Which organ stores blood and releases it into circulation when the body's oxygen demand increases?

Which organ stores blood and releases it into circulation when the body's oxygen demand increases?

• A. Pancreas
• B. Spleen
• C. Parathyroid
• D. Liver

Answer: (B)

The spleen stores a reserve of red blood cells and can contract to release them into circulation when needed, such as during increased physical activity or stress. This release boosts the blood’s oxygen-carrying capacity, helping tissues meet higher oxygen demands quickly. Other organs listed have different primary roles: the pancreas produces digestive enzymes and hormones like insulin; the parathyroid glands regulate calcium levels; and the liver stores glycogen and handles various metabolic and detoxification tasks.

The spleen stores a reserve of red blood cells and can contract to release them into circulation when needed, such as during increased physical activity or stress. This release boosts the blood’s oxygen-carrying capacity, helping tissues meet higher oxygen demands quickly.

Other organs listed have different primary roles: the pancreas produces digestive enzymes and hormones like insulin; the parathyroid glands regulate calcium levels; and the liver stores glycogen and handles various metabolic and detoxification tasks.