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  1. 1. LESSON 14 THE ENDOCRINE SYSTEM INTRODUCTION The endocrine system is composed of glandular tissue located in most areas of the body. They are referred to as endocrine glands because they release their specific chemicals directly into the bloodstream. These chemicals are called hormones because they can regulate many different body functions. Hormones stimulate the growth of bones, cause the maturation of sex organs and reproductive cells, and control the metabolic rate within the individual cells of the body. A few endocrine glands secrete a wide variety of different hormones that travel through the bloodstream and regulate the activities of other endocrine glands. Hormones produce their effects by connecting onto receptor sites. There are receptor sites on the various target cells on which hormones act. The receptors initiate specific physiological effects when the hormones connect to them. Each hormone has its own receptor; the connecting of a receptor to a hormone is much like the function of a key opening a lock. All of the endocrine glands secrete their hormones directly into the bloodstream rather than into ducts leading to the exterior of the body. Those glands that send their chemical substances into ducts and out of the body are called exocrine glands. Examples of exocrine glands are sweat, mammary, mucous, salivary and lacrimal glands. The ductless, internally secreting, endocrine glands are listed below: thyroid gland parathyroid glands adrenal glands pancreas, islets of Langerhans pituitary gland ovaries in female testes in male pineal gland thymus gland The pineal gland, located in the central portion of the brain, secretes a substance called melatonin. Melatonin is believed to affect the brain and influence the rate of sex organ maturation. Melatonin is thought to help in the ability to sleep at night by reducing the amount of brain serotonin. The thymus gland, located behind the sternum, resembles a lymph gland in structure. It contains lympathic tissue and antibody-producing lymphocytes. The gland produces a
  2. 2. hormone called thymosin. The thymus gland is important in the development of immune responses, especially in newborns. It is large in children but becomes smaller in most adults. Removal of the thymus gland is used in treating a muscular-neurological disorder called myasthenia gravis, and other autoimmune diseases, such as lupus and multiple sclerosis. Some hormones are produced by organs. For example, the kidney secretes a hormone called erythropoietin, which stimulates the production of red blood cells by the bone marrow. The gastrointestinal tract secretes three hormones: gastuin, secretin, and cholecystokinin. These hormones stimulate the secretion of gastric acid and enzymes, the secretion of pancreatic enzymes, and the contraction of the gallbladder. The skin produces vitamin D, which is considered a hormone, when sunlight is allowed to shine on it for a length of time. Vitamin D stimulates the calcium absorption from the gastrointestinal tract and is necessary for the maintenance of proper amounts of calcium in the tissues, especially in the bones and in the bloodstream. Prostaglandins are hormone-like substances that affect the body in many ways. They are produced in cells throughout the body. Protaglandins stimulate the contraction of the uterus, regulate body temperature, platelet aggregation, and acid secretion in the stomach, and have the ability to lower blood pressure. They are released from cells and tissue to instigate pain. THYROID GLAND Location and Structure The thyroid gland is located on either side of the trachea just below the thyroid cartilage. The thyroid cartilage covers the larynx and produces the prominence on the neck known as the Adam’s apple. The isthmus of the thyroid gland is a narrow strip of glandular tissue that connects the two lobes on the front surface of the trachea. Function Two hormones are secreted by the thyroid gland, thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3). These hormones are synthesized in the thyroid gland from iodine which is picked up from the blood stream and from an amino acid called tyrosine. T4 contains four atoms of iodine and is much more concentrated in the blood. T3 contains three atoms of iodine and is far more potent in affecting the metabolic rate within cells. Most thyroid hormones are bound to a protein molecule when they travel through the bloodstream. T3 and T4 are necessary in the body to maintain a normal metabolic rate in all cells. Thyroid hormones help in the uptake of oxygen. Injections of thyroid hormone will
  3. 3. increase the metabolic rate. Removal of the thyroid gland lowers the thyroid hormone concentration in the body which results in a lower metabolic rate, heat loss, and poor mental and physical development. Another hormone produced by the thyroid gland is called calcitonin. Calcitonin is secreted when calcium levels in the blood are high. It stimulates calcium to leave the blood and enter the bones, thus lowering blood calcium back to normal. PARATHYROID GLANDS Location and Structure: The parathyroid glands are four small oval bodies located on the back side of the thyroid gland. Function Parathyroid hormone is secreted by the parathyroid glands. This hormone mobilizes calcium from bones into the bloodstream where calcium is necessary for proper functioning. Calcium in food is absorbed from the intestine and carried by the blood to the bones, where it is stored. The level of calcium in the blood is a good example of the way hormones control the homeostasis of the body. A decrease in blood calcium causes the parathyroid hormone to be secreted in larger amounts, which in turn causes calcium to leave the bones and enter the bloodstream bringing blood calcium back to normal. In a situation of increased blood calcium, the parathyroid hormone secretion decreases, and blood calcium is again brought back to normal. ADRENAL GLANDS Location and Structure: The adrenal glands are two small glands situated one on top of each kidney. Each gland consists of two parts, an outer portion called the adrenal cortex and an inner portion called the adrenal medulla. The cortex and medulla are two glands in one, each secreting its own different endocrine hormones. The cortex secretes hormones called coriticosteroids, and the medulla secretes hormones called catecholarnines. The adrenal cortex secretes three types of steroid hormones known as corticosteroids: Mineralocorticoids. These hormones are essential to life because they regulate the amounts of electrolytes that are retained in the body. A proper balance of water and salt in the blood and tissues is essential to the normal function of the body.
  4. 4. The most important mineralocorticoid hormone is called aldosterone. The secretion of aldosterone by the adrenal cortex increases the reabsorption of sodium into the bloodstream by the kidney tubules. At the same time, aldosterone stimulates the excretion of the electrolyte potassium. Glucocorticoids. These steroid hormones have an important influence on the metabolism of fats, sugars, and protein within cells and have an anti-inflammatory effect. Cortisol, also called hydrocortisone, is the most important glucocorticoid hormone. Cortisol increases the ability of cells to make new sugars out of fats and proteins and regulates the quantity of fats, sugars, and proteins in the blood and cells. Cortisone is a hormone very similar to cortisol and can be prepared synthetically. Cortisone is useful in treating inflammatory conditions such as multiple sclerosis and arthritis. Androgens, Estrogens, and Progesterone. These are male and female hormones that maintain the secondary sex characteristics such as beard and breast development, and are necessary for reproduction. These hormones are also produced in the ovaries and testes. Excess adrenal androgen secretion in females leads to the development of male characteristics; for example, facial hair. Excess adrenal estrogen and progesterone secretion in males develops feminine characteristics such as soft skin and higher pitched voices. The adrenal medulla secretes two types of catecholamine hormones: Epinephrine. Its trade name is adrenaline, by which it is mostly known. This hormone increases cardiac rate, dilates bronchial tubes, and stimulates the production of glucose from glycogen when glucose is needed by the body. Norepinephrine. Its common or trade name is noradrenaline. This hormone constricts vessels and raises blood pressure. Both epinephrine and norepinephrine are called sympathomimetic and parasympathomimetic agents because they mimic the actions of the sympathetic nervous system or the parasympathic nervous system. During stress, these hormones are secreted by the adrenal medulla in response to stimulation. They help the body respond to stressful situations by raising blood pressure, increasing heartbeat and respiration, and bringing sugar out of storage and into the cell for more energy.
  5. 5. PANCREAS Location and Structure The pancreas is located behind the stomach in the region lumbar region. The specialized cells in the pancreas that produce hormones are called the islets of Langerhans. Function The islets of Langerhans produce two important hormones, insulin and glucagon. Both of these hormones play an important role in the proper metabolism of carbohydrates in the body. Insulin is necessary in the bloodstream so that sugars can cross from the blood into the cells of the body where they are burned and then released as energy. When blood sugars are high, insulin is released by the islet of Langerhans cells. The insulin causes glucose either to enter body cells to be used as energy or converts it to glycogen to be stored in muscle tissue or in the liver. Sugar can leave the blood to be stored as glycogen or used to release energy. Glucagon, the opposite “twin” of insulin, is released into the blood when sugar levels are below normal. It causes the breakdown of stored liver glycogen into glucose so that there is a rise in the sugar content of blood leaving the liver. The islets of Langerhans carry on an endocrine function of releasing digestive enzymes and juices. These cells secrete their digestive enzymes and juices into the gastrointestinal tract. PITUITARY GLAND Location and Structure The pituitary gland, also called the hypophysis, is a small, pea-sized gland located at the base of the brain in a small, pocket-like depression of the skull called the sella turcica. The pituitary consists of two parts: an anterior lobe called the adenohypophysis; and a posterior lobe called the neurohypophysis. The hypothalamus is an area of the brain that is located next to the pituitary gland. Signals transmitted from the hypothalamus control the secretions by the pituitary gland. Secretion from the neurohypophysis is controlled by nerve fibers originating in the hypothalamus and ending in the neurohypophysis. Secretion by the adenohypophysis is controlled by special hormones called releasing and inhibiting factors. These hormones are secreted by the hypothalamus and passed to the adenohypophysis via the bloodstream.
  6. 6. Function The hormones of the anterior pituitary gland are: Growth hormone, also called somatotropin. This hormone affects bone tissue to accelerate its growth in the body. Thyroid-stimulating hormone, also called thyrotropin. This hormone stimulates the growth of the thyroid gland and its secretion of thyroxine. Adrenocorticotropic hormone (ACTH)). This hormone stimulates the growth of the adrenal cortex and increases its secretion of steroid hormones. Gonadotropic hormones. There are several gonadotropic hormones that affect the growth and hormone secretion of the ovaries in females and testes in males. In the female, the follicle-stimulating hormone (FSH), and the luteinizing hormone (LH), stimulate the growth of eggs in the ovaries, production of hormones, and ovulation. The lutotrophic hormone (LTH) stimulates the development of endometrial tissue inside the uterus. In the male, FSH influences the production of sperm and LH stimulates the testes to produce testosterone. Prolactin. This hormone stimulates and sustains milk production after birth. Melanocyte-stimulating hormone. This hormone influences the formation of melanin and causes increased pigmentation of the skin. This effect occurs only when hypersecretion of the hormone occurs. The posterior pituitary gland secretes two important hormones. These hormones are formed in the hypothalamus but secreted through the posterior pituitary gland. Antidiuretic hormone (ADH). This hormone, also known as vasopressin, stimulates the reabsorption of water by the kidney tubules. ADH can increase blood pressure by constricting arterioles. Oxytocin. This hormone stimulates the uterus to contract during childbirth and maintains labor during childbirth. Oxytocin is secreted during suckling and helps in the production of milk from the mammary glands.
  7. 7. LESSON 14 GRAPHICS TERMS FOR LESSON 14 THE ENDOCRINE SYSTEM Endocrine Glands to Know pituitary or hypophysis
  8. 8. anterior lobe or adenohypophysis growth hormone GH) or somatrophin adrenocorticotrophic (ACTH) thyroid-stimulating hormone (TSH) FSH - follicle stimulating LH - luteinizing hormone LTH - lutotrophic hormone prolactin melanocyte-stimulating hormone posterior lobe or neurohypophysis antidiuretic hormone (ADH) oxytocin thyroid gland throxin, triiodothyronine parathyroid gland calcitonin, parathyroid hormone islets of Langerhans (pancreas) insulin glucagon adrenal glands cortex (outer portion) medulla (inner portion) cortisol aldosterone epinephrine or adrenaline norepinephrine androgens, estrogens, progestins ovaries estrogen progesterone testes
  9. 9. testosterone androgen Word Parts to Know: Endocrine System adren/o adrenal/o cortic/o parathyroid/o thyroid/o thyr/o acr/o calc/i dips/o kal/i toxic/o Prefixes and Suffixes to Know: Endocrine System ex- exo- -drome -one Diagnostic Terms to Know: Endocrine System acromegaly adrenalitis adrenomegaly hypercalcemia hyperglycemia hyperkalemia hyperthyroidism hypocalcemia hypoglycemia hypokalemia
  10. 10. hypothyroidism parathyroidoma thyrotoxicosis acidosis Addison’s disease cretinism Cushing’s syndrome diabetes insipidus diabetes mellitus gigantism goiter ketosis myxedema tetany Surgical Terms to Know: Endocrine System adrenalectomy parathyroidectomy thyoidectomy thyroidotomy thyroparathyroidectomy Additional Terms to Know: Endocrine System adrenocorticohyperplasia adenopathy calcipenia cortical corticoid exophthalmic polydipsia syndrome isthmus metabolism
  11. 11. PRACTICE EXERCISES FOR LESSON 14 THE ENDOCRINE SYSTEM DEFINE THE FOLLOWING COMBINING FORMS: aden/o adren/o adrenal/o andr/o calc/o cortic/o crin/o dips/o estr/o gluc/o glyc/o gonad/o home/o kal/o lact/o oxy/o natr/o pancreat/o parathyroid/o phys/o pituitar/o somat/o ster/o thyr/o thyroid/o toc/o toxic/o ur/o DEFINE SUFFIXES:
  12. 12. -agon -ectomy -emia -genic -ene -in -ine -megaly -oid -one -osis -physis -stasis -tocin -tropin -uria MATCHING ---- adrenal cortex a stimulates adrenal cortex ---- adrenal glands b secreted by posterior lobe of pituitary gland ---- oxytocin c regulate electrolytes ---- adrenal medulla d norepinephrine secreted by ---- adrenocorticotropic hormone/ e located above kidney ---- adenohypophysis f secretes aldosterone ---- aldosterone g secretes insulin ---- antidiuretic hormone h maintains blood calcium level ---- islets of Langerhans i located in neck ---- neurohypophysis j secreted by posterior lobe ---- parathyroid gland k secret antidiuretic hormone ---- pituitary gland l anterior lobe of pituitary gland ---- thyroid gland m master gland DEFINE PREFIXES: cys- eu- hyper- hypo-
  13. 13. oxy- pan- tetra- tri-
  14. 14. ASSIGNMENT FOR LESSON 14 Medical Terminology, HS 280 The Endocrine System MATCHING ---- 1 ex- a poison ---- 2 -one b cortex ---- 3 kal/i c excessive ---- 4 toxic/o d deficient ---- 5 adren/o e adrenal gland ---- 6 cortic/o f potassium ---- 7 thry/o g hormone ---- 8 acro/o h extremities ---- 9 hyper- i thyroid gland ---- 10 hypo- j outside MATCHING ---- 11 hypokelemia a enlargement of legs and arms ---- 12 acromegaly b muscle in spasm ---- 13 hypercalcemia c poisons produced by thyroid ---- 14 acidosis d enlargement of all bones ---- 15 ketosis e blood Ph to acidic ---- 16 tetany f blood high in ketone ---- 17 thyrotoxicosis g excessive production of thyroxin ---- 18 gigantism h low production of thyroxin ---- 19 hypothyroidism i low potassium blood levels ---- 20 hyperthyroidism j high calcium blood levels MATCHING ---- 21 somatropin a causing maturation of egg ---- 22 follicle-stimulating hormone b build up endometrium ---- 23 luteinizing hormone c growth hormone ---- 24 antidiuretic hormone d female hormone ---- 25 oxytocin e male hormone ---- 26 epinephrine f causing deliver of baby ---- 27 estrogen g stress hormones ---- 28 testosterone h retain water ---- 29 insulin i fights infections ---- 30 cortisol j moves sugar
  15. 15. Assignment for Lesson 14, Endocrine System, pg. 2 DEFINE: 31.myxedema 32.goiter 33.Cushing syndrome 34.diabetes insipidus 35.diabetes mellitus 36.Addison’s disease 37.corticoid 38.exophthalmic 39.metabolism 40.parathyroidism 41.cretinism 42.thyroparathyroidectomy