Cardiac Anatomy
Margins of the Heart
Right Border – right atrium
Superior Border – right and left auricles
Left Border – left ventricle
Inferior Border – mostly right ventricle
Components of the Heart
Layers of the Heart: from out to in Þ epicardium, myocardium, endocardium;
Pericardium – surrounds heart in a sac forming a "third space" or potential space between itself and the epicardium
Pericardium can fill with liquid and put pressure on the heart
Heart Chambers, Valves and Arteries
Right Atrium
Fossa ovalis is found between in the interatrial septum; when it is patent, it is called a foramen ovale
Propatent Fossa ovalis – when the fossa ovalis is closed but susceptible to opening
Sinoatrial node is found on the anterior wall and is normally the pacemaker of the heart
Right Ventricle
separated from the right atrium by the tricuspid valve
contains papillary muscles which extend from the posterior ventricle walls and the interventricular septum and attach to chordae tendineae; the chordae tendineae then attach to the tricuspid valve
the papillary muscles and chordae tendineae control closure of the valves and prevent valve prolapse
the papillary muscles may be damaged by a myocardial infarction
Left Atrium
smaller and has thicker walls than the right atrium; most posterior of the four chambers
Pathology: right and left atrial appendages (auricles) can cause stasis of blood and the formation of blood clots
Left Ventricle
separated from the left atrium by the mitral valve
has much thicker walls than the right ventricle; the wall may hypertrophy with Ý systemic pressure
also contains papillary muscles and chordae tendineae
Valves:
Þ 3 cusps
Mitral Valve Þ considered a bicuspid valve but actually has four cusps (2 are very small)
Semilunar valves: Aortic and Pulmonic
Arteries – Coronary Arteries begin just distal to the aortic valve; the right and left coronary arteries are the only blood supply to the heart
- Left Coronary Artery
– gives rise to the circumflex branch and the anterior interventricular (left anterior descending, LAD) branch; LAD supplies the left anterior heart wall and the ventricular septum; Circumflex branch supplies the posterior wall of the left and right ventricles
- Right Coronary Artery
– forms the sinus node artery, marginal artery and the posterior ventricular (right posterior descending) artery
- Left Internal Thoracic
(Internal Mammary) – descends on the internal surface of the thorax and lies on the pleura; can be used as a graft for a coronary artery bypass
Views of the Heart
Cross Sectional View of the Mediastium
Descending aorta – located between heart and spinal column; susceptible to injury with compression of chest wall Þ lethal
Esophagus – located immediately posterior to the heart; can place an ultrasound down the esophagus to obtain images of the heart Þ Transesophageal Ultrasound
Pulmonary Arteries – emboli from the heart may lodge at the bifurcation of the artery Þ saddle embolus
Anterior, Posterior (AP) View of the Heart
atrial-ventricular (AV) valves (tricuspid and mitral) are located more anterior
pulmonic and aortic valves are located more posterior
Pacemaker
Normally placed down the superior vena cava into the right atrium. Studies are being performed to place the lead through the right atrium and into the coronary sinus. The coronary sinus leads to the posterior wall of the left ventricle and this will allow the pacemaker to directly stimulate the left ventricle.
Dissection
Two methods:
- (1) Identify right atrium by following superior and inferior vena cava; expose right atrium. Then expose right ventricle by cutting along the lateral side. Next cut up the middle of the right ventricle forming a "V". The left atrium and ventricles are exposed in a similar manner
- (2) With a suspected myocardial infarction the heart should be serial sectioned; called "bread loafing". Beginning at the apex and continuing to the base. Horizontal slices of the heart are removed and examined.