Dear medical students, biology or related students, doctors.... Please help me answer these questions: 1. Other than the presence of valves in the veins, can the pumping action of the heart help to maintain the continuous flow of blood towards the heart? 2. If you caught a common cold and got a blocked nose, will sense of smelling be affected? WHY? 3. does sexual reproduction must involve male and female gametes? I think no because i barely remember some animal like sea horses can reproduce by fusion of two male gametes. Is this true? your kind help will be highly appreciated!