Ch 18 Lecture Presentation (Pituitary Gland) PDF

18-3 The Pituitary Gland  Pituitary gland (hypophysis) – Lies within sella turcica Sellar diaphragm isolates pituitary gland from cranial cavity – Hangs inferior to hypothalamus Connected by infundibulum – Releases nine i...

18-3 The Pituitary Gland  Pituitary gland (hypophysis) – Lies within sella turcica Sellar diaphragm isolates pituitary gland from cranial cavity – Hangs inferior to hypothalamus Connected by infundibulum – Releases nine important peptide hormones Bind to extracellular receptors Use cAMP as second messenger 1 © 2018 Pearson Education, Inc. Figure 18–5a The Orientation and Anatomy of the Pituitary Gland. Third Mammillary ventricle body Hypothalamus e e nc in em Optic chiasm dian Infundibulum Me Sellar diaphragm Anterior Pituitary Lobe Pars tuberalis Pars distalis Posterior pituitary Pars intermedia lobe Sphenoid (sella turcica) a Relationship of the pituitary gland to the hypothalamus 2 Figure 18–5b The Orientation and Anatomy of the Pituitary Gland. Anterior Pituitary Lobe Posterior pituitary Pars Pars lobe distalis intermedia Secretes other Secretes Releases pituitary MSH ADH and hormones OXT Pituitary gland LM × 77 b Histology of the pituitary gland showing the anterior and posterior lobes 3  18-3 The Pituitary Gland  The hypothalamus – Regulates functions of the pituitary gland – Synthesizes ADH and OXT and transports them to posterior pituitary gland for release – Secretes regulatory hormones that control secretory activity of anterior pituitary gland – Contains autonomic centers that exert direct control over adrenal medulla 4 © 2018 Pearson Education, Inc. Figure 18–6 Three Mechanisms of Hypothalamic Control over Endocrine Function. Production of Secretion of regulatory Control of antidiuretic hormones to control sympathetic hormone (ADH) activity of the anterior output to adrenal and oxytocin (OXT) lobe of the pituitary gland medulla HYPOTHALAMUS Preganglionic motor fibers Adrenal Gland Infundibulum Adrenal cortex Adrenal medulla Anterior lobe Posterior lobe of pituitary gland of pituitary gland Hormones secreted by Release of antidiuretic Secretion of epinephrine (E) the anterior lobe control hormone (ADH) and oxytocin and norepinephrine (NE) other endocrine organs (OXT) from posterior lobe from adrenal medulla 5  18-3 The Pituitary Gland  Anterior lobe of pituitary gland – Also called adenohypophysis Hormones “turn on” endocrine glands or support functions of other organs Has three regions – Pars distalis – Pars tuberalis – Pars intermedia 6 © 2018 Pearson Education, Inc.  18-3 The Pituitary Gland  Median eminence – Swelling near attachment of infundibulum – Where hypothalamic neurons release regulatory hormones into interstitial fluids Hormones then enter bloodstream through fenestrated capillaries (fenestra = window) 7 © 2018 Pearson Education, Inc.  18-3 The Pituitary Gland  Portal vessels – Blood vessels that link two capillary networks – Entire complex is a portal system – Hypophyseal portal system Ensures that regulatory hormones reach cells in anterior pituitary before entering general circulation 8 © 2018 Pearson Education, Inc. Figure 18–7 The Hypophyseal Portal System and the Blood Supply to the Pituitary Gland. Supra-optic nuclei Paraventricular nuclei Neurosecretory neurons Mammillary body The superior hypophyseal artery delivers Optic blood to a capillary network in the upper chiasm infundibulum. Capillary network Infundibulum The portal vessels deliver blood containing regulatory hormones to the capillary network in the anterior lobe of the pituitary. Anterior lobe of the pituitary gland Capillary network in The inferior hypophyseal artery delivers the anterior lobe blood to the posterior lobe of the pituitary Posterior lobe of gland. the pituitary gland Endocrine cells Hypophyseal veins carry blood containing the pituitary hormones to the cardiovascular system for delivery to the rest of the body. 9  18-3 The Pituitary Gland  Hypothalamic control of anterior lobe – Two classes of hypothalamic regulatory hormones Releasing hormones (RH) – Stimulate synthesis and secretion of one or more hormones at anterior lobe Inhibiting hormones (IH) – Prevent synthesis and secretion of hormones from anterior lobe – Rate of secretion is controlled by negative feedback 10 © 2018 Pearson Education, Inc. Figure 18–8a Feedback Control of Endocrine Secretion. Typical pattern of regulation when multiple endocrine organs are involved a The hypothalamus produces a releasing hormone (RH) to stimulate hormone production by other glands. Homeostatic control occurs by negative feedback. Stimulation KEY Hypothalamus Inhibition The effects of hypothalamic releasing hormones that follow the typical pattern of regulation RH Releasing TRH CRH GnRH hormone (RH) Pituitary gland Anterior lobe Negative feedback Hormone 1 Hormone 1 (from pituitary) TSH ACTH FSH LH Endocrine Endocrine Thyroid Adrenal Testes Ovaries Testes Ovaries organ target organ gland cortex Hormone 2 Hormone 2 Thyroid Inhibin Progesterone (from endocrine hormones Glucocorticoids Inhibin Estrogens Androgens Estrogens target organ) Target cells 11  18-3 The Pituitary Gland  Hormones of anterior lobe – Thyroid-stimulating hormone (TSH) – Adrenocorticotropic hormone (ACTH) Released due to corticotropin-releasing hormone (CRH) – Prolactin (PRL) Release inhibited by prolactin-inhibiting hormone (PIH) Release stimulated by prolactin-releasing hormone (PRH) – Growth hormone (GH), or somatotropin – Gonadotropins 12 © 2018 Pearson Education, Inc.  18-3 The Pituitary Gland  Gonadotropins – Follicle-stimulating hormone (FSH) – Luteinizing hormone (LH) In females, it induces ovulation and stimulates secretion of estrogens and progesterone In males, it stimulates production of androgens – Production of FSH and LH is stimulated by gonadotropin-releasing hormone (GnRH) – Hypogonadism Caused by low production of gonadotropins 13 © 2018 Pearson Education, Inc. Figure 18–9 Pituitary Hormones and Their Targets (Part 1 of 2). Hypothalamus KEY TO PITUITARY HORMONES: Direct Control Indirect Control through Release ACTH Adrenocorticotropic hormone by Nervous of Regulatory Hormones TSH Thyroid-stimulating hormone System GH Growth hormone Regulatory hormones are released into the hypophyseal portal system PRL Prolactin for delivery to the anterior lobe of the FSH Follicle-stimulating hormone pituitary gland LH Luteinizing hormone MSH Melanocyte-stimulating hormone ADH Antidiuretic hormone OXT Oxytocin Anterior lobe of Adrenal pituitary gland medulla Adrenal ACTH gland Adrenal GH cortex TSH Epinephrine and Liver MSH Thyroid norepinephrine PRL FSH LH gland Somatomedins Glucocorticoids (cortisol, Melanocytes (uncertain corticosterone) significance in healthy adults) Bone, muscle, Ovaries Testes of female other tissues Mammary of male glands Thyroid hormones (T3, T4) Inhibin Testosterone Estrogen Progesterone Inhibin 14 Figure 18–8a Feedback Control of Endocrine Secretion. 15 Figure 18–8b Feedback Control of Endocrine Secretion. Variations on the typical pattern of regulation of endocrine organs by the hypothalamus and anterior pituitary lobe b The regulation of prolactin (PRL) production by the anterior lobe. Stimulation In this case, the PIH hypothalamus Inhibition PRH produces both a releasing hormone (PRH) and an inhibiting hormone (PIH). When one is Anterior stimulated, the lobe other is inhibited. PRL Stimulates mammary glands 16  18-3 The Pituitary Gland  Growth hormone stimulates – Liver cells to release somatomedins that stimulate tissue growth Somatomedins cause skeletal muscle fibers and other cells to increase uptake of amino acids – Stem cells in epithelia and connective tissues to divide – Breakdown of triglycerides in adipocytes, which leads to glucose-sparing effect – Breakdown of glycogen by liver cells causing diabetogenic effect 17 © 2018 Pearson Education, Inc.  18-3 The Pituitary Gland  Production of growth hormone is regulated by – Growth hormone–releasing hormone (GH–RH) – Growth hormone–inhibiting hormone (GH–IH) 18 © 2018 Pearson Education, Inc. Figure 18–8c Feedback Control of Endocrine Secretion. Variations on the typical pattern of regulation of endocrine organs by the hypothalamus and anterior pituitary lobe c The regulation of growth hormone (GH) production by the anterior lobe. When GH–RH release is Stimulation inhibited, GH–IH release GH–IH is stimulated. GH–RH Inhibition Anterior lobe Epithelia, GH adipose tissue, liver Liver Somatomedins Stimulate growth of skeletal muscle, cartilage, and many other tissues 19  18-3 The Pituitary Gland  Pars intermedia – Secretes melanocyte-stimulating hormone (MSH) Stimulates melanin production – Virtually nonfunctional in adults except in Pregnant women Those with certain diseases 20 © 2018 Pearson Education, Inc.  18-3 The Pituitary Gland  Posterior lobe of the pituitary gland – Also called neurohypophysis – Contains unmyelinated axons of hypothalamic neurons – Supra-optic and paraventricular nuclei manufacture (respectively) Antidiuretic hormone (ADH) Oxytocin (OXT) – Stimulates contraction of uterus during labor – Promotes ejection of milk after delivery 21 © 2018 Pearson Education, Inc. Figure 18–9 Pituitary Hormones and Their Targets (Part 2 of 2). Hypothalamus KEY TO PITUITARY HORMONES: Direct Release ACTH Adrenocorticotropic hormone of Hormones TSH Thyroid-stimulating hormone Sensory Osmoreceptor GH Growth hormone stimulation stimulation PRL Prolactin FSH Follicle-stimulating hormone LH Luteinizing hormone MSH Melanocyte-stimulating hormone ADH Antidiuretic hormone OXT Oxytocin Posterior lobe of pituitary gland ADH Kidneys OXT Males: Smooth muscle in ductus deferens and prostate gland Females: Uterine smooth muscle and mammary glands 22 Figure 18–9 Pituitary Hormones and Their Targets. Hypothalamus KEY TO PITUITARY HORMONES: Direct Control Indirect Control through Release Direct Release ACTH Adrenocorticotropic hormone by Nervous of Regulatory Hormones of Hormones TSH Thyroid-stimulating hormone System Regulatory hormones are released Sensory Osmoreceptor GH Growth hormone into the hypophyseal portal system stimulation stimulation PRL Prolactin for delivery to the anterior lobe of the FSH Follicle-stimulating hormone pituitary gland LH Luteinizing hormone MSH Melanocyte-stimulating hormone ADH Antidiuretic hormone OXT Oxytocin Posterior lobe Anterior lobe of of pituitary gland Adrenal pituitary gland medulla ADH Adrenal ACTH gland Adrenal TSH GH Kidneys cortex OXT Males: Smooth Epinephrine and Liver MSH muscle in ductus Thyroid norepinephrine PRL FSH LH deferens and gland Somatomedins prostate gland Females: Uterine smooth muscle and mammary glands Glucocorticoids (cortisol, Melanocytes (uncertain corticosterone) significance in healthy adults) Bone, muscle, Ovaries Testes of female other tissues Mammary of male glands Thyroid hormones (T3, T4) Inhibin Testosterone Estrogen Progesterone Inhibin 23  18-4 The Thyroid Gland  Thyroid gland – Lies inferior to thyroid cartilage of larynx – Consists of two lobes connected by narrow isthmus Thyroid follicles – Hollow spheres lined by cuboidal epithelium – Surrounded by capillaries – Cells absorb iodide ions (I–) from blood – Follicle cavity contains viscous colloid C (clear) cells, or parafollicular cells 24 © 2018 Pearson Education, Inc. Figure 18–10a Anatomy of the Thyroid Gland. Hyoid bone Superior thyroid artery Thyroid cartilage of larynx Internal jugular vein Superior thyroid vein Cricoid cartilage Common of larynx carotid artery Left lobe of Right lobe of thyroid gland thyroid gland Isthmus of thyroid gland Middle thyroid vein Inferior thyroid artery Thyrocervical trunk Inferior thyroid Trachea veins Outline of clavicle Outline of sternum a Location and anatomy of the thyroid gland 25 Figure 18–10b Anatomy of the Thyroid Gland. Thyroid follicles The thyroid gland LM × 122 b Histological organization of the thyroid 26 Figure 18–10c Anatomy of the Thyroid Gland. Capillary Capsule C cell Cuboidal epithelium Follicle of follicle cavities Thyroid follicle Thyroid Thyroglobulin follicle stored in colloid of follicle C cell Follicles of the thyroid gland LM × 260 c Histological details of the thyroid gland showing thyroid follicles and both cell types in the follicular epithelium ATLAS: Plate 18c 27  18-4 The Thyroid Gland  Thyroglobulin – Globular protein synthesized by follicle cells – Secreted into colloid of thyroid follicles – Contains the amino acid tyrosine The building block of thyroid hormones  Thyroid hormones – Thyroxine (T4), or tetraiodothyronine Contains four iodine atoms – Triiodothyronine (T3) Contains three iodine atoms 28 © 2018 Pearson Education, Inc. Figure 18–11a Synthesis and Regulation of Thyroid Hormones. 1 Iodide ions are absorbed from the digestive tract and 3 Thyroglobulin delivered to the thyroid gland by the bloodstream. Follicle (contains T3 and T4) Follicle cavity cavity 2 4 Endocytosis Iodide ions diffuse to the apical surface of each follicle cell where they are converted into an atom of iodine (I0). The 2 Thyroglobulin tyrosine portion of thyroglobulin bind the iodine atoms. Iodine 5 Lysosomal 3 atoms (I0) Other amino acids digestion Iodine-containing thyroxine molecules become linked to Tyrosine form thyroid hormones (T3 and T4) T4 T3 4 Diffusion Follicle cells remove thyroglobulin from the follicles by endocytosis. TSH- Diffusion 6 5 sensitive Lysosomal enzymes break down the thyroglobulin, and the ion pump Follicle cell amino acids and thyroid hormones enter the cytoplasm. 1 7 6 CAPILLARY The released T3 and T4 diffuse from the follicle cell into the bloodstream. Iodide ions (I–) 7 TBG, transthyretin, A majority of the T3 and T4 bind to transport proteins. T4 & T3 or albumin a The synthesis, storage, and secretion of thyroid hormones. 29 Figure 18–11b Synthesis and Regulation of Thyroid Hormones. HOMEOSTASIS Homeostasis Normal T3 and T4 concentrations, Homeostasis DISTURBED BY normal body temperature RESTORED BY DECREASING STIMULUS RESTORED INCREASING T3 and T4 T3 and concentrations Receptor Anterior lobe T3 and T4 T4 concentrations in blood or low concentrations increase in blood body temperature in blood and body Hypothalamus temperature rises TRH Effector Anterior Anterior lobe lobe Thyroid gland TSH Hypothalamus Anterior lobe Thyroid follicles releases TRH releases TSH release T3 and T4 b The regulation of thyroid secretion. 30  18-4 The Thyroid Gland  Thyroid-binding globulins (TBGs) – Proteins that bind about 75 percent of T4 and 70 percent of T3 entering the bloodstream  Transthyretin and albumin – Bind most of the remaining thyroid hormones  About 0.3 percent of T3 and 0.03 percent of T4 remain unbound and free to diffuse into tissues 31 © 2018 Pearson Education, Inc.  18-4 The Thyroid Gland  Thyroid-stimulating hormone (TSH) – Absence causes thyroid follicles to become inactive Neither synthesis nor secretion occurs – Binds to plasma membrane receptors Activates key enzymes in thyroid hormone production 32 © 2018 Pearson Education, Inc.  18-4 The Thyroid Gland  Thyroid hormones – Affect almost every cell in body – Enter target cells by transport system – Bind to receptors In cytoplasm On surfaces of mitochondria In nucleus – In children, essential to normal development of skeletal, muscular, and nervous systems 33 © 2018 Pearson Education, Inc.  18-4 The Thyroid Gland  Thyroid hormones activate genes involved in glycolysis and ATP production – Results in calorigenic effect Increased energy consumption and heat generation of cells Responsible for strong, immediate, and short-lived increase in rate of cellular metabolism 34 © 2018 Pearson Education, Inc.  18-4 The Thyroid Gland  C cells – Produce calcitonin (CT) Helps regulate concentrations of Ca2+ in body fluids Stimulates Ca2+ excretion by kidneys Prevents Ca2+ absorption by digestive tract 35 © 2018 Pearson Education, Inc.  18-4 The Thyroid Gland  Effects of thyroid hormones – Elevate oxygen and energy consumption; in children, may cause rise in body temperature – Increase heart rate and force of contraction – Increase sensitivity to sympathetic stimulation – Maintain normal sensitivity of respiratory centers to oxygen and carbon dioxide concentrations – Stimulate red blood cell formation – Stimulate activity in other endocrine tissues – Accelerate turnover of minerals in bone 36 © 2018 Pearson Education, Inc.