Final answer:
The skin is not a method for regulating the hydrogen ion concentration in blood. The lungs, kidneys, and liver are the organs involved in maintaining the pH balance of the blood.The correct option is D.
Step-by-step explanation:
The correct answer is d) Skin.
The hydrogen ion concentration in blood, also known as pH, is regulated by several organs in the body. The kidneys, lungs, and liver are all involved in maintaining the pH balance of the blood. However, the skin does not play a direct role in regulating the hydrogen ion concentration in blood.
The lungs regulate pH by controlling the level of carbon dioxide in the blood. When the blood is acidic, the lungs increase breathing rate to remove excess carbon dioxide and raise the pH. Conversely, when the blood is alkaline, the lungs decrease breathing rate to retain carbon dioxide and lower the pH.
The kidneys regulate pH by controlling the level of bicarbonate ions in the blood. If the blood is acidic, the kidneys excrete excess hydrogen ions and reabsorb bicarbonate ions to raise the pH. If the blood is alkaline, the kidneys excrete bicarbonate ions and retain hydrogen ions to lower the pH.
The liver, on the other hand, plays a role in the production and regulation of bicarbonate ions in the blood, which indirectly helps to maintain pH balance.
Therefore, the correct answer is d) Skin, as it is not involved in regulating the hydrogen ion concentration in blood.