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Urinary Homeostasis and Formation

Urinary Homeostasis and Formation

Author: Amanda Soderlind

This lesson will identify the role of the kidneys in maintaining homeostasis in extracellular fluids.

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Maintaining Homeostasis as Body Fluids Change

Source: Video and Images Created by Amanda Soderlind

Video Transcription

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Welcome to this lesson on the urinary system. Today we are going to be discussing how the body maintains homeostasis of its body fluids. So basically, the urinary system helps to maintain homeostasis of extracellular fluids. And remember, extracellular fluids are fluids found on the outside of cells, such as blood, for example. So these fluids, these extracellular fluids, have a tendency to change as our body intakes water and solutes or loses water and solutes. So in order to maintain homeostasis, our body has to try and maintain these extracellular fluids at a certain level and a certain concentration and pH.

So as you intake water and solutes and lose water and solutes, as I mentioned, these extracellular fluids will change. So when I talk about intaking water and solutes, this could be through food, liquids. So food and liquid that you intake or that you ingest. It could be through respiration. And it could be through metabolism. These are all ways that water and solutes can be added to your system.

And when I talk about losing water and solutes, the way that you can lose water and solutes is through urination, feces, sweat, and evaporation. So these are all ways in which your extracellular fluids can change. You can either lose those extracellular fluids or gain water and solutes in the extracellular fluids. So the kidneys play a really important role in homeostasis of these extracellular fluids by forming urine. So urine is produced and excreted by the body. And hormones also play a role in this process as well in helping to form urine and maintain homeostasis of these fluids.

So basically, the kidneys can conserve or excrete fluids as necessary. And they can produce concentrated or diluted urine. So these are some of the ways that that homeostasis of extracellular fluids is maintained as it forms urine. So if there needs to be more water in the extracellular fluid, maybe the water level of extracellular fluids is low, and we need to increase that, then the body can produce more concentrated urine and allow there to be more water in the system than would otherwise be. So these are just some different ways that the body maintains that homeostasis. And if you're interested in more detail about how this process of urine formation occurs, you could look up the steps of urine formation.

But basically here just to give you a quick overview, these are the kidneys. We have two of them. So that's actually where urine is produced, is in the kidneys. And then we have the ureter, the urinary bladder, and the urethra. So urine is produced in the kidneys, will move down the ureter to be stored in the urinary bladder, and then is expelled from the body through the urethra.

So this lesson has been an overview on the urinary system and how the urinary system contributes to maintaining homeostasis of extracellular fluid.

Terms to Know
Bowman's Capsule

A section of a nephron where afferent arterioles deliver blood to the nephron for water and solutes to be filtered out.

Extracellular Fluid

Fluid of the body that is contained outside of cells. Plasma is an example of extracellular fluid outside of blood cells.


The first step in urine formation in which urine is filtered from afferent arterioles in the Bowman's capsule of a nephron.


A tangle of blood vessels in the Bowman's capsule where water and solutes are forced out of blood and into the Bowman's capsule to begin the next stage of urine formation.


Organs of the body that produce urine and help to regulate the composition and volume of body fluids.

Peritubular Capillaries

Capillaries associated with nephrons which allow water and solutes to be exchanged between the nephron and the blood during urine formation.


The second step in urine formation, in which valuable water and solutes are reabsorbed back into the blood.


The third step in urine formation in which filtrate moves toward collecting ducts; secretion helps maintain the body's acid-base balance.


A reflex that occurs when the urinary bladder fills to capacity and is stimulated to empty itself.


A substance formed by the kidneys and excreted from the body as a means to regulate the composition and volume of extracellular fluids.