Anatomy of the Endocrine System - Research Paper Example

 Anatomy of the Endocrine System INTRODUCTION: The endocrine system is one of the most important systems of human body. It basically comprises of a number of glands, specified to perform different activities. These are the ductless glands which act by producing certain hormones and secreting them in the blood stream to reach their specific sites of action. These hormones regulate the growth, metabolism and sexual development and function of the body. The hormones actually act as the chemical messengers. They perform the function of transferring information from one set of cells to another. The endocrine system is basically regulated by the ‘feedback’ mechanism. When the required level of the hormone is reached in the blood stream, the endocrine gland is informed by this feedback mechanism to stop secreting any further hormone. This thus keeps the levels of the hormones controlled in the body (1). The only exception lies for the pituitary gland, where the signals are sent by the hypothalamus to the pituitary gland in the form of a releasing hormone. As a result, a stimulating hormone is released into the circulation. This then stimulates the target gland to release the required amount of the hormone. When the required amount is reached in the blood stream, the hypothalamus and the pituitary stop the production of the releasing and the stimulating hormone. Any malfunctioning in this whole system results either in an increased or a decreased release of the hormones in the body, thereby producing different kind of diseases accordingly. As an example, an increase in the production of the growth hormone results in an abnormally tall height, while a decrease results in a condition called as dwarfism, characterized by a very short height. Thus a proper functioning of the endocrine system is essential for our bodies to have a normal pattern of growth, metabolism and sexual functions. (1) ENDOCRINE SYSTEM GLANDS: The endocrine system comprises of following glands: 1. Hypothalamus, 2. Pituitary, 3. Thyroid, 4. Parathyroids, 5. Adrenals, Demosthene 3 6. Pineal body, 7. Pancreas and 8. The reproductive organs i.e. ovaries and testes. (1) HORMONES The hormones are the chemical messengers released by the endocrine glands. They are the main regulators of metabolism, growth, development and reproduction. they play an important role in homeostasis and the fluid and electrolyte balance. They are released either by the specialized endocrine cells, or the specialized nerve cells called the ‘neurosecretory cells’ (2). Based on their chemical structures, the hormones can be classified into the following four catagories: 1. Amines: They have their origin from the amino acids. Examples include the epinephrine and the thyroid hormone. 2. Prostaglandins: These are the cyclic unsaturated hydroxyl fatty acids. These are synthesized in the membranes from the 20 carbon fatty acid chains. 3. Steroid hormones: These are the cyclic hydrocarbon derivatives. They are synthesized from the precursor steroid, cholesterol. Examples include the testosterone and the estrogens. 4. Peptide and protein hormones: These are the largest and the most complex of all other hormones. Example includes insulin. (2) The protein hormones act as first messengers by providing direct communication between the endocrine glands and the target organs. The steroid hormones pass through the cell membrane of the target organ and then through a complex process, lead to the production of a new protein that produces the specific effects. Demosthene 3 The prostaglandins or the tissue hormones are found in a variety of tissues and they influence different body functions like respiration, blood pressure, gastrointestinal secretions and reproduction. (3) STRUCTURE AND FUNCTION OF ENDOCRINE GLANDS: 1. Hypothalamus: The hypothalamus lies in the lower central part of the brain. The main functions performed by the hypothalamus include the regulation of satiety, metabolism and the body temperature. Moreover, it controls the production of the hormones by the pituitary gland by secreting hormones itself to go and act on the pituitary gland. These are called the ‘releasing hormones’. The releasing hormones are carried to the pituitary gland by an artery called the ‘hypophyseal portal system’. They then lead to the secretion of the stimulating hormones by the pituitary. The hypothalamus also releases another hormone called as the ‘somatostatin’. The somatostatin signals the pituitary gland to stop the production of the growth hormone (1). 2. Pituitary gland: The pituitary gland lies beneath the hypothalamus at the base of the brain. Although its size is no larger than a pea, but its role is of utmost importance. The main importance of the pituitary lies in the fact that it the hormones produced by it in turn controls the functions of the other endocrine glands. Hypopituitarism is a condition describing the lack of pituitary to produce one or more of its hormones. The pituitary gland has two lobes: a. The anterior lobe and b. The posterior lobe. These are also called as the anterior and the posterior pituitary respectively. The anterior pituitary produces: a. Thyroid-stimulating hormone (TSH), b. Adrenocorticotropin hormone (ACTH), c. Luteinizing hormone (LH) and Follicle stimulating hormone (FSH), Demosthene 4 d. Prolactin. The posterior pituitary produces: a. Antidiuretic hormone, also called as the ‘vasopressin’ and b. Oxytocin. Given below is a brief description of these hormones: a. Growth hormone: It stimulates the growth of bones and tissues. The deficiency of this hormone in children results in the growth failure. In adults, its deficiency results in a poor maintenance of a proper amount of body fat, muscle and bone mass. It also has a role in the emotional well being. b. Thyroid stimulating hormone: As its name indicates, it stimulates the thyroid gland to produce the thyroid hormone. Hypothyroidism is a diseased condition resulting from a poor production of thyroid hormone. It can result either due to a defect in the pituitary gland, or the thyroid itself. c. Adrenocorticotropin hormone: It stimulates the adrenal glands to produce the steroid hormones. d. Luteinizing hormones and Follicle stimulating hormone: These are responsible for a proper sexual function and a normal production of the sex steroids, namely, estrogens and progesterone in females and testosterone in males. e. Prolactin: It stimulates the milk production in females. These all are the hormones produced by the anterior lobe of pituitary. The posterior lobe produces the antidiuretic hormone and the oxytocin. They are briefly described below: a. Antidiuretic hormone: It controls the water loss by the kidneys. b. Oxytocin: It is responsible for the uterine contraction during the child birth and stimulation of the milk production. These two hormones produced by the posterior pituitary gland, are actually produced in the brain, then transported to the pituitary gland via nerves, and are stored there. They are not actually produced by the pituitary gland (1). 3. Thyroid gland: Demosthene 5 The thyroid gland lies in the lower front part of the neck. It produces the thyroid hormones and is responsible for a normal metabolic function of the body. Its other important functions include a role in the bone growth and the development of the brain and nervous system in children. It also controls the blood pressure, heart rate, digestion, muscle tone and reproduction. A decrease in the thyroid hormones results in slowing of all these processes, while an increase results in an increased rate of them. A deficiency of thyroid hormones is called as ‘hypothyroidism’, while an increase is called as ‘hyperthyroidism’ (1). 4. Parathyroid glands: These are a pair of two small glands. They lie embedded in the surface of the thyroid gland. They are responsible for the production of the parathyroid hormones. These hormones play a role in maintaining a normal calcium level in the blood a normal bone metabolism (1). 5. Adrenal glands: These are a pair of triangular glands. They lie one on top of each kidney. They are comprised of two parts: . Adrenal cortex and . Adrenal medulla. The adrenal cortex is the outer portion. The inner one is the adrenal medulla. The two portions produce different kinds of hormones. The adrenal cortex produces the hormones called as ‘corticosteroids’. The corticosteroids are responsible for controlling the body’s metabolism, the electrolytes balance, the immune system and the sexual function. The adrenal medulla produces the hormones called as the ‘catecholamines’. These comprise of the adrenaline and nor adrenaline, also called as the epinephrine and nor epinephrine. They play a part in the stressful conditions and help the body to cope with such situations by increasing the heart rate and blood pressure (1). 6. Pineal body: This small endocrine structure lies in the middle of the brain. The pineal body is responsible for producing a hormone called as ‘melatonin’. This hormone controls the wake-sleep cycle of the body (1). Demosthene 6 7. Reproductive glands: These are the testes in the males and the ovaries in the females. The pair of testes is located in the scrotum. The testes secrete the hormones namely ‘androgens’. The most important of these androgens are the testosterones. The testosterones are responsible for the development of many male characteristics like the sexual development, facial and the pubic hair growth and the sperm production. There are two ovaries lying on either side of the uterus. The ovaries produce the estrogens, progesterones and the eggs. They are important in controlling the female organs development, like the growth of breast and are also involved in controlling the normal menstruation and pregnancy (1). 8. Pancreas: The pancreas lies behind the stomach. It has two functions: a. Digestive and b. Hormonal. The pancreas consists of two parts: a. The exocrine and the b. The endocrine pancreas. Out of these two, the digestive enzymes are released by the exocrine pancreas the and endocrine pancreas secrete the insulin and the glucagon (1). DISEASES AND DISORDERS OF THE ENDOCRINE SYSTEM: The most common diseases of the endocrine system include: 1. Diabetes mellitus 2. Growth disorders 3. Hyperthyroidism 4. Hypothyroidism 5. Osteoporosis 6. Polycystic ovarian disease Demosthene 8 The hormone disorders include: 1. Cushing’s disease 2. Addison’s disease Described below is a brief description of all these diseases and disorders. 1. DIABETES MALLITUS: Diabetes mellitus is a disease resulting from an insufficient release of insulin from pancreas. Insulin is responsible for the conversion of the glucose from our food into energy; a process known as the glucose metabolism. Diabetes can result either because the pancreas are unable to produce insulin, or the insulin they produce is just not sufficient for the conversion of glucose into energy, or either due to any defect in the glucose metabolism itself. There are two main types of diabetes mellitus: a. Type I also called as the insulin dependent diabetes. b. Type II also called as the non-insulin dependent diabetes (4). Type I Diabetes: It mostly occurs in children and young adults. In this type, the pancreas is unable to produce insulin at all. So, the patients suffering from type I diabetes need the insulin injections to maintain a normal level of blood glucose. In this type, the symptoms appear suddenly and need a serious attention, because they can be life threatening if left untreated (4). Type II Diabetes: It occurs mostly in adults above 40 years of age, but can be found in all ages. These patients do not have sufficient insulin to maintain a normal level of blood glucose. This condition can be controlled by a good diet plan, regular exercise and weight control. But if uncontrolled, it also needs tablets or insulin injections. In this type, there may not be any symptoms at all. Or otherwise, the symptoms are notices very late when other complications may already have occurred (4). Demosthene 9 Common symptoms: Some of the most common symptoms of both types include increased thirst, increased frequency of urine, fatigue, increased hunger, and delayed healing of wounds, blurring of vision, mood swings, headaches, dizziness and leg cramps. One difference should be notified here that in type I diabetes, there is unexplained weight loss. While, in type II diabetes, the patient gradually puts on weight. Diabetic patients gradually develop damage to their small and large blood vessels in the body affecting vital organs like heart, eyes, kidneys, feet and nerves. It also affects the digestive and immune systems as well skin. (4) 2. GROWTH DISORDERS: Growth disorders result either due to an excessive release of the growth hormone, or a reduced release. An excessive release results in a condition called as ‘acromegaly’ in which there is an overgrowth of the body tissues. Along with an increased length, there is associated reduced muscle strength. These patients get easily fatigued. There are enlarged bones of the face, and enlarged hands and feet. A reduced release of growth hormones results in a condition called as ‘dwarfism’. In this condition there is a reduced growth of the body most prominently a reduced height (5). 3. HYPERTHYROIDISM AND HYPOTHYROIDISM: Hyerthyroidism is characterized by an increased production of the thyroid hormones by the thyroid gland. These hormones are: a. Thyroxine also called as T4 and b. Triiodothyronine also called as T3. The causes include increased thyroxine level, grave’s disease, autoimmune disease and thyroiditis. The major symptoms include weight loss, palpitations, nervousness, restlessness, hand tremor, abnormal heart rhythms, protruding eye, altered heart rate, difficulty in sleeping, high blood pressure and loss of part of visual field. Demosthene 9 Hypothyroidism is characterized by a reduced production of the thyroid hormones, T3 and T4. Major causes include decreased triiodothyronine level and decreased thyroxine levels. It is characterized by constipation, weight loss, dry skin, muscle weakness, cold intolerance, menstrual irregularity, slow heart rate, pain, depression, fatigue, hair loss, headache, joint and muscle pains and joint stiffness. (5) 4. OSTEOPOROSIS: It is a diseased condition characterized by a loss of normal bone density, leading to an increased fragility of bones. This leads to an increased risk of bone fractures. Thesefracture can either be in the form of hip fracture or the vertebrae fractures. This disease can go on symptomless for decades, only to appear for the first time when the fractures appear. (6) 5. POLYCYSTIC OVARIAN DISEASE: This is a diseased condition characterized by an increased level of the androgens in females. It affects a woman’s menstrual cycle, fertility, hormones, heart, blood vessels and appearance. The patient typically represents missed or irregular periods. The ultrasound examination shows many small cysts in the ovaries. These cysts are filled with the fluid. The cause of PCOD is still unknown. There are different thoughts about it. Some say that it may have a genetic factor. Some researchers say that insulin also plays a role in it. (7) 6. CUSHING’S DISEASE: Cushing’s disease is characterized by an excess of the hormone called as cortisol. It can also occur as a result of an increased intake of cortisol or any other steroid hormones. The important causes include: 1. Pheochromocytoma Demosthene 10 2. Steroid therapy 3. Pituitary neoplasms 4. Pituitary dependant cushing’s disease. It represents in the development of a figure called as the ‘drum-stick’ appearance, with a distended abdomen and thin limbs. Other symptoms include weight gain, buffalo hump, and excessive hair growth, pain, impotence, acne, high blood pressure, generalized weakness, central obesity, delayed puberty, no menstrual period and excessive thirst. (8) 7. ADDISON’S DISEASE: The Addison’s disease is also called as the adrenal insufficiency, adrenocortical hypofunction or hypocortisolism. Adrenal glands secrete the adrenal hormone which is responsible for the body’s response to stress and the maintenance of our body’s salt and water balance. They are also responsible for the control of blood pressure. This disease results due to the problem in immune system. It is an auto immune disease, in which the immune system attacks the patient’s own body tissues. As a result of the attack on adrenal glands, they are damaged and produce less amount of cortisol thereby resulting in the addison’s disease. Major symptoms include: a. Weight loss b. Muscle weakness, c. Increasing fatigue, d. Hypotension and e. Patchy or dark skin (9). CONCLUSION: The endocrine system is one of the most important systems of our bodies. Besides being important, it is also very complex. The hormonal treatment has never been so easy. The treatments of the hormonal diseases require a proper Demosthene 11 knowledge of the dose administration. So this also makes it more important for this system to remain working properly. To conclude, we can say that we understand from the above discussion that the endocrine system consists of a number of glands, which unlike the exocrine glands do not have ducts. So, in the absence of ducts, the mode of transmission of their secretions is via the blood. These glands secrete certain chemical messengers called as the hormones. These are then transported via the blood to their specific sites of action. The hormones are of different kinds and different composition. Some are proteins, some are steroids etc. These hormones after being released to their sites of action, then carry out their functions, like the growth hormone is responsible for the growth of body tissues, insulin is responsible for the glucose metabolism, thyroid hormones are responsible for the increase of blood pressure and heart rate etc The endocrine diseases and disorders occur as a result of an increased or a decreased amount of these hormones due to any cause. An over production of any hormone results in an enhanced effect of it while an under production results in a reduced effect. For example, acromegaly is a condition in which there is an over growth of the hand, feet and face bones. It results from an increased production of the growth hormone, while an under production results in a condition called as dwarfism, where there is a short stature and height of the affected person. Similarly diabetes is a condition in which there is an increase in the blood sugar level. It results due to an insufficiency of insulin; a hormone responsible for controlling the glucose metabolism in our bodies. The endocrine system is controlled by the feed back mechanism. As soon as the level of a required hormone are reached up to the amount needed, the feed back signals are sent organ of production of that hormone and it stops any further release of it. Although now with the advancement of medical science and knowledge, the treatments are available for such disorders, and still more research is being carried out, yet still it is important to carefully evaluate such orders before giving Demosthene 12 any hormonal treatment for them, because an over dose or under dose of the hormonal treatment itself has its side effects. Demosrhene 13 REFERENCES 1. Marianne Rieser (2005). Anatomy of the Endocrine System (Online) Retrieved November 28th, 2009 from the World Wide Web: http://www.emedicinehealth.com/anatomy_of_the_endocrine_system/article_em.htm 2. The Endocrine System. Retrieved November 28th, 2009 from the World Wide Web: http://www.cartage.org.lb/en/themes/Sciences/Zoology/AnimalPhysiology/EndocrineSystem/EndocrineSystem.htm 3. The Body Art Project (2009). Health Services; University of New Hampshire. Retrieved November 29th, 2009 from the World Wide Web: http://www.unh.edu/health-services/ohep/body-project_endocrine.html 4. Diabetes (2009). Australian Government. Retrieved November 29th, 2009 from the World Wide Web: http://www.jobaccess.gov.au/joac/advice/disabilityone/diabetes.htm 5. Endocrine Disorders Learning Center (2009). Healthline. Retrieved November 29th, 2009 from the World Wide Web: http://www.healthline.com/channel/endocrine-disorders.html 6. Osteoporosis (2009). MedicineNet.com. Retrieved November 29th, 2009 from the World Wide Web: http://www.medicinenet.com/osteoporosis/article.htm 7. Polycystic Ovarian Syndrome (2007). Womenshealth.gov. Retrieved November 29th, 2009 from the World Wide Web: http://www.womenshealth.gov/faq/polycystic-ovary-syndrome.cfm#a 8. Cushing Syndrome Learning Center (2009). Healthline. Retrieved November 29th, 2009 from the World Wide Web: http://www.healthline.com/channel/cushing-syndrome.html Demosthene 14 9. Addison’s disease (2009). Medlineplus. Retrieved November 29th, 2009 from the World Wide Web: http://www.nlm.nih.gov/medlineplus/addisonsdisease.html Read More