The 'master gland' of the human body is the: MCQ with Answer and Explanation

Explanation:
The superior vena cava drains deoxygenated blood from the head, neck, arms, and upper thorax into the right atrium. The inferior vena cava drains the lower body. Pulmonary veins carry oxygenated blood, aorta carries oxygenated blood from left ventricle to body.

Explanation:
Insulin, secreted by the pancreas, promotes cellular glucose uptake, lowering blood sugar levels. Adrenaline (epinephrine) from the adrenal medulla triggers the fight-or-flight response, increasing heart rate and energy supply. Thyroxine, produced by the thyroid gland, requires iodine as an essential component for its synthesis; iodine deficiency causes goiter. All statements are correct.

Explanation:
The cell theory states that the cell is the fundamental unit of structure and function. Not all cells have a nucleus (prokaryotes), prokaryotes lack mitochondria, viruses are not cells.