Prophase is the first stage of mitosis where the chromatin condenses into visible chromosomes, the nuclear membrane begins to break down, and the spindle fibers start to form. In an animal cell, the centrioles move to opposite poles of the cell.
- Chromosomes are visible as two chromatids joined at the centromere.
- The nuclear membrane starts to disintegrate.
- The spindle fibers begin to form and extend from the centrioles.
In the diagram, four chromosomes should be clearly visible, and labels should indicate the centromere, chromatid, nuclear membrane, spindle fibers, and centrioles.
Study the diagram given below and match the structure with its functions:


During the ventricular systole, the atrioventricular valves (P) ________ and the semilunar valves (Q) _________.