Endocrine system


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Endocrine system

  1. 2. <ul><li>Water balance </li></ul><ul><li>Uterine contractions and milk release </li></ul><ul><li>Growth, metabolism, and tissue maturation </li></ul><ul><li>Ion regulation </li></ul><ul><li>Heart rate and blood pressure regulation </li></ul><ul><li>Blood glucose control </li></ul><ul><li>Immune system regulation </li></ul><ul><li>Reproductive functions control </li></ul>
  2. 3. <ul><ul><li>Are molecules released from one location that move to another location to produce a response. </li></ul></ul><ul><li>Intracellular chemical signals </li></ul><ul><ul><li>Are produced in one part of a cell (cell membrane) and travel to another part of the same cell and bind to receptors (cytoplasm or nucleus). </li></ul></ul><ul><li>Intercellular chemical signals </li></ul><ul><ul><li>Are released from one cell, are carried in the intercellular fluid, and bind to their receptors, which are found in some cells, but usually not all cells in the body. </li></ul></ul>
  3. 4. <ul><li>Autocrine chemical signals </li></ul><ul><ul><li>Are released by cells and have a local effect on the same cell type from which the chemical signals are released </li></ul></ul><ul><li>Paracrine chemical signals </li></ul><ul><ul><li>Released by cells that have effects on other cell types near the cells from which they are released, without being transported in blood </li></ul></ul><ul><li>Neuromodulators and neurotransmitters </li></ul><ul><ul><li>Are intercellular chemical signals, secreted by nerve cells, which play important roles in the function of the nervous system </li></ul></ul><ul><li>Pheromones </li></ul><ul><ul><li>Are chemical signals secreted into the environment that modify the behavior and the physiology of other individuals. </li></ul></ul>
  4. 7. <ul><li>Receptors - are proteins or glycoproteins where in ligands bind to produce a response. </li></ul><ul><li>Receptor site – portion of each receptor molecule where a chemical signal binds. </li></ul><ul><li>Specificity – the tendency for each receptor site to bind to a specific chemical signal and not to others. </li></ul>
  5. 9. <ul><li>Membrane-bound receptors </li></ul><ul><ul><li>Extend through the cell membrane, with their receptor sites on the outer surface. </li></ul></ul><ul><ul><li>Respond to large water-soluble molecules that do not diffuse through the cell membrane. </li></ul></ul><ul><li>Intracellular receptors </li></ul><ul><ul><li>Located in either the cytoplasm or the nucleus. </li></ul></ul><ul><ul><li>Intercellular chemical signals diffuse through the cell membrane then bind to receptor sites on intracellular receptors. </li></ul></ul>
  6. 13. <ul><li>Receptors that directly alter membrane permeability </li></ul><ul><ul><li>Intercellular chemical signals bind to receptor sites, causing ion channels in the cell membrane to open or close. </li></ul></ul><ul><ul><li>The change in membrane permeability alters the movement of ions across the cell membrane, which is responsible for the cells response. </li></ul></ul>
  7. 16. <ul><li>Receptors and G Proteins </li></ul><ul><ul><li>Activation of a complex of proteins at the inner surface of the cell membrane called G proteins </li></ul></ul><ul><ul><li>The inactive G protein complex has alpha (α), beta (β), and gamma (γ) subunits. </li></ul></ul><ul><ul><li>Bound to the alpha (α) subunit is Guanosine diphosphate (GDP) </li></ul></ul><ul><ul><li>The binding of intercellular chemicals causes the conversion of Guanosine diphosphate (GDP) to Guanosine triphosphate (GTP). </li></ul></ul><ul><ul><li>The alpha (α) subunit with GTP bound to it can either </li></ul></ul><ul><ul><ul><li>Open or close membrane channels, to produce a response </li></ul></ul></ul><ul><ul><ul><li>Activate enzymes that produce intracellular chemical signals </li></ul></ul></ul><ul><ul><ul><li>Affect gene expression </li></ul></ul></ul>
  8. 19. <ul><li>Receptors that directly alter the activity of enzymes </li></ul><ul><ul><li>Some intercellular chemical signals bind to receptor sites and directly increase or decrease the activity of enzymes </li></ul></ul>
  9. 24. <ul><li>Membrane-bound receptor responses </li></ul><ul><ul><li>Produce rapid responses  cascade effect </li></ul></ul><ul><li>Intracellular receptor responses </li></ul><ul><ul><li>Several hours </li></ul></ul>
  10. 27. <ul><li>Derived from the Greek word endo and krino meaning “within” and “to separate” </li></ul><ul><li>The word implies that intercellular chemical signals are produced within and secreted from endocrine glands, but the chemical signals have effects at locations that are away from, or separate from, the endocrine glands that secreted them. </li></ul>
  11. 28. <ul><li>Intercellular chemical signals secreted by the endocrine system. </li></ul><ul><li>Derived from the Greek word hormon meaning “set into motion” </li></ul><ul><li>Defined as an intercellular chemical signal, produced in minute amounts by a collection of cells, that is secreted into the interstitial fluid and enters the circulatory system to be transported some distance, and that acts on tissue at another site in the body to influence their activity in a specific way. </li></ul><ul><li>Target tissue – are certain tissues that respond to each type of hormone and are made up of cells that have receptor molecules for the hormone. </li></ul>
  12. 31. <ul><li>Proteins </li></ul><ul><ul><li>Amino acids bound together by peptide bonds </li></ul></ul><ul><ul><li>Carbohydrate molecules are bound to some of the protein hormones. </li></ul></ul><ul><ul><li>Hormones of the anterior pituitary gland </li></ul></ul><ul><li>Peptide hormones </li></ul><ul><ul><li>Short chains of amino acids </li></ul></ul><ul><ul><li>Hormones of the posterior pituitary gland </li></ul></ul><ul><li>Amino Acids </li></ul><ul><ul><li>Consist of single amino acids that have been chemically modified. </li></ul></ul><ul><ul><li>Hormones secreted by the adrenal medulla </li></ul></ul>
  13. 32. <ul><li>Steroid Hormones </li></ul><ul><ul><li>Derived from cholesterol </li></ul></ul><ul><ul><li>Produces mostly by the adrenal cortex and the gonads </li></ul></ul><ul><ul><li>Diffuse across the cell membrane </li></ul></ul><ul><li>Eicosanoids </li></ul><ul><ul><li>Make up a class of chemicals derived from the fatty acid arachidonic acid. </li></ul></ul><ul><ul><li>Include prostaglandins, thromboxanes, prostacyclins, and leukotrienes </li></ul></ul>
  14. 33. <ul><ul><li>Controlled by negative feedback </li></ul></ul><ul><li>Blood Levels of Chemicals </li></ul><ul><li>Hormones </li></ul><ul><li>Nervous system </li></ul>
  15. 36. <ul><li>Is also called the hypophysis </li></ul><ul><li>Small gland about the size of a pea </li></ul><ul><li>Rests in the depression of the sphenoid bone inferior to the hypothalamus </li></ul><ul><li>Anterior pituitary is made up of epithelial cells derived from the embryonic oral cavity </li></ul><ul><li>Posterior pituitary is an extension of the brain and is made up of nerve cells. </li></ul><ul><li>“ Master Gland” </li></ul>
  16. 39. <ul><li>Endocrine control center of the brain located inferior to the thalamus </li></ul><ul><li>The pituitary gland is controlled in 2 ways by the Hypothalamus: </li></ul><ul><ul><li>Neurohormones, produced and secreted by neurons of the hypothalamus, act on cells of the anterior pituitary gland. </li></ul></ul><ul><ul><li>Secretion of hormones from the posterior pituitary is controlled by nervous system stimulation of nerve cells within the hypothalamus. </li></ul></ul>
  17. 43. <ul><li>Stimulates the growth of bones, muscles, and other organs by increasing protein synthesis </li></ul><ul><li>Resists protein breakdown during periods of food deprivation and favors fat breakdown. </li></ul><ul><li>The secretion of growth hormone is controlled by 2 hormones from the hypothalamus (releasing hormone and inhibiting hormone) </li></ul><ul><li>Daily peak levels of GH occur during sleep and also increase during periods of fasting and exercise </li></ul><ul><li>In addition to GH, genetics, nutrition and sex hormones influence growth </li></ul>
  18. 44. <ul><li>GIANTISM </li></ul><ul><li>Excess growth hormone is present before bones complete their growth in length therefore exaggerated bone growth occurs. </li></ul><ul><li>DWARFISM </li></ul><ul><li>Result from decrease GH secretion during childhood </li></ul><ul><li>The features of the body develop in appropriate proportion to one another, but the rate of development is greatly decreased. </li></ul>
  19. 46. <ul><li>ACROMEGALY </li></ul><ul><li>Excess GH is secreted after growth in bone length is complete, growth in bone diameter, but not in length, continues </li></ul><ul><li>Enlargement is especially marked in bones of the hands and feet, cranium, noses, bosses of the forehead, supraorbital ridges, lower jawbone, and portions of the vertebrae. </li></ul><ul><li>The lower jaw protrudes forward, the forehead slants forward, the nose increase to as much as twice normal size, the feet requires size 14 or larger shoes, and the fingers become extremely thickened so that the hands develop a size almost twice normal </li></ul><ul><li>Develop kyphosis (hunched back). </li></ul>
  20. 48. <ul><li>Binds to membrane-bound receptors on cells of the thyroid gland and cause the cells to secrete thyroid hormone </li></ul><ul><li>The rate of TSH secretion is increased by a releasing hormone from the hypothalamus. </li></ul>
  21. 49. <ul><li>Binds to membrane-bound receptors on cells in the cortex of the adrenal glands. </li></ul><ul><li>Increases the secretion of a hormone from the adrenal cortex called Cortisol also called Hydrocortisone . </li></ul><ul><li>Required to keep the adrenal cortex from degenerating </li></ul><ul><li>Also bind to melanocytes in the skin and increases skin pigmentation. </li></ul><ul><li>The rate of ACTH is increased by a releasing hormone from the hypothalamus. </li></ul>
  22. 50. <ul><li>Bind to membrane-bound receptors on the cells of the gonads </li></ul><ul><li>Regulate the growth, development, and functions of the gonads </li></ul><ul><li>Luteinizing Hormone (LH) </li></ul><ul><ul><li>In females causes ovulation of the oocytes and the secretion of the sex hormones estrogen and progesterone from the ovaries </li></ul></ul><ul><ul><li>In males, stimulates the secretion of sex hormone testosterone from the testes. It is sometimes referred to as Interstitial Cell-Stimulating Hormone (ICSH) because it stimulates interstitial cells of the testes to secrete testosterone. </li></ul></ul><ul><li>Follicle-stimulating Hormone </li></ul><ul><ul><li>Stimulates the development of follicles in the ovaries and sperm cells in the testes. </li></ul></ul>
  23. 51. <ul><li>Binds to membrane-bound receptors in cells of the breast and helps promote development of the breast during pregnancy and stimulates the production of milk in the breast following pregnancy. </li></ul>
  24. 52. <ul><li>Binds to membrane-bound receptors on melanocytes and causes them to synthesize melanin. </li></ul>
  25. 54. <ul><li>Binds to membrane-bound receptors and increases water reabsorption by kidney tubules </li></ul><ul><li>Can also cause blood vessels to constrict when released in large amounts </li></ul><ul><li>Sometimes called vasopressin </li></ul><ul><li>Reduced ADH released from the posterior pituitary results in the formation of large amounts of dilute urine. </li></ul><ul><li>Lack of ADH secretion causes diabetes insipidus – production of a large amount of dilute urine therefore resulting in an increase in the osmolality of the body fluids and the loss of important electrolytes such as Ca2+, Na+, and K+ in the large urine volume. </li></ul>
  26. 55. <ul><li>Binds to membrane-bound receptors and causes contraction of the smooth muscle cells of the uterus and milk ejection, or milk “let-down,” from the breast in lactating women </li></ul>
  27. 57. <ul><li>Made up of 2 lobes connected by a narrow band called Isthmus located on either side of the trachea, just inferior to the larynx. </li></ul><ul><li>One of the largest endocrine glands and is highly vascularized </li></ul><ul><li>Thyroid follicles </li></ul><ul><ul><li>Small spheres with walls that consist of simple cuboidal epithelium </li></ul></ul><ul><ul><li>Filled with proteins to which thyroid hormones are attached </li></ul></ul><ul><ul><li>The cells synthesized thyroid hormones, which are stored in the follicles </li></ul></ul><ul><li>Parafollicular cells </li></ul><ul><ul><li>A network of loose connective tissue located between follicles that contains capillaries. </li></ul></ul>
  28. 61. <ul><li>Bind to intracellular receptors in cells and regulate the rate of metabolism in the body </li></ul><ul><li>Iodine is required to synthesize thyroid hormone and is taken up by the thyroid follicles in which synthesis occurs. </li></ul><ul><li>Thyroxine or tetraiodothyronine contains 4 iodine atoms  T4 </li></ul><ul><li>Triiodothyronine contains 3 iodine atoms  T3 </li></ul><ul><li>If the quantity of iodine is not sufficient, the production and secretion of the thyroid hormone decreases. </li></ul><ul><li>Thyroid hormones are stored in combination with a protein called thyroglobulin (located within the thyroid follicle) </li></ul><ul><li>Regulated by TSH from the anterior pituitary </li></ul><ul><li>Have a negative-feedback effect on the hypothalamus and pituitary. </li></ul>
  29. 63. <ul><li>From the parafollicular cells </li></ul><ul><li>Secreted if the blood concentration Ca+ becomes too high, and it causes Ca+ levels to decrease to their normal range </li></ul><ul><li>Bind to membrane-bound receptors of osteoclasts and reduces the rate of Ca+ resorption from bone by inhibiting them. </li></ul>
  30. 65. <ul><li>Results in an elevated rate of metabolism, extreme nervousness, and chronic fatigue </li></ul><ul><ul><li>Grave’s Disease – results from the production of abnormal proteins by the immune system that are similar in structure and function to TSH. Grave’s disease is often accompanied by exophthalmia. </li></ul></ul>
  31. 67. <ul><li>Lack of thyroid hormones </li></ul><ul><ul><li>Cretinism – hypothyroidism in infants where in the person is mentally retarded and has a short stature with abnormally formed skeletal structures </li></ul></ul><ul><ul><li>In adults, this would result in reduced rate of metabolism, sluggishness, a reduced ability to perform routine tasks, and myxedema which is the accumulation of fluid and other molecules in the subcutaneous tissue. </li></ul></ul>
  32. 70. <ul><li>Essential in the regulation of blood Ca levels. </li></ul><ul><li>Binds to membrane-bound receptors of renal tubules, which increases active vitamin D formation which in turn causes the epithelial cells of the intestine to increase Ca+ resorption. </li></ul><ul><li>Binds to receptors on osteoblasts which release substances that increase osteoclast activity and cause resorption of bone tissue to release Ca+ into the circulatory system </li></ul><ul><li>Binds to receptors on cells of the renal tubules and decreases the rate at which Ca+ are lost in urine </li></ul><ul><li>Acts on its target tissues to raise blood Ca+ levels to normal. </li></ul><ul><li>Increasing blood Ca+ levels cause a decrease in PTH secretion  results in a reduction in blood Ca+ levels </li></ul><ul><li>Increasing blood Ca+ levels stimulate calcitonin secretion, which also causes blood Ca+ levels to decline. </li></ul>
  33. 74. <ul><li>Can result from a tumor of a parathyroid gland </li></ul><ul><li>Elevated blood levels of PTH increase bone resorption and elevated blood Ca+ levels  soft, deformed, and easily fractured bone </li></ul><ul><li>Makes nerve muscle less excitable resulting in fatigue and muscle weakness </li></ul><ul><li>The excess Ca+ can be deposited in soft tissue of the body and kidney stones can result. </li></ul>
  34. 75. <ul><li>Result of injury or the surgical removal of the thyroid and parathyroid glands. </li></ul><ul><li>Decrease blood Ca+ levels  nerves and muscles become excitable and produce spontaneous action potential  frequent muscle cramps or tetanus  can affect the respiratory muscles: breathing stops, resulting in death. </li></ul>
  35. 76. <ul><li>Occurs mainly in children </li></ul><ul><li>Results from calcium or phosphate deficiency in the extracellular fluid, usually caused by lack of vitamin D </li></ul>
  36. 78. <ul><li>Rickets in adults  “Adult Rickets” </li></ul>
  37. 79. <ul><li>Results in diminished organic bone matrix </li></ul><ul><li>Causes: </li></ul><ul><ul><li>Lack of physical stress on the bones because of inactivity </li></ul></ul><ul><ul><li>Malnutrition to the extent that sufficient protein matrix cannot be formed </li></ul></ul><ul><ul><li>Lack of vitamin C </li></ul></ul><ul><ul><li>Postmenopausal lack of estrogen secretion </li></ul></ul><ul><ul><li>Old age </li></ul></ul><ul><ul><li>Cushing’s disease </li></ul></ul>
  38. 82. <ul><li>Epinephrine or adrenalin and small amounts of norephinephrine </li></ul><ul><li>Released in response to stimulation by the sympathetic nervous system, which becomes most active when a person is excited or physically active </li></ul><ul><li>Membrane-bound receptors in their target tissue </li></ul><ul><li>Stress and low blood glucose levels can also result in increased sympathetic stimulation of the adrenal medulla </li></ul><ul><li>Fight-or-flight hormones </li></ul>
  39. 84. <ul><ul><li>Increases in the breakdown of glycogen to glucose in the liver, the release of the glucose into the blood, and the release of fatty acids from fat cells. </li></ul></ul><ul><ul><li>Increase in heart rate, which causes blood pressure to increase </li></ul></ul><ul><ul><li>Stimulation of smooth muscle in the walls of the arteries supplying the internal organs and the skin, but not those supplying skeletal muscles. </li></ul></ul><ul><ul><li>Increase in blood pressure because of smooth muscle contraction in the walls of blood vessels in the internal organs and the skin. </li></ul></ul><ul><ul><li>Increase in the metabolic rate of several tissues, especially skeletal muscles, cardiac muscles, and nervous tissue. </li></ul></ul>
  40. 85. <ul><li>Secretes 3 classes of steroid hormones that enter their target cells and bind to intracellular receptor molecules </li></ul>
  41. 86. <ul><ul><ul><li>Help regulate blood nutrient levels in the body </li></ul></ul></ul><ul><li>Cortisol </li></ul><ul><ul><ul><ul><li>a major glucocorticoid increases the breakdown of protein and fat and increases their conversion to forms that can be used as energy sources by the body. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Cortisol reduces the inflammatory and immune responses. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Secreted in large amounts in response to stressful conditions. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Aids the body in responding to stressful conditions by providing energy sources for tissues. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>When blood glucose levels decline, cortisol secretion increases: low blood glucose acts on the hypothalamus  ↑secretion of ACTH-releasing hormone  stimulates ACTH secretion from the anterior pituitary  ACTH stimulates cortisol secretion </li></ul></ul></ul></ul><ul><li>ACTH molecules bind to membrane-bound receptors and regulate the secretion of cortisol from the adrenal cortex. </li></ul>
  42. 88. <ul><li>Help regulate blood volume and blood levels of K+ and Na+ </li></ul><ul><li>Aldosterone </li></ul><ul><ul><li>Binds to receptor molecules primarily in the kidney, but it also affects the intestine, sweat glands, and salivary glands. </li></ul></ul><ul><ul><li>Causes Na+ and H2O to be retained in the body and increase the rate at which K+ are eliminated. </li></ul></ul><ul><ul><li>The rate of aldosterone secretion increases when blood K+ levels increase or when blood Na+ levels decrease. </li></ul></ul>
  43. 90. <ul><li>Renin </li></ul><ul><ul><li>Protein molecule released from the kidneys when there is low blood pressure </li></ul></ul><ul><ul><li>Acts an enzyme that causes a blood protein angiotensinogen to converted to angiotensin I  angiotensin-converting enzyme  converted to angiotensin II which causes smooth muscle in blood vessels to constrict and acts on adrenal cortex to increase aldosterone secretion  causes retention of sodium and water which causes an increase in blood volume. </li></ul></ul>
  44. 91. <ul><li>Stimulate the development of male sexual characteristics </li></ul><ul><li>Secreted in both male and female </li></ul><ul><li>Male: secreted by the testes </li></ul><ul><li>Female: influence the female sex drive </li></ul>
  45. 93. <ul><li>Hypoadrenalism </li></ul><ul><li>Failure to produce adrenocortical hormones </li></ul><ul><li>Mineralocorticoid deficiency – decrease in renal tubular sodium  allowing sodium ions, chloride ions, and water to be lost into urine  great decrease in extracellular fluid volume. Hyponatremia, hyperkalemia, and mild acidosis develops because of failure of potassium and hydrogen ions to be secreted in exchange for sodium reabsorption  ↓in plasma volume  RBC concentration rises markedly  cardiac output decreases  patient dies in shock </li></ul>
  46. 94. <ul><li>Glucocorticoid deficiency – difficulty in maintaining normal blood glucose concentration between meals because he cannot synthesize significant quantities of glucose by gluconeogenesis. Lack of cortisol reduces the mobilization of both proteins and fats from the tissues, thereby depressing many other metabolic functions of the body. </li></ul><ul><li>Melanin pigmentation – melanin is deposited in blotches especially in thin skin areas such as the lips, and the thin skin of the nipples. </li></ul>
  47. 96. <ul><li>Hypersecretion of the adrenal cortex </li></ul><ul><li>Results from either a cortisol-secreting tumor of one adrenal cortex or general hyperplasia of both adrenal cortices  increase secretion of ACTH </li></ul><ul><li>Mobilization of fat from the lower part of the body, with concomitant extra deposition of fat in the thoracic and upper abdominal regions, giving rise to a buffalo torso. </li></ul><ul><li>Excess secretion of steroids  edematous appearance of the face </li></ul><ul><li>Androgenic potency of some of the hormones  acne and hairsutism </li></ul><ul><li>“ Moon Face ” </li></ul>
  48. 98. <ul><li>Pancreatic cells called islets of langerhans which secretes 2 hormones  insulin and glucagon  which function to help regulate blood nutrient levels especially blood glucose </li></ul><ul><li>Alpha cells  glucagon; beta cells  insulin </li></ul><ul><li>↓ blood glucose level  nervous system malfunction  fats and proteins are broken down rapidly by other tissues to provide an alternative source of energy  some of the fatty acids are converted by the liver to acidic ketones  released into the circulatory system  cause the pH of the body fluids to decrease below normal  acidosis </li></ul><ul><li>↑ blood glucose level  kidney produce large volumes of urine containing substantial amounts of glucose  dehydration </li></ul>
  49. 100. <ul><li>Released in response to the elevated blood glucose level and increased parasympathetic stimulation that is associated with digestion of a meal </li></ul><ul><li>Stimulated when there is an increase in blood levels of certain amino acids </li></ul><ul><li>↓ insulin secretion results from decreasing blood glucose levels and from stimulation by the sympathetic nervous system  occurs during physical activity  allows blood glucose to be conserved to provide the brain with adequate glucose and to allow other tissues to metabolize fatty acids and glycogen stored in the cells. </li></ul><ul><li>Major target tissue: liver, adipose tissue, muscles, area in the hypothalamus that controls appetite  satiety center </li></ul>
  50. 101. <ul><li>DM type I </li></ul><ul><ul><li>Secretion of too little insulin from the pancreas </li></ul></ul><ul><ul><li>Tissues cannot take up glucose effectively  blood glucose become very high  hyperglycemia  glucose cannot enter cells in the satiety center  exaggerated appetite  excess glucose is excreted in urine  ↑ in urine volume  dehydration and being thirsty </li></ul></ul><ul><li>DM type II </li></ul><ul><ul><li>Insufficient numbers of insulin receptors on target cells or defective receptors that do not respond normally to insulin </li></ul></ul>
  51. 102. <ul><li>Released when blood glucose levels are low </li></ul><ul><li>Bind to membrane-bound receptors primarily in the liver and cause the conversion of glycogen in the liver to glucose  glucose is released into the blood to increase blood glucose levels </li></ul>
  52. 106. <ul><li>Secrete sex hormones </li></ul><ul><li>Testosterone </li></ul><ul><ul><li>Males </li></ul></ul><ul><ul><li>Secreted by the testes </li></ul></ul><ul><ul><li>Responsible for growth and development of the male reproductive structures, muscle enlargement, growth of body hair, voice changes, male sexual drive </li></ul></ul><ul><li>Estrogen and progesterone </li></ul><ul><ul><li>Contribute to the development and function of female reproductive structures and other female sexual characteristics </li></ul></ul><ul><ul><li>Enlargement of the breasts and distribution of fat, which influences the shape of the hips, breasts, and thighs </li></ul></ul><ul><ul><li>Control female menstrual cycle </li></ul></ul>
  53. 107. <ul><li>Lies in the upper part of the thoracic cavity </li></ul><ul><li>Important in the function of the immune system </li></ul><ul><li>Thymosin </li></ul><ul><ul><li>Helps in the development of T cells which help protect the body against infection by foreign organisms </li></ul></ul><ul><li>Important early in life, becoming smaller in older adults </li></ul>
  54. 108. <ul><li>A small pinecone-shaped structure located superior and posterior to the thalamus of the brain </li></ul><ul><li>Melatonin </li></ul><ul><ul><li>Decrease the secretion of LH and FSH by decreasing the release of hypothalamic-releasing hormones </li></ul></ul><ul><ul><li>Act to inhibit the functions of the reproductive system </li></ul></ul>
  55. 110. <ul><li>Hormones that stimulate the production of digestive juices from the stomach, pancreas, and liver </li></ul><ul><li>Aid in the process of digestion by causing secretion of digestive juices when food is present in the digestive system </li></ul><ul><li>Hormones secreted in the small intestine also help regulate the rate at which food passes from the stomach into the small intestine, so that food enters the small intestine at an optimal rate </li></ul>
  56. 111. <ul><li>Function as intercellular signals </li></ul><ul><li>Function mainly as autocrine or paracrine chemical signals  effects occur in the tissues where they are produced </li></ul><ul><li>Some causes relaxation of smooth muscles such as contraction of the uterus during delivery </li></ul><ul><li>Play a role in inflammation  released by damage tissues and causes blood vessel dilation, localized swelling, and pain  necessary for blood clotting </li></ul>
  57. 112. <ul><li>Secreted in the kidneys to reduced oxygen levels in the kidneys </li></ul><ul><li>Acts on the bone marrow to increase the production of RBC </li></ul>
  58. 113. <ul><li>Important source of hormones that function to maintain pregnancy and stimulate breast development </li></ul><ul><li>Include estrogen, progesterone, and human chorionic gonadotropin </li></ul>
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