Heart Layers and Pericarditis

• The parietal layer of the serous pericardium, also called the parietal pericardium, adheres to the inside of the fibrous pericardium.
• The serous pericardium folds back on itself to form a layer covering the entire outer surface of the heart.
• The innermost layer of the serous pericardium is the visceral pericardium, also known as the epicardium.
• The visceral pericardium covers and adheres to the heart's surface.
• A fluid-filled space between the visceral and parietal layers allows them to glide over each other as the heart beats.
• The prefix endo- means "inside" or "within," and epi- means "upon" or "on."
• Pericarditis is the inflammation of the pericardium, which is caused by trauma, viral or bacterial infection, tumors, and other factors.
• Pericarditis is characterized by pericardial edema, causing the visceral and parietal layers to rub together.
• The friction from pericarditis can cause severe chest pain and a raspy or scratchy breathing sound.

Heart Action

• The heart serves as a muscular pumping device that distributes blood to all parts of the body.
• Contraction of the heart is called systole, and relaxation is called diastole.
• Atrial systole happens first, forcing blood toward the ventricles.
• Ventricular systole happens after, forcing blood out of the heart.
• The direction of blood flow must be controlled for the heart to be efficient, accomplished by four sets of valves.

Heart Valves

• Atrioventricular (AV) valves separate the atrial chambers from the ventricles below.
• The left AV valve is also known as the bicuspid or mitral valve, located between the left atrium and ventricle, and has two leaflets.
• The right AV valve is also known as the tricuspid valve, located between the right atrium and ventricle and has three leaflets.
• The AV valves prevent backflow of blood from the ventricles into the atria during ventricular contraction.
• Chordae tendineae are numerous stringlike structures attached to the edges of the leaflets of each AV valve and the wall of the corresponding ventricle.
• Papillary muscles are fingerlike projections in the ventricular walls that attach to the chordae tendineae.
• Semilunar (SL) valves are located between each ventricular chamber and its corresponding large artery.
• Ventricles contract simultaneously, so the two SL valves open and close at the same time.
• The pulmonary SL valve is located where the pulmonary artery emerges from the right ventricle, allowing blood to move into the pulmonary artery during systole and preventing backflow during diastole.
• The aortic SL valve is located where the aorta emerges from the left ventricle, allowing blood to flow into the aorta and preventing backflow.

Heart Sounds

• Two distinct heart sounds can be heard with a stethoscope on the anterior chest wall, described as lub dub.
• The first sound, or lub, is caused by vibrations from the abrupt closure of the AV valves during ventricular contraction, preventing blood from rushing back into the atria.
• The first sound is of longer duration and lower pitch than the second sound, or dup.
• The second heart sound results from the closure of both SL valves during ventricular diastole (or relaxation).
• Heart murmurs are atypical heart sounds caused by conditions of the valves, such as incompetent valves causing a swishing sound or stenosed valves causing swishing sounds.

Blood Flow Through the Heart

• A heartbeat includes atrial systole (contraction of the two atria) followed by ventricular systole (contraction of the two ventricles).
• The right and left sides of the heart act as separate pumps.