Question

which of the following is not a function of the heart?
a serves as an endocrine gland, producing anh
b creates blood pressure
c keeps oxygen - poor blood separated from oxygen - rich blood
d maintains the acidity level of the blood

Explanation:

• Option A: The heart can act as an endocrine gland. Atrial natriuretic hormone (ANH) is produced by the heart's atria. When blood volume or blood pressure is too high, ANH is secreted, which can promote sodium excretion and diuresis, and reduce blood volume and blood pressure. So this is a function of the heart.
• Option B: The heart's pumping action (contraction and relaxation) creates blood pressure. When the heart contracts, it ejects blood into the arteries, creating systolic pressure; when it relaxes, the elastic recoil of the arteries maintains diastolic pressure. So this is a function of the heart.
• Option C: In the normal heart (in mammals and birds), there are structural features (such as the septum) that keep oxygen - poor blood (in the right side of the heart) and oxygen - rich blood (in the left side of the heart) separated. So this is a function of the heart.
• Option D: The acidity level (pH) of the blood is mainly regulated by the respiratory system (through regulating carbon dioxide excretion) and the urinary system (through regulating the excretion of hydrogen ions and reabsorption of bicarbonate ions). The heart's main functions are related to blood circulation, endocrine (to a certain extent), and blood separation (in some animals), not the direct regulation of blood pH.

Answer:

D. Maintains the acidity level of the blood