Role of the Kidney in Fluid Balance
Lab 7: The Kidney’s Role in Fluid Balance
Introduction
The renal system performs a vital role in homeostasis. The kidneys’ ability to retain valuable constituents and expel metabolic wastes from the body enables this system to regulate the volume, osmolarity, and pH of body’s internal fluid environment (Sherwood, 2007, p. 511). The functional unit of the kidney, referred to as the nephron, is composed of both tubular components—Bowman’s capsule proximal tubule, loop of Henle, the distal tubule, and the collecting duct—and vascular components—afferent arteriole, glomerulus, efferent arteriole, and peritubular capillaries (Sherwood, 2007, p. 514).
Through its vascular and tubular components, the nephron performs three basic functions in order to carry out its regulatory role in the kidney: glomerular filtration, tubular reabsorption, and tubular secretion. In the initial phase of urine creation, otherwise known as glomerular filtration, roughly 20% of plasma from the afferent arteriole flows through the glomerular capillaries and into the Bowman’s capsule. As this newly formed filtrate travels through the nephron, it is subject to proximal and distal tubular reabsorption, where substances from the filtrate return to circulation by moving into the peritubular capillaries. On the other hand, substances can move in the opposite direction, from the peritubular capillaries into the filtrate, referred to as proximal and distal tubular secretion (Sherwood, 2007, p. 515).
A critical determinant of urine composition lies is the differences between the proximal and distal tubule. The proximal tubule is specialized for bulk reabsorption (67-80% of filtrate) to balance the glomerular filtration rate without hormones or sympathetic nervous system innervation. Whereas the distal tubule reabsorption is hormonally regulated, allowing the nephron to form dilute or concentrated urine to maintain internal fluid homeostasis (Sherwood, 2007, p. 548).
The aim of this study
Introduction
The renal system performs a vital role in homeostasis. The kidneys’ ability to retain valuable constituents and expel metabolic wastes from the body enables this system to regulate the volume, osmolarity, and pH of body’s internal fluid environment (Sherwood, 2007, p. 511). The functional unit of the kidney, referred to as the nephron, is composed of both tubular components—Bowman’s capsule proximal tubule, loop of Henle, the distal tubule, and the collecting duct—and vascular components—afferent arteriole, glomerulus, efferent arteriole, and peritubular capillaries (Sherwood, 2007, p. 514).
Through its vascular and tubular components, the nephron performs three basic functions in order to carry out its regulatory role in the kidney: glomerular filtration, tubular reabsorption, and tubular secretion. In the initial phase of urine creation, otherwise known as glomerular filtration, roughly 20% of plasma from the afferent arteriole flows through the glomerular capillaries and into the Bowman’s capsule. As this newly formed filtrate travels through the nephron, it is subject to proximal and distal tubular reabsorption, where substances from the filtrate return to circulation by moving into the peritubular capillaries. On the other hand, substances can move in the opposite direction, from the peritubular capillaries into the filtrate, referred to as proximal and distal tubular secretion (Sherwood, 2007, p. 515).
A critical determinant of urine composition lies is the differences between the proximal and distal tubule. The proximal tubule is specialized for bulk reabsorption (67-80% of filtrate) to balance the glomerular filtration rate without hormones or sympathetic nervous system innervation. Whereas the distal tubule reabsorption is hormonally regulated, allowing the nephron to form dilute or concentrated urine to maintain internal fluid homeostasis (Sherwood, 2007, p. 548).
The aim of this study
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