Atrioventricular valves

Examples of Atrioventricular valves in the following topics:

• Operation of Semilunar Valves

  • These valves do not have chordae tendineae, and are more similar to valves in veins than to atrioventricular valves.
  • The semilunar valves act in concert with the atrioventricular valves to direct blood flow in the heart.
  • When the atrioventricular valves are open, the semi lunar valves are shut and blood is forced into the ventricles.
  • When the atrioventricular valves shut, the semilunar valves open, forcing blood into the aorta and pulmonary artery.
  • Describe the operation of the semilunar valves, the aortic and pulmonary valves

• Operation of Atrioventricular Valves

  • The atrioventricular valves separate the atria from the ventricles and prevent backflow from the ventricles into the atria during systole.
  • A heart valve allows blood flow in only one direction through the heart, and the combination of the atrioventricular and semi-lunar heart valves determines the pathway of blood flow.
  • Valves open or close based on pressure differences across the valve.
  • The atrioventricular (AV) valves separate the atria from the ventricles on each side of the heart and prevent backflow of blood from the ventricles into the atria during systole.
  • Describe the operation of the atrioventricular valves: bicuspid (mitral) and tricuspid

• Heart Murmurs

  • Heart murmurs are pathologic heart sounds indicative of valve and blood flow abnormalities.
  • Yet most heart problems do not produce any murmur and most valve problems also do not produce an audible murmur.
  • Anatomical sources of heart murmurs include stenosis of the bicuspid aortic valve which tends to appear between 40 and 70 years of age, and stenosis of the tricuspid aortic valve where symptoms more likely to appear after 80 years of age.
  • The first heart sound is caused by the atrioventricular valves--Mitral (M) and Tricuspid (T)--and the second heart sound is caused by the semilunar valves--Aortic (A) and Pulmonary/Pulmonic (P).
  • Heart murmurs are often the result of leaky valves.

• Anatomy of the Heart

  • The atria and ventricle on each side of the heart are linked together by valves that prevent backflow of blood.
  • The pulmonary vein and aorta also have valves connecting them to their respective ventricle.
  • The sinoatrial (SA) and atrioventricular (AV) nodes are bundles of nerve fibers that form this conduction system.
  • It also merges with the inner lining of blood vessels and covers heart valves.
  • The position of valves ensures proper directional flow of blood through the cardiac interior.

• Heart Valve Disorders

  • Valvular heart disease is any disease process involving one or more of the valves of the heart (the aortic and mitral valves on the left and the pulmonary and tricuspid valves on the right).
  • Valvular heart disease includes aortic and mitral valve disorders, and pulmonary and tricuspid valve disorders.
  • Pulmonary valve diseases are the least common heart valve disease in adults.
  • The most common types of pulmonary valve diseases are: pulmonary valve insufficiency, pulmonary valve incompetence, and pulmonary valve regurgitation.
  • Both tricuspid and pulmonary valve diseases are less common than aortic or mitral valve diseases due to the lower pressure those valves experience.

• Heart Sounds

  • The two major heart sounds are 'lub' (from the closure of AV-valves) and 'dub' (from the closure of aortic and pulmonary valves).
  • The closing of the heart valves produces a sound.
  • S2 is split because aortic valve closure occurs before pulmonary valve closure.
  • During inspiration (breathing in) there is slightly increased blood return to the right side of the heart, which causes the pulmonary valve to stay open slightly longer than the aortic valve.
  • Abnormal heart sounds may indicate problems with the health of the valves.

• Varicose Veins

  • Varicose veins, typically found in the legs, are those that have become enlarged and tortuous due to malfunctioning valves.
  • Veins have leaflet valves to prevent blood from flowing backwards; this backflow is called retrograde or reflux flow.
  • When veins become varicose, the leaflets of the valves no longer meet properly, and the valves no longer work.
  • Figure A shows a normal vein with a working valve and normal blood flow.
  • Figure B shows a varicose vein with a deformed valve, abnormal blood flow, and thin, stretched walls.

• Fibrous Skeleton of the Heart

  • The aortic ring encircles the aortic valve.
  • The pulmonary ring encircles the pulmonary valve.
  • Similar to the aortic ring, it provides structural support for the pulmonary valve.
  • The left fibrous ring encircles the bicuspid valve.
  • The right fibrous ring encircles the tricuspid valve.

• Lymphatic Vessel Structure

  • Valves are found in larger lymph vessels and collecting vessels and are absent in the lymphatic capillaries.
  • The function of the valves is to prevent the backflow of fluid in the lymph, so that lymph fluid eventually flows forward instead of falling backwards.
  • As the pressure falls, the open valve then closes so that the lymph fluid cannot flow backwards.
  • A lymphagion is the term for the space between two semilunar valves in a lymphatic vessel, and represents a functional unit of the lymphatic system.
  • Blood vessels also have valves, but only in low pressure venous circulation, and they function similarly to lymphatic valves, though are comparatively more dependent on skeletal muscle contractions by comparison.

• Myocarditis and Endocarditis

  • It usually involves the heart valves (native or prosthetic valves).
  • Since the valves of the heart do not receive any dedicated blood supply, defensive immune mechanisms (such as white blood cells) cannot directly reach the valves via the bloodstream.
  • If an organism (such as bacteria) attaches to a valve surface and forms a vegetation, the host immune response is blunted.
  • The lack of blood supply to the valves also has implications on treatment, since drugs also have difficulty reaching the infected valve.
  • Normally, blood flows smoothly through these valves.