Final answer:
The term 'alkaline tide' implies that the blood pH in gastric veins is higher during digestion than after fasting, due to bicarbonate ions released into the bloodstream which buffer the pH, with the correct answer being option (a).
Step-by-step explanation:
The term 'alkaline tide' refers to an increase in the pH of the blood in gastric veins, which occurs during digestion of a meal. The correct answer is option a. This happens because when the stomach produces hydrochloric acid to aid digestion, the equivalent amount of bicarbonate is released into the bloodstream, raising the pH and making the blood more alkaline. Hence, the pH of blood in gastric veins is greater during digestion of a large meal than following a 24-hour fast. This is due to the bicarbonate system in the human body, which acts as a buffer. Normal blood pH falls in the range of 7.35-7.45, whereas gastric acidity during digestion can be as low as pH 1-2. It is important to understand that the body has mechanisms like buffers to moderate fluctuations in pH, crucial for maintaining physiological functions.