There are valves in the vessels that prevents backflow, just like in the viens. ... the lymph vessels to ensure that the flow of lymph 
        
             
        
        
        
The gland that controls formation would be testes.
 
        
                    
             
        
        
        
Blood enters the pulmonary vein with close to 100% of the blinding site for oxygen saturated. 
        
             
        
        
        
Water boils at 100<span>°C</span>