Endocrine System Endocrinology is the medical specialty that studies the glands that produce hormones, that is, the ductless glands or endocrine glands.
Endocrinologists study normal effects of the secretions from these glands, and the harmful effects of malfunction of the same. The most important endocrine glands are: • the hypothalamus and pituitary gland • the thyroid · the parathyroid • the pancreas · the adrenal · the ovaries · the testicles
The Endocrine System is the set of organs and tissues that release a class of substances called hormones. The endocrine organs are also called ductless glands or endocrine glands because their secretions are released directly into the bloodstream, while exocrine glands release their secretions on the inner or outer surface of skin tissue, the lining of the stomach or the lining of the pancreatic ducts. The hormones secreted by the endocrine glands regulate growth, development and functions of many tissues, and coordinate the body's metabolic processes.
hormone-producing tissues can be classified into three groups: endocrine glands, whose function is the exclusive production of hormones, endo-exocrine glands that produce secretions also other hormones as well, and certain glandular tissues such as nervous tissue of the autonomic nervous system that produces hormone-like substances .
Pituitary The pituitary, also called the pituitary gland, is made up of three lobes: the anterior, intermediate, that in primates there is only for a short period of life, and back. Located at the base of the brain and has been called the "master gland." Anterior and posterior lobes of the pituitary diferentes.El lobes secrete hormones anterior pituitary releases several hormones that stimulate the function of other endocrine glands, such as corticotropin, adrenocorticotropic hormone or ACTH, which stimulates the adrenal cortex, stimulating hormone or thyroid hormone (TSH ) which controls the thyroid, the follicle-stimulating hormone or follicle stimulating hormone (FSH) and luteinizing hormone (LH), which stimulate the sex glands, and prolactin, which, like other special hormones, influences milk production by the mammary glands. The anterior pituitary is a source of production of growth hormone or somatotropin, which favors the development of body tissues, including bone matrix and muscle, and influences the metabolism of carbohydrates. The anterior pituitary also secretes a hormone called melanocyte stimulating, stimulating the synthesis of melanin in the pigment cells or melanocytes. In the 1970's, scientists found that the anterior pituitary also produces substances called endorphins, which are peptides that act on the central and peripheral nervous system to reduce sensitivity to pain.
The hypothalamus, part of the brain from where the pituitary gland produces hormones "controlling." These hormones regulate processes body such as metabolism and control the release of hormones from glands like the thyroid, adrenals and gonads (testes or ovaries). Also secretes an antidiuretic hormone (which controls water excretion) called vasopressin, which circulates and is stored in the posterior pituitary lobe. Vasopressin controls the amount of water excreted by the kidneys and increases blood pressure. The posterior pituitary lobe also stores a hormone produced by the hypothalamus called oxytocin. This hormone stimulates muscle contractions, especially the uterus, and excretion of milk by the mammary glands.
Hormone Metabolism
Pituitary The pituitary, also called the pituitary gland, is made up of three lobes: the anterior, intermediate, that in primates there is only for a short period of life, and back. Located at the base of the brain and has been called the "master gland." Anterior and posterior lobes of the pituitary diferentes.El lobes secrete hormones anterior pituitary releases several hormones that stimulate the function of other endocrine glands, such as corticotropin, adrenocorticotropic hormone or ACTH, which stimulates the adrenal cortex, stimulating hormone or thyroid hormone (TSH ) which controls the thyroid, the follicle-stimulating hormone or follicle stimulating hormone (FSH) and luteinizing hormone (LH), which stimulate the sex glands, and prolactin, which, like other special hormones, influences milk production by the mammary glands. The anterior pituitary is a source of production of growth hormone or somatotropin, which favors the development of body tissues, including bone matrix and muscle, and influences the metabolism of carbohydrates. The anterior pituitary also secretes a hormone called melanocyte stimulating, stimulating the synthesis of melanin in the pigment cells or melanocytes. In the 1970's, scientists found that the anterior pituitary also produces substances called endorphins, which are peptides that act on the central and peripheral nervous system to reduce sensitivity to pain.
The hypothalamus, part of the brain from where the pituitary gland produces hormones "controlling." These hormones regulate processes body such as metabolism and control the release of hormones from glands like the thyroid, adrenals and gonads (testes or ovaries). Also secretes an antidiuretic hormone (which controls water excretion) called vasopressin, which circulates and is stored in the posterior pituitary lobe. Vasopressin controls the amount of water excreted by the kidneys and increases blood pressure. The posterior pituitary lobe also stores a hormone produced by the hypothalamus called oxytocin. This hormone stimulates muscle contractions, especially the uterus, and excretion of milk by the mammary glands.
three secretion of anterior pituitary hormones is subject to control by hypothalamic releasing factors: thyrotropin secretion is stimulated by thyrotropin releasing factor (TRF), and luteinizing hormone by hormone releasing hormone (LHRH). Dopamine is usually prepared by the hypothalamus to inhibit the release of prolactin by the anterior pituitary. Furthermore, the release of growth hormone is inhibited by somatostatin, also synthesized in the pancreas. This means that the brain also functions as a gland.
adrenal glands The two glands are located above the kidneys.
Each adrenal gland consists of an inner zone called the medulla and an outer zone called the cortex. The adrenal medulla produces adrenaline, also called epinephrine and norepinephrine, which affects a large number of body functions. These substances stimulate the activity of the heart, increase blood pressure, and act on the contraction and dilation of blood vessels and muscles. Epinephrine raises blood glucose levels (glucose). All these actions help the body cope with emergencies more effectively. The bark adrenal produces a group of hormones called glucocorticoids, including corticosterone and cortisol, and mineralocorticoids, including aldosterone and other hormonal substances essential for the maintenance of life and adaptation to stress. Adrenal secretions regulate the balance of water and salt from the body, affect blood pressure, acting on the lymphatic system, influence the mechanisms of the immune system and regulate the metabolism of carbohydrates and proteins. In addition, the adrenal glands also produce small amounts of male and female hormones. Thyroid
Thyroid bilobed gland is located in the neck. Thyroid hormones, thyroxine and triiodothyronine increases oxygen consumption and stimulate the rate of metabolic activity, regulate the growth and maturation of body tissues and act on the physical alertness and mental. The thyroid also secretes a hormone called calcitonin, which lowers blood levels of calcium in the blood and inhibits bone resorption.
The parathyroid glands are located in an area close to or are embedded in the thyroid gland. Parathyroid hormone or parathyroid hormone regulates blood levels calcium and phosphorus and stimulates bone resorption. Ovaries
The ovaries are female reproductive organs or female gonads. Paired structures are almond shaped on both sides of the uterus. Ovarian follicles produce eggs, or eggs, and also secrete a group of hormones called estrogens, which are necessary for the development of reproductive organs and secondary sexual characteristics, such as fat distribution, extent of pelvic and breast growth pubic and underarm hair.
Progesterone exerts its main action on the uterine mucosa in the maintenance of pregnancy. It also acts with estrogens favoring the growth and the elasticity of the vagina. The ovaries also produce a hormone called relaxin, which acts on the ligaments of the pelvis and the cervix and causes their relaxation during labor, thus facilitating delivery. Testicles
male gonads or testes pairs are ovoid bodies that are suspended in the scrotum. Leydig cells of the testes produce one or more male hormones, called androgens. The most important is testosterone, which stimulates the development secondary sexual characters, influences the growth of the prostate and seminal vesicles, and stimulates the secretory activity of these structures. The testicles also contain cells that produce sperm or male gametes. Pancreas
Most pancreatic exocrine tissue is formed by releasing enzymes into the duodenum. There are clusters of endocrine cells, called islets of Langerhans, scattered throughout the tissue that secretes insulin and glucagon. Insulin acts on the metabolism of carbohydrates, proteins and fats, increasing the rate of glucose utilization and favoring the formation protein and fat storage. Glucagon transiently increased levels of blood glucose by releasing glucose from the liver. Placenta The placenta, an organ formed during pregnancy from the membrane surrounding the fetus, takes several endocrine functions of the pituitary gland and ovaries that are important in maintaining pregnancy. Secretes the hormone called chorionic gonadotropin, a substance present in the urine during pregnancy and is the basis of pregnancy tests. The placenta produces progesterone and estrogen, chorionic somatotropin (a hormone with some of the characteristics of growth hormone) placental lactogen lactogenic hormones.
Other bodies
Other tissues in the body produce hormones or similar substances. The kidneys secrete a known agent that activates the renin angiotensin hormone produced in the liver. This hormone in turn raises blood pressure, and is believed to be caused largely by stimulating the adrenal glands. The kidneys also produce a hormone called erythropoietin, which stimulates production of red blood cells from the bone marrow. The gastrointestinal tract produces a number of substances that regulate the functions of the digestive tract such as stomach gastrin, which stimulates acid secretion, and secretin and colescistoquinina of the small intestine, which stimulates the secretion of pancreatic enzymes and hormones. The colescistoquinina also causes contraction of the gallbladder. In the 1980's, it was observed that the heart also secretes a hormone called atrial natriuretic factor, involved in the regulation of blood pressure and body fluid balance.
The confusion over the functional definition of the endocrine system due to the discovery that many hormones typically seen in places where they have a hormonal activity. Norepinephrine is present in the nerve endings, which transmits nerve impulses. The components of the renin-angiotensin system have been found in the brain, where their functions are unknown. Intestinal peptides gastrin, cholecystokinin, vasoactive intestinal peptide (VIP) and gastric inhibitory peptide (GIP) were also located in the brain. Endorphins are present in the gut and growth hormone appears in the cells of the islets of Langerhans. In the pancreas, growth hormone appears to act locally by inhibiting the release of insulin and glucagon from the endocrine cells.
Hormone Metabolism
known hormones fall into three chemical groups: proteins, steroids and amines. Those who belong to the group of proteins or polypeptides include hormones produced by the anterior pituitary, parathyroid, placenta and pancreas. In the group of steroid hormones are the adrenal cortex and gonads. Amines are produced by the adrenal and thyroid. Hormone synthesis takes place inside cells and, in most cases, the product is stored inside until it is released into the blood. However, the thyroid and the ovaries contain special areas for storage of hormones.
The release of hormones depends on blood levels of certain hormones and other metabolic products under hormonal influence, as well as nerve stimulation. The production of the hormones of the anterior pituitary is inhibited when the gland caused by target (target) particular, adrenal cortex, thyroid and gonads circulate in the blood. For example, when a certain amount of thyroid hormone in the bloodstream the pituitary disrupts production of thyroid stimulating hormone to the thyroid hormone levels drop. Therefore, circulating hormone levels are maintained in a constant balance. This mechanism, known as homeostasis or negative feedback, is similar to the activation system with a thermostat for the temperature of a room on or off a prolonged administration caldera.La from outside adrenocortical hormones, thyroid, sexual and almost completely stopped the production of hormones for stimulating of the pituitary gland, causing temporary atrophy of the glands target. On the contrary, if the target gland production is far below the normal level, the continuous production-stimulating hormone produced by the pituitary gland hypertrophy, such as goiter yodo.La deficit hormone release is also regulated the amount substances circulating in blood, whose presence or use is under hormonal control. High levels of glucose in the blood stimulate the production and release of insulin while low levels stimulate the adrenal glands to produce adrenaline and glucagon, and maintaining the balance in the metabolism of carbohydrates. Similarly, a deficit of calcium in the blood stimulates the secretion of PTH, whereas high levels stimulate the release of calcitonin by tiroides.La endocrine function is also regulated by the nervous system, as evidenced by the adrenal response to stress. The different endocrine organs are subjected to various forms of nervous control. The adrenal medulla and posterior pituitary glands are richly innervated and controlled directly by the nervous system. However, the adrenal cortex, thyroid and gonads, although nerve respond to various stimuli, lack of specific innervation and maintain their function when transplanted to other parts of the body. The anterior pituitary innervation is sparse, but can not work if trasplanta.Se know how hormones exert many metabolic and morphological effects. However, it is thought that the effects on cell function is due to its action on cell membranes or enzymes, by regulating the expression of genes or by regulating the release of ions or other small molecules. Although apparently not consumed or changed in the metabolism, hormones can be largely destroyed by chemical degradation. Final hormone products quickly and are excreted in the urine found in large quantities, and also in feces and sweat.
endocrine cycles
The endocrine system exerts a regulatory effect on the cycles of reproduction, including the development of the gonads, the period of functional maturation and subsequent aging and menstrual cycle and pregnancy period. The cyclical pattern of estrus, which is the period during which it is possible fertile breeding animals, is also regulated by hormonas.La puberty, sexual maturation period is determined by an increased secretion of pituitary hormones that stimulate the gonads or gonadotropins, which produce the maturation of the testes or ovaries and increase the secretion of sex hormones. In turn, sex hormones act on the sexual organs and sexual development subsidiary GENERAL. women, puberty is associated with the onset of menstruation and ovulation. Ovulation is the release that of an egg from an ovarian follicle, occurs approximately every 28 days, between day 10 and 14 of the menstrual cycle in women. The first part of the cycle is marked by the menstrual period, which covers an average of three to five days, and the maturation of the ovarian follicle under the influence of follicle stimulating hormone from the pituitary. After ovulation and under the influence of another hormone, called luteinizing hormone, the empty follicle forms an endocrine body called the corpus luteum, which secretes progesterone, estrogen, and it is likely that during pregnancy, relaxin. Progesterone and estrogen prepare the uterine lining for pregnancy. If this does not occur, the corpus luteum regresses, and the uterine lining, deprived of hormonal stimulation, it disintegrates and peels produce menstrual bleeding. The rhythmic pattern of menstruation is explained by the inhibition-stimulation reciprocal relationship between estrogen and the pituitary-stimulating hormones gónadas.Si pregnancy occurs, the placental secretion of gonadotropins, progesterone and estrogen maintains the corpus luteum and endometrium and prepares the breasts for milk production and lactation. The secretion of estrogen and progesterone is high during pregnancy and reaches its peak just before birth. Lactation occurs shortly after birth, presumably as a result of changes in hormonal balance after separation of the placenta .
With the progressive aging of the ovaries, and decreased production of estrogen, menopause occurs. In this period of gonadotropin secretion increases as a result of the absence of inhibition of estrogen. In men the corresponding period is marked by a gradual reduction in the secretion of androgens.
With the progressive aging of the ovaries, and decreased production of estrogen, menopause occurs. In this period of gonadotropin secretion increases as a result of the absence of inhibition of estrogen. In men the corresponding period is marked by a gradual reduction in the secretion of androgens.
disorders of endocrine function
Changes in production can be classified as endocrine hyperfunction (excess activity) or hypofunction (insufficient activity). An overactive thyroid gland may be caused by a hormone-producing tumor is benign or, less commonly, malignant. Hypofunction may be due to birth defects, cancer, inflammatory lesions, degeneration, disorders affecting the pituitary target organs, trauma, or, in the case of thyroid disease, iodine deficiency. Hypofunction may also result from surgical removal of a gland or destruction by radiotherapy. Hyperfunction of the anterior pituitary with the overproduction of growth hormone causes acromegaly or gigantism sometimes, or if there is excess hormone production stimulating the adrenal cortex may be a group of symptoms known as Cushing syndrome, including hypertension, weakness, polycythemia, purple striae, and a special type of obesity. The anterior pituitary deficiency leads to dwarfism (if it appears at the beginning of life), lack of sexual development, weakness, and sometimes severe malnutrition. A decrease in the activity of the adrenal cortex causes Addison's disease, while excessive activity may cause Cushing syndrome or virilism result, the appearance of male secondary sexual characteristics in women and children. Alterations function of the gonads mainly affect the development of primary and secondary sexual characteristics. Thyroid deficiencies produce cretinism and dwarfism in infants, and myxedema, characterized by coarse features and decreased mental and physical reactions in the adult. Overactive thyroid (Graves' disease, toxic goiter) is characterized by bulging eyes, trembling and sweating, increased pulse rate, heart palpitations and nervous irritability. Diabetes insipidus is due to antidiuretic hormone deficiency, and diabetes mellitus , a defect in the production of the pancreatic hormone insulin, or can be the result of inadequate response of the organism.
