What is the urinary system?
The urinary system is made up of the kidneys, ureters, bladder, and urethra.
What are the kidneys?
The kidneys are a pair of organs within the abdominal cavity and are the start of the urinary tract. The medical term for referring to the kidneys is renal. Their main jobs include filtering blood, reabsorbing essential nutrients, helping maintain blood pressure, and producing certain hormones.
The kidneys filter blood and excrete toxins to be urinated out of the body. Inside the kidneys there are millions of tiny filtration structures called nephrons. The blood must pass through the first section of the nephron called the glomerulus. Here the blood's liquid portion, the plasma, separates and crosses over a barrier from the glomerulus and is collected in the Bowman's Capsule. This liquid is called ultrafiltrate (it will soon turn into urine).
From the Bowman's Capsule, the ultrafiltrate journeys to the proximal renal tubules. The proximal tubules are long filtering tubes allowing electrolytes and nutrients like amino acids and glucose, to return back into the bloodstream.
Along with toxins like blood urea nitrogen (BUN) produced by the body's metabolism, drugs can also cross the barrier into the ultrafiltrate so they can be excreted by the body.
The next section is called the Loop of Henle, and this is where water is reabsorbed back into the bloodstream. Sodium and chloride are also reabsorbed to help maintain electrolyte balance.
A special function of the Loop of Henle is the production of a hormone called erythropoietin. This hormone helps stimulate the production of red blood cells and helps prevent early red blood cell death.
The next section is the distal convoluted tubule where the ultrafiltrate has even more water filtered out of it, concentrating the waste produced by the body into what we call urine. The balance of how much water is absorbed or excreted is essential for maintaining a healthy blood pressure.
The urine passes into a collection duct system and is then into the pelvis of the kidneys. It then leaves the kidneys through the ureters, to the bladder, and then out of the body through the urethra.
The kidneys filter blood and excrete toxins to be urinated out of the body. Inside the kidneys there are millions of tiny filtration structures called nephrons. The blood must pass through the first section of the nephron called the glomerulus. Here the blood's liquid portion, the plasma, separates and crosses over a barrier from the glomerulus and is collected in the Bowman's Capsule. This liquid is called ultrafiltrate (it will soon turn into urine).
From the Bowman's Capsule, the ultrafiltrate journeys to the proximal renal tubules. The proximal tubules are long filtering tubes allowing electrolytes and nutrients like amino acids and glucose, to return back into the bloodstream.
Along with toxins like blood urea nitrogen (BUN) produced by the body's metabolism, drugs can also cross the barrier into the ultrafiltrate so they can be excreted by the body.
The next section is called the Loop of Henle, and this is where water is reabsorbed back into the bloodstream. Sodium and chloride are also reabsorbed to help maintain electrolyte balance.
A special function of the Loop of Henle is the production of a hormone called erythropoietin. This hormone helps stimulate the production of red blood cells and helps prevent early red blood cell death.
The next section is the distal convoluted tubule where the ultrafiltrate has even more water filtered out of it, concentrating the waste produced by the body into what we call urine. The balance of how much water is absorbed or excreted is essential for maintaining a healthy blood pressure.
The urine passes into a collection duct system and is then into the pelvis of the kidneys. It then leaves the kidneys through the ureters, to the bladder, and then out of the body through the urethra.
Kidney Animation
Check out the video below for an animation about how kidneys work
Learn About Kidney Disease
There are several types of kidney disease, but the thing they all have in common is decreased function of the kidneys to filter properly.
Here are some terms to know about kidney disease:
Below is a list of some of the common kidney diseases. Click on the links to get more information about these diseases.
Here are some terms to know about kidney disease:
- Kidney - there are two bean-shaped organs located next to the spine in the abdominal cavity
- Renal - medical term for kidneys (this can be interchangeable with the word kidney)
- Acute - sudden onset and present condition
- Chronic - condition lasting longer than three months
- Acute on Chronic - sudden onset of clinical disease, with chronic condition
- Failure - organ no longer functioning. A kidney will 'fail' when they have less than 25% of their function. Prior to this threshold, the kidneys can compensate fairly well and you may not see any clinical signs
Below is a list of some of the common kidney diseases. Click on the links to get more information about these diseases.
- Chronic Kidney Disease
- Acute Kidney Disease
Last updated March 2019