Renal Basics – Answers

1.  Identify the 4 major parts of the urinary system. What does each one do?

·         Organ: Kidneys

o   Function: Filter blood

·         Organ: Ureters

o   Function: Allow urine to flow from kidneys to bladder.

·         Organ: Bladder

o   Function: Store/Hold urine until it is appropriate to void.

·         Organ: Urethra

o   Function: Allow urine to flow from bladder to the toilet…hopefully.


2. Let’s go waaay back to A&P. Remember the nephron, the functional unit of the kidneys? Not so much? Well it’s time to review! Describe the different part of the nephron, and identify what each part does. You could even draw a picture if you want! (Don’t peek ahead to #4 until you answer this question first!)

·         Glomerulus

o   Capillary network that has a semi-permeable membrane that only allows certain things to leave the blood stream. Bascially, it is just a fancy name for blood vessels that happen to go inside of Bowman’s Capsule. This is where the first step of the blood filtering process happens.

·         Bowman’s Capsule

o   Everything that leaves the blood through the glomerulus is collected in Bowman’s Capsule.

·         Tubular System (there are 3 sub-parts to this): This is the section of the nephron that allows certain things to re-enter the blood stream.

o   Proximal Convoluted Tubule

§ Reabsorbs electrolytes, glucose, amino acids, and small proteins. This is why a normal, non-diabetic person wouldn’t have glucose in their urine!

o   Loop of Henle

§ Reabsorbs water so that the urine becomes more concentrated (i.e. concentrated = less water, more particles)

o   Distal Convoluted Tubule

§ Regulates water and acid-base balance. Does so by reabsorbing bicarbonate (base) and getting rid of H (acid).


3. What is the glomerular filtration rate (GFR)? I want a definition AND a number. What factors can affect GFR?

The GFR is 125 mL/min (normal range is 85-135 mL/min). It is a measure of how much blood (in mL) gets filtered by the glomeruli every minute. GFR is affected by anything that would decrease the amount of blood flowing through the kidneys. This could include heart failure, atherosclerosis (do you know what this is??), or hypotension, among other things.

4. Describe how the blood is filtered on a cellular level. Basically, if you were floating along in the blood stream, what would happen to you when you get to the kidneys? Where would you go and how would you get there? And don’t you dare just copy it out of the book, you’ll never begin to understand it that way! J

In the Glomerulus: the hydrostatic pressure (i.e. “water” pressure) inside of the capillaries is greater than the pressure outside the capillaries. This pressure is what pushes some of the blood out of the capillaries and into the Bowman’s Capsule. Draw yourself a picture so that you can visualize what’s going on here.

The Bowman’s Capsule basically just catches the blood coming out of the capillaries, and funnels it down into the Proximal Distal Tubule.

In the Proximal Convoluted Tubule: Some of the electrolytes, glucose, amino acids, and small proteins that was pushed out of the glomerulus leave the Tubule and re-enter the blood stream. The body wants to keep those!

In the Loop of Henle: A lot of the water that was pushed out of the glomerulus leaves the Loop of Henle and re-enters the blood stream. The body wants to stay appropriately hydrated! The more water that re-enters the blood stream, the less water will be in the urine, and the more concentrated your urine will be. (Remember how yellow-orange your urine looks when you’re not drinking enough? That’s concentrated…)

In the Distal Convoluted Tubule: Able to reabsorb even more water, and also regulates our body’s acid-base balance. It is able to put bicarbonate (base) back into the blood stream, and kick Hydrogen (H; acid) out of the body.

BONUS NOTE: Urine does not CONTAIN the waste products of the body. Urine IS the waste product of the body. Another way to think about it is that urine is simply filtered blood. Everything that is in urine can be found in the blood stream first.

5) Name a common medication that has its effect on the Loop of Henle. What classification is this medication, what does it do, and why is it given? How does it works?

Lasix (furosemide): It is a loop diuretic (duh!). It causes the body to lose more water. It is given for any condition that you would want the patient to lose more water. These conditions could include Congestive Heart Failure (CHF), hypertension, cirrhosis of the liver, or any other condition that might result in edema. It works by telling the Loop of Henle NOT to let water be reabsorbed into the blood stream. So if the water does not go back into the blood stream, where IS it going? I’m not telling you that one…where do YOU think?

6)   The kidneys have 3 other important functions besides filtering blood. What are they and what effect do they have on the body?

·         Make erythropoietin

o   Erythropoietin causes Red Blood Cells (RBCs) to be created in the bone marrow.

·         Activate Vitamin D

o   Activated Vitamin D allows the GI tract to absorb more Calcium.

·         Make and Release renin

o   Renin plays an important role in the renin-angiotensin-aldosterone system in the body. When released, this system works to increase blood pressure.


7) Now that you know the 3 major functions of the kidneys (besides filtering blood), what kinds of signs and symptoms would a patient have if the kidneys weren’t able to do these things?

·         Can’t make erythropoietin

o   Body wouldn’t be able to make many new RBCs. This would lead to anemia, and anemia leads to fatigue.

·         Can’t activate Vitamin D

o   GI tract would not be able to absorb as much calcium, so would have a risk for hypocalcemia.

o   And what do you think will happen when the parathyroid gland notices there isn’t enough calcium in the blood??

·         Can’t make renin

o   Can’t be made, so can’t be released. With no renin, the rening-angiotensin-aldosterone system won’t work.

o   This will lead to hypotension, unless other mechanisms in the body compensate (which they often will, at least for a while).