The dye in urine is known as urobilinogen, which gives it a distinct yellow tint and is formed from the breakdown of bilirubin.
Chocolate wrappers, soda cans and paper waste… these are just a few examples of the waste we generate in our daily lives. Our bodies also function 24/7 and produce waste products too!
The waste that our bodies produce due to our many biological processes comes in many forms. It is excreted by three main excretory organs: lungs, kidneys and skin. These organs process several waste products, including urine, feces, sweat, and even the carbon dioxide we exhale.
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Let’s talk about the liquid waste we produce, mainly urine and sweat. They are very different, even if their shape is the same. Sweat is mostly clear, while urine has a distinctly yellow tint most of the time. So what gives urine its color?
How is urine formed?
To understand where our urine gets its color, we first look at its formation.
Urine is created by the excretory system present in our body, specifically the kidneys, bladder, urinary tract and urethra. If the excretory system were a factory, the kidneys would be the manufacturing sector, the bladder the storage, the urinary tract the delivery system, and the urethra the final destination of packaging.
The kidneys, reddish bean-shaped organs, lie on either side of our spinal cord, slightly above the midpoint. The kidneys (and the renal system) mainly work to extract and remove waste products generated in our body from processes such as digestion.
As a result of the digestion of proteins, amino acids are formed, which are broken down in the liver to form toxic ammonia. This ammonia is then converted to urea, a less toxic form.
Urea gets into our blood. The kidneys remove this urea from our blood in three steps: filtration, reabsorption, and secretion. All of these steps take place in tiny units known as nephrons, which make up the kidney.
The nephron is the microscopic structural and functional unit of the kidney. Nephrons are the functional units of the kidneys in which the process of urine formation takes place.
Filtration occurs in the glomeruli, a network of blood capillaries that act as a filter. As our blood passes through this mesh, its components, salts, glucose and urea, are filtered out. We know that urea is toxic to our body, but glucose and salts like sodium and potassium are essential for survival and our body cannot afford to lose them all.
This is where the reabsorption process takes place. This process also takes place in the nephrons, nutrients and most of the water are absorbed back into the body. However, during reabsorption, excess water, salt, and even urea are reabsorbed. Therefore, the secretory process works to secrete back some of these salts and other metabolites in order to maintain the appropriate concentration of these molecules required by the body.
After these processes, the end product of urine is formed, which passes through the ureters to the bladder, where it is stored. Our bladders can hold up to 1000 ml of urine. However, 300-400 ml is usually our call to action.
So how does urine get its color?
Red blood cells in our body are broken down to form a green pigment known as biliverdin, which is further broken down to form a yellow pigment known as bilirubin.
Bilirubin is responsible for the distinct ocher yellow color given to waste products, bile and stool. Some of this bilirubin also enters the bloodstream, forming urobilinogen, which is excreted in the urine.
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Through the process of filtration and reabsorption, our kidneys filter this urobilinogen (or urochrome) from the blood and excrete it in the urine. It is this urobilinogen that gives the urine a distinctly yellowish tint.
However, the color spectrum of urine primarily depends on our level of hydration. If we drink a lot of water, our urine contains a lot of water, diluting the urochrome pigment and making our urine very light yellow or completely colorless.
On the other hand, in severely dehydrated people, urine contains negligible amounts of water and is dark amber in color due to high concentrations of urochrome.
The color of urine can also change depending on our diet or medication. For example, taking vitamin B capsules turns urine bright green neon green, and if a person ate a lot of carrots or sweet potatoes, the red pigments in these vegetables, known as carotenoids, would turn urine dark yellow or dark green. yellow.
However, the main colorant of urine is urobilinogen, and the color of urine becomes lighter when a person drinks more water and stays well hydrated.