Different parts of the heart:
Right atrium: This chamber receives de-oxygenated blood from the body through the superior vena cava (head and upper body) and inferior vena cava (legs and lower torso) and even from heart itself (through coronary sinus). It has a wide based blunt appendage. A ridge on the inside at the lateral side called crista terminalis separates its trabeculated from non-trabeculated portion.
Elements of the right atrium:
- SVC and IVC
- Crista terminalis
- Coronary sinus
- Tricuspid valve
- Fossa ovalis
- Triangle of Koch
- Tendon of Todaro
- Inferior isthmus
Left atrium: Long, narrow appendage, smooth walls. The left atrium receives oxygenated blood from the lungs through the pulmonary vein. As the contraction triggered by the sinoatrial node progresses through the atria, the blood passes through the mitral valve into the left ventricle.
Right ventricle: Coarsely trabeculated inlet/sinus, outlet portion. The right ventricle receives de-oxygenated blood as the right atrium contracts. The pulmonary valve leading into the pulmonary artery is closed, allowing the ventricle to fill with blood. Once the ventricles are full, they contract. As the right ventricle contracts, the tricuspid valve closes and the pulmonary valve opens. The closure of the tricuspid valve prevents blood from backing into the right atrium and the opening of the pulmonary valve allows the blood to flow into the pulmonary artery toward the lungs.
Right ventricle has three portions (parts) and its sudivisions c.f;
- Inlet portion which supports tricuspid valve
- Trabecular sinus portion (main body of the RV) 1) Moderator band 2) Medial papillary muscle (of conus)
- Outlet portion: This has five components; 1) Infundibular (also called Conal) septum: This separates aortic and pulmonary semilunar valves. 2) Crista supra ventricularis: This part of the RV seperates trabecular sinus portion from outlet portion of the right ventricle. 3) Septal band (trabecula septomarginalis) 4) Parietal band (ventriculo-infundibular fold) 5) Pulmonary valve
Left ventricle: This ventricle receives oxygenated blood from the left atrium through the mitral valve. It features fine trabeculations in its entirety. When the left ventricle contracts the mitral valve closes and the aortic valve opens. The closure of the mitral valve prevents blood from backing into the left atrium and the opening of the aortic valve allows the blood to flow only into the aorta (main artery of the heart and body), throughout the body. This thicker than the right side ventricle has 3 parts;
- Inlet portion supports mitral valve
- Body of the left ventricle conatins anterior and posterior papillary muscles.
- Outlet portion is situated beneath aortic valve: Outlet portion is commonly called Left Ventricular Outflow Tract consists of; 1) Semilunar aortic valve cusps attached to a fibrous annulus which is actually, not a true annulus. 2) Three Interleaflet triangles 3) Aortoventricular junction 4) Three sinuses of Valsalva 5) Sinotubular junction (sinus rim) = junction of sinus of Valsalva and ascending aorta 6) NCC-LCC (posterior) commissure is related to the mid point of anterior mitral valve leaflet
Conduction System: consists of the following components and pathways;
- Sinoatrial node – is situated at the junction of superior vencava and anterolateral right atrium. The sinoatrial node sends an impulse that causes the smooth muscles of the atrium to contract in a coordinated, wave-like manner.
- Interatrial conduction pathways are not well defined and somewhat controversial
- Atrioventricular node is situated in the triangle of Koch’s.
- Bundle of His pierces the membranous septum, at the apex of triangle of Koch’s usually located on the inferior/posterior wall of the membranous septum.
- Left bundle branch innervates the left ventricular septal surface through its multiple branches
- Right bundle branch is situated below the medial papillary muscle and traverses via the septal and moderator bands to the anterior papillary muscle.
- Inferior isthmus (right atrium)
- Bachman's bundle (left atrium) Heart Valves: There are two atrioventricular (Mitral and Tricuspid) and two ventriculo-arterial (Aortic and Pulmonary) valves.
A. Mitral valve: The mitral valve (Greek: μίτρα and βαλβίς, Latin mitra and valva, bicuspid valve or left atrioventricular valve) is a dual-flap (bi from the Latin, meaning double, and mitral from the Latin, meaning shaped like a miter) valve in the heart. The miter (sometimes also spelled mitre), from the Greek 'headband' or 'turban', is a type of headgear, the traditional, ceremonial head-dress of bishops. This valve normally admits 2 fingers through its orifice.
It has;
1) Anterior (anteromedial or aortic) leaflet wide but short (1/3 of annular circumference)
2) Posterior (posterolateral) leaflet narrow and long (2/3 of annular circumference)