Chapter 19 ENDOCRINE SYSTEM Compare the basic organization and function of the ES and the NS Describe the structural and functional organization of the hypothalamus and the pituitary and explain their relationship Discuss the locations and structures of the thyroid, parathyroid, and adrenal glands as well as the thymus and the endocrine part of the pancreas. List the hormones (and their function) produced by these glands. Briefly review the results of abnormal hormone production

Endocrine System Overview Ductless glands produce hormones Gland may be entire organ or interspersed bits of tissue Chemical classification of hormones Target tissues are identified by receptors

Hypothalamus Control Center for internal environment Regulates nervous and endocrine systems via 3 mechanisms: ANS centers exert nervous control on adrenal medulla ADH and Oxytocin production Regulatory hormone production (RH and IH) controls pituitary gland directly and all other endocrine glands indirectly Fig 19-3

Pituitary Gland (= Hypophysis) Structure: Infundibulum - connection to hypothalamus In the sella turcica Two parts with an embryonic double origin Posterior Pituitary = neurohypophysis Storage shed for ADH and Oxytocin (produced in ?) Anterior Pituitary = adenohypophysis production of 7 peptide hormones, see fig 19.5 Histology Fig 19-4

Hypophyseal Portal System Portal systems: two capillary networks in serial arrangement Advantage? Named after their destination: . . . Portal veins: blood vessels that link two capillary networks effect that RHs and IHs released from the hypothalamus go immediately without dilution to their target. Fig 19-6

Fig 19-7 Thyroid Gland Anterior surface of trachea just inferior of thyroid cartilage (or Adam’s apple) Two lobes connected by isthmus Microscopic thyroid follicles produce thyroid hormone C Cells - produce calcitonin (Ca2+)

Thyroid Gland Function Thyroxin (T4) and triiodothyronine (T3)  speed up metabolic rate Calcitonin  lowers blood Ca2+ levels Thyroid pathologies: Hyper- and Hypothyroidism Goiter Exophthalmus

Hypothyroidism Hyperthyroidism Slowing of mind and body

Four Parathyroid Glands 4 tiny glands embedded in the back of the thyroid (superior and inferior) Parathyroid hormone (PTH; sometimes also called parathormone) Function: antagonist to Calcitonin Fig 19-9

Thymus Gland Inside thoracic cavity immediately posterior to sternum above the heart Most active in infancy and childhood - Largest just before puberty Thymosin - enhances lymphocyte production and competence. (important for immune system)

Adrenal or Suprarenal Gland Cortex: corticosteroid production aldosterone, cortisol, sexhormone Medulla: modified sympathetic ganglion produces adrenaline and noradrenaline (parallels sympathetic division of ANS) Histology Fig 19-10

Pancreas The End Pancreatic islets or islets of Langerhans Part of endocrine and digestive systems. (99% exocrine) Pancreatic islets or islets of Langerhans  cells: glucagon ( blood sugar levels by stimulating liver to convert glycogen to glucose)  cells: insulin ( blood sugar levels by causing the cells to take up glucose for use by the mitochondria)  cells: somatostatin The End