One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+), as noted below.

Yes, carbonic acid is the part of blood buffer system.

Explanation:

Carbonic acid is a part of blood buffer system which helps in regulating of pH of the blood. Hydronium ion is responsible for the increase in acidity of the blood. The carbonic acid dissociates into bicarbonate and hydrogen ion, this bicarbonate ions react with the hydronium ion and prevent the pH of the blood from decreasing so we can say that carbonic acid is an essential part of blood buffer system.