Both urine and filtrate are products of the urine creation. Kidneys filter unwanted substances from the blood in order to produce urine and excrete it. There are three main steps in the urine creation: glomerular filtration, reabsorption, and secretion.
The key difference between urine and filtrate is that urine is the nitrogenous liquid that contains filtering wastes and extra water from blood formed by the nephron of the kidney, while filtrate is the fluid filtered out from the blood through the capillary walls of glomeruli into Bowman’s capsule.
CONTENTS
1. Overview and Key Difference
2. What is Urine
3. What is Filtrate
4. Similarities – Urine and Filtrate
5. Urine vs Filtrate in Tabular Form
6. Summary – Urine vs Filtrate
7. FAQ – Urine and Filtrate
What is Urine?
Urine is a liquid waste material produced and excreted by nephrons of the kidney. It is composed of approximately 95% percent water. However, it also contains many other components, both solid and liquid.
Figure 01: Color Change in Urine
Urine generally has a pH of 6.2. But it can range from 5.5–7.0. Its specific gravity may range from 1.002 to 1.037. Though urine is mainly made up of water, it may also contain urea, sodium, potassium, chloride, creatinine, and other dissolved ions, as well as inorganic and organic compounds. Furthermore, urine helps to keep everything in balance in the body by removing wastes.
What is Filtrate?
Filtrate is also known as glomerular filtrate. It is formed after glomerular filtration, the first step in urine formation. The blood pressure in the glomerular capillary causes filtration of blood through three layers. Almost all the constituents of the plasma except proteins and blood cells pass onto the lumen of the Bowman’s capsule. That is why this process is also called ultrafiltration.
Figure 02: Fluid Flow in the Bowman’s Capsule and Glomerulus
This filtrate that comes out from the glomerulus normally contains nitrogenous waste like ammonia, water, glucose, and ions. But it is devoid of blood cells and major proteins. Generally,20% of the total blood volume is filtered into the Bowman’s capsule, whereas the rest of the remaining 80% volume flows back to the body again.
Similarities Between Urine and Filtrate
- Urine and filtrate are liquids.
- Both contain water as the main constituents.
- Both contain substances like glucose, urea, and electrolytes.
- They help to purify the blood and the body.
Difference Between Urine and Filtrate
Definition
- Urine is the watery, yellowish fluid produced by the nephron of the kidney at the end of the urine formation.
- Filtrate is the fluid that passes from the blood through the capillary walls of the glomeruli into Bormann’s capsule.
Formation
- Urine forms at the end part of the nephron.
- Filtrate forms in the Bormann’s capsule.
Composition
- Urine contains water, urea, chloride, sodium, potassium, creatinine, and other dissolved ions, as well as inorganic and organic compounds.
- Filtrate contains urea, water, vitamins, fatty acids, glucose, nitrogen, salts, etc.
Importance in Clinical Setups
- Color, odor, pH, turbidity, and volume of urine are important in the diagnosis of various diseases.
- Glomerular filtration rate (GFR), or the flow of filtrate from the glomerulus into Bowman’s space at a specified time, is important in detecting kidney function.
The following table summarizes the difference between urine and filtrate.
Summary – Urine vs Filtrate
Both urine and filtrate are products of the formation process. Urine is a yellow color liquid waste formed at the end part of the nephron after filtration, reabsorption, and secretion of the urine formation process. Urine mainly constitutes water (95%). The other constituents are urea, chloride, sodium, potassium, creatinine, and other dissolved ions, as well as inorganic and organic compounds. On the other hand, filtrate is the liquid formed from the blood in the Bowman’s capsule through a process known as ultrafiltration. Its composition is very similar to the composition of the blood plasma. This is the summary of the difference between urine and filtrate.
FAQ: Urine and Filtrate
1. Does filtrate become urine?
- The liquid filtrate is ultimately modified into true urine. The principal task of the nephron is to balance the blood plasma to homeostatic set points and excrete potential toxins in the form of urine.
2. What is the composition of filtrate?
- Filtrated is also known as glomerular filtrate or nephric filtrate. The filtrate contains substances that are filtered out from the glomerulus. The glomerular filtrate normally contains urea, water, vitamins, fatty acids, glucose, nitrogen, salts, etc.
3. What is normal urine?
- The color of the normal urine ranges from clear to pale yellow. But certain things can change the color. Foods such as beets, blackberries, and fava beans can turn urine pink or red. Some medicines can give urine vivid colors, such as orange or greenish-blue. Moreover, according to American Association for Clinical Chemistry, the normal urine pH range is between 4.5 and 8.
4. What is the composition of human urine?
- Human urine is composed mainly of water (95%). The rest of the components are urea (2%), creatinine (0.1%), uric acid (0.03%), chloride, sodium, potassium, sulfate, ammonium, phosphate, and other ions.
5. What is the composition of urine protein?
- Protein is only found in trace amounts compared to their values in blood plasma in the urine. The composition of urine protein is mostly albumin (30%–40%) and Tamm Horsfall protein (50%), with smaller contributions from other proteins such as immunoglobulins (5%–10%) and light chains (5%).
Reference:
1. Dr. Liji Thomas, MD. “Urine Composition: What’s Normal?” News – Medical Net.
2. “Glomerular Filtrate.” Oxford Reference.
Image Courtesy:
1. “Clinical urine tests” By Scientificanimations.com (CC BY-SA 4.0) via Commons Wikimedia
2. “Fluid Flow in the Bowman’s Capsule and Glomerulus” By Sierramarines – Own work (CC BY-SA 4.0) via Commons Wikimedia
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