Dr. Alexander Winemann is a Biologist who specializes in organic chemistry.
The answer is stem cells, they consist of classes of cells
that are undifferentiated and are able to be classified them into types like
specialized cells. They consist of having two main sources that will help them
develop and mature, these main sources are called the embryonic stem cell and
the adult stem cell.
The valves are responsible for preventing blood from flowing in the wrong direction, they are present in the veins, and the arteries don't need them because the aorta (biggest artery) pumps or in other words pushes it with such a force that no other force can change its direction, in the veins there is no structure present for pumping them as a result we have got valves so that they go in one direction...... the meaning of the word valve is to allow in one direction
