Endocrine System Student Copy PDF

ENDOCRINE SYSTEM PREPARED BY: JIAN MIDJ A. OCO, PTRP PRESENTED BY: ORIEL M. REPIL, PTRP, MD, OHP  OVERVIEW + The hormones of the endocrine system contribute to homeostasis by regulating the activity and growth of target cells in your body. Hormones also regulate your metabolism. + In gi...

ENDOCRINE SYSTEM PREPARED BY: JIAN MIDJ A. OCO, PTRP PRESENTED BY: ORIEL M. REPIL, PTRP, MD, OHP  OVERVIEW + The hormones of the endocrine system contribute to homeostasis by regulating the activity and growth of target cells in your body. Hormones also regulate your metabolism. + In girls, ESTROGEN promote accumulation of adipose tissue in the breasts and hips, sculpting a feminine shape. + At the same time or a little later, increasing levels of TESTOSTERONE in boys begin to help build muscle mass and enlarge the vocal cords, producing a lower-pitched voice. + NERVOUS SYSTEM - acts through nerve impulses conducted along axons of neurons. At synapses, nerve impulses trigger the release of mediator (messenger) molecules called neurotransmitters + ENDOCRINE SYSTEM - controls body activities by releasing mediators, called hormones.  OVERVIEW + HORMONE - is a molecule that is released in one part of the body but regulates the activity of cells in other parts of the body. + Most hormones enter interstitial fluid and then the bloodstream. + The circulating blood delivers hormones to cells throughout the body. + Responses of the endocrine system often are slower than responses of the nervous system + Nervous System – acts on specific muscles and glands + Endocrine System – regulates virtually in all types of body cells. (much broader in influence) NS & ES function together as an interlocking “supersystem.”  ENDOCRINE GLAND +EXOCRINE GLANDS - secrete their products into ducts that carry the secretions into body cavities, into the lumen of an organ, or to the outer surface of the body. + sudoriferous, sebaceous, mucous, and digestive glands +ENDOCRINE GLANDS - secrete their products (hormones) into the interstitial fluid surrounding the secretory cells rather than into ducts. + pituitary, thyroid, parathyroid, suprarenal, and pineal glands +HORMONE-SECRETING CELLS - are not exclusively classified as endocrine glands but contain cells that secrete hormones. + hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, and placenta. +Taken together, all endocrine glands and hormone-secreting cells constitute the ENDOCRINE SYSTEM HYPOTHALAMUS and PITUITARY GLAND +PITUITARY GLAND/hypophysis - was called the “master” endocrine gland because it secretes several hormones that control other endocrine glands. (secretes seven) +HYPOTHALAMUS – master of pituitary gland, a small region of the brain below the thalamus is the major link between the nervous and endocrine systems. (synthesize at least nine different hormones) +Together, these hormones play important roles in the regulation of virtually all aspects of growth, development metabolism, and homeostasis.  PITUITARY GLAND + PITUITARY GLAND - is a pea-shaped structure that measures 1–1.5 cm (0.5 in.) in diameter and lies in the hypophysial fossa of the sella turcica of the sphenoid bone. + INFUNDIBULAR STALK - attaches PG to the hypothalamus, has two anatomically and functionally separate portions: A. ANTERIOR PITUITARY (anterior lobe)/adenohypophysis - accounts for about 75% of the total weight of the gland and is composed of epithelial tissue. a. PARS DISTALIS - is the larger portion b. PARS TUBERALIS - forms a sheath around the infundibular stalk B. POSTERIOR PITUITARY (posterior lobe)/ neurohypophysis - is composed of neural tissue. a. PARS NERVOSA - the larger bulbar portion, and the infundibular stalk. b. PARS INTERMEDIA - third region of the pituitary gland that atrophies during human fetal development and ceases to exist as a separate lobe in adults  ANTERIOR PITUITARY - secretes hormones that regulate a wide range of bodily activities, from growth to reproduction. 1. SOMATOTROPHIC CELLS - secrete GROWTH HORMONE 4. PROLACTIN CELLS - secrete PROLACTIN (pRL), (GH)/somatotropin. Growth hormone stimulates which initiates milk production in the mammary general body growth and regulates aspects of glands. metabolism. 5. CORTICOTROPHIC CELLS - secrete 2. THYROTROPHIC CELLS - secrete THYROID STIMULATING ADRENOCORTICOTROPHIC HORMONE HORMONE (tSH)/thyrotropin. TSH controls the secretions and other activities of the thyroid gland. (aCtH)/corticotropin, which stimulates the suprarenal cortex to secrete glucocorticoids such 3. GONADOTROPHIC CELLS - secrete two gonadotropins: as CORTISOL. FOLLICLE STIMULATING HORMONE (FSH) and LUTEINIZING HORMONE (LH). FSH and LH both act on Some corticotrophs, remnants of the pars the gonads (testes and ovaries). intermedia, also secrete MELANOCYTE- STIMULATING HORMONE (MSH). In men, they stimulate the testes to produce sperm and to secrete testosterone. In women, they stimulate the ovaries to mature oocytes (eggs) and to secrete estrogens and progesterone.  POSTERIOR PITUITARY +POSTERIOR PITUITARY - does not synthesize hormones, but it does store and release two hormones +It consists of axons and axon terminals of more than 10,000 hypothalamic neurosecretory cells. +PARAVENTRICULAR and SUPRAOPTIC NUCLEI of the hypothalamus, their axons form the HYPOTHALAMIC–HYPOPHYSEAL TRACT (begins in the hypothalamus and ends near blood capillaries in the posterior pituitary) +2 hormones released by neuronal cell bodies of both the paraventricular and the supraoptic nuclei: 1. OXYTOCIN (OT) – contraction of uterus, milk ejection 2. ANTIDIURETIC HORMONE (aDH)/vasopressin – decreases urine production  POSTERIOR PITUITARY +2 hormones released by neuronal cell bodies of both the paraventricular and the supraoptic nuclei: 1. OXYTOCIN (OT) +FEMALE: During and after delivery of a baby, it affects two target tissues: the mother’s uterus and breasts. During delivery, stretching of the cervix of the uterus stimulates the release of oxytocin which, in turn, enhances contraction of smooth muscle fibers in the wall of the uterus After delivery, it stimulates milk ejection from the mammary glands in response to the mechanical stimulus provided by a suckling infant. +MALE and NON-PREGNANT FEMALE: unknown function It may also be responsible, in part, for the feelings of sexual pleasure during and after intercourse.  POSTERIOR PITUITARY 2. ANTIDIURETIC HORMONE (aDH)/vasopressin +causes the kidneys to return more water to the blood, thus decreasing urine volume/production. +In the absence of ADH, urine output increases more than tenfold, from the normal 1 to 2 liters to about 20 liters a day +Drinking alcohol often causes frequent and copious urination because alcohol inhibits secretion of ADH. + (This dehydrating effect of alcohol may cause both the thirst and the headache typical of a hangover.) +ADH also decreases the water lost through sweating and causes constriction of arterioles, which increases blood pressure.  THYROID GLAND +THYROID GLAND - butterfly- shaped gland located just inferior to the larynx (voice box). +It is composed of RIGHT and LEFT LOBES, one on either side of the trachea, that are connected by an ISTHMUS anterior to the trachea +About 50% of thyroid glands have a small third lobe, called the PYRAMIDAL LOBE. It extends superiorly from the isthmus. The normal mass of the thyroid is about 30 g (1 oz). +THYROID FOLLICLES - microscopic spherical sacs that make up most of the thyroid gland. + The wall of each follicle consists primarily of cells called T THYROCYTES (follicular cells), most of which extend to the lumen (internal space) of the follicle. +BASEMENT MEMBRANE - surrounds each follicle. + When the T thyrocytes are inactive, their shape is low cuboidal to squamous, but under the influence of TSH they become active in secretion and range from cuboidal to low columnar in shape.  THYROID GLAND +The T THYROCYTES/follicular cells produce two hormones: 1. THYROXINE/tetraiodothyronine (T4) - because it contains four atoms of iodine 2. TRIIODOTHYRONINE (T3) - which contains three atoms of iodine. T3 and T4 together are also known as THYROID HORMONES +T thyrocytes also produce THYROGLOBULIN +C THYROCYTES /(parafollicular cells) - lie between follicles, produces hormone CALCITONIN (Ct)  ACTIONS OF THYROID HORMONES (T3/T4) 1. Increase basal metabolic rate. Thyroid hormones raise the basal metabolic rate (BMR), the rate of energy expenditure under standard or basal conditions (awake, at rest, and fasting). 2. Enhance actions of catecholamines. (epinephrine and norepinephrine) The “fight or flight” response of the sympathetic nervous system. Therefore, symptoms of excess levels of thyroid hormone include increased heart rate, more forceful heartbeats, and increased blood pressure. 3. Regulate development and growth of nervous tissue and bones. + Nervous system: promote synapse formation, myelin production, and growth of dendrites. + Growth of the skeletal system: They promote formation of ossification centers in developing bones, synthesis of many bone proteins, and secretion of growth hormone (GH) and insulin-like Growth factors (IGFs). + Deficiency of thyroid hormones during fetal development, infancy, or childhood causes severe mental retardation and stunted bone growth. CALCITONIN +produced by the C thyrocytes of the thyroid gland +CT can decrease the level of calcium in the blood by inhibiting the action of OSTEOCLASTS (the cells that break down bone extracellular matrix) +When its blood level is high, calcitonin lowers the amount of blood calcium and phosphates by inhibiting bone resorption (breakdown of bone extracellular matrix) by osteoclasts and by accelerating uptake of calcium and phosphates into bone extracellular matrix.  PARATHYROID GLANDS/HORMONE +PARATHYROID GLANDS - small, round masses of tissue partially embedded in the posterior surface of the lobes of the thyroid gland +Each has a mass of about 40 mg (0.04 g). Usually, one superior and one inferior parathyroid gland are attached to each thyroid lobe for a total of four. +PARATHYROID HORMONE (PTH) - +The specific action of PTH is to increase the number and activity of osteoclasts. The result is elevated bone resorption, which releases ionic calcium (Ca2+) and phosphates (HPO4 2−) into the blood. + CALCITRIOL – active form of vitamin D, PTH on kidneys promote formation of this hormone, it increases the rate of Ca2+, HPO4 2−, and Mg2+ absorption from the digestive canal into the blood.  SUPRARENAL (ADRENAL) GLAND + SUPRARENAL GLAND/adrenal glands (paired) - one of which lies superior to each kidney in the retroperitoneal space, have a flattened pyramidal shape. (highly vascularized) + In an adult, each suprarenal gland is 3–5 cm in height, 2–3 cm in width, and a little less than 1 cm thick, with a mass of 3.5–5g, only half its size at birth 1. SUPRARENAL CORTEX - large, peripherally located, comprising 80–90% of the gland + ZONA GLOMERULOSA – outer zone, secretes hormone called MINERALOCORTICOIDS – ALDOSTERONE (affect mineral homeostasis) + ZONA FASCICULATA – middle zone, widest, secretes GLUCOCORTICOIDS – Cortisol (Glucose homeostasis) + ZONA RETICULARIS – inner zone, synthesize small amounts of weak ANDROGENS (steroid hormones that have masculinizing effects) 2. SUPRERENAL MEDULLA – small, inner region of the suprarenal gland, is a modified sympathetic ganglion of the autonomic nervous system (ANS). – the hormones released intensify sympathetic responses that occur in other parts of the body. + CHROMAFFIN CELLS –hormone-producing cells, are innervated by sympathetic preganglionic neurons of the ANS. + NOREPINEPHRINE/adrenaline/noradrenaline – 80%; EPINEPHRINE – 20%  PANCREAS + PANCREAS - is both an endocrine gland and an exocrine gland. + A flattened organ that measures about 12.5–15 cm (5–6 in.) in length, the pancreas is in the curve of the duodenum, the first part of the small intestine, and consists of a head, a body, and a tail + PANCREATIC ACINI – cluster of exocrine cells that makes up roughly 99% of the cells of the pancreas + The pancreatic acini produce DIGESTIVE ENZYMES, which flow into the digestive canal through a network of ducts. + PANCREATIC ISLETS/Islets of Langerhans - 1–2 million tiny clusters of endocrine cells scattered among the pancreatic acini. + Each pancreatic islet includes four types of hormone- secreting cells: + 1. Alpha or A cells constitute about 17% of pancreatic islet cells and secrete GLUCAGON + 2. Beta or B cells constitute about 70% of pancreatic islet cells and secrete INSULIN + 3. Delta or D cells constitute about 7% of pancreatic islet cells and secrete SOMATOSTATIN + 4. Pancreatic polypeptide cells constitute the remainder of pancreatic islet cells and secrete PANCREATIC POLYPEPTIDE  OVARIES and TESTES +GONADS - organs that produce gametes— sperm in males and oocytes in females. In addition to their reproductive function, the gonads secrete hormones. 1. OVARIES +paired oval bodies located in the female pelvic cavity, produce several steroid hormones, including two ESTROGEN (estradiol and estrone) and PROGESTERONE. + These 2 hormones together with FSH and LH (anterior pituitary) - regulate the menstrual cycle, maintain pregnancy, and prepare the mammary glands for lactation. + They also promote enlargement of the breasts and widening of the hips at puberty and help maintain these female secondary sex characteristics. +INHIBIN - a protein hormone that inhibits secretion of FSH. + During pregnancy, the ovaries and placenta produce a peptide hormone called RELAXIN (RLX), which increases the flexibility of the pubic symphysis during pregnancy and helps dilate the uterine cervix during labor and delivery. These actions help ease the baby’s passage by enlarging the birth canal. OVARIES and TESTES 2. TESTES + are oval glands that lie in the scrotum. + TESTOSTERONE – androgen or male sex hormone + Testosterone stimulates descent of the testes before birth, regulates production of sperm, and stimulates the development and maintenance of male secondary sex characteristics, such as beard growth and deepening of the voice. + INHIBIN - which inhibits secretion of FSH.  PINEAL GLAND and THYMUS + PINEAL GLAND + is a small endocrine gland attached to the roof of the third ventricle of the brain at the midline + Part of the epithalamus, it is positioned between the two superior colliculi, has a mass of 0.1–0.2 g, and is covered by a capsule formed by the pia mater. + PINEALOCYTES - masses of neuroglia and secretory cells + MELATONIN - an amine hormone derived from serotonin. + Melatonin appears to contribute to the setting of the body’s biological clock, which is controlled by the suprachiasmatic nucleus of the hypothalamus. + As more melatonin is liberated during darkness than in light, this hormone is thought to promote sleepiness. + THYMUS - located behind the sternum between the lungs. + The hormones produced by the thymus—thymosin, thymic humoral factor (THF), thymic factor (TF), and thymopoietin promote the maturation of T cells (a type of white blood cell that destroys microbes and foreign substances) and may retard/slow down the aging process. QUESTIONS?