Final answer:
The left ventricle forms the left lateral border and is the main pumping chamber sending oxygenated blood through the systemic circuit.
Step-by-step explanation:
The left ventricle, positioned along the left lateral border of the heart, is the primary force behind systemic circulation. Serving as the main pumping chamber, its crucial role involves propelling oxygenated blood into the aorta through the aortic semilunar valve. This orchestrated contraction ensures that oxygen-rich blood is efficiently distributed throughout the entire systemic circuit, nourishing tissues and organs. The left ventricle's prominence in shaping the left lateral border underscores its significance in maintaining overall cardiovascular function, exemplifying the intricate design of the heart to sustain life-sustaining blood flow throughout the body.