Anatomy and Physiology of the Renal System
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This chapter discusses renal function and structure. By 35 weeks’ gestation the renal system is fully developed, although the kidneys do not fully function until several days after birth. The kidneys continue to grow until adolescence when overall body growth stops. The regulation of fluid volume, blood pressure, excretion of metabolic waste products, and drug metabolites are the primary functions of the renal system. The kidneys are also responsible for conversion of vitamin D to its active form, serum pH regulation, and synthesis of hormones, such as erythropoietin and renin.
The kidneys do not fully function until several days after birth.Atrial natriuretic peptide, a hormone discovered in 1981, is released from muscle cells in the atria when the atrial walls are stretched. This hormone causes the vasodilation of afferent arterioles, which lead into the glomerulus, and efferent arterioles, which lead out of the glomerulus, resulting in an increased glomerular filtration rate. Atrial natriuretic peptide also inhibits aldosterone secretion and sodium reabsorption from the collecting tubules. All these actions result in increased urine production and a reduction in blood volume.
All these actions result in increased urine production and a reduction in blood volume.The hormone erythropoietin stimulates the bone marrow to produce red blood cells in response to hypoxia from conditions such as anemia or from cardiac and/or pulmonary disease. If iron stores are adequate, an increase in red blood cells results in added oxygen-carrying capacity and reduced tissue hypoxia. As renal insufficiency progresses to renal failure, the kidneys’ ability to produce erythropoietin declines, causing one form of anemia.
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