Overview of Renal System Flashcards
What are the functions of the renal system?
What is the clinical significance of monitoring kidney function?
How do substances “enter” the kidney?
What are the possible ways they can be processed in the kidney (3)?
Describe the ways in which substances can be filtered, secreted, reabsorbed and excreted along the nephron.
What substances can be secreted at the level of the proximal tubule?
What substances can be reabsorbed?
What substances can be reabsorbed at the level of the thin loop of henle?
Water only
What substances can be secreted at the bottom of the loop of henle?
Urea only
What substances can be reabsorbed in the thick ascending limb of the loop of henle?
What substances can be secreted at the level of the distal convoluted tubule?
What substances can be reabsorbed?
What substances are secreted at the level of the proximal collecting duct?
What substances are reabsorbed at the level of the distal collecting duct?
- What is renal blood flow?
- How much blood do the kidneys receive in a day?
- What is a normal RBF?
- Volume of blood delivered to kidney per unit time
- 25%
- 1.25 L/min
- Why do you use renal plasma flow to assess kidney function instead of renal blood flow?
- What is the Fick Principle and how does it apply to the kidney?
- How can you calculate the arterial input of a substance to the kidney?
The kidney does not […] substances. What enters the kidney leaves either via the […] or the […].
change, add to, or utilize
renal vein
urine
- What is PAH?
- Why can it be used to measure RPF?
- What equation relates PAH to renal plasma flow?
- Is this technique used in a clinical or research setting?
Used in research setting
- What is clearance?
- What is renal clearance?
- What is the difference between high and low clearance of a substance?
- What is the clearance of albumin and glucose?
- Why can inulin be used to measure clearance?
- Are clearance measurements using inulin done in a clinical or research setting?
- Inulin is a fructose polymer that is delivered via IV that is freely filtered across the glomerulus, but is not reabsorbed along the nephron and it is also not secreted from the plasma anywhere else along the nephron. Therefore, its clearance from the blood reflects purely the rate of filtration at the glomerulus (GFR).
- Research
How can we clinically measure GFR?
Using creatinine. Creatinine is a byproduct of muscle metabolism that is essentially purely filtered at the glomerulus. It is not reabsorbed from the filtrate, and very little is secreted (so little it’s negligible). Therefore, creatinine clearance represents purely the filtration of the glomerulus.
What is fractional excretion?
What is tubular transport?
What is filtered load?
- What is the filtration fraction?
- What is a normal FF?
- What is the equation for FF?
- Aren’t GFR and RPF the same thing? What would happen to GFR if RPF decreased?
GFR and RPF are not the same. GFR just reflects the proportion of the plasma that is filtered in the glomerulus. The plasma can be be filtered throughout the remainder of the nephron at different points due to secretion / reabsorption of specific substances along the nephron. If the efferent arteriole of the glomerulus were kinked (decrease in RPF) or obstructed, then GFR would increase because less of the plasma would be filtered in the remainder of the nephron since blood wouldn’t be reaching it.
- Describe the forces that push / pull water into and out of the glomerulus into bowman’s capsule.
- What is the net amount of pressure driving water out of the arterioles and into the filtrate of bowman’s capsule?
- Arterial blood flows with a certain amount of pressure, which means that pressure can exert a force on the fenestrated capillary membrane of the glomerulus to force water out of the arterial system and into the filtrate of bowman’s capsule.
- Once water is forced out of the arterial system, the blood that is left in the arterioles of the glomerulus is dehydrated, so it’s oncotic pressure (due to proteins) is high, meaning it will want to pull water back into the arterioles.
- Once the area around the glomerulus fills with filtrate, the capsule itself will exert pressure on the arterioles in the glomerulus which will also push water out of filtrate and back into arterioles.
- 10mmHg
Describe the mechanism of reabsorption of Na+ in the PCT.
Na+/K+ ATPase pump moves 3Na+ out of epithelial cells between PCT and peritubular capillaries –> creates low [Na+] inside epithelial cell which generates a favorable thermodynamic gradient for Na+ to enter the epithelial cell –> Na+ can enter epithelial cell via symporter (Na+ and substance X are transported in same direction, into the cell) or a transporter that moves Na+ into cell and H+ out of cell as a means of clearing H+ from the blood.
As you move deeper into the renal medulla, the osmolarity gradient increases. How does the body maintain this increasing osmolarity gradient and what physiologic purpose does it serve?
In the ascending (thick) loop of Henle, there are Na+/K+ ATPase pumps that move 3Na+ out of cells that line the nephron here and into renal medulla. This creates a low [Na+] inside these cells, making the movement of more Na+ from the filtrate into these cell favorable. A Na+/K+/2Cl- symporter then is able to use the now thermodynamically favorable Na+ gradient to co-transport these molecules out of the filtrate and into the renal medulla. This is done so that there is a high osmolarity in the deeper parts of the loop of Henle, which will draw water out of the filtrate and back into the body.
What is the mechanism of action of furosemide?
When might this be used clinically?
Furosemide is a diuretic. It inhibits the Na+/K+/2Cl- co transporter thus disrupting the osmolarity gradient in the kidney. If the osmolarity gradient is diminished, then less water will be reabsorbed, leading to increased filtrate and increased urine production.
What is the affect of ADH on the nephron?
