What explains the decrease in the amount of oxygen in tissues and the increase in the amount of carbon dioxide in them?

As a result of the vital activity of cells and metabolic processes in tissues, the amount of oxygen decreases and the amount of carbon dioxide increases. Oxygen is necessary for cells to receive energy.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.