FNAP0115 Anatomy & Physiology (Laboratory) - Endocrine System PDF

FNAP0115 : ANATOMY AND PHYSIOLOGY (LABORATORY) ENDOCRINE SYSTEM Endocrine System – is the second major controlling system of the body. Acting with the nervous system, it helps coordinate and integrate the activity of the body’s cells. ▪ The nervous system us...

FNAP0115 : ANATOMY AND PHYSIOLOGY (LABORATORY) ENDOCRINE SYSTEM Endocrine System – is the second major controlling system of the body. Acting with the nervous system, it helps coordinate and integrate the activity of the body’s cells. ▪ The nervous system uses nerve impulses to bring about rapid control, whereas the more slowly acting endocrine system employs chemical messengers, or hormones, which are released into the blood to be transported throughout the body. ▪ The body’s hormones are steroids or amino acid–based molecules. Although hormones travel through the blood, a given hormone affects only a specific organ or organs. ▪ Cells within an organ that respond to a particular hormone are referred to as the target cells (also target) of that hormones. The ability of the target to respond depends on the ability of the hormone to bind with specific cellular receptors. ▪ Although the function of most hormone-producing glands is purely endocrine, the function of others (the pancreas and gonads) are mixed—both endocrine and exocrine. In addition, there are varied numbers of hormone-producing cells within the intestine, stomach, kidney, and placenta, organs whose functions are primarily nonendocrine. GROSS ANATOMY AND BASIC FUNCTION OF THE ENDOCRINE GLANDS A. PITUITARY GLANDS ▪ The pituitary gland is located in the sella turcica of the sphenoid bone. It has two functional areas, the anterior pituitary, which is glandular tissue, and the posterior pituitary (nervous tissue). A.1. ANTERIOR PITUITARY HORMONES The anterior pituitary, or adenohypophysis, secretes a number of hormones, four of which are tropic hormones. The target organ of a tropic hormone is another endocrine gland. Target organ hormones then produce their effects on other body organs and tissues. The anterior pituitary controls the activity of so many other endocrine glands that it has often been called the master endocrine gland. However, the anterior pituitary is not all-powerful, because release of its hormones is controlled by releasing or inhibiting hormones produced by the hypothalamus. These hypothalamic hormones are liberated into the blood of the portal circulation, which connects the blood supplies of the hypothalamus and anterior pituitary. A.2. POSTERIOR PITUITARY HORMONES The posterior pituitary is not an endocrine gland, because it does not synthesize the hormones it releases. Instead it acts as a storage area for hormones produced by the hypothalamus. Page 1 of 7 HORMONES OF THE ANTERIOR PITUITARY GLAND AND THIER MAJOR TARGET HORMONES STORED IN THE POSTERIOR PITUITARY GLAND HORMONES STORED IN THE POSTERIOR PITUITARY GLAND Page 2 of 7 B. THYROID GLAND ▪ The thyroid gland is composed of two lobes joined by a central mass, or isthmus. It is located in the anterior neck, just inferior to the larynx. ▪ It produces two major hormones, thyroid hormone and calcitonin. C. PARATHYROID GLANDS ▪ The parathyroid glands are embedded in the posterior surface of the thyroid gland. Typically, there are two small oval glands on each lobe, but there may be more and some may be located in other regions of the neck. They secrete parathyroid hormone (PTH). ANATOMY OF THYROID AND PARATHYROID GLANDS Page 3 of 7 D. ADRENAL GLANDS ▪ the two adrenal, or suprarenal, glands are located atop the kidneys. Anatomically, the adrenal medulla develops from neural tissue and is directly controlled by sympathetic nervous system. ▪ The medullary cells respond to this stimulation by releasing epinephrine (adrenaline) (80%) or norepinephrine (noradrenaline) (20%), which act with the sympathetic nervous system to produce the “fight-or-flight” response to stressors. ANATOMY OF ADRENAL GLAND Page 4 of 7 E. PANCREAS ▪ The pancreas, located posterior to the stomach in the abdomen, acts both as an exocrine and an endocrine gland. ▪ It produces digestive enzymes as well as insulin and glucagon, important hormones concerned with regulating blood sugar. ANATOMY OF PANCREAS F. THE GONADS ▪ The female gonads, or ovaries, are paired, almond-sized organs located in the pelvic cavity. In addition to producing the female sex cells (ova), the ovaries produce two groups of steroid hormones, estrogens and progesterone. The endocrine and exocrine functions of the ovaries do not begin until puberty, when the anterior pituitary gonadotropic hormones prod the ovary into action. The result is rhythmic ovarian cycles in which ova develop and hormone levels rise and fall. ▪ The paired oval testes of the male are suspended in a pouchlike sac, the scrotum, outside the pelvic cavity. Besides the male sex cells (sperm), the testes produce the male sex hormone, testosterone. Page 5 of 7 G. THYMUS ▪ The thymus is situated in the superior thorax, posterior to the sternum and overlying the heart. It is large in the infant, begins to atrophy at puberty, and by old age it is relatively inconspicuous. ▪ The thymus produces several hormones, including thymosin, thymulin, and thymopoietins. These hormones are thought to be involved in the development of T lymphocytes and the immune response. ANATOMY OF THYMUS H. PINEAL GLAND ▪ The small, pinecone-shaped pineal gland hangs from the roof of the third ventricle of the brain. ▪ Its major endocrine product is melatonin, which appears to be involved in the sleep-wake cycle. Melatonin levels peak at night, making us drowsy, and are lowest around noon. Recent evidence suggests that melatonin has anti-aging properties. Melatonin appears to play a role in the production of antioxidants. LOCATION OF PINEAL GLAND Page 6 of 7 SUMMARY OF SELECT ENDOCRINE HOMEOSTATIC IMBALANCE THE ENDOCRINE SYSTEM Prepared by: CAHS - School of Midwifery Anatomy and Physiology Cluster Page 7 of 7