Position of the Heart
It is projected to the anterior surface of the thorax, it lies behind and to the left of the sternum.
Location of the Heart
It is located in the middle mediastinum. Apex of the heart - formed by the tip of the left ventricle. It is directed forwards, down and to the left, and slightly medial to the midclavicular line.
Base of the Heart - faces posteriorly toward T6-T9 vertebra
Pericardium (Pericardial Sac)
A tough fibroserous sac surrounding the heart.
Fibrous Pericardium
The outer tough fibrous layer of the pericardium, continuous with the central tendon of the diaphragm.
Serious Pericardium
Two layered thin membranous lining (mesothelium)
Parietal Serous Pericardium
Lines the internal wall of the fibrous pericardium.
Visceral Serious Pericardium
Epicardium - directly adheres to the surface of the heart
Transverse Pericardial Sinus and Oblique Pericardial Sinus
Junction where the visceral and parietal layers of the serous pericardium become continuous where the great vessels and enter and exit the heart.
Pericardial Cavity
Located between the visceral and parietal serous pericardia, and contains a small amount of serous fluid. The heart is NOT contained in the pericardial cavity. It prevents friction during heart movements.
Clinical Correlation of Pericardial Cavity
Rapid accumulation of excess fluid in the pericardial cavity (blood from stab wound) can compress the heart and compromise its movement. This is called cardiac tamponade.
Pericarditis
inflammation of the pericardium
Pericardial Effusion
excessive amount of pericardial fluid, usually result of inflammation, which can compromise heart movement.
Blood Supply and Innervation to Pericardium
Pericardiophrenic artery.
Phrenic Nerve - sensory innervation, pain sensation (often referred, C3-C5 dermatomes - shoulder pain)
Vagus Nerve
Sympathetic Trunk - vasomotor innervations
Heart Layers
Epicardium, Myocardium, Endocardium
Epicardium
outer layer - visceral serous pericardium and subepicardial fatty loose connective tissue.
Myocardium
Middle layer - thickest layer - cardiac muscle
Endocardium
inner layer - endothelial lining and subendothelial connective tissue
Fibrous Skeleton of the Heart
Four fibrous rings surrounding the orifices of the valves. Provide attachment and support for the myocardium and the leaflets and cusps of the valves. Serves as an electrical insulator, thus allows for independent contractions of the atria and ventricles.
Surface Anatomy of the Heart
Usually covered with variable amounts of fat. Includes the apex, base, surfaces, borders
Apex of the Heart
formed by the tip of the left ventricle
Base of the Heart (posterior aspect)
Formed primarily by the left atrium and a small contribution from the right atrium and proximal parts of the great veins.
surfaces of the Heart
Anterior, diaphragmatic, left pulmonary, right pulmonary
Anterior (Sternocostal) Surface of the Heart
mostly the right ventricle with some of the right atrium and the left ventricle
Diaphragmatic Surface
mostly the left ventricle with some of the right ventricle separated by the posterior interventricular groove
The Left Pulmonary Surface
left ventricle with some of the left atrium - faces the left lung
The Right Pulmonary Surface
mainly the right atrium, faces the right lung
Borders of the Heart
Right, Left, Inferior, Superior
Right Border of Heart
The right atrium between the SVC and the IVC.
Inferior Border
mostly the right ventricle with some of the left ventricle (apex)
Left Border
Mostly the left ventricle
Superior Border
Mostly the left atrium with some of the right atrium, the ascending aorta and the pulmonary trunk, SVC entering the right atrium.
External Sulci (grooves of the heart)
Coronary (atrioventricular) Sulcus - groove on the surface of the heart that delineates the separation of the atria from the ventricles. The sulcus encircles the heart.
Anterior and Posterior Interventricular Sulci - surface grooves delineating the interv
The Great Vessels
SVC, IVC, pulmonary trunk, right and left pulmonary veins, ascending aorta
SVC/IVC
enter the right atrium to bring deoxygenated blood into the heart.
Pulmonary Trunk
Blood exits the right ventricle through the pulmonary valve and into the pulmonary trunk. It exits from the right ventricle to carry deoxygenated blood to the lungs. Trunk divides into the right and left pulmonary arteries.
Right and Left Pulmonary Veins
carry oxygenated blood from the lungs to the heart. There are usually four pulmonary veins - superior and inferior right pulmonary veins, superior and inferior left pulmonary veins - usually open into the left atrium
Ascending Aorta
exits from the left ventricle to carry oxygenated blood from the heart to the rest of the body
Right Atrium
Forms the right border of the heart - the right auricle - an ear like appendage which increases the capacity of the atrium. The SVC enters its superior margin. The IVC and the coronary sinus enter the posterior surface. The IVC reaches the heart after pas
Pectinate Muscles
Bundles of cardiac muscles that form the rough anterior wall of right atrium. They merge on the anterolateral wall into a ridge of tissue called the crista terminalis. This extends from the opening of the SVC to the opening of the IVC.
Sulcus terminalis -
Fossa Ovalis
Oval depression located in the interatrial septum, which is a remnant of the foramen ovale in the fetus.
Tricuspid Valve
located in the right atrioventricular orifice, allows blood to flow into the right ventricle.
Right Ventricle
Forms the largest part of the sternocostal, and a small part of the diaphragmatic aspects of the heart. It defines almost the entire inferior border of the heart. Its middle myocardial layer is thinner than that of the left ventricle.
Trabeculae Carnae
Muscular bundles lining the interior of RV. These bundles form elevated ridges and some form finger-like projections called papillary muscles (usually three).
Papillary Muscles
connect to the tricuspid valve by cord like strands called chordae tendinae.
Septomarginal Trabecular (Marginal Band)
distinct band that connects the interventricular septum to the anterior papillary m.
Right Atrioventricular (Tricuspid) Valve
three leaflets attached to the AV orifice. During ventricular contraction the papillary muscles also contract. this prevents the valve leaflets from eversion by blood reflux into the right atrium.
Left Atrium
Forms most of the base of the heart - left auricle of the left atrium forms the superior part of the left border of the heart - the interior has a large smooth surface and a smaller rough surface - rough surface corresponds to the pectinate muscles of the
Bicuspid Valve
allows blood flow from the left atrium into the left ventricle. Has two leaflets, but is otherwise similar to tricuspid valve.
Left Ventricle
forms the left margin, the apex and most of the diaphragmatic surface of the heart - middle myocardial layer is thicker than that of the right ventricle since it has to pump blood into systemic circulation - interior is lined by trabeculae carneae - papil
Aortic Valve
marks the entrance into the aorta from the left ventricle - has three leaflets - the left and right coronary arteries branch from the aorta in close proximity to the aortic valve.
Interatrial Septum and Interventricular Septum
atrial is thinner, separate atria
separate ventricles - thin membranous part continuous with the skeleton of the heart - thick muscular part. respectively.
Blood Flow Through the Heart
deoxygenated blood flows through the right atrium from the SVC and IVC, then into the right ventricle through the tricuspid valve. Next, blood is pumped through the pulmonic valve into the pulmonary trunk and pulmonary arteries into the lungs for oxygenat
Auscultation Sites of the Cardiac Valves
Aortic Valve - right 2nd intercostal space (at the sternal margin)
Pulmonary Valve - left 2nd intercostal space (at the sternal margin)
Tricuspid Valve - midleft sternal margin (neart the 4th intercostal space)
Bicuspid Valve - left 5th intercostal space
Clinical Correlation - Heart Valve Disease
Has two general causes - narrowing of the orifice (stenosis) caused by failure of the valve to fully open (i.e. aortic valve stenosis) or valvular incompetence (regurgitation) caused by a failure of the valve to close completely (prolapsed mitral valve).
Blood Supply to the Heart
Coronary arteries and cardiac veins located on the outer surface of the heart, usually embedded in a fatty tissue of epicardium.
Arteries to the Heart
the left and right coronary arteries - arise from the aorta immediately after it emerges from the left ventricle.
Right Coronary Artery
gives off the SA nodal branch which supplies the SA node then travels to the right in the coronary sulcus - branches to give right marginal artery - courses along the right margin of the heart - RCA continues posteriorly along the posterior portion of the
Left Coronary Artery
Immediately divides into two branches - the anterior interventricular artery that courses in the anterior interventricular sulcus and the circumflex artery that courses to the left in the coronary sulcus. It gives off a left marginal branch and sometimes
Regions Supplied by the RCA
the right atrium, SA node (60% of people), AV node (80% of people), most of the right ventricle, part of the left ventricle (diaphragmatic surface) and part of the interventricular septum (usually the posterior third)
Regions Supplied by the LCA
The left atrium, most of the left ventricle, part of the right ventricle, most of the interventricular septum including the AV bundles, the SA node (40% of people)
Variations in Arterial Branches
Right dominant pattern - the right coronary artery has a prominent transverse branch that extends across the base of the heart in the coronary groove, at the expense of the circumflex a.
Codominant Pattern - both the RCA and LCA give off branches that cou
Clinical Correlation - blockage
Sudden blockage of blood flow in the coronary circulation (by an embolus) can result in ischemia and necrosis of the cardiac muscle (myocardial infarction). The most common area of occlusion is the anterior interventricular a. followed by the RCA and the
Venous Drainage
Mainly via the cardiac veins that empty into the coronary sinus, and partly by small veins that empty directly into the heart chambers. The coronary sinus is located on the posterior part of the coronary sulcus. The sinus drains into the RA adjacent to th
Great Cardiac Vein
drains the areas of the heart supplied by the LCA. It is the main tributary of the coronary sinus. It begins in the anterior interventricular sulcus and courses superiorly to the coronary sulcus.
Middle Cardiac Vein
accompanies the posterior interventricular artery - drains most areas supplied by RCA.
Small Cardiac Vein
parallels the right marginal artery and joins the coronary sinus as the sinus enters the right atrium. Drain most areas supplied by RCA.
Anterior cardiac veins
small - open directly into the right atrium
Venae Cordis Minimae
smallest - opens directly into each chamber of the heart.
Lymphatic Drainage
the vessels follow the coronary arteries and drain mainly into the tracheobronchial nodes.
Autonomic Innervation
regulation of the heart rate and the force of contraction - the role of this innervation is to modify the heart rhythm, not generate it.
Superficial and Deep Cardiac Plexuses
Formed by branches from parasympathetic and sympathetic systems plus visceral afferent fibers
Cardiac Sympathetics
Arise from T1-T4 level of sympathetic trunks (preganglionic fibers). Postganglionic fibers reach heart via cervical and upper thoracic branches. They function to increase heart rate and increase the strength of the contraction.
Afferent Visceral Pain Fibers
Accompany sympathetic fibers - enter the spinal cord mainly at T1-T4 level, especially on the left side. This means that pain from the heart may be perceived as pain originating from superficial regions of the body (skin) with sensory input at the same, T
Cardiac Parasympathetics
preganglionic fibers from the vagus nerve - decrease heart rate, reduce force of contraction.
Conducting System of the Heart
has an intrinsic automatic beat - generates its own rhythm - consists of nodes and networks of specialized myocardial cells
Sinoatrial (SA) Node
the pacemaker - located in the right atrium in the notch formed by the SVC and the right auricle. It initiates the heartbeat.
Atrioventricular (AV) Node
in the wall of the right atrium near the opening of the coronary sinus - receives electrical signals from the SA node and will then stimulate the AV bundle.
AV Bundle of His
located deep to the endocardium - divides into right and left bundle branches that coure on each side of the interventricular septum to reach the base of the papillary muscle - right branch of AV bundle reaches the anterior papillary muscle via the septom
Purkinje Fibers
Subendocardial plexus of conduction cells lining the two sides of the interventricular septum.
Clinical Correlation of Conducting System
The coronary heart disease, since it can cause insufficient blood supply, often affects the cardiac conduction system. Atrial fibrillation occurs when the heart's electrical signals do not begin in the SA node, but originate in another part of the atria o