Each repetition of its back and forth motion is a little less vigorous than its previous repetition. If the head sways 3 cm to the right of its equilibrium position during the first repetition, it may only sway 2.5 cm to the right of its equilibrium position during the second repetition.
The atria and the ventricles are separated by valves, which allow the blood to flow through the heart in one direction and prevent back flow of blood. The wall of the heart is made up of three layers. The outer layer is called the epicardium. The middle layer is the actual heart muscle and is called the myocardium. The inner layer of the heart is called the endocardium. The heart is contained within a sac called the pericardium. The sole purpose of the heart is to pump blood to and from the rest of the body.
Related terms: pericardium, inflammation of the heart membrane. The pericardium is a thin, sac-like covering (a membrane) that surrounds your heart. The outer layer of the pericardium surrounds the roots of your heart's major blood vessels.Ligaments attach this layer to your spinal column, diaphragm, and other parts of your body. The inner layer of the pericardium is attached to the heart muscle.elated terms: pericardium, inflammation of the heart membrane. The pericardium is a thin, sac-like covering (a membrane) that surrounds your heart. The outer layer of the pericardium surrounds the roots of your heart's major blood vessels.