Cardiac cells extract what percentage of oxygen from arterial blood?
75%
50%
90%-100%
25%-30%
The correct answer and explanation is:
The correct answer is 75%.
Cardiac muscle cells, or myocardial cells, are highly dependent on a continuous supply of oxygen for their function. The heart works tirelessly to pump blood throughout the body, and because of its constant activity, it requires a significant amount of oxygen. The oxygen extracted by cardiac cells from the arterial blood is about 75%. This is considerably higher than other tissues in the body, where oxygen extraction is typically around 25%.
The reason the heart extracts such a high percentage of oxygen from the blood is due to its continuous need for energy. Cardiac cells have a high density of mitochondria, which are the energy-producing structures within the cell. Mitochondria rely on oxygen to produce ATP (adenosine triphosphate), which is the energy currency of the cell. Since the heart is constantly contracting and requires substantial energy, it has adapted to extract a higher amount of oxygen from the blood to meet its needs.
The coronary circulation, which supplies the heart muscle with oxygen-rich blood, has a unique structure that allows for this high oxygen extraction. The blood in the coronary arteries is delivered under pressure, and as it travels through the coronary capillaries, a large proportion of the oxygen is transferred to the myocardial cells. This is critical because the heart cannot store oxygen like other tissues can, meaning it must extract nearly all the oxygen available in the arterial blood as it passes through.
If the heart’s oxygen supply is compromised, for instance in conditions like coronary artery disease, the myocardial cells become oxygen-deprived, which can lead to ischemia and ultimately to a heart attack. This high oxygen demand and extraction underscore the importance of maintaining a healthy cardiovascular system for proper heart function.