Final answer:
The correct sequence of partial pressures from highest to lowest as oxygen moves from the atmosphere to the tissues is: PatmosphereO2 > PAO2 > PaO2 > PvO2. This reflects oxygen's diffusion down its pressure gradient through the respiratory system into the blood and eventually to the tissues.
Step-by-step explanation:
The question relates to understanding the partial pressures of oxygen at different points in the respiratory and circulatory system. The correct sequence of partial pressures starting from the highest to the lowest, as oxygen travels from the atmosphere to the alveoli, into the blood, and then to the tissues, is: atmospheric oxygen PatmosphereO₂ (approximately 159 mm Hg at sea level) > alveolar oxygen PAO₂ (approximately 104 mm Hg) > arterial blood oxygen PaO₂ (approximately 95-100 mm Hg) > venous blood oxygen PvO₂ (approximately 40 mm Hg).
At each step in the exchange process, oxygen tension decreases due to various physiological processes including gas exchange, oxygen consumption by tissues, and differing solubilities and diffusion rates of oxygen and carbon dioxide. During this process, oxygen diffuses down its pressure gradient, moving from areas of higher pressure to areas of lower pressure; from alveoli (PAO₂) into the pulmonary capillaries, and eventually to the tissues.
Therefore, the correct answer from the provided options would be: PatmosphereO₂ > PAO₂ > PaO₂ > PvO₂, which aligns with option (a).