L35-2 Endocrine System PDF

L35-2- ENDOCRINE SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES At the end of this lecture, students should be able to  Definition,  Exocrine vs endocrine,  Target organs and hormones,  Response...

L35-2- ENDOCRINE SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES At the end of this lecture, students should be able to  Definition,  Exocrine vs endocrine,  Target organs and hormones,  Response time,  Endocrine glands, role of hormone receptors and responses. The Endocrine System  Second messenger system of the body  Uses chemical messages (hormones) that are released into the blood  Hormones control several major processes  Reproduction  Growth and development  Mobilization of body defenses  Maintenance of much of homeostasis  Regulation of metabolism Slide 9.1 Hormone Overview  Hormones are produced by specialized cells  Cells secrete hormones into extracellular fluids  Blood transfers hormones to target sites  These hormones regulate the activity of other cells Slide 9.2  The Chemistry of Hormones  Amino acid-based hormones  Proteins  Peptides  Amines  Steroids – made from cholesterol  Prostaglandins – made from highly active lipids Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.3 Mechanisms of Hormone Action  Hormones affect only certain tissues or organs (target cells or organs)  Target cells must have specific protein receptors  Hormone binding influences the working of the cells Slide 9.4 Control of Hormone Release  Hormone levels in the blood are maintained by negative feedback  A stimulus or low hormone levels in the blood triggers the release of more hormone  Hormone release stops once an appropriate level in the blood is reached Slide 9.10 Hormonal Stimuli of Endocrine Glands  Endocrine glands are activated by other hormones  Changing blood levels of certain ions stimulate hormone release Figure 9.2a Slide 9.11 Pituitary Gland  Size of a grape  Hangs by a stalk from the hypothalamus  Protected by the sphenoid bone  Has two functional lobes  Anterior pituitary – glandular tissue  Posterior pituitary – nervous tissue Slide 9.15  Hormones of the Anterior Pituitary  Six anterior pituitary hormones  Two affect non-endocrine targets  Four stimulate other endocrine glands (tropic hormones)  Characteristics of all anterior pituitary hormones  Proteins (or peptides)  Act through second-messenger systems  Regulated by hormonal stimuli, mostly negative feedback Hormones of the Anterior Pituitary Figure 9.4 Slide 9.17 Growth Hormone (GH)  General metabolic hormone  Major effects are directed to growth of skeletal muscles and long bones  Causes amino acids to be built into proteins  Causes fats to be broken down for a source of energy Slide 9.18 Functions of Other Anterior Pituitary Hormones  Prolactin (PRL)  Stimulates and maintains milk production following childbirth  Function in males is unknown  Adrenocorticotropic hormone (ACTH)  Regulates endocrine activity of the adrenal cortex  Thyroid-stimulating hormone (TSH)  Influences growth and activity of the thyroid Slide 9.19 Functions of Other Anterior Pituitary Hormones  Gonadotropic hormones  Regulate hormonal activity of the gonads  Follicle-stimulating hormone (FSH)  Stimulates follicle development in ovaries  Stimulates sperm development in testes Slide 9.20a Functions of Other Anterior Pituitary Hormones  Gonadotropic hormones (continued)  Luteinizing hormone (LH)  Triggers ovulation  Causes ruptured follicle to become the corpus luteum  Stimulates testosterone production in males  Referred to as interstitial cell-stimulating hormone (ICSH) Slide 9.20b Hormones of the Posterior Pituitary  Oxytocin  Stimulates contractions of the uterus during labor  Causes milk ejection  Antidiuretic hormone (ADH)  Can inhibit urine production  In large amounts, causes vasoconstriction leading to increased blood pressure (vasopressin) Slide 9.22 Thyroid Gland  Consists of two lobes and a connecting isthmus  Produces two hormones  Thyroid hormone  Calcitonin Slide 9.23a Thyroid Gland Figure 9.6 Slide 9.23b Thyroid Hormone  Major metabolic hormone  Composed of two active iodine- containing hormones  Thyroxine (T4) – secreted by thyroid follicles  Triiodothyronine (T3) – conversion of T4 at target tissues Slide 9.24 Calcitonin  Decreases blood calcium levels by causing its deposition on bone  Antagonistic to parathyroid hormone  Produced by C (parafollicular) cells Figure 9.9 Slide 9.25 Parathyroid Glands  Tiny masses on the posterior of the thyroid  Secrete parathyroid hormone  Stimulate osterclasts to remove calcium from bone  Stimulate the kidneys and intestine to absorb more calcium  Raise calcium levels in the blood Slide 9.26 Adrenal Glands  Two glands  Cortex – outer glandular region in three layers  Medulla – inner neural tissue region  Sits on top of the kidneys Slide 9.27 Hormones of the Adrenal Cortex  Mineralocorticoids (mainly aldosterone)  Produced in outer adrenal cortex  Regulate mineral content in blood, water, and electrolyte balance  Target organ is the kidney  Production stimulated by renin and aldosterone  Production inhibited by atrial natriuretic peptide Slide 9.28a Hormones of the Adrenal Cortex  Glucocorticoids (including cortisone and cortisol)  Produced in the middle layer of the adrenal cortex  Promote normal cell metabolism  Help resist long-term stressors  Released in response to increased blood levels of ACTH Slide 9.29a Hormones of the Adrenal Cortex  Sex hormones  Produced in the inner layer of the adrenal cortex  Androgens (male) and some estrogen (female) Slide 9.29b Hormones of the Adrenal Medulla  Produces two similar hormones (catecholamines)  Epinephrine  Norepinephrine  These hormones prepare the body to deal with short-term stress Slide 9.30 Pancreatic Islets  The pancreas is a mixed gland  The islets of the pancreas produce hormones  Insulin – allows glucose to cross plasma membranes into cells from beta cells  Glucagon – allows glucose to enter the blood from alpha cells  These hormones are antagonists that maintain blood sugar homeostasis Slide 9.32a Pancreatic Islets Figure 9.13 Slide 9.32b Pineal Gland  Found on the third ventricle of the brain  Secretes melatonin  Helps establish the body’s wake and sleep cycles  May have other as-yet-unsubstantiated functions Slide 9.34 Thymus  Located posterior to the sternum  Largest in infants and children  Produces thymosin  Matures some types of white blood cells  Important in developing the immune system Slide 9.35 Hormones of the Ovaries  Estrogens  Produced by Graafian follicles or the placenta  Stimulates the development of secondary female characteristics  Matures female reproductive organs  Helps prepare the uterus to receive a fertilized egg  Helps maintain pregnancy  Prepares the breasts to produce milk Slide 9.36 Hormones of the Ovaries  Progesterone  Produced by the corpus luteum  Acts with estrogen to bring about the menstrual cycle  Helps in the implantation of an embryo in the uterus Slide 9.37 Hormones of the Testes  Interstitial cells of testes are hormone- producing  Produce several androgens  Testosterone is the most important androgen  Responsible for adult male secondary sex characteristics  Promotes growth and maturation of male reproductive system  Required for sperm cell production Slide 9.38 Other Hormone-Producing Tissues and Organs  Parts of the small intestine  Parts of the stomach  Kidneys  Heart  Many other areas have scattered endocrine cells Slide 9.39 Endocrine Function of the Placenta  Produces hormones that maintain the pregnancy  Some hormones play a part in the delivery of the baby  Produces HCG in addition to estrogen, progesterone, and other hormones Slide 9.40 Developmental Aspects of the Endocrine System  Most endocrine organs operate smoothly until old age  Menopause is brought about by lack of efficiency of the ovaries  Problems associated with reduced estrogen are common  Growth hormone production declines with age  Many endocrine glands decrease output with age Slide 9.41 References Susan. 2008. Gray’s Anatomy- The Anatomical Basis of clinical Practise. 40th edition. New York: Elsvier. Snell, R.S. 2008. Clinical Anatomy by Regions. 8th edition. Philadelphia: Lippincott Williams & Wilkins. Ellis, H. 2006. Clinical Anatomy- A revision and Applied Anatomy for Clinical Students. 11th edition. Victoria: Blackwell Publishing. Moore, K.L., Dalle,A.F. & Agur, A.M. 2010. Clinically Oriented Anatomy. 6th edition.Philadelphia: Lippincott Williams & Wilkins.