myocardium

Examples of myocardium in the following topics:

• Myocardial Thickness and Function

  • As a type of muscle tissue, the myocardium is unique among all other muscle tissues in the human body.
  • The thickness of the myocardium determines the strength of the heart's ability to pump blood.
  • The myocardium has variable levels of thickness within the heart.
  • Chambers of the heart with a thicker myocardium are able to pump blood with more pressure and force compared to chambers of the heart with a thinner myocardium.
  • The right ventricle myocardium is thicker than the atrial myocardium, as this muscle must pump all blood returning to the heart into the lungs for oxygenation.

• Heart Circulation

  • The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries.
  • Subendocardial coronary arteries run deep within the myocardium to provide oxygen throughout the muscle tissue of the cardiac wall.
  • With the subendocardial coronary vessels compressed, blood flow essentially stops below the surface of the myocardium.
  • Since there is very little unnecessary blood supply to the myocardium, blockage of these vessels can cause serious damage.
  • When these vessels become blocked, the myocardium becomes oxygen-deprived, a condition called ischemia.

• Layers of the Heart Walls

  • The heart wall is comprised of three layers: the outer epicardium, the middle myocardium, and the inner endocardium.
  • The heart wall is comprised of three layers, the epicardium (outer), myocardium (middle), and endocardium (inner).
  • The middle layer of the heart wall is the myocardium—the muscle tissue of the heart and the thickest layer of the heart wall.
  • The wall of the heart is composed of three layers, the thin outer epicardium, the thick middle myocardium, and the very thin inner endocardium.
  • Distinguish between the epicardium, myocardium, and endocardium layers of the heart wall

• Coronary Artery Disease

  • Coronary artery disease (CAD; also atherosclerotic heart disease) is the result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium (the muscle of the heart) with oxygen and nutrients.
  • When the myocardium becomes ischemic, it does not function optimally.
  • When large areas of the myocardium become ischemic, there can be impairment in the relaxation and contraction of the myocardium.
  • Image showing right coronary artery (RCA), left coronary artery (LCA) and a infarct (1) with necrotic or dead myocardium (2).

• Congestive Heart Failure

  • Initially, this helps compensate for heart failure by maintaining blood pressure and perfusion, but it places further strain on the myocardium, increasing coronary perfusion requirements, which can lead to worsening of ischemic heart disease.
  • Hypertrophy (an increase in physical size) of the myocardium also results as a compensatory mechanism when the terminally differentiated heart muscle fibers increase in size in an attempt to improve contractility.
  • Binding to beta-1 receptors in the myocardium increases the heart rate and make contractions more forceful, in an attempt to increase cardiac output.
  • The increased peripheral resistance and greater blood volume place further strain on the heart and accelerates the process of damage to the myocardium.

• Aging and the Cardiovascular System

  • The health of the myocardium can be impaired with age as the arteries narrow or become clogged due to atherosclerosis.
  • The health of the myocardium depends on its blood supply, and with age there is greater likelihood that arthrosclerosis will narrow the coronary arteries.
  • The term myocardial infarction is derived from myocardium (the heart muscle) and infarction (tissue death).

• Anastomoses

  • As blockage of one coronary artery generally results in death of the heart tissue due to lack of sufficient blood supply from the other branch, when two arteries or their branches join, the area of the myocardium receives dual blood supply.
  • If one coronary artery is obstructed by an atheroma, a degradation of the arterial walls, the second artery is still able to supply oxygenated blood to the myocardium.

• Operation of Atrioventricular Valves

  • The relaxation of the ventricular myocardium and the contraction of the atrial myocardium cause a pressure gradient that allows for rapid blood flow from the left atrium into the left ventricle across the mitral valve.

• Aging and the Heart

  • The health of the myocardium depends on its blood supply, and with age there is greater likelihood that arthrosclerosis will narrow the coronary arteries.

• Blood Flow in the Heart

  • The coronary arteries derive from the aorta and run along the surface of the heart and within the muscle to deliver oxygen-rich blood to the myocardium, while the coronary veins remove deoxygenated blood from the heart muscle returning it through the coronary sinus into the right atrium.