Did you learn it in the experiment? Through the villus wall of small intestine, through the capillary wall, it enters the blood, flows into alveoli with the blood, enters the arterial blood through the alveolar wall and capillary, then reaches the kidney, breaks through the capillary wall, reaches the renal capsule, and is reabsorbed by the renal vein. You can make up your own story all the way. This is what the teacher wants. You just need to bring them in.