syndrome DiGeorge Syndrome is AD/sporadic disease that is associated with low levels of Ca 2+ which can cause seizures Some other symptoms of the disease are Heart abnormalities Dysmorphic facial features Compromised immune system Developmental Delay The prevalence is 1/4000 Most people with the syndrome have a small 3 million bp deletion in the q11.2 region of chromosome 22 and in particular the deletion of the TBX1 gene which is probably the cause of the low Ca 2+ levels along with the heart anomalies. http://ghr.nlm.nih.gov/condition/22q112-deletion-syndrome
Adrenal Gland The adrenal gland is a composite of two endocrine glands. One produces steroid hormones and the other produces catecholamines. The adrenal gland is located on top of the kidney and it is made up of a cortex and a medulla which produce different hormones. Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 77
Adrenal Gland Hormone Aldosterone Cortisol DHEA Epinephrine Norepinephrine Function Increases renal retention of Na + and loss of K + Effects many forms of metabolism in the body Is produced by the Zona Reticularis and is an important precursor androgen Produced in the medulla. Binds to adrenergic receptors. Has similar effect as stimulating sympathetic nerves Produced in the medulla. Binds to adrenergic receptors. Has similar effect as stimulating sympathetic nerves Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 77 http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/adrenal/medhormones.html
Adrenal Gland
Adrenal Gland One of the most interesting hormones produced in the adrenal cortex is cortisol As seen in the previous slide, it is produced by cells within the Zona fasciculata Cortisol causes Suppresses immune system Decreases permeability of capillaries Stimulates Gluconeogenesis Cortisol is excreted in response to Infection Surgery Trauma of almost any type Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 77
Pancreas The pancreas is interesting because it is both an exocrine and endocrine organ Both of its function helps to aid the digestion and absorption of nutrients after meals Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 78
Pancreas Hormone Insulin Glucagon Amylin Somatostatin Pancreatic Polypeptide Function Secreted by beta cells. Regulates blood glucose levels Secreted by alpha cells. Regulates blood glucose levels Secreted by beta cells. Function is unknown. Secreted by delta cells. Inhibits the release of GH. Secreted by PP cells. Regulates pancreatic secretion (both endocrine and exocrine) Guyton and Hall Textbook of Medical Physiology Twelfth Edition Chapter 78
Pancreas www.meduweb.com web.campbell.edu
Ovaries The ovaries are the female gonads Within the ovaries, the oocytes develop and are released on a monthly basis from puberty until menopause The ovaries convert testosterone to estrogen through the enzyme aromatase. http://en.wikipedia.org/wiki/ovary
Ovaries Hormone Estradiol Progesterone Function Functions through estrogen receptors. It is important in the development of secondary sexual characteristics in females. It is also involved with the regulation of the menstrual cycle. Functions through progesterone receptors. It is important for regulating the menstrual cycle, pregnancy, and embryogenesis in females. http://en.wikipedia.org/wiki/ovary
Menstrual Cycle http://sbi4u3.weebly.com/endocrine-hormones-basic-mechanisms-and-the-menstrual-cycle.html
Testes The testes are the male gonads Within the testes, the sperm develop daily from puberty until death There are two cell types within the testes Sertolli Cells-supports the development of the spermatogonia Leydig Cells-produce testosterone Testicle%20-%20Wikipedia,%20the%20free%20encyclopedia.webarchive
Testosterone Hormone Testosterone Function It functions through an androgen receptor. It is important in the development of secondary male sexual characterization. It also important in the production and maintenance of sperm. Testicle%20-%20Wikipedia,%20the%20free%20encyclopedia.webarchive
Testes An interesting disease that is associated with the inability to recognize androgens is androgen insensitivity syndrome These individuals have an XY karyotype but can have female, ambiguous, or male genitalia depending on the individuals sensitivity to androgens. The individuals internal organs are male due to the presence of AMH during development. An individual can have complete or incomplete AIS. AIS is a X-linked recessive disorder that occurs in approximately 2-5/100000 individuals Androgen insensitivity syndrome - Genetics Home Reference, http://ghr.nlm.nih.gov/condition/androgen-insensitivity-syndrome