the.com/vein
the highway home, hauling tired blood back to refill its tank
low pressureVeins carry blood gently, no powerful heartbeat surge needed
one-way valvesTiny flaps stop blood from sliding backward downhill
blood storageHold roughly 70 percent of your body's blood
muscle pumpLeg muscles squeeze veins to push blood upward
why blueSkin scatters light; the blood inside stays red