Why is urine yellow?

The video explains the process of urine production and excretion. It starts by discussing why urine is always yellow due to the presence of urobilin. Blood circulates through the body, collecting waste products, which are then filtered by the kidneys to produce urine. Urine is composed mainly of water, salts, and urea, a byproduct of protein breakdown. The urine flows from the kidneys through ureters to the bladder, which expands to store it. When full, the bladder signals the brain, which coordinates the release of urine through the urethra.

What is urobilin and how does it affect the color of urine?

Describe the process that occurs when the bladder is full.