Cell wall because their has to be something protecting it.
Answer: By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.
Explanation:
The Mitral valve which is also known as left atrioventricular prevents blood movement from left ventricle to left atrium.
Explanation:
- Human heart is four chambered.
- Two of these are receiving chambers known as atria and the other two are distributing chamber known as Ventricles.
- Atria are superior chambers and ventricles are inferior chambers.
- The heart has four valves broadly grouped as Atrioventricular valves and Semi lunar valves.
- Atrioventricular valves allows flow of blood from atria to ventricle. These are tricuspid valve and bicuspid valve.
- Semi-lunar valves allow blood to pass out of the heart. These include the pulmonary and aortic valves.
- The pulmonary valve allows blood to flow from right ventricle to the heart while aortic valve allows blood to flow from left ventricle to the Aorta.
- The Tricuspid valve located between the right atrium and right ventricle allows blood to flow from right atrium to the right ventricle.
- The Bicuspid valve ( Mitral valve) located between the left atrium and left ventricle allows the blood flow from left atria to left ventricle.
- Valves maintain the unidirectional flow of blood and thus prevent its back flow.
