Answer:
Arteries carry blood away from the heart; veins carry blood back to the heart.
Explanation:
In Human anatomy, cardiac cycle can be defined as a complete heartbeat of the human heart which comprises of sequential alternating contraction and relaxation of the atria and ventricles, therefore causing blood to flow unidirectionally (one direction) throughout the human body.
Generally, the cardiac cycle occurs in two (2) stages;
Diastole: in this stage, the ventricles is relaxed and would be filled with blood.
Systole: at this stage, the muscles contracts and thus, allow blood to be pushed through the atria.
The best description for arteries and veins is that arteries carry oxygenated blood away from the heart to other parts of the body such as brain, lungs, tissues, etc; veins carry blood that is low in oxygen content back to the heart.
Answer:
Diseases of the immune system are especially dangerous because they attack the very cells that destroy other diseases. AIDS (auto immunodeficiency syndrome) basically makes the immune system kill itself. Basically, white blood cells kill other cells, (including its own white blood cells) instead of killing viruses or bacteria, in turn making your immune system very weak. If your immune system is weak, a simple cold can turn into a nightmare, and can even result in death.
Yes it is really true about ancient times.
