Answer:
The genetic material in the sperm combines with the genetic material in the egg to create a new cell that starts dividing rapidly. You're not actually pregnant until that bundle of new cells, known as the embryo, travels the rest of the way down the fallopian tube and attaches itself to the wall of your uterus.
Explanation:
 
        
             
        
        
        
Answer:
Answer is Sinoatrial node, SA.
Explanation:
The sinoatrial node, SA, is known to be a group of cells which are found at the top of the heart. 
The electrical signal that is initiated by the sinoatrial node bring about or stimulates the atria and then the ventricle of the heart.
It should be noted that, the sinoatrial node are regarded as the pacemaker cells.
 
        
             
        
        
        
Neutrophils which are Leukocytes