Does the systematic circuit only contain oxygen-rich blood?

Answer 1

The simple answer is no...BUT...the correct answer is half the time. A circuit is a continuous path which, when followed in one direction, returns to the starting point.

There are two interactive circuits in the human circulation system -- Systemic and Pulmonary. Think of a figure 8 toy train track. The heart is the 'main station' at the intersection of the two loops. On one end, imagine a Lungs 'substation'. At the other end, the Body 'substation.' Our blood travels endlessly on the figure-8 tracks in circuits like this:

Systemic circuit -- Heart-to-body and back, and then...

Pulmonary circuit-- Heart-to-lungs and back.

The Systemic circuit delivers oxygenated blood to the body via our arteries (arterial system); collects wastes (carbon dioxide) and returns the deoxygenated blood to the heart through our veins (venous system). Then the blood must be cleaned by the Pulmonary circuit.

The Pulmonary circuit: The heart pumps deoxygenated blood (with carbon dioxide waste) to the lungs. Diffusion occurs whereby carbon dioxide leaves the cells and oxygen enters them. The waste is expelled as we breathe out and more oxygen is taken in as we breathe in. The now oxygenated blood is returned returned to the heart.

Thus, our blood is circulating constantly, half the time delivering oxygen from the heart TO the cells in our arteries and the other half of the time retrieving carbon dioxide FROM our cells back to the heart in our veins.

How the blood travels:

From the body cells, oxygen-depleted blood travels through veins to the heart where it enters via the Superior Vena Cava or the Inferior Vena Cava. This oxygen-depleted blood flows into the Right Atrium and through the Tricuspid Valve down into the Right Ventricle. Then it flows up through the Pulmonary Semilunar Valve through Pulmonary Arteries to the Lungs. In the lungs, a passive process -- called diffusion, occurs wherby carbon dioxide is dropped off and oxygen picked up via gas exchange.

The oxygenated blood then travels from the lungs back to the heart via the Pulmonary Veins into the Left Atrium; down through the Mitral Valve and into the Left Ventricle thereby oxygenating the heart. Next the oxygenated blood continues up through the Aortic Semilunar Valve and out through the Aorta which forks into major arteries that supply the upper and lower body. The oxygenated blood flows through the arteries, then through smaller arterioles onto tiny capillaries and finally alveoli. In the Alveoli the gas exchange of oxygen and carbon dioxide occurs, feeding the cells and relieving them of waste. The 'waste'/de-oxygenated blood travels back to the heart in our veins.