<span> How does pulmonary circulation work? In my example below, we will start with the blood not reaching the heart yet. The heart beats around 75 beats a minute. Deoxygenated blood is in the veins, going to the heart. Note that veins will always carry deoxygenated blood, excluding the pulmonary veins. The deoxygenated blood goes into the heart through the superior or inferior vena cava, and goes into the right atrium. It then gets pumped into the right ventricle, and gets pumped through the pulmonary arteries to the lungs to get oxygenated. The blood, now oxygenated, comes back to the heart through the pulmonary veins, into the left atrium. The blood gets pumped from the left atrium to the left ventricle, where it gets pumped through the aorta to all of the body systems. The red blood cells travel through capillaries, which is where most of the gas exchange occurs between body cells and red blood cells. Red blood cells have no nuclei. When the red blood cells are no longer red, but blue due to lack of oxygen, they go back to the heart to get pumped to the lungs, and enter the heart through the superior or inferior vena cava. The cycle starts over. Just like the veins, arteries always carry oxygenated blood, excluding the pulmonary arteries. Also, the right side of the heart will have deoxygenated blood, or blue blood, and the left side of the heart will have oxygenated blood. </span>
A valence electron is a negatively charged particle, located in the outermost shell of an atom, that can be transferred to or shared with another atom.
Option A.
An example of an dramatic environmental event can be deforestation, or it can be animals losing their homes.
Bacteria is used to produce human insulin
Respiratory System
Circulatory System
Digestive System<span />
