Typically, the accessory renal artery courses into the renal hilum to perfuse the upper or lower renal poles. They may also enter the renal parenchyma directly from the renal cortex (called a polar artery). Rarely, they may arise from the lower thoracic aorta, as well as from the lumbar and mesenteric arteries.
The chain rule can be used to find whether they are getting closer or further apart. For example, one can consider the kinematics problem where one vehicle is heading west toward an intersection at 80 miles per hour while another is heading north away from the intersection at 60 miles per hour.
A standard acre as described above was one chain (66 feet) wide by ten chains (660 feet) long, or ten square chains. Before the age of pocket calculators and computers, surveyors used chain measure to measure land because it simplified the calculations.he length and width of a rectangular tract of land could be measured using a chain measure with the area expressed in square chains. Since there are ten square chains to an acre, the conversion from square chains to acres could be done mentally.