We are currently being taught "Homeostasis through excretory system" in college. After seeing the structure of a nephron, it is not quite evident as to why should the Loop of Henle be the thinnest.
Only sense that I could make out of it is that- "Thin cross sectional area implies higher fluid velocity". Since, water and ions are majorly reabsorbed in the proximal convoluted tube, the loop of Henle is thin to increase the flow of fluid because there isn't much left to reabsorb and hence it won't require as much reabsorption time as the PCT. This decreases the filtration time and makes the process faster. I am not quite sure if this makes sense.
Can someone help?