Answer:
The human muscular system is the machinery that drives athletic performance. Among their functions, the more than 600 skeletal muscles generate skilled movements and produce energy for sport-specific competition. ... These contractions pull on the bones of the skeleton to cause movement.
Explanation:
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The AV valves close first, then the semilunars open and close, then the AV valves open
Answer:
The baby starts breathing
Explanation:
While in the womb, a fetus has its oxygen delivered to it, and the waste products removed (all via the mother's bloodstream), so there is no reason to separate all the chambers of the heart while still in the womb.
However, once the baby is born and it is breathing, the chambers need to differentiate in order to allow the blood to reach the lungs, and the oxygenated blood and deoxygenated blood do not mix.