The Normal Heart
Robert H. Anderson
General Cardiac Morphology
General Cardiac Morphology
- Attitudinal Orientation [Low bandwidth] [High bandwidth]
- Sequential Segmental Analysis [Low bandwidth] [High bandwidth]
- Right Atrium [Low bandwidth] [High bandwidth]
- Oval Fossa [Low bandwidth] [High bandwidth]
- Triangle of Koch [Low bandwidth] [High bandwidth]
- Left Atrium [Low bandwidth] [High bandwidth]
- Atrioventricular Junctions [Low bandwidth] [High bandwidth]
- Right Ventricle [Low bandwidth] [High bandwidth]
- Left Ventricle [Low bandwidth] [High bandwidth]
- Arterial Trunks [Low bandwidth] [High bandwidth]
- Coronary Arteries [Low bandwidth] [High bandwidth]
- Coronary Veins [Low bandwidth] [High bandwidth]
- Conduction System [Low bandwidth] [High bandwidth]
Cardiac Anatomy
The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of a clenched fist. By the end of a long life heart may beat (expanded and contracted) more than 3.5 billion times. Each day, the average heart beats 100,000 times, pumping about 2,000 gallons (7,571 liters) of blood. Heart is located between both lungs in the middle of the chest, behind and slightly to the left of sternum. A double-layered membrane called the pericardium surrounds the heart like a sac. The outer layer of the pericardium surrounds the origins of the heart's major blood vessels and is attached by ligaments to the spinal column, diaphragm, and other parts of the body. The inner layer of the pericardium is attached to the heart muscle. A coating of fluid separates the two layers of membrane, letting the heart move frictionless as it beats.
Your heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. Muscular wall which separates the left and right atria and the left and right ventricles is called atrial and ventricular septum respectively. The left ventricle is the largest and strongest chamber in the heart.
Cardiac Chambers
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:
1. SVC and IVC
2. Crista terminalis
3. Coronary sinus
4. Tricuspid valve
5. Fossa ovalis
6. Triangle of Koch
7. Tendon of Todaro
8. 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;
1. Inlet portion which supports tricuspid valve
2. Trabecular sinus portion (main body of the RV)
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 thick ventricle has 3 parts;
1. Inlet portion supports mitral valve
2. Body of the left ventricle conatins anterior and posterior papillary muscles.
3. 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;
1. 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.
2. Interatrial conduction pathways are not well defined and somewhat controversial
3. Atrioventricular node is situated in the triangle of Koch’s.
4. 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.
5. Left bundle branch innervates the left ventricular septal surface through its multiple branches
6. Right bundle branch is situated below the medial papillary muscle and traverses via the septal and moderator bands to the anterior papillary muscle.
7. Inferior isthmus (right atrium)
8. 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) 3) It has 2 commissures; anteromedial and posterolateral commissures
4) It has 2 papillary muscles; anterior and posterior papillary muscles and several chordae tendineae
B. Tricuspid valve: The tricuspid valve separates the right atrium from the right ventricle, and opens to allow the passage of de-oxygenated blood collected in the right atrium to flow into the right ventricle. It has three leaflets; anterior (infundibular), posterior, medial (septal) leaflets and three commissures; ………… and three papillary muscles;..............
Tricuspid valve normally admits 3 fingers through its orifice.
C. Aortic: It has one anterior and 2 posterior cusp.
D. Pulmonary valves: It has two anterior and one posterior cusp.
Common anatomic features to both aortic and pulmonary valves;
1) 3 cusps, semilunar
2) 3 Sinuses of Valsalva
3) 3 Nodulus Aranti and lunulae
Aortic valve is normally wedged between mitral and tricuspid vlaves. Pulmonary valve is separated and is anterior to aortic valve.
9. Ventricular Band (Torrent-Guasp band)
Francisco Torrent-Guasp (1931-2005): In 1973, Torrent-Guasp described the structure of the heart as a band of muscle that starts at the pulmonary artery entry-point and ends below the aorta exit, wrapping itself into a double helical coil that bounds both ventricular cavities with a wall to separate them (see Figure). On this basis, in 1997 he presented a theory that provided an explanation as to how progressive contraction of the band accounted for the forceful ejection and suction assisted entry of the blood into the heart.
Salient features of ventricular band of Torrent-Guasp:
Your heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. Muscular wall which separates the left and right atria and the left and right ventricles is called atrial and ventricular septum respectively. The left ventricle is the largest and strongest chamber in the heart.
Cardiac Chambers
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:
1. SVC and IVC
2. Crista terminalis
3. Coronary sinus
4. Tricuspid valve
5. Fossa ovalis
6. Triangle of Koch
7. Tendon of Todaro
8. 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;
1. Inlet portion which supports tricuspid valve
2. Trabecular sinus portion (main body of the RV)
- Moderator band
- Medial papillary muscle (of conus)
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 thick ventricle has 3 parts;
1. Inlet portion supports mitral valve
2. Body of the left ventricle conatins anterior and posterior papillary muscles.
3. 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;
1. 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.
2. Interatrial conduction pathways are not well defined and somewhat controversial
3. Atrioventricular node is situated in the triangle of Koch’s.
4. 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.
5. Left bundle branch innervates the left ventricular septal surface through its multiple branches
6. Right bundle branch is situated below the medial papillary muscle and traverses via the septal and moderator bands to the anterior papillary muscle.
7. Inferior isthmus (right atrium)
8. 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) 3) It has 2 commissures; anteromedial and posterolateral commissures
4) It has 2 papillary muscles; anterior and posterior papillary muscles and several chordae tendineae
B. Tricuspid valve: The tricuspid valve separates the right atrium from the right ventricle, and opens to allow the passage of de-oxygenated blood collected in the right atrium to flow into the right ventricle. It has three leaflets; anterior (infundibular), posterior, medial (septal) leaflets and three commissures; ………… and three papillary muscles;..............
Tricuspid valve normally admits 3 fingers through its orifice.
C. Aortic: It has one anterior and 2 posterior cusp.
D. Pulmonary valves: It has two anterior and one posterior cusp.
Common anatomic features to both aortic and pulmonary valves;
1) 3 cusps, semilunar
2) 3 Sinuses of Valsalva
3) 3 Nodulus Aranti and lunulae
Aortic valve is normally wedged between mitral and tricuspid vlaves. Pulmonary valve is separated and is anterior to aortic valve.
9. Ventricular Band (Torrent-Guasp band)
Francisco Torrent-Guasp (1931-2005): In 1973, Torrent-Guasp described the structure of the heart as a band of muscle that starts at the pulmonary artery entry-point and ends below the aorta exit, wrapping itself into a double helical coil that bounds both ventricular cavities with a wall to separate them (see Figure). On this basis, in 1997 he presented a theory that provided an explanation as to how progressive contraction of the band accounted for the forceful ejection and suction assisted entry of the blood into the heart.
Salient features of ventricular band of Torrent-Guasp:
A. Biventricular myocardial band (Torrent Guasp Band) extending from pulmonary artery to aorta
B. Two loops: basal and apical
C. Double helix derived from spiral fold
D. Apex has figure of eight configuration
10. Coronary Arteries: There are two, right and left coronary arterial system
Dominance of one of the two arterial patterns is determined by the origin of posterior descending artery. PDA usually arise from the RCA and thus dominance is usually right side or co-dominace (balanced): In only 10-15% patients left arterial dominance is present. When the PDA is both from RCA and Cx arteries the pattern is called balanced pattern since no particular dominance is present. The 2/3rd ventricluar septal blood supply is through left anterior descending (LAD) artery and 1/3 through the posterior descending (PDA) artery. In 55% cases sinus node artery arise from RCA. AV node artery arise from U bend at crux, just beyond the takeoff of the PDA, if circulation is right dominant.
Segmental description of pathological anatomy: (Van Praagh’s Classification)
A. Situs of thoracic viscera and atria: Best identified from the bronchial anatomy (3 bronchi on the right, 2 on the left). Situs can be of three types;
B. Situs of ventricles: Normal ventricular situs is concordant, D-loop, right-handedness. However, opposite of the normal is called ventricular inversion which is charcaterised by discordant, L-loop, left-handedness of the ventricles.
C. Dominance of ventricles: Normally both left right and left have equal dominance (Balanced). However, when either of the ventricles dominate there could be right (left small), left (right small) dominance.
D. Cardiac connections: Normal atrioventricular and ventriculoarterial connections are concordant (left atrium to left ventricle and left ventricle to aorta and similarly on the right side, right atrium to right ventricle and right ventricle to pulmonary artery). Reversal of this at any level is called discordant (transposed) connection.
E. Cardiac apex and arterial position:
1) Cardiac apex can point towards; levoposition (Normal left side), dextroposition (opposite of normal i.e. right side), mesocardia (midline)
2) Great arteries can be; transposed (opposite of normal i.e. aorta connected to right ventricle and pulmonary artery connected to left ventricle), malposition (abnormally positioned)
3) The patient’s heart is usually normal in structure in dextrocardia. This condition only refers to the position of the cardiac apex.
Cardiac Skeleton: It is also called “Fibrous skelton” of the heart which is truly a frame of connective tissue. It consists of a set of fibrous rings made of collagen. In simplistic terms the majority of the skeleton lies at the base of the ventricles, roughly parallel to the coronary sinus.
It has three major functions;
It consists of;
A. Fibrous body: (Annuli Fibrosi or fibrous rings) surrounding four openings; mitral, tricuspid, aoric and pulmonary valves
B. Right and left trigones: connect annuli fibrosi (the rings) together. Expansions of fibrous tissues at either extreme of the area of continuity between mitral annulus and aortic annulus form the right and left fibrous trigones (fig 3). The atrioventricular conduction bundle passes through the right fibrous trigone. The trigones are expansions of fibrous tissue at either end of the area of aortic–mitral valvar continuity. The right fibrous trigone together with the membranous septum forms the “central fibrous body”. Central fibrous body is the toughest structure in the heart.
Figure: Sketch showing fibrous skeleton at the base of the heart (seen from above) in anatomical position
Coronary Arteries: Like all other tissues in the body, the heart muscle needs oxygen-rich blood to function (done through coronary arteries), and oxygen-depleted blood must be carried away (done by coronary veins draining into coronary sinus). Coronary arteries supply blood to the heart muscle.
Coronary arterial system consists of;
A. Right and Left coronary arteries originating from proximal part of the ascending aorta via respective right and left main coronary ostia
B. Branches from main coronary arteries
A. Left coronary system: The left main coronary artery (LMCA), divides into two major arteries c.f. the left anterior descending artery and the circumflex branch. This system supplies blood to the left ventricle and left atrium.
1) Left main
2) Left anterior descendingà septal and diagonal branches
3) Circumflexàobtuse marginal arteries and posterior descending artery (PDA) in left dominant system.
B. Right coronary artery system: Acute marginal, AV nodal, sinus node arteries and posterior descending artery (PDA) in right dominant system.
Heart borders: From above downwards;
A. Right border of the heart (Mediastinal Border) is formed by;
B. Left Border of the heart is formed by;
Surgical Anatomy Atrioventricular (Mitral and Tricuspid) Valve Apparatus
The Mitral Valve Apparatus: The mitral apparatus includes mitral leaflets, annulus, chordae tendineae, papillary muscles, and the left ventricular myocardium where these pappilary muscels are attached. The valve is obliquely located in the heart and has a close relation to the aortic valve (See Figure). Unlike the tricuspid valve which is separated by muscle from its counterpart, the pulmonary valve, the mitral valve is immediately adjacent to the aortic valve.
Figure 1 (A) View of the four heart valves at the base of the heart in anatomical orientation showing their spatial relations. The left heart valves (mitral and aortic) are close together whereas the right heart valves (tricuspid and pulmonary) are separated by myocardium. Dotted line marks the limit of atrial myocardium around the mitral orifice. (B) This figure of the heart viewed from the anterior aspect shows the close relation between aortic and mitral valves in situ. Fibrous continuity between the valves (blue arrows) is related to the non and left coronary sinuses of the aorta.
B. Two loops: basal and apical
C. Double helix derived from spiral fold
D. Apex has figure of eight configuration
10. Coronary Arteries: There are two, right and left coronary arterial system
Dominance of one of the two arterial patterns is determined by the origin of posterior descending artery. PDA usually arise from the RCA and thus dominance is usually right side or co-dominace (balanced): In only 10-15% patients left arterial dominance is present. When the PDA is both from RCA and Cx arteries the pattern is called balanced pattern since no particular dominance is present. The 2/3rd ventricluar septal blood supply is through left anterior descending (LAD) artery and 1/3 through the posterior descending (PDA) artery. In 55% cases sinus node artery arise from RCA. AV node artery arise from U bend at crux, just beyond the takeoff of the PDA, if circulation is right dominant.
Segmental description of pathological anatomy: (Van Praagh’s Classification)
A. Situs of thoracic viscera and atria: Best identified from the bronchial anatomy (3 bronchi on the right, 2 on the left). Situs can be of three types;
- Situs solitus,
- Situs inversus, and
- Situs ambiguous.
B. Situs of ventricles: Normal ventricular situs is concordant, D-loop, right-handedness. However, opposite of the normal is called ventricular inversion which is charcaterised by discordant, L-loop, left-handedness of the ventricles.
C. Dominance of ventricles: Normally both left right and left have equal dominance (Balanced). However, when either of the ventricles dominate there could be right (left small), left (right small) dominance.
D. Cardiac connections: Normal atrioventricular and ventriculoarterial connections are concordant (left atrium to left ventricle and left ventricle to aorta and similarly on the right side, right atrium to right ventricle and right ventricle to pulmonary artery). Reversal of this at any level is called discordant (transposed) connection.
E. Cardiac apex and arterial position:
1) Cardiac apex can point towards; levoposition (Normal left side), dextroposition (opposite of normal i.e. right side), mesocardia (midline)
2) Great arteries can be; transposed (opposite of normal i.e. aorta connected to right ventricle and pulmonary artery connected to left ventricle), malposition (abnormally positioned)
3) The patient’s heart is usually normal in structure in dextrocardia. This condition only refers to the position of the cardiac apex.
Cardiac Skeleton: It is also called “Fibrous skelton” of the heart which is truly a frame of connective tissue. It consists of a set of fibrous rings made of collagen. In simplistic terms the majority of the skeleton lies at the base of the ventricles, roughly parallel to the coronary sinus.
It has three major functions;
- It functions to electrically isolate the atria from the ventricles. The atrioventricular conducting system is the only electrical connection between the atria and the ventricles in a normal heart.
- It also provides rigidity to the heart to prevent the dilatation of individual valves or outflow tracts.
- It provides a point of attachment for valve leaflets and the myocardium. The fibrous rings which surround the both right and left atrioventricular canals and origins of the aorta and the pulmonary artery, both of which are wedged within the fibrous skeleton.
It consists of;
A. Fibrous body: (Annuli Fibrosi or fibrous rings) surrounding four openings; mitral, tricuspid, aoric and pulmonary valves
B. Right and left trigones: connect annuli fibrosi (the rings) together. Expansions of fibrous tissues at either extreme of the area of continuity between mitral annulus and aortic annulus form the right and left fibrous trigones (fig 3). The atrioventricular conduction bundle passes through the right fibrous trigone. The trigones are expansions of fibrous tissue at either end of the area of aortic–mitral valvar continuity. The right fibrous trigone together with the membranous septum forms the “central fibrous body”. Central fibrous body is the toughest structure in the heart.
Figure: Sketch showing fibrous skeleton at the base of the heart (seen from above) in anatomical position
Coronary Arteries: Like all other tissues in the body, the heart muscle needs oxygen-rich blood to function (done through coronary arteries), and oxygen-depleted blood must be carried away (done by coronary veins draining into coronary sinus). Coronary arteries supply blood to the heart muscle.
Coronary arterial system consists of;
A. Right and Left coronary arteries originating from proximal part of the ascending aorta via respective right and left main coronary ostia
B. Branches from main coronary arteries
A. Left coronary system: The left main coronary artery (LMCA), divides into two major arteries c.f. the left anterior descending artery and the circumflex branch. This system supplies blood to the left ventricle and left atrium.
1) Left main
2) Left anterior descendingà septal and diagonal branches
3) Circumflexàobtuse marginal arteries and posterior descending artery (PDA) in left dominant system.
B. Right coronary artery system: Acute marginal, AV nodal, sinus node arteries and posterior descending artery (PDA) in right dominant system.
Heart borders: From above downwards;
A. Right border of the heart (Mediastinal Border) is formed by;
- Right atrium
- Superior vena cava
B. Left Border of the heart is formed by;
- Aortic arch
- Pulmonary trunk
- Left atrial appendage
- Left ventricle
Surgical Anatomy Atrioventricular (Mitral and Tricuspid) Valve Apparatus
The Mitral Valve Apparatus: The mitral apparatus includes mitral leaflets, annulus, chordae tendineae, papillary muscles, and the left ventricular myocardium where these pappilary muscels are attached. The valve is obliquely located in the heart and has a close relation to the aortic valve (See Figure). Unlike the tricuspid valve which is separated by muscle from its counterpart, the pulmonary valve, the mitral valve is immediately adjacent to the aortic valve.
Figure 1 (A) View of the four heart valves at the base of the heart in anatomical orientation showing their spatial relations. The left heart valves (mitral and aortic) are close together whereas the right heart valves (tricuspid and pulmonary) are separated by myocardium. Dotted line marks the limit of atrial myocardium around the mitral orifice. (B) This figure of the heart viewed from the anterior aspect shows the close relation between aortic and mitral valves in situ. Fibrous continuity between the valves (blue arrows) is related to the non and left coronary sinuses of the aorta.
Figure: Relationship of mitral and tricuspid valve to their respective outlet valves).
The mitral valve has two leaflets, the anterior (truly is aortic) and posterior (truly is mural) leaflets. None of the two mitral leaflets are attached to ventricular septum.
1. Anterior mitral leaflet (AML or Aortic): This leflet hangs like a curtain between the left ventricular inflow and outflow and as you can appreciate from the (Figure) it is attached only to the fibrous skeleton with right and left fibrous trigone on the either sides.
1. Anterior mitral leaflet (AML or Aortic): This leflet hangs like a curtain between the left ventricular inflow and outflow and as you can appreciate from the (Figure) it is attached only to the fibrous skeleton with right and left fibrous trigone on the either sides.
- This leaflet is contiguous with the left and noncoronary cusps of the aortic valve.
- Area beneath the intervening aortic commissure, termed the fibrous subaortic curtain.
- An important characteristic of the anterior mitral leaflet is it has rounded free edge and occupies only 35% to 45% of its mitral annular circumference. However intrestingly the total leaflet area is almost identical to that of the posteriorly situated mural leaflet due to its larger height compared to long and narrow posterior mitral leaflet.
- Fan-shaped chordae insert into and define the clefts between the individual posterior scallops.
- Even when posterior mural leaflet is much less mobile compared to that of the anterior aortic leaflet, both mitral leaflets contribute importantly to effective mitral valve closure.
- The rough (coapting) zone: is the leading edge of the anterior and posterior mitral leaflets. This zone is the contact surface of the mitral leaflets during systole.
- The clear zone: is peripheral to the rough zone and represents most of the body of the leaflet; this portion of the mitral valve billows into the atrium during ventricular contraction.
- The basal zone: between the clear zone and the annulus, receives the insertion of the basal chordae tendineae (tertiary chordae), which originate directly from the trabeculae of the left ventricle. The basal zone is found only on the posterior leaflet.
Mitral annulus: The annulus marks the hingeline of the mitral valve leaflets. Its shape is more or less “D shaped than the circular”. It is flexible and dynamic structure. The anteromedial straight border (1/3rd of the annular circumference) is in relation with the non-coronary and left coronary cusps of aortic valve. Thus you can appreciate (see figure) how the origin of the aorta (left ventricular outflow tract / aortic root) comes to be wedged between the ventricular septum and the anterior mitral valve leaflet displacing the anterior (aortic mitral leaflet posteriorly and laterally away from the interventricular septum.
