VIEW CHAPTER EXPORT CITATION

Chapter-01 The Endocrines or Ductless Glands

BOOK TITLE: Human Physiology

Author
1. Muthayya NM
ISBN
9788184487367
DOI
10.5005/jp/books/10366_9
Edition
4/e
Publishing Year
2009
Pages
23
Author Affiliations
1. Madurai Medical College, Thanjavur Medical College, Coimbatore Medical College, Rajah Muthiah Medical College, Annamalai University, University of Health Sciences, Antigua, West Indies; Thanjavur Medical College; Vinayaka Missions Kirupananda Variar Medical College Salem, India
Chapter keywords
Endocrines or ductless glands, Neurohypophysis, Study of endocrines, Anterior pituitary gland, Adenohypophysis, Growth hormones, Prolactin, Thyroid stimulating hormone, Adrenocorticotrophic hormone, Follicle stimulating hormone, Luteinizing hormone, Interstitial stimulating hormone, Chemical nature, Control of secretion of hormones, Effects on different organs, Hormonal action and regulation, Thyroid gland, Structure of thyroid gland, Histology of thyroid, Nerve supply, Blood supply, Biosynthesis of thyroid hormones, Enzymes participating in different steps, Thyroxin (T4), Triiodothyronine (T3), Important functions of thyroid, Metabolic effects, Calorigenic effects, Hyperthyroidism and hypothyroidism, Structure of parathyroid gland, Color plate illustrating its histology, Para thyroid hormones, Calcitonin and thyrocalcitonin secretion, Control of para hormone secretion, Role in calcium metabolism, Blood namely tetany, Physiology of bone, Para thyroid physiology, Bone form

Abstract

This chapter deals with General aspects of endocrines, anterior pituitary and neurohypophysis. After a brief introductory note on endocrines—general aspects, methods of study of endocrines are detailed. The anterior pituitary gland or adenohypophysis, its histological structure, its different types of cells, its different hormones are described in detail. The different hormones namely: Growth hormones, prolactin, thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), follicle stimulating hormone (F.S.H), luteinizing hormone (LH) and interstitial stimulating hormone (ICSH) are systematically explained. These hormones chemical nature, the cells producing these hormones, the control of secretion of these hormones, the target sites of their actions, the effects on different organs are discussed in detail. Finally the clinical conditions produced by excess activity or deficiency of these hormones discussed in detail. To enable the study of histological structure of these glands colored diagrams are given as aids. Clinical disorders are supported by sketch diagrams for easy understanding and reproduction. The study of the neurohypophysis includes the study of its structure, hormones, hormonal action and regulation of its secretion and related clinical aspects diabetes insipidus is described. Chapter two deals with thyroid gland physiology: The structure of Thyroid gland is described and color plate is given as an aid for understanding the histology of Thyroid. The nerve supply and its blood supply are described. Biosynthesis of thyroid hormones is given in detail with enzymes participating in different steps. Its storage form described. Transport form of thyroid hormones in the blood namely. Thyroxin (T4), and triiodothyronine (T3) and their difference in action are described. The T3, T4 carriers are mentioned. The important functions of thyroid, its metabolic effects and calorigenic effects and other functions are discussed in detail. Clinical conditions Hyperthyroidism and Hypothyroidism are explained with supporting figures. Chapter three deals with the Para thyroid physiology: Structure of parathyroid gland described with a color plate illustrating its histology. Parathyroid hormones, parathormone, calcitonin and thyrocalcitonin secretion, their action with their target organs are discussed in detail. Control of parahormone secretion and its role in calcium metabolism is discussed with due emphasis. The clinical conditions associated with calcium level in the blood namely Tetany is discussed in detail describing all features. As calcium is closely associated with bone formation the physiology of bone is taken up along with the parathyroid physiology. Bone formation and bone resorption and the hormones influencing them are given in a Tabular statement for easy and clear understanding. Chapter four deals with adrenal glands: Its components adrenal cortex and Adrenal Medulla are dealt separately. Their development structure, innervations are described. The classification of cortical hormones as glucocorticoids, mineralocorticoids, sex steroids, biosynthesis of these hormones, enzymes involved in different steps are discussed in a detailed manner. A color plate of adrenal histology is given as an aid for study. Functions of glucocorticoids, mineralocorticoids-aldosterone and sex corticoids are discussed elaborately as they are inevitable hormones for human life. Regulation of secretion of these hormones discussed, clinical conditions associated with adrenal cortex-Cushing’s syndrome, Addison’s disease, Adrenogenital syndrome, Aldosteronism are discussed. Chapter five deals with adrenal medulla, is taken as a separate entity. Biosynthesis of adrenal medullary hormones adrenaline and noradrenaline, different enzymes involved in different steps are discussed. Action of these hormones and the close relationship to sympathetic nervous systems is described. The actions of noradrenaline and adrenaline on different organs are described with an illustrative diagram. As adrenal medulla is closely related to sympathetic nervous system which in turn is closely related to stress, this phenomenon of stress, its stages, and general adaptation syndrome are discussed along with adrenal medulla. Chapter 6 deals with endocrine function of the pancreas and its hormone-insulin. Structure of the pancreatic islets, its different types of cells and the different hormones-insulin, glucagon, somatostatin and pancreatic polypeptide are described with historical background. The functions of these hormones in different targets and the mechanisms involved in the regulation of blood sugar level are discussed in detail. Control of secretion of insulin is given in a detailed manner. Insulin antagonists are mentioned. Hyperglycemic and hypoglycemic agents are described in detail. Being an important common disease in the whole universe the Diabetes mellitus is discussed much elaborately. Types of diabetes mellitus are given in a tabular statement for easy understanding. Chapter seven, deals with physiology of reproduction in the female. Sex differentiation, sex development, development of gonads, development of genitalia is described. Disorders of sex development are given in a table. Reproductive phase of the female coincides with starting of the menstrual cycle. Hence menstrual cycle is described first. The different phases and changes occurring in the ovary, uterine endometrium and mammary glands during the different phases are discussed in detail. Enough diagrams are given for clear understanding of the menstrual cycle. Structure of the corpus luteum and its function are discussed. With the discussion on the disturbances of menstrual cycle, menstrual disorders this chapter comes to an end. Chapter eight dealt with physiology of pregnancy and lactation. Fertilization of the ovum and the implantation of the fertilized ovum in the uterine endometrium are explained adequately. The development of placenta and its organization is described. Endocrinology of pregnancy with more emphasis on Human chorionic gonadotrophic hormone is discussed in detail. The pregnancy tests are listed and common tests which are practically done are described. Placental functions are described. Other various changes occurring in the mother during pregnancy are described. The structural changes in the mammary glands during pregnancy and secretion of milk are described. Hormones which promote milk secretion and milk ejection are explained. Comparison of Human milk and cow’s milk is given in a table. Chapter 9 dealt with physiology of male reproduction. Structure of the testis and different type of cells are described. Both functions namely spermatogenesis and endocrine functions, production of androgens and oestrogens are discussed in detail. Regulation of testicular function and the role of sertoli cells in spermatogenesis are discussed. Seminal tracts and related glands are described—epididymis, vas deferens, seminal vesicles, prostate and Bulbourethral glands. Composition of semen is described. Biosynthesis of testosterone by Leydig cells and its regulation is described. Functions of Testosterone are enumerated. Mechanism of testosterone action is given in detail. Lastly physiology of coitus is described. Fertility control is discussed in order to create awareness of increasing population among students. Chapter ten dealt with pineal gland. The location of pineal gland, its nerve supply and its secretary hormones are described. The inhibitory effect on gonadotrophic hormones secretion by the anterior pituitary is explained. Pineal stimulatory effect on prolactin secretion and prostaglandin synthesis has been notified. The pineal influences on central nervous system are brought into light. The central nervous system is considered as a major regulator of many functions in the body. By its influences on various central nervous system functions the pineal is presumed to be a regulator of regulators. Chapter 11 deals with essential fatty acids and eicosanoids. The three polyunsaturated fatty acids (essential fatty acids) namely linolenic acid, linoleic acid, and arachidonic acid and their derivatives namely prostaglandins, prostacyclins, Thromboxanes, lipoxygenase, leukotrienes are described with the help of a flow chart. The physiological functions of prostaglandins, leukotrienes, Thromboxanes and prostacyclins are explained. Anti-inflammatory steroids and non-steroidal anti-inflammatory agent aspirin are accounted. Chapter twelve deal with physiology of ageing. The causes for ageing are enumerated and the mechanisms which contribute to the promotion of ageing processes are detailed. The changes occurring in various organs of the body due to ageing are described at depth. Common diseases of old age are described; causes of death due to ageing are enumerated and explained.

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