Blood first enters the heart's right atrium. A muscle contraction forces the blood through the tricuspid valve into the right ventricle. When the right ventricle contracts, blood is forced through the pulmonary semilunar valve into the pulmonary artery. Then it travels to the lungs
God, He is the one that created the earth.
Answer:
The skin
Explanation:
because it protects the internal organs just like the cellwall of the cell
Because it works on more than just one or two parts of you body... it works on your stomach, thighs, legs, arms, etc.
