Textbook Question
The sphincter between the stomach and duodenum is:
a. The pyloric sphincter
b. The gastroesophageal sphincter
c. The hepatopancreatic sphincter
d. The ileocecal valve
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23. The Digestive System
The Stomach
Problem 28
Textbook Question
Nutritionists have found that after a heavy meal, the pH of blood increases slightly, especially in the veins that carry blood away from the stomach. What causes this increase in blood pH?
Verified step by step guidance1
Step 1: Understand that pH is a measure of hydrogen ion concentration, where an increase in pH means the blood is becoming more alkaline (fewer hydrogen ions).
Step 2: Recall that after a heavy meal, the stomach produces more gastric acid (HCl) to aid digestion, which increases acidity in the stomach lumen but does not directly acidify the blood.
Step 3: Recognize that the blood leaving the stomach (via the veins) carries absorbed nutrients and metabolic byproducts, including bicarbonate ions (HCO₃⁻) released from the pancreas to neutralize stomach acid in the small intestine.
Step 4: Understand that the release of bicarbonate into the bloodstream raises the blood's pH by neutralizing hydrogen ions, causing the slight increase in blood pH observed after a meal.
Step 5: Summarize that the increase in blood pH after a heavy meal is primarily due to the influx of bicarbonate ions into the blood from the pancreas, which neutralizes acid and makes the blood more alkaline.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Blood pH and Acid-Base Balance
Blood pH measures how acidic or basic the blood is, normally maintained around 7.35-7.45. The body regulates this balance through buffers, respiration, and kidney function to keep enzymes and metabolic processes functioning properly.
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Acids and Bases
Digestion and Metabolic Byproducts
During digestion, food is broken down into nutrients, producing metabolic byproducts like carbon dioxide and acids. After a heavy meal, increased metabolism and nutrient absorption can alter the concentration of these substances, influencing blood pH.
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Role of Carbon Dioxide in Blood pH
Carbon dioxide (CO2) dissolves in blood forming carbonic acid, which lowers pH. After eating, blood leaving the stomach may have reduced CO2 due to increased oxygen use and metabolic changes, causing a slight rise in blood pH (more alkaline).
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