Which of the following drains lymph from the majority of the body and enters into the left subclavian vein?

A. Endocardium: The endocardium is the inner endothelial lining of the heart chambers (endothelium + connective tissue), not cardiac muscle, so it does not contain intercalated discs.
B. Parietal pericardium: The parietal pericardium is the outer layer of the serous/fibrous sac surrounding the heart (protective membrane), not muscle tissue, so it lacks intercalated discs.
C. Epicardium: The epicardium (visceral layer of serous pericardium) covers the heart surface and contains connective tissue and fat; it overlies the myocardium but is not the muscle layer itself, so it does not have intercalated discs.
D. Myocardium: The myocardium is the heart’s muscular wall composed of cardiac muscle cells that are connected by intercalated discs (for electrical and mechanical coupling).

A. Hypothalamus -The hypothalamus regulates autonomic functions like temperature, but not primary breathing rhythms.
B. Pons and medulla oblongata -The medulla sets the basic rhythm of breathing, and the pons fine-tunes it.
C. Alveoli -Alveoli are sites of gas exchange, not neural control.
D. Cerebral cortex -The cortex allows voluntary control of breathing but is not the main respiratory control center.