they also form a rete by which venous blood is warmed and arterial blood is cooled. Why is this necessary?

Question

The spermatic artery and vein don't just traverse the same canal. They are so closely associated with one another that they exhibit countercurrent properties – not only do they run side by side through the inguinal canal, they also form a rete by which venous blood is warmed and arterial blood is cooled. Why is this necessary?

Answer 1

because sperm have to be at a certain temp for optimal fertility so leaving body cooler to sperm entering body warmer from sperm