Cardiac Anatomy and the Pericardium PDF

Cardiac Anatomy and the Pericardium Cardiovascular System General Considerations  Heart Arteries Veins Chambers of the Heart PERICARDIUM and Mediastinum  PERICARDIUM The pericardium is a fibroserous membrane that covers the heart and the beginning of its great...

Cardiac Anatomy and the Pericardium Cardiovascular System General Considerations  Heart Arteries Veins Chambers of the Heart PERICARDIUM and Mediastinum  PERICARDIUM The pericardium is a fibroserous membrane that covers the heart and the beginning of its great vessels. Composed of the fibrous pericardium and serous pericardium.  PERICARDIUM Fibrous Pericardium Is a strong, dense, fibrous layer that blends with the adventitia of the roots of the great vessels and the central tendon of the diaphragm. Serous Pericardium Consists of the parietal layer, which lines the inner surface of the fibrous pericardium, and the visceral layer, which forms the outer layer (epicardium) of the heart wall and the roots of the great vessels. PERICARDIUM and other Serous Membranes PERICARDIUM  PERICARDIUM The pericardial cavity is the potential space between opposing layers of the parietal and visceral layers of serous pericardium. It normally contains a thin film of fluid that prevents friction during contractions. PERICARDIUM  Fibrous Pericardial Attachments Superiorly: Blends with the tunica adventitia of the great vesseles Inferiorly: Attached to the central tendon of the diaphragm Anteriorly: Attached to the sternum by the sternopericardial ligament  Relations of the Pericardium Inferior: -Central tendon of the Diaphragm -The site of continuity has been referred to as the pericardiacophrenic ligament Via diaphragm -Left lobe of the liver -Fundus of the stomach  Relations of the Pericardium Anterior: Related to the lungs and pleura, (except a small area where the cardiac notch) to the sternum, costal cartilages, and anterior ends of the 3rd–5th ribs on the left side  Relations of the Pericardium Posterior: Related to the -Principle bronchii -Esophagus -Descending aorta -Posterior part of the mediastinal surface of the lungs  Relations of the Pericardium Lateral: Mediastinal pleura on each side  Pericardial Sinuses The reflection of the pericardium during the folding of the embryonic heart results in recesses -Oblique Sinus -Transverse Sinus  Pericardial Sinuses Transverse Sinus A subdivision of the pericardial sac, lying posterior to the ascending aorta and pulmonary trunk, anterior to the SVC, and superior to the left atrium and the pulmonary veins. It is of great importance to the cardiac surgeon because while performing surgery on the aorta or pulmonary artery, a surgeon can pass a finger and make a ligature through the sinus between the arteries and veins, thus stopping the blood circulation with the ligature.  Pericardial Sinuses Oblique Sinus A subdivision of the pericardial sac behind the heart, surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferior vena cava (IVC).  Arterial supply of the Pericardium 1. Pericardiacophrenic artery (From Internal Thoracic) – main supply 2. Musculophrenic artery 3. Pericardial branches from: bronchial, esophageal, superior phrenic arteries 4. Visceral layer is supplied by coronary arteries  Venous drainage of Pericardium 1. Pericardiacophrenic veins (to brachiocephalic or internal thoracic veins) 2. Azygos system  Innervation of the Pericardium 1. Phrenic nerves (C3–C5): primary source of sensory fibers – pain refers to C3-C5 dermatomes (ipsilateral top of the shoulder) 2. Vagus nerve 3. Sympathetic trunk: vasomotor functions  Clinical Correlations of the Pericardium Pericardial effusion: Accumulation of fluid in the pericardial space resulting from inflammation caused by acute pericarditis, and the accumulated fluid compresses the heart, inhibiting cardiac filling. It has signs of an enlarged heart, a water bottle appearance of the cardiac silhouette, faint heart sounds, and vanished apex beat. It can be treated by pericardiocentesis.  Clinical Correlations of the Pericardium Pericardiocentesis is a surgical puncture of the pericardial cavity for the aspiration of fluid, which is necessary to relieve the pressure of accumulated fluid in the heart. A needle is inserted into the pericardial cavity through the fifth intercostal space left to the sternum. Because of the cardiac notch, the needle misses the pleura and lungs, but it penetrates the pericardium.  Clinical Cardiac tamponade : Correlations of the An acute compression of the heart caused by a rapid Pericardium accumulation of fluid or blood in the pericardial cavity from wounds to the heart or pericardial effusion. Tamponade can be treated by pericardiocentesis. It causes compression of venous return to the heart.  HEART Slightly larger than a clenched fist Double, self adjusting suction and pressure pump, the parts of which work in unison to propel blood to all parts of the body. The right side of the heart (right heart) receives poorly oxygenated blood (venous) from the body through the SVC and IVC, pumps it through the pulmonary trunk and arteries to the lungs for oxygenation The left side of the heart (left heart) receives well-oxygenated (arterial) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body. Chambers of the Heart  Layers of the Heart 1. Epicardium: visceral layer of serous pericardium 2. Myocardium: is the contractile layer of the heart 3. Endocardium: Endothelial layer lining the chambers of the heart & valves  Orientation of the Heart The general shape and orientation is like a pyramid that has fallen over and is resting on one of its sides In the thoracic cavity, the apex of this pyramid projects anterior, inferior, and to the left The base of the pyramid is opposite the apex and faces posterior  Orientation of the Heart The sides of the pyramid consist of: -A diaphragmatic (inferior) surface on which the pyramid rests, -An anterior (sternocostal) surface oriented anteriorly, -A right pulmonary surface, -A left pulmonary surface.  External Features of the Heart Base (posterior surface) Is the heart’s posterior aspect (opposite the apex). Is formed mainly by the left atrium, with a lesser contribution by the right atrium. Faces posteriorly toward the bodies of vertebrae T6–T9 Is separated from the vertebral column by 1- Descending aorta 2- Esophagus 3- Oblique sinus of pericardium  External Features of the Heart Base (posterior surface) Separated from the diaphragmatic surface by posterior part of coronary sulcus (houses coronary sinüs)  External Features of the Heart Base (posterior surface)  External Features of the Heart The apex of the heart Is formed by the inferolateral part of the left ventricle. Lies posterior to the left 5th intercostal space in adults, usually approximately 9 cm (a hand’s breadth) from the median plane. Remains motionless throughout the cardiac cycle. Is where the sounds of mitral valve closure are maximal (apex beat); the apex underlies the site where the heartbeat may be auscultated on the thoracic wall.  External Features of the Heart The apex of the heart  External Features of the Heart The apex of the heart External Features of the Heart Anterior (sternocostal) surface Divided by coronary (atrio-ventricular) groove into : 1- Atrial part: formed mainly by right atrium. 2- Ventricular part : the right ⅔ is formed by right ventricle, the left ⅓ is formed by left ventricle. External Features of the Heart Anterior (sternocostal) surface The coronary groove the right coronary artery and the Anterior cardiac vein The anterior interventricular groove, -Separates 2 ventricles -Has Anterior interventricular artery(branch of left coronary). and the Great cardiac vein.  External Features of the Heart Anterior (sternocostal) surface External Features of the Heart Diaphragmatic (inferior) surface posterior interventricular groove - separates ventricles - Posterior interventricular artery. -Middle cardiac vein Borders of the heart Borders and Margins of the heart The right and left margins are the same as the right and left pulmonary surfaces of the heart. The inferior margin is defined as the sharp edge between the anterior and diaphragmatic surfaces of the heart The obtuse margin separates the anterior and left pulmonary surfaces External sulci of the Heart Internal partitions divide the heart into four chambers (i.e. , two atria and two ventricles) and produce surface or external grooves referred to as sulci Cardiac Chambers  Right Atrium The right atrium forms the right border of the heart Receives venous blood from the SVC, IVC, and coronary sinus Right auricle is a conical muscular pouch Right Atrium  Right Atrium The sulcus terminalis: A vertical groove between the right atrium and the right auricle Extends from front of S.V.C to the front of I.V.C on the inside forms a ridge called the crista terminalis.  Right Atrium – Internal Structure Crista terminalis divides right atrium into 2 parts: 1. Anterior part: rough and trabeculated by bundles of muscle fibres (musculi pectinati). 2. Posterior part: (sinus venarum) is smooth  Right Atrium – Internal Structure Contains the valve (Eustachian) of the IVC and the valve (Thebesian) of the coronary sinus  Right Atrium – Internal Structure Sinus Venarum (Sinus Venarum Cavarum) Is a posteriorly situated, smooth-walled area that is separated from the more muscular atrium proper by the crista terminalis.  Right Atrium – Internal Structure Pectinate Muscles (musculi pectinati): Prominent ridges of atrial myocardium located in the interior of both auricles and the right atrium.  Right Atrium – Internal Structure Fossa ovalis: An oval depression in the posterior part of the interatrial septum Annulus Ovalis: The margin of Fossa ovalis. The fossa ovalis is the remnant of a thin fibrous sheet that covered the foramen ovale during fetal development. The blood leaves right atrium to right ventricle via tricuspid valve. Clinical Correlations – Atrial Septal Defect  Right Atrium – Internal Structure Openings in right atrium: 1. SVC (no valve) 2. IVC (Eustachian valve) 3. Coronary sinus : (Thebesian valve) 4. Right atrioventricular orifice: lies anterior to IVC opening, it is surrounded by a fibrous ring which gives attachment to the tricuspid valve 5. Small orifices of small veins (anterior and small cardiac vein)  Right Ventricle The right ventricle communicates with : the right atrium through the right atrioventricular orifice. the pulmonary trunk through the pulmonary orifice.  Right Ventricle Has a thinner wall Contains muscular projections called trabeculae carneae. Trabeculae carneae: are anastomosing muscular ridges of myocardium in the ventricles.  Right Ventricle Conus arteriosus: Smooth area of the right ventricle approaching the pulmonary orifice.  Right Ventricle Papillary muscles: Cone-shaped muscles enveloped by endocardium. Extend from the anterior and posterior ventricular walls and the septum, and their apices are attached to the chordae tendineae  Right Ventricle Papillary muscles: 1. Anterior papillary muscle 2. Posterior papillary muscle 3. Septal Papillary muscle  Right Ventricle Chordae tendineae: tendinous threads attaching the cusps of tricuspid valve to papillary muscles  Right Ventricle Papillary muscles: Contract to tighten the chordae tendineae, preventing regurgitation of ventricular blood into the right atrium.  Right Ventricle Moderator band (Septomarginal Trabecula) forms a bridge between the septum and the base of the anterior papillary muscle of the anterior wall of the right ventricle. prevents overdistention of the ventricle carries the right limb (Purkinje fi bers) of the atrioventricular (AV) bundle  Right Ventricle InterVentricular Septum The place of origin of the septal papillary muscle. Mostly muscular but has a small membranous upper part, which is a common site of ventricular septal defects (VSDs).  Right Ventricle InterVentricular Septum Clinical Correlations – Ventricular Septal Defect  Right Ventricle Blood leaves the right ventricle to pulmonary trunk through pulmonary orifice.  Left Atrium Smaller and has thicker walls than the right atrium, but its walls are smooth, except for a few pectinate muscles in the auricle. It is the most posterior of the four chambers lying posterior to the right atrium but anterior to the esophagus It forms the greater part of base of heart Receives oxygenated blood through four pulmonary veins  Left Atrium The left atrium communicates with the left ventricle through the left atrioventricular orifice Sends blood to left ventricle through the left atrioventricular orifice which is guarded by mitral valve (Bicuspid valve). Left Atrium  Left Ventricle Its wall is thicker than that of right ventricle It is longer, narrower, and more conical-shaped than the right ventricle.  Left Ventricle The part of left ventricle leading to ascending aorta is called the aortic vestibule. The blood leaves the left ventricle to the ascending aorta through the aortic orifice. Left Ventricle  Skeleton of the Heart Keeps the orifices of the AV and semilunar valves patent Provides attachments for the leaflets and cusps of the valves Provides attachment for the myocardium Forms an electrical “insulator,” by separating the myenterically conducted impulses of the atria and ventricles Skeleton of the Heart  Heart Valves Semilunar valves: No chordae tendineae or papillary muscles are attached to these cusps - Aortic valve - Pulmonary valve Atrioventricular valves: -Tricuspid valve -Mitral valve  Heart Valves Aortic Valve Lies behind the left half of the sternum opposite the third intercostal space. It is closed during ventricular diastole its closure at the beginning of ventricular diastole causes the second (“dub”) heart sound. It is most audible over the right second intercostal space just lateral to the sternum 3 Semilunar cusps. The position of the cusps : - 1 anterior - 2 posterior Heart Valves Aortic Valve  Heart Valves Pulmonary Valve Lies behind the medial end of the left third costal cartilage and adjoining part of the sternum. It is most audible over the left second intercostal space just lateral to the sternum. 3 semilunar cusps : - 2 anterior - 1 posterior  Heart Valves Tricuspid (Right AV) Valve Lies between the right atrium and ventricle, behind the right half of the sternum opposite the fourth intercostal space. It is most audible over the right (or left for some people) lower part of the body of the sternum. It has anterior, posterior, and septal cusps Cusps are attached to the papillary muscles by the chordae tendineae It is closed during the ventricular systole (contraction) Its closure contributes to the first heart sound (“lub”)  Heart Valves Tricuspid (Right AV) Valve  Heart Valves Bicuspid (Mitral Valve or Left AV) Valve It is shaped like a bishop’s miter. Lies between the left atrium and ventricle, behind the left half of the sternum at the 4th costal cartilage Has 2 cusps: a larger anterior and a smaller posterior. Its closure at the onset of ventricular systole causes the first heart sound (“lub”). It is most audible over the apical region of the heart in the left 5th intercostal space at the midclavicular line.  Heart Valves Mitral Valve Heart Valves  Heart Sounds and Auscultation First (“Lub”) Sound Caused by the closure of the tricuspid and mitral valves at the onset of ventricular systole. Second (“Dub”) Sound Caused by the closure of the aortic and pulmonary valves (and vibration of walls of the heart and major vessels) at the onset of ventricular diastole. Heart Sounds and Auscultation Heart Sounds and Auscultation Heart Sounds and Auscultation Clinical Correlations – Valvular Heart Diseases  Innervation and Conduction System The heart is supplied by sympathetic & parasympathetic fibers via the cardiac plexus situated below arch of aorta. The sympathetic fibres arise from the cervical & upper thoracic ganglia of sympathetic trunks (increase the heart rate) The parasympathetic fibres arise from the vagus nerves (decrease the heart rate) Autonomic NS innervation affects the conduction system of the heart (Sinoatrial Node, AV Node, AV Bundle (Bundle of His)) Innervation and Conduction System Innervation and Conduction System  The Conduction System Composed of modified, specialized cardiac muscle cells that lie immediately beneath the endocardium Carry impulses throughout the cardiac muscle, signaling the heart chambers to contract in the proper sequence.  The Conduction System Sinoatrial Node (SA) A small mass of specialized cardiac muscle fi bers that lies in the myocardium at the upper end of the crista terminalis near the opening of the SVC in the right atrium. Known as the pacemaker of the heart and initiates the heartbeat, which can be altered by autonomic nervous Supplied by the sinus node artery, which is a branch of the right coronary artery  The Conduction System Sinoatrial Node  The Conduction System Sinoatrial Node  The Conduction System Atrioventricular Node (AV) Lies in the interatrial septum, superior and medial to the opening of the coronary sinus in the right atrium, Receives the impulse from the sinoatrial (SA) node and passes it to the AV bundle. Supplied by the AV nodal artery, which usually arises from the right coronary artery  The Conduction System Atrioventricular Node (AV)  The Conduction System Atrioventricular Node (AV)  The Conduction System AV Bundle (Bundle of His) Begins at the AV node and runs along the membranous part of the interventricular septum. Splits into right and left branches, which descend into the muscular part of the interventricular septum Bundle branches give rise to terminal conducting fibers (Purkinje fibers) to spread out into the ventricular walls.  The Conduction System AV Bundle (Bundle of His) ) The Conduction System Clinical Correlates  Arterial Supply – The Coronary Arteries Arise from the ascending aorta (first branches arising from aorta) and are filled with blood during the ventricular diastole. Have maximal blood flow during diastole and minimal blood flow during systole because of compression of the arterial branches in the myocardium during systole. Right Coronary Artery Left Coronary Artery Arterial Supply – The Coronary Arteries  Arterial Supply – The Coronary Arteries Right Coronary Artery Arises from the anterior (right) aortic sinus of the ascending aorta, runs between the root of the pulmonary trunk and the right auricle, and then descends in the right coronary sulcus, and generally supplies the right atrium and ventricle.  Arterial Supply – The Coronary Arteries Right Coronary Artery Branches: 1. SA Nodal Artery Passes between the right atrium and the root of the ascending aorta, encircles the base of the SVC, and supplies the SA node and the right atrium. 2. Marginal Artery Runs along the inferior border toward the apex and supplies the inferior margin of the right ventricle. 3. Posterior IV (Posterior Descending) Artery Larger terminal branch and supplies a part of the IV septum and left ventricle and the AV node. 4. AV Nodal Artery Arises opposite the origin of its posterior IV artery and supplies the AV node. Right Coronary Artery Right Coronary Artery  Arterial Supply – The Coronary Arteries Left Coronary Artery Arises from the left aortic sinus of the ascending aorta, just above the aortic semilunar valve. Shorter than the right coronary artery and usually is distributed to more of the myocardium.  Arterial Supply – The Coronary Arteries Left Coronary Artery Branches: 1. Anterior Interventricular Artery (Left Anterior Descending) Generally supplies anterior aspects of the right and left ventricles the chief source of blood to the IV septum and the apex. 2. Circumflex Artery Runs in the coronary sulcus, Gives off the left marginal artery Supplies the left atrium and left ventricle Anastomoses with the terminal branch of the right coronary artery. Left Coronary Artery Left Coronary Artery Clinical Correlates - Coronary Artery Disease Clinical Correlates - Coronary Angiography Clinical Correlates - Coronary Artery Disease  Cardiac Veins and Coronary Sinus Coronary Sinus Largest vein draining the heart Lies in the coronary sulcus Opens into the right atrium between the opening of the IVC and the AV opening. Has a one-cusp valve at the right margin of its aperture. Receives the great, middle, and small cardiac veins; the oblique vein of the left atrium; and the posterior vein of the left ventricle. Cardiac Veins and Coronary Sinus  Cardiac Veins and Coronary Sinus Great Cardiac Vein Begins at the apex of the heart and ascends along with the IV branch of the left coronary artery. Turns to the left to lie in the coronary sulcus and continues as the coronary sinus.  Cardiac Veins and Coronary Sinus Middle Cardiac Vein Begins at the apex of the heart and ascends in the posterior IV groove, accompanying the posterior IV branch of the right coronary artery. Drains into the right end of the coronary sinus. Small Cardiac Vein Runs along the right margin of the heart in company with the marginal artery and then posteriorly in the coronary sulcus to end in the right end of the coronary sinus. Oblique Vein of the Left Atrium Descends to empty into the coronary sinus, near its left end. Anterior Cardiac Vein Drains the anterior right ventricle, crosses the coronary groove, and ends directly in the right atrium. Smallest Cardiac Veins (Venae Cordis Minimae) Begin in the wall of the heart and empty directly into the chambers of the heart. Cardiac Veins and Coronary Sinus Cardiac Veins and Coronary Sinus Chest X-Ray and Heart Chest X-Ray and Heart