When blood is filtered through the glomerulus, what is primarily retained in the bloodstream?

During the process of filtration in the kidneys, specifically in the glomerulus, the focus is on what components of the blood are retained in the bloodstream versus what is filtered out into the renal tubule. The correct answer highlights that cells, such as red blood cells and white blood cells, along with large proteins like albumin, are not able to pass through the filtration barrier due to their size and characteristics.

The glomerular filtration barrier is composed of specialized cells that allow certain small molecules and solutes, such as water, electrolytes, urea, and small substances, to pass through while preventing larger entities from escaping into the urine. This is crucial for maintaining the appropriate composition of blood. Retaining cells and large proteins ensures that essential components of the blood are not lost and that the blood can continue to function effectively in transporting nutrients, gases, and immune responses throughout the body.

In contrast, smaller waste products and solutes are filtered out during this process, which explains why components such as urea and ammonia are not retained. Understanding the selective nature of this filtration process is vital in grasping how the kidneys maintain homeostasis and regulate blood composition.