Renal System Chapter 14 PDF
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West Virginia University
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This document contains notes on the renal system, covering topics such as the function of the kidney, nephron structure, vascular and tubular components, the difference between two types of nephrons, and the pathway of blood through the kidney.
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Chapter 14 – Renal -What are the main functions of the kidney? Know the general structure/anatomical components. Kidneys supplied by a single renal artery and vein Body roughly divided into cortex and medulla Medula consisting of pyramids Urine collecte...
Chapter 14 – Renal -What are the main functions of the kidney? Know the general structure/anatomical components. Kidneys supplied by a single renal artery and vein Body roughly divided into cortex and medulla Medula consisting of pyramids Urine collected by major and minor calices; drains into pelvis and to ureter -Theoretically if you compare the renal artery to the renal vein, you’ll be able to figure out what the kidney did. What is the nephron? Functional unit of the kidney consisting of filtering glomerulus and tubule system surrounded by capillaries What are the vascular components of nephron? Afferent arteriole, efferent arteriole, glomerulus, peritubular capillaries and vasa recta Tubular components of nephron? Bowman’s capsule Proximal tubules Loop of henle Distal tubules Collecting ducts What are the two types of nephrons? About 1 million nephrons per kidney Two types: superficial (cortical) nephrons and juxtamedullary nephrons Cortical nephronsare more numerous than juxtamedullarynephrons. About 85% of the nephrons in the kidney are cortical nephrons, while the remaining 15% are juxtamedullary nephrons. Juxtamedullary nephrons have long loops of henle surrounded by vasa recta Superficial nephrons have short loops of henle surrounded by peritubular capillaries Cortical nephrons function: reabsorption and secretion Juxtamedullary nephrons function: reabsorption and secretion alongside contributing electrolytes to the vertical osmotic gradient Know the pathway of blood through the kidney focusing on only the pieces I said you needed to know Heart - Aorta - Renal Artery - Segmental Artery - Lobar Artery - Arcuate Artery - Interlobular Artery - Afferent Arteriole - Glomerulus (capillaries) - Efferent Arteriole - Peritubular Capillaries - Interlobular Vein - Arcuate Vein - Interlobar Vein - Renal Vein - Inferior Vena Cava - Heart Big picture: our kidney’s job is to filter the blood, we want to keep the good stuff and get rid of the bad via urine. Blood enters the kidney which then (1) filters into the tubular components. That filtrate then traverses the tubular components where it undergoes (2) reabsorption and (3) secretion until eventually we have produced urine. Urine is excreted via the ureters, bladder, urethra. Know the difference between tubular reabsorption and tubular secretion Tubular Reabsorption: selective transfer of specific substances in the filtrateback into the bloodof the peritubular capillaries Tubular Secretion: selective transfer of substances from the peritubular capillary blood into the tubular lumen Know the micturition reflex. Micturition reflex: urine is temporarily stored in the bladder and emptied Involves bladder contraction and opening of both the internal and external urethral sphincters Bladder wall: detrusor smooth muscle Internal sphincter: smooth muscle and involuntary control External sphincter: skeletal muscle and voluntary control Sympathetic activity: relaxes the bladder allowing it to fill Parasympathetic activity: stretch receptors trigger parasympathetic activity and causes smooth muscle in bladder to contract and internal sphincter opens GLOMERULUS -Go back and review the general rules of bulk flow across capillary beds. hydrostatic pressure > colloid osmotic pressure = ultrafiltration [ in glomerulus] hydrostatic pressure < colloid osmotic pressure = reabsorption [in peritubular capillaries] -What are the three things that allow the glomerulus a greater rate of exchange? -Be able to think through what happens when I...what does this do to GFR? (1) constrict the afferent arteriole leave efferent alone Constriction of the afferent arteriole → Reduced blood flow into the glomerulus → Lower glomerular pressure → Decreased GFR (2) constrict the afferent arteriole and constrict the efferent the glomerular filtration rate (GFR) is likely to decrease due to a reduction in renal blood flow (RBF) (3) constrict the afferent arteriole and dilate the efferent Constriction of the Afferent Arteriole reduces blood flow into the glomerulus, which lowers the glomerular capillary pressure, tending to decrease GFR. Dilation of the Efferent Arteriole allows blood to exit the glomerulus more easily, further reducing glomerular capillary pressure and lowering GFR. Together, these actions decrease the pressure within the glomerulus, leading to a significant reduction in GFR. (4) dilate the afferent arteriole leave efferent alone Dilation of the Afferent Arteriole increases blood flow into the glomerulus, raising the glomerular capillary pressure, which promotes filtration and increases GFR. No change to the Efferent Arteriole means there is no additional resistance to blood leaving the glomerulus, so the increased inflow directly results in higher glomerular pressure. In summary, dilating the afferent arteriole while keeping the efferent unchanged results in an increase in GFR due to the higher glomerular capillary pressure. (2) dilate the afferent arteriole and constrict the efferent Dilation of the Afferent Arteriole increases blood flow into the glomerulus, raising the pressure in the glomerular capillaries, which promotes filtration. Constriction of the Efferent Arteriole increases resistance to blood leaving the glomerulus, further raising glomerular capillary pressure. These combined effects lead to a significant rise in glomerular capillary pressure and, consequently, a substantial increase in GFR. (3) dilate the afferent arteriole and dilate the efferent If you dilate both the afferent and efferent arterioles,the glomerular filtration rate (GFR) will increase What is NFP? Net Filtration Pressure (NFP)is the overall pressurethat drives fluid and solutes out of the blood in the glomerulus and into the Bowman’s capsule, initiating the process of filtration in the kidneys. NFP is determined by the balance of several pressures across the glomerular capillaries Glomerular Capillary Hydrostatic Pressure (PGC_{\text{GC}}GC):The blood pressure within the glomerular capillaries that pushes water and solutes out of the blood and into the filtrate (typically around 55 mm Hg). Bowman’s Capsule Hydrostatic Pressure (PBC_{\text{BC}}BC): The pressure exerted by the fluid already in Bowman’s capsule, which opposes filtration (typically around 15 mm Hg). Glomerular Capillary Colloid Osmotic Pressure (πGC_{\text{GC}}GC):The osmotic pressure exerted by proteins in the blood, which pulls water back into the glomerular capillaries and opposes filtration (typically around 30 mm Hg). What happens to GFR when NFP goes up? WhenNet Filtration Pressure (NFP) increases, theglomerular filtration rate (GFR) also increases. This is because NFP is the drivingforce behind the filtration process in the glomerulus. An increase in NFP means that there is a higher pressure pushing fluid and solutes out of the blood in the glomerulus and into Bowman’s capsule, resulting in a greater rate of filtration, which directly raises GFR. What happens to GFR when NFP goes down? WhenNet Filtration Pressure (NFP) decreases, theglomerular filtration rate (GFR) also decreases. This is because NFP is the drivingforce for moving fluid and solutes from the blood in the glomerulus into Bowman’s capsule to form filtrate. A lower NFP means there is less pressure pushing fluid out of the glomerular capillaries, resulting in a reduced rate of filtration. Consequently, GFR declines. How are we able to keep the BP across the glomerulus constant?
