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Endocrine & Reproductive Systems Chapter 19 & 27 Human Anatomy, 3rd edition Prentice Hall, © 2001 Introduction – The endocrine system consists of cells, tissues, & organs that secrete hormones into the blood – Hormone – an organic substance secreted by a cell that has an effect on the metabolic activity of another cell or tissue – Target cells – cells that are affected by the hormone • Have specific receptors for the hormones – Types of hormones • Steroid • Amino acid derivative • Peptide Human Anatomy, 3rd edition Prentice Hall, © 2001 How Hormones Work – Activation of 2nd messengers • Hormone (first messenger) binds to a receptor on the plasma membrane • Receptor/hormone complex activates another substance in the cell (2nd messenger) which then triggers the cell’s response – Activation of genes • Hormone crosses the cell membrane • Hormone binds to a receptor in the cytoplasm or the nucleus • Receptor/hormone complex binds to the DNA and alters gene activity Human Anatomy, 3rd edition Prentice Hall, © 2001 How Hormones Work Human Anatomy, 3rd edition Prentice Hall, © 2001 The Hypothalamus – Three methods of endocrine regulation • Sympathetic neurons control the adrenal medulla • Releases hormones – Antidiuretic hormone (ADH) – Oxytocin • Secretes regulatory hormones (regulatory factors) that control the anterior pituitary gland – Releasing factors – Inhibiting factors Human Anatomy, 3rd edition Prentice Hall, © 2001 Hypothalamic Regulation Human Anatomy, 3rd edition Prentice Hall, © 2001 Overview of the Endocrine System Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pituitary Gland – aka hypophysis = “growing below” • Located in sella turcica • Connected to the hypothalamus by the infundibulum – Master gland of the endocrine system – 2 parts • Posterior pituitary = Neurohypophysis – “Nervous part” • Anterior pituitary = adenohypophysis – Hypophyseal portal veins supply the anterior pituitary from the hypothalamus Human Anatomy, 3rd edition Prentice Hall, © 2001 Hypophyseal Portal System – Carries RFs and IFs from the hypothalamus to the anterior pituitary – 2 capillary beds connected by portal veins – Median eminence – neurons secrete regulatory factors • Diffuse into fenestrated capillaries – Portal veins connect to second capillary network in anterior pituitary • Releasing factors diffuse out, stimulate surrounding endocrine cells Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pituitary Gland Human Anatomy, 3rd edition Prentice Hall, © 2001 Posterior Pituitary Hormones – Neurohypophysis is nervous tissue • Cell bodies are in the hypothalamus – Make hormones • Axons run down the infundibulum – Carry hormones to axon terminals • Axon terminals are in the posterior pituitary – Store hormones – Produces 2 hormones • Antidiuretic hormone (ADH) – Target – kidneys – Effect – reabsorption of water • Oxytocin – Targets – reproductive organs – Effects – contractions of smooth muscles (labor contractions, milk ejection; ductus deferens, prostate gland – ejaculations) Human Anatomy, 3rd edition Prentice Hall, © 2001 Anterior Pituitary Hormones – Gonadotropins stimulate growth & development of gonads • Follicle stimulating hormone (FSH) stimulates gametes – Targets – follicle cells (females), testes (males) – Effects – follicle development & estrogen secretion (females), sperm maturation (males) • Luteinizing hormone (LH) – Targets – follicle cells (females), interstitial cells of testes (males) – Effects – ovulation, formation of corpus luteum, secretion of progesterone (females), testosterone secretion (males) Human Anatomy, 3rd edition Prentice Hall, © 2001 Anterior Pituitary Hormones – Thyroid stimulating hormone (TSH) • Target – thyroid gland • Effect – triggers the release of thyroid hormones – Adrenocorticotropic hormone (ACTH) • Target – adrenal cortex • Effect – cells that produce steroid hormones called glucocorticoids Human Anatomy, 3rd edition Prentice Hall, © 2001 Anterior Pituitary Hormones – Prolactin • Target - breast • Effect - stimulates milk production – Growth hormone • Target – all cells • Effect - stimulates growth in general and the skeletal system in particular – Melanocyte stimulating hormone (MSH) • Target - melanocytes • Effect – increases melanin production and distribution Human Anatomy, 3rd edition Prentice Hall, © 2001 Pituitary Hormones Human Anatomy, 3rd edition Prentice Hall, © 2001 The Thyroid Gland – Location – inferior to thyroid cartilage – Thyroid follicles • Follicle cells make thyroglobulin (contains tyrosine) & absorb iodine from the interstitial fluid • Tyrosine + iodine makes thyroxine (T4) or triiodothyronine (T3) • Target cells – most cells • Effect of thyroid hormones – increase energy utilization, oxygen consumption, growth, development • Thyroid hormone release is controlled by TSH from the anterior pituitary – Structure also includes C cells • Produce calcitonin (CT) • Targets – bone, kidneys • Effect of calcitonin – lowers blood calcium levels Human Anatomy, 3rd edition Prentice Hall, © 2001 The Thyroid Gland Human Anatomy, 3rd edition Prentice Hall, © 2001 Thyroid Follicles and C Cells Human Anatomy, 3rd edition Prentice Hall, © 2001 Control of Thyroid Hormones Human Anatomy, 3rd edition Prentice Hall, © 2001 The Parathyroid Glands – Location – posterior surfaces of the thyroid gland – Principal cells (chief cells) produce parathyroid hormone (PTH) – Target cells – bone, kidneys, intestines – Effect of PTH – increases blood calcium levels Human Anatomy, 3rd edition Prentice Hall, © 2001 The Parathyroid Glands Human Anatomy, 3rd edition Prentice Hall, © 2001 The Thymus – Location – posterior to the sternum – Produces thymosins which enhance lymphycyte production – Development • Childhood – large • Puberty – largest • Adulthood – decreases in size Human Anatomy, 3rd edition Prentice Hall, © 2001 The Thymus Gland Human Anatomy, 3rd edition Prentice Hall, © 2001 The Adrenal Gland – Location – on top of the kidney – Structure – outer cortex and inner medulla – Medulla • Secretes epinephrine & norepinephrine • Target – most cells • Effect – Epinephrine – increase cardiac activity, blood pressure, blood glucose; constricts blood vessels in skin, dilates blood vessels in skeletal & cardiac muscle – Norepinephrine – increases cardiac activity, constricts most blood vessels Human Anatomy, 3rd edition Prentice Hall, © 2001 The Adrenal Glands – The adrenal cortex is composed of 3 layers • Zona glomerulosa secretes mineralocorticoids, mostly aldosterone – Target – kidneys – Effect – increases blood sodium levels, decreases blood potassium levels • Zona fasciculata – secretes glucocorticoids (cortisol, corticosterone) – Target – most cells – Effect – conserve blood glucose, anti-inflammatory effects – Controlled by ACTH • Zona reticulares – secretes androgens – Effects are uncertain Human Anatomy, 3rd edition Prentice Hall, © 2001 The Adrenal Glands Human Anatomy, 3rd edition Prentice Hall, © 2001 The Adrenal Glands Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pancreas – Location – between the spleen and the duodenum – Its functions are both exocrine and endocrine – The endocrine cells are in the Islets of Langerhans • Alpha cells secrete glucagon – Targets – liver, adipose tissues – Effect - increase blood sugar levels • Beta cells secrete insulin – Most cells – Effect - decrease blood sugar levels • Delta cells secrete somatostatin – Targets – alpha & beta cells, digestive epithelium – Effect - antagonistic to growth hormone – Diabetes mellitis Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pancreas Human Anatomy, 3rd edition Prentice Hall, © 2001 Islet of Langerhans Human Anatomy, 3rd edition Prentice Hall, © 2001 The Male Reproductive System – Sperm are produced in the seminiferous tubules of the testes (spermatogenesis) – Sperm are stored in the epidymus, then transported through the vas deferens, and leave the body through the urethra – Seminal fluids (semen) are added to the sperm by the seminal vesicles, prostate gland, and bulbourethral gland Human Anatomy, 3rd edition Prentice Hall, © 2001 The Male Reproductive System Human Anatomy, 3rd edition Prentice Hall, © 2001 Testes – Interstitial cells secrete androgens (male sex hormones); testosterone is the most important • Target – most cells • Effects – maturation of sperm; protein synthesis in skeletal muscle; male secondary sex characteristics & behaviors – Some interstitial cells secrete inhibin • Target – anterior pituitary • Effect – inhibits the secretion of FSH Human Anatomy, 3rd edition Prentice Hall, © 2001 The Testes Human Anatomy, 3rd edition Prentice Hall, © 2001 Seminiferous Tubules Human Anatomy, 3rd edition Prentice Hall, © 2001 Seminiferous Tubule Human Anatomy, 3rd edition Prentice Hall, © 2001 The Female Reproductive System – Ova (oocytes) are produced in the ovaries (oogenesis) – Approximately every 28 days one ovum is expelled from the ovary (ovulation) – An ovum transported through the fallopian tube to the uterus where it becomes embedded in the uterine lining • Fertilization occurs in the fallopian tube – If the egg is not fertilized, the uterine lining detaches and is shed in menstruation – If the egg is fertilized, the uterine lining is held in place and supported by progesterone Human Anatomy, 3rd edition Prentice Hall, © 2001 The Female Reproductive System Human Anatomy, 3rd edition Prentice Hall, © 2001 Ovaries – Follicle cells secrete estrogen • Targets – most cells • Effects – follicle maturation; female secondary sex characteristics and behaviors – Follicle cells also secrete inhibin • Target – anterior pituitary • Effect – inhibits secretion of FSH – Corpus luteum secretes progesterone and relaxin • Progesterone – Targets – uterus, mammary glands – Effects – prepare uterus for implantation and mammary glands for secretion • Relaxin – Targets – pubic symphysis, uterus, mammary glands – Effects – loosens pubic symphysis, relaxes cervical muscles, stimulates mammary gland development Human Anatomy, 3rd edition Prentice Hall, © 2001 Hormonal Regulation of the Female Reproductive System Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pineal Gland – Location = epithalamus – Pinealocytes secrete melatonin • Derived from the neurotransmitter seratonin • Light inhibits production – Regulates circadian rythms • Target – hypothalamus • Effects – Inhibits the releasing factors that control FSH & LH secretion – Slows maturation of sperm, oocytes, & reproductive organs Human Anatomy, 3rd edition Prentice Hall, © 2001 Endocrine Disorders Human Anatomy, 3rd edition Prentice Hall, © 2001