Anatomy of the heart Flashcards
Describe the borders of the heart
- Anterior surface: predominantly the RV, part of the RA and small strip of LV
- Posterior surface: predominantly LA, pulmonary veins, small part of RA
- Right border: SVC, right pulmonary veins, RA, IVC
- Left border: aorta, left pulmonary veins, LV
- Inferior border: RV
Describe the pericardium
A fibroserous sac that encloses the heart.
* Outer fibrous layer: tough, fuses with the adventitia of the great vessels superiorly and with the central tendon of the diaphragm inferiorly
* Inner serous pericardium (2 layers)
1. Parietal layer: lines inner surface of fibrous sac
2. Inner visceral layer, in direct contact with the heart.
A potential space exists between the two layers containing a thin film of pericardial fluid.
The double layer of serous pericardium is formed during embrylogical development by invagination of the heart into the fetal serous sac.
Folding of the pericardium creates sinuses within the reflections of the pericardium:
- Oblique sinus
- Transverse sinus
1.
What are the oblique and transverse sinuses of the pericardium? (borders)
Spaces (sinuses) within the reflections of the pericardium.
Oblique sinus lies in a blind recess behind the LA and is bordered by the four pulmonary veins and the IVC
Transverse sinus lies between the aorta and pulmonary trunk in front, and the SVC and LA behind
What are the surface markings of the pericardial sac?
Start at the 2nd left costal cartilage, 2 cm from the midline
Move downwards and laterally to the 5th left intercostal space, 8 cm from the midline (this corresponds to the apex beat)
Across to the 6th right costal cartilage, 2 cm from the midline
Up to the 3rd right costal cartilage, 2 cm from the midline
Describe the fibrous skeleton of the heart
The heart has a fibrous skeleton that provides a structural framework to which the valves of the heart are attached.
- Three u-shaped cords which form the aortic annulus (labelled ‘annular cords’ on diagram)
- Left and right trigones which extend down from two of these cords to form part of the mitral valve annulus
Describe the structure of the mitral valvular apparatus (leaflets, surrounding structures)
Two assymetrical leaflets (an anterior and posterior cusp) each attached to a flexible, saddle-shaped annulus
* The posterior leaflet is long and thin
* The anterior leaflet has a shorter annular attachment but a much longer ‘base to tip’ length
Supported by two papillary muscles attached to the valve leaflets by thin fibrous chordae tendinae
* First-order tendinae attach to the leaflet tips
* Second-order tendinae attach ot the lower surface of the leaflets
* Third-order tendinae attach to the base of the leaflets
Describe the structure and surroundings of the aortic valve
- Above the AV: aortic root runs from the aortic annulus to the sinotubular junction.
- Below the AV: LVOT
- AV has three leaflets, of similar size and shape, which attach to the root of the aorta
- Each leaflet sits in front of one of three aortic sinuses (aka sinuses of valsalva). Each sinus and leaflet are named according to its adjacent coronary artery (left, right, and non-coronary)
- Non-coronary cusp lies adjacent to the inter-atrial septum
- Each leaflet attaches in a U-shaped fashion, with the upper attachment along the sinotubular junction
What are the sinuses of valsalva?
- The three aortic sinuses, each sitting behind a leaflet of the aortic valve. Names according to adjacent coronary artery (left coronary, right coronary, non-coronary)
- Dilatations of the aortic root, that function as resevoirs for coronary blood flow during diastole and ensure the valve leaflets do not obstruct the coronary ostia
Describe the structure of the tricuspid valve
- Three leaflets of unequal size (anterior, posterior and septal)
- Septal is the largest, posterior is the smallest
- Leaflets are thinner than those of the left-sided valves
- Three papillary muscles, each associated with a corresponding leaflet. Chordae tendinae attach the free edges and inferior surfaces of the three leaflets to the papillary muscles
Describe the structure of the pulmonary valve (and compare to aortic)
- Three leaflets
- Similar in appearance to the aortic valve
- Leaflets tend to be much thinner than the aortic valve, and sinuses of valsalva are less prominent than those in the aortic root.
Describe the structure of the right atrium (inflow, outflow, features of walls)
- Lies anteriorly
- Receives blood from SVC, IVC, coronary sinus. Blood flows out during diastole through the TV into the RV
- Posteriomedial wall is formed by interatrial septum. Fossa ovalis is a shallow depression in this septum, and is an embryonic remnant of the foramen ovale
Describe the structure of the right ventricle (and what separates it from the RA)
Separated from the RA by the right atrioventricular groove in which the right coronary artery lies
Crescent-shaped in cross section
Lined by trabeculae: rough, muscular ridges (except in outflow tract)
* Specialised trabeculae form the three papillary muscles, which attach to the tricuspid valve, via the chordae tendinae
* One lies free within the RV cavity and carries the part of the cardiac conducting system known as the moderator band
* However the outflow tract has smooth walls (no trabeculae) - trabeculae line the remainder
Describe the structure of the left atrium (position, walls)
- Lies directly behind the right atrium
- Receives blood from the four pulmonary veins posteriorly (left upper and lower, right upper and lower)
- Smooth walled, with the exception of the LA appendage which is trabeculated by pectinate muscles
Describe the structure of the left ventricle (separation from LA, walls)
Separated from the LA by the left atrioventricular groove in which the branches of the left coronary artery lie
Thick and muscular. Wall thickness is approx 3-4x that of the RV wall
Circular in cross-section, prominent trabeculae carnae
