Anatomy & Physiology Genitourinary #8


Which is the first step in the process of urine production?


  1. Filtration of the blood.
    • Rationale:

      Blood filtration is the second, not first, step in the production of urine.

  2. Production of ultrafiltrate.
    • Rationale:

      The production of ultrafiltrate is the third, not first, step in the production of urine.

  3. Reabsorption from the blood.
    • Rationale:

      The reabsorption of blood is the fourth, not first, step in the production of urine.

  4. Entry of circulating blood into the kidneys.
    • Rationale:

      The first step for the production of urine is circulating blood entering the kidneys. This must occur for the other steps of urine production to take place thereby maintaining homeostasis.


There are three main processes that occur within the body in order for urine formation to occur. These processes include glomerular filtration, reabsorption, and secretion.


Learning Outcomes

The process of urine production, in sequential order, is as follows:
Blood enters into the kidneys by circulation.
Blood filtration.
Production of ultrafiltrate.
Blood reabsorption.
Secretion into the blood.
Excretion of urine from the body.
These processes guarantee that waste products, and excess water, are removed from the body. At the same time, this process also ensures the reabsorption of needed chemicals to maintain homeostasis.

Test Taking Tip

Consider the specific order of events that must occur in urine production to correctly answer this question.

Video Rationale