<span>Estrogen is involved in a feedback mechanism associated with the follicular phase of menstruation. </span>
Answer:
Your heart is a single organ, but it acts as a double pump. The first pump carries oxygen-poor blood to your lungs, where it unloads carbon dioxide and picks up oxygen. ... The second pump delivers oxygen-rich blood to every part of your body. Blood needing more oxygen is sent back to the heart to begin the cycle again.
Explanation:
