Final answer:
The fluid that is similar to blood plasma but with almost no protein is called glomerular filtrate, produced in the kidneys. It is a result of the filtration process that separates blood cells and large proteins from the plasma, allowing substances like urea to pass through and form urine. Blood urea nitrogen (BUN) is used as a marker for kidney function. Option c.
Step-by-step explanation:
The substance similar to blood plasma but with almost no protein is known as glomerular filtrate. This filtrate is formed in the Bowman's capsule, which encloses the glomerulus, a network of capillaries vital for the kidney's function within the urinary system. When the blood reaches the kidneys, its filtration begins in these glomeruli. Unlike plasma, glomerular filtrate has large components like red and white blood cells and large proteins filtered out due to their size, leaving a composition very similar to plasma behind.
The kidneys play a crucial role in managing nitrogenous wastes like urea, which is a molecule made when the body breaks down protein-containing foods. As these wastes are filtered, blood urea nitrogen (BUN) can be measured as an estimate of urea in the blood and as an indicator of kidney function. Healthy kidneys produce urine, which is composed mainly of water, along with urea, chloride, sodium, potassium, creatinine, and other dissolved ions. An essential function of the urinary system is to remove these waste products such as urea and uric acid from the body with the formation and elimination of urine.