Which organ has the lowest oxygen consumption per unit weight under normal physiologic conditions?

The kidney exhibits the lowest oxygen consumption per unit weight under normal physiological conditions due to its unique function and structure. While the kidneys are vital for filtering blood, regulating electrolytes, and maintaining fluid balance, they do not require as high an oxygen supply per gram of tissue compared to other organs such as the brain, liver, and lungs.

The brain, for instance, is highly metabolically active and depends heavily on a continuous oxygen supply to support its functions. It consumes a significant amount of oxygen relative to its weight, as neurons require energy for action potentials and neurotransmission.

The liver, involved in numerous metabolic processes, detoxification, and energy production, also has a high oxygen demand. It processes nutrients from digestion and performs complex biochemical functions that necessitate increased oxygen consumption.

The lungs' role in gas exchange involves substantial blood flow and oxygen transfer; however, their overall oxygen utilization efficiency does not compete with that of the brain and liver.

Consequently, the kidney's metabolic and physiological demands lead to a lower overall oxygen consumption per unit weight in comparison to these other organs, confirming that it is the correct answer.