Lungs – air filled sacs on each side of the chest that exchange carbon dioxide and oxygen. The trachea (windpipe) conducts air to the lungs. The trachea splits into the bronchi, which split into smaller tubes called bronchioles. The bronchioles end in the alveoli, where the gases are exchanged. Oxygen is taken in here, and carbon dioxide is given off as waste. Room air contains 21% oxygen. We use about 5% of this, and release about 16% back into the atmosphere.
Brain – Without oxygen, brain cells begin to die within 4-6 minutes. The medulla is located in the brain stem, and controls respiratory and cardiovascular function. The medulla is a sort of respiratory ‘pacemaker’, and tells our body to take breaths without us thinking about it. Damage to the brainstem can alter our breathing.
Heart – Four chambers. Right and left atria and right and left ventricles. Atria are above the ventricles. Heart pumps deoxygenated blood to the lungs. Oxygenated blood then reenters the left side of the heart, and is then pumped out to the tissues. The coronary arteries supply the heart muscle itself, and are the arteries that can cause a heart attack if occluded.
