Lecture 17: Endocrine System 2024 PDF

Chapter 18 Endocrine System B305 – Human Anatomy Dr. Preston  Mechanisms of Communication The body has 4 principal mechanisms of communication between cells: Gap junctions Neurotransmitters Paracrines Hormones © McGraw Hill 2...

Chapter 18 Endocrine System B305 – Human Anatomy Dr. Preston  Mechanisms of Communication The body has 4 principal mechanisms of communication between cells: Gap junctions Neurotransmitters Paracrines Hormones © McGraw Hill 2  The Endocrine System – Overview Endocrine system— Parathyr glands, tissues, and cells oid that secrete hormones glands Endocrinology— study of endocrine system, diagnosis and treatment of endocrine disorders Endocrine glands— organs that are traditional sources of hormones © McGraw Hill 3  Hypothalamus and the Pituitary Gland © McGraw Hill 4  Master Regulator of the Endocrine System © McGraw Hill 5  Hypothalamic Control of Endocrine System Hypothalamus is a control center of the endocrine system Secretes regulatory hormones that control release of pituitary hormones o Hypothalamus secretes releasing hormones (RH) and inhibiting hormones (IH) © McGraw Hill 6  Hypothalamic Control of Endocrine System Regulates multiple primitive functions – water balance, thermoregulation, sex drive, childbirth Many of its functions have closed connections to pituitary gland © McGraw Hill 7  Hypothalamus Anatomy The hypothalamus is shaped like a flattened funnel Forms floor and walls of third ventricle of brain © McGraw Hill 8  Pituitary Gland o Also called the hypophysis o Location: inferior to hypothalamus—connected by infundibulum o Housed in sella turcica of sphenoid bone © McGraw Hill 9  Pituitary Gland Anatomy Divided into Anterior Pituitary (Adenohypophysis) Posterior Pituitary (Neurohypophysis) © McGraw Hill 10  Posterior Pituitary – Neurohypophysis o Posterior one-quarter of the pituitary o Nerve tissue, not a true gland o Hypothalamus and Neurohypophysis connect through hypothalamo– hypophysial tract o Hypothalamic neurons secrete hormones that are stored in neurohypophysis until released into blood © McGraw Hill 11  Anterior Pituitary – Adenohypophysis o Anterior three-quarters of pituitary o Linked to hypothalamus by hypophysial-portal system o Hypothalamic hormones regulate adenohypophysis cells © McGraw Hill 12 Hypothalamus–Pituitary–Target Organs © McGraw Hill 13  Hypothalamic and Pituitary Hormones © McGraw Hill 14 Hypothalamus and Pituitary Gland – CT Scan hypothalamus infundibulum pituitary gland Midsagittal view © McGraw Hill Anatomy and Physiology Revealed, McGraw Hill15 Pituitary Adenoma Neoplasms of the neuroendocrine epithelial cells Majority originate from the Adenohypophysis ~50% microadenomas (< 10mm), rest are macroadenomas (> 10mm) White arrow = Pituitary gland Green arrow = Optic chiasm © McGraw Hill https://www.nanosweb.org/i4a/pages/index.cfm?pageid=410716  Thymus © McGraw Hill 17  The Thymus Thymus plays a role in 3 systems: endocrine, lymphatic, immune Bilobed gland located in mediastinum superior to the heart Goes through involution after puberty © McGraw Hill 18  Thymuses of the Newborn and Adult Hormones: Thymopoietin Thymosin Thymulin © McGraw Hill 19  Thyroid and Parathyroid Glands © McGraw Hill 20  Thyroid Gland o Located inferior to thyroid cartilage and anterior to the trachea o Butterfly shape with right and left lobes connected by midline isthmus © McGraw Hill 21  Thyroid Gland o Thyroid follicles—sacs that make up most of thyroid o Follicle lumen contain protein-rich colloid (traps iodine, center of thyroid hormone production) o Follicular cells: simple cuboidal epithelium that lines follicles © McGraw Hill (b) Dr. Alvin Telser/McGraw-Hill Education 22  Parathyroid Glands o Small glands on posterior area of thyroid gland o Usually four Two types of cells in parathyroid gland: Chief cells: secrete parathyroid hormone (PTH) Oxyphil cells: function unknown © McGraw Hill 23  Adrenal Glands © McGraw Hill 24  Adrenal Glands o Located on superior borders of the kidneys o Composed of: o Adrenal cortex o Adrenal medulla © McGraw Hill 25  Adrenal Cortex Made up by 3 layers – producing different corticosteroid hormones: o Zona glomerulosa: produces mineralocorticoids (aldosterone) o Zona fasciculata: produces glucocorticoids (cortisol) o Zona reticularis: produces gonadocorticoids including androgens © McGraw Hill 26  Adrenal Medulla o The adrenal medulla is the gland’s inner core o Consists of chromaffin cells – modified ganglionic cells of sympathetic nervous system o Secrete norepinephrine and epinephrine—involved with fight-or-flight response © McGraw Hill 27  Pancreas © McGraw Hill 28  Pancreas o Located between duodenum and spleen; posterior to stomach o Has both exocrine and endocrine functions © McGraw Hill 29  Pancreas o Pancreatic acini (exocrine tissue) – produce alkaline secretions into ducts that lead to duodenum for digestion o Pancreatic islets (islets of Langerhans) – small clusters of endocrine cells (four types: alpha, beta, delta and F cells) © McGraw Hill 30  Pancreas 10% ~80% ~1% ~3% © McGraw Hill 31  Other Tissues and Organs © McGraw Hill 32  Endocrine Functions of Other Tissues/Organs Brain © McGraw Hill 33  Endocrine Functions of Other Tissues/Organs Heart Cardiac muscle secretes two natriuretic peptides ANP synthesized mainly by the atria BNP synthesized by the ventricles Decrease blood volume and blood pressure Kidneys—play role in production of three hormones Convert calcidiol to calcitriol, the active form of vitamin D Secrete Renin – converts angiotensinogen to angiotensin I Produces 85% of erythropoietin © McGraw Hill 34  Endocrine Functions of Other Tissues/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) Secretes 15% of erythropoietin (stimulates bone marrow) Source of IGF-I that controls action of growth hormone Hepcidin: promotes intestinal absorption of iron © McGraw Hill 35  End of Main Content Because learning changes everything. ® www.mheducation.com © 2021 McGraw Hill. 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