Final answer:
The tubular fluid is referred to as urine once it exits the collecting ducts of the kidneys. This occurs after the fluid has been processed and concentrated through absorption and secretion mechanisms within the renal tubule system.
Step-by-step explanation:
Once the tubular fluid leaves the collecting ducts, it is called urine.
The journey of fluid through the kidney involves several steps. It starts as a filtrate in the glomerulus, then travels through the renal tubule system where reabsorption and secretion occur. When the fluid reaches the collecting ducts, antidiuretic hormone can act to concentrate the urine by reabsorbing water into the bloodstream. After processing in the collecting ducts, the fluid is now considered urine and makes its way to the renal pelvis, then via the ureters to the bladder, and eventually leaves the body through the urethra during the process of urination.