Figure 3.53 Sagittal section of the pericardium.
Pericardium• The pericardium is a fibroserous sac surrounding the heart and the roots of the great vessels. It consists of two components, the fibrous pericardium and the serous pericardium. The fibrous pericardium is a tough connective tissue outer layer that defines the boundaries of the middle mediastinum. The serous pericardium is thin and consists of two parts :• the parietal layer lines the inner surface of the fibrous ;• the visceral layer) epicardium (of serous pericardium adheres to the heart and forms its outer covering .• The parietal and visceral layers of serous pericardium are continuous at the roots of the great vessels. The narrow space created between the two layers of serous pericardium, containing a small amount of fluid, is the pericardial cavity. This potential space allows for the relatively uninhibited movement of the heart.• Fibrous pericardium:• fibrous pericardium is a cone-shaped bag with its base on the diaphragm and its apex continuous with the adventitia of the great vessels. The base is attached to the central tendon of the diaphragm and to a small muscular area of the diaphragm on the left side. Anteriorly, it is attached to the posterior surface of the sternum by sternopericardial ligaments. These attachments help to retain the heart in its position in the thoracic cavity. The sac also limits cardiac distention.• The phrenic nerves, which innervate the diaphragm and originate from spinal cord levels C3 to C5, pass through on both sides of the fibrous pericardium & in front of the hilum of the lungs, and innervate the fibrous pericardium too.. Similarly, the pericardiacophrenic vessels are also accompany the phrenic nerves and supply the fibrous pericardium as they pass through the thoracic cavity.•
Phrenic nerves and pericardiacophrenic vessels.
Posterior portion of pericardial sac showing reflections of serous pericardium.
Cardiac orientation• The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides. Placed in the thoracic cavity, the apex of this pyramid projects forward, downward, and to the left, whereas the base is opposite the apex and faces in a posterior direction .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 .• (posterior surface) and apex The base of the heart is quadrilateral and directed posteriorly. It consists of :• the left atrium ;• a small portion of the right atrium ;• the proximal parts of the great veins (superior and inferior venae cavae and the pulmonary veins• The apex of the heart is formed by the inferolateral part of the left ventricle and is positioned deep to the left fifth intercostal space, 8-9 cm from the midsternal line.
Schematic illustration of the heart showing orientation, surfaces, and margins.
Surfaces& borders of the heart• The anterior surface faces anteriorly and consists mostly of the right ventricle with some of the right atrium on the right and some of the left ventricle on the left. Heart in the anatomic position rests on the diaphragmatic surface ,which consists of the left ventricle and a small portion of the right ventricle separated by the posterior interventricular groove. This surface faces inferiorly, rests on the diaphragm, is separated from the base of the heart by the coronary sinus, and extends from the base to the apex of the heart ..• The left pulmonary surface faces the left lung, is broad and convex, and consists of the left ventricle and a portion of the left atrium.• right pulmonary surface faces the right lung, is broad and convex, and consists of the right atrium• Margins and borders• Some general descriptions of cardiac orientation refer to right, left, inferior (acute), and obtuse margins :• 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. -it is formed mostly by the right ventricle and a small portion of the left ventricle near the apex ;• the obtuse margin separates the anterior and left pulmonary surfaces. it is round and extends from the left auricle to the cardiac apex ,and is formed mostly by the left ventricle and superiorly by a small portion of the left auricle .
Radiological examination of the heart• For radiologic evaluations, a thorough understanding of the structures defining the cardiac borders is critical. The right border in a standard posterior-anterior view consists of the superior vena cava, the right atrium, and the inferior vena cava. The left border in a similar view consists of the arch of the aorta, the pulmonary artery, and the left ventricle. The inferior border in this radiologic study consists of the right ventricle and the left ventricle at the apex. In lateral views, the right ventricle is seen anteriorly, and the left atrium is visualized posteriorly
Chestradiographs.A. Standard posterior-anterior viewof the chest..
Chest radiographs.. B. Standard lateral view of the heart.
External sulci• 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 .• The coronary sulcus circles the heart, separating the atria from the ventricles. As it circles the heart, it contains the right coronary artery, the small cardiac vein, the coronary sinus, and the circumflex branch of the left coronary artery .• The anterior and posterior interventricular sulci separate the two ventricles-the anterior interventricular sulcus is on the anterior surface of the heart and contains the anterior interventricular artery and the great cardiac vein, and the posterior interventricular sulcus is on the diaphragmatic surface of the heart and contains the posterior interventricular artery and the middle cardiac vein .
Sulci of the heart. A. Anterior surface of the heart. B. Diaphragmatic surface and base of the heart.
Sulci of the heart. A. Anterior surface of the heart. B. Diaphragmatic surface and base of the heart.
A. The heart as two pumps. B. Magnetic resonance image of midthorax showing all four chambers and septa.
. The heart as two pumps. B. Magnetic resonance image of midthorax showing all four chambers and septa.
Right Atrium• The right atrium consists of a main cavity and a small outpouching, the auricle. On the outside of the heart at the junction between the right atrium and the right auricle is a vertical groove, the sulcus terminalis , which on the inside forms a ridge, the crista terminalis .The main part of the atrium that lies posterior to the ridge is smooth walled and is derived embryologically from the sinus venosus. The part of the atrium in front of the ridge is roughened or trabeculated by bundles of muscle fibers, the musculi pectinati ,which run from the crista terminalis to the auricle. This anterior part is derived embryologically from the primitive atrium.• Openings into the Right Atrium• The superior vena cava: opens into the upper part of the right atrium; it has no valve. It returns the blood to the heart from the upper half of the body. The inferior vena cava (larger than the superior vena cava) opens into the lower part of the right atrium; it is guarded by a rudimentary, nonfunctioning valve. It returns the blood to the heart from the lower half of the body.• The coronary sinus ,which drains most of the blood from the heart wall ,opens into the right atrium between the inferior vena cava and the atrioventricular orifice. It is guarded by a rudimentary, nonfunctioning valve.• The right atrioventricular orifice lies anterior to the inferior vena caval opening and is guarded by the tricuspid valve .• Many small orifices of small cardiac veins also drain the wall of the heart and open directly into the right atrium.• Fetal Remnants• In addition to the rudimentary valve of the inferior vena cava are the fossa ovalis and anulus ovalis .These latter structures lie on the atrial septum ,which separates the right atrium from the left atrium .The fossa ovalis is a shallow depression, which is the site of the foramen ovale in the fetus .
Right Ventricle• The right ventricle communicates with the right atrium through the atrioventricular orifice and with the pulmonary trunk through the pulmonary orifice. As the cavity approaches the pulmonary orifice it becomes funnel shaped, at which point it is referred to as the infundibulum.• The walls of the right ventricle are much thicker than those of the right atrium and show several internal projecting ridges formed of muscle bundles. The projecting ridges give the ventricular wall a spongelike appearance and are known as trabeculae carneae .The trabeculae carneae are composed of three types. The first type comprises the papillary muscles ,which project inward, being attached by their bases to the ventricular wall; their apices are connected by fibrous cords (the chordae tendineae )to the cusps of the tricuspid valve. The second type is attached at the ends to the ventricular wall, being free in the middle. One of these, the moderator band ,crosses the ventricular cavity from the septal to the anterior wall. It conveys the right branch of the atrioventricular bundle, which is part of the conducting system of the heart. The third type is simply composed of prominent ridges.• The tricuspid valve guards the atrioventricular orifice and consists of three cusps formed by a fold of endocardium with some connective tissue enclosed :anterior, septal ,and inferior (posterior) cusps. The bases of the cusps are attached to the fibrous ring of the skeleton of the heart, whereas their free edges and ventricular surfaces are attached to the chordae tendineae .The chordae tendineae connect the cusps to the papillary muscles .When the ventricle contracts, the papillary muscles contract and prevent the cusps from being forced into the atrium and turning inside out as the intraventricular pressure rises. To assist in this process, the chordae tendineae of one papillary muscle are connected to the adjacent parts of two cusps.• The pulmonary valve guards the pulmonary orifice and consists of three semilunar cusps formed by folds of endocardium with some connective tissue enclosed. The open mouths of the cusps are directed upward into the pulmonary trunk.
Left atrium& left ventricle• Left Atrium• Similar to the right atrium, the left atrium consists of a main cavity and a left auricle. The left atrium is situated behind the right atrium and forms the greater part of the base or the posterior surface of the heart .Behind it lies the oblique sinus of the serous pericardium, and the fibrous pericardium separates it from the esophagus.• The interior of the left atrium is smooth, but the left auricle possesses muscular ridges as in the right auricle.• Openings into the Left Atrium• The four pulmonary veins, two from each lung, open through the posterior wall and have no valves. The left atrioventricular orifice is guarded by the mitral valve.• Left Ventricle• The left ventricle communicates with the left atrium through the atrioventricular orifice and with the aorta through the aortic orifice. The walls of the left ventricle are three times thicker than those of the right ventricle. (The left intraventricular blood pressure is six times higher than that inside the right ventricle.) . In cross section, the left ventricle is circular; the right is crescentic because of the bulging of the ventricular septum into the cavity of the right ventricle . There are well-developed trabeculae carneae, two large papillary muscles, but no moderator band. The part of the ventricle below the aortic orifice is called aortic vestibule• The mitral valve guards the atrioventricular orifice . It consists of two cusps, one anterior and one posterior, which have a structure similar to that of the cusps of the tricuspid valve. The attachment of the chordae tendineae to the cusps and the papillary muscles is similar to that of the tricuspid valve.• The aortic valve guards the aortic orifice and is precisely similar in structure to the pulmonary valve . One cusp is situated on the anterior wall (right cusp) and two are located on the posterior wall (left and posterior cusps). Behind each cusp the aortic wall bulges to form an aortic sinus. The anterior aortic sinus gives origin to the right coronary artery, and the left posterior sinus gives origin to the left coronary artery. .
The great blood vessels and the interior of the pericardium .
The posterior surface, or the base, of the heart .
Cardiac skeleton• The cardiac skeleton is a collection of dense, fibrous connective tissue in the form of four rings with interconnecting areas in a plane between the atria and the ventricles. The four rings of the cardiac skeleton surround the two atrioventricular orifices, the aortic orifice and opening of the pulmonary trunks. They are the anulus fibrosus .The interconnecting areas include :• the right fibrous trigone ,which is a thickened area of connective tissue between the aortic ring and right atrioventricular ring• the left fibrous trigone ,which is a thickened area of connective tissue between the aortic ring and the left atrioventricular ring.• The cardiac skeleton helps maintain the integrity of the openings it surrounds and provides points of attachment for the cusps. It also separates the atrial musculature from the ventricular musculature. The atrial myocardium originates from the upper border of the rings, whereas the ventricular myocardium originates from the lower border of the rings.• The cardiac skeleton also serves as a dense connective tissue partition that electrically isolates the atria from the ventricles. The atrioventricular bundle, which passes through the anulus, is the single connection between these two groups of myocardium
• Cardiac conduction system the musculature of the atria and ventricles is capable of contracting spontaneously. The cardiac conduction system initiates and coordinates contraction. The conduction system consists of nodes and networks of specialized myocardial cells organized into four basic components :• the sinu-atrial node ;• the atrioventricular node ;• the atrioventricular bundle with its right and left bundle branches ;• the subendocardial plexus of conduction cells (the Purkinje fibers.)• Sinu-atrial node• Impulses begin at the sinu-atrial node, the cardiac pacemaker. This collection of cells is located at the superior end of the crista terminalis at the junction of the superior vena cava and the right atrium .• The excitation signals generated by the sinu-atrial node spread across the atria, causing the muscle to contract.• Atrioventricular node:• Concurrently, the wave of excitation in the atria stimulates the atrioventricular node, which is located near the opening of the coronary sinus& within the atrioventricular septum. The atrioventricular node is a collection of specialized cells. The atrioventricular bundle is a direct continuation of the atrioventricular node. It follows along the lower border of the membranous part of the interventricular septum before splitting into right and left bundles.• The right bundle branch continues on the right side of the interventricular septum toward the apex of the right ventricle. From the septum it enters the septomarginal trabecula to reach the base of the anterior papillary muscle. At this point, it divides and is continuous with the final component of the cardiac conduction system, the subendocardial plexus of ventricular conduction cells or Purkinje fibers. This network of specialized cells spreads throughout the ventricle to supply ventricular musculature including the papillary muscles.• The left bundle branch passes to the left side of the muscular interventricular septum and descends to the apex of the left ventricle . Along its course it gives off branches that eventually become continuous with the subendocardial plexus of conduction cells (Purkinje fibers). As with the right side, this network of specialized cells spreads the excitation impulses throughout the ventricle.
Conduction system of theheart. A. Right chambers. B. Left chambers.
Pass taken by theCardiac Impulse from the Sinu-atrial Node to thePurkinje NetworkIndicated by black arrows LA RA LV RV
The conducting system of the heart. Note the internodal pathways
Blood supply of the heart By Dr. Noura El Tahawy
The right coronary artery• Arterial Supply of the Heart• The arterial supply of the heart is provided by the right and left coronary arteries, which arise from the ascending aorta immediately above the aortic valve .The coronary arteries and their major branches are distributed over the surface of the heart• The right coronary artery arises from the anterior aortic sinus of the ascending aorta and runs forward between the pulmonary trunk and the right auricle . It descends almost vertically in the right atrioventricular groove, and at the inferior border of the heart it continues posteriorly along the atrioventricular groove to anastomose with the left coronary artery in the posterior interventricular groove. The following branches from the right coronary artery supply the right atrium and right ventricle and parts of the left atrium and left ventricle and the atrioventricular septum.• Branches• The right conus artery supplies the anterior surface of the pulmonary conus (infundibulum of the right ventricle) and the upper part of the anterior wall of the right ventricle.• The anterior ventricular branches are two or three in number and supply the anterior surface of the right ventricle. The marginal branch is the largest and runs along the lower margin of the costal surface to reach the apex.• The posterior ventricular branches are usually two in number and supply the diaphragmatic surface of the right ventricle.• The posterior interventricular (descending) artery runs toward the apex in the posterior interventricular groove. It gives off branches to the right and left ventricles, including its inferior wall. It supplies branches to the posterior part of the ventricular septum but not to the apical part, which receives its supply from the anterior interventricular branch of the left coronary artery. A large septal branch supplies the atrioventricular node .In 10% of individuals the posterior interventricular artery is replaced by a branch from the left coronary artery.• The atrial branches supply the anterior and lateral surfaces of the right atrium. One branch supplies the posterior surface of both the right and left atria. The artery of the sinuatrial node supplies the node and the right and left atria; in 35% of individuals it arises from the left coronary artery.
The left coronary artery• The left coronary artery ,which is usually larger than the right coronary artery, supplies the major part of the heart, including the greater part of the left atrium, left ventricle, and ventricular septum. It arises from the left posterior aortic sinus of the ascending aorta and passes forward between the pulmonary trunk and the left auricle . It then enters the atrioventricular groove and divides into an anterior interventricular branch and a circumflex branch.• Branches• The anterior interventricular (descending) branch runs downward in the anterior interventricular groove to the apex of the heart .In most individuals it then passes around the apex of the heart to enter the posterior interventricular groove and anastomoses with the terminal branches of the right coronary artery. In one third of individuals it ends at the apex of the heart. The anterior interventricular branch supplies the right and left ventricles with numerous branches that also supply the anterior part of the ventricular septum. One of these ventricular branches) left diagonal artery(may arise directly from the trunk of the left coronary artery. A small left conus artery supplies the pulmonary conus.• The circumflex artery is the same size as the anteriorinterventricular artery .It winds around the left margin of the heart in the atrioventricular groove. A left marginal artery is a large branch that supplies the left margin of the left ventricle down to the apex .Anterior ventricular and posterior ventricular branches supply the left ventricle .Atrial branches supply the left atrium.
Cardiac vasculature. A. Anterior view. B. Superior view (atria removed).
Cardiac vasculature. A. Anterior view. B. Superior view (atria removed).
A. Anterior view of coronary arterial system. B. Left anterior oblique view of right coronary artery. C. Right anterior oblique view of left coronary artery.
Major cardiac veins. A. Anterior view of major cardiac veins. B. Posteroinferior view of major cardiac veins.
Summary of blood supply of the heart• Summary of the Overall Arterial Supply to the Heart in Most Individuals• The right coronary artery supplies all of the right ventricle (except for the small area to the right of the anterior interventricular groove), the variable part of the diaphragmatic surface of the left ventricle, the posteroinferior third of the ventricular septum, the right atrium and part of the left atrium, and the sinuatrial node and the atrioventricular node and bundle. The LBB also receives small branches.• The left coronary artery supplies most of the left ventricle, a small area of the right ventricle to the right of the interventricular groove, the anterior two thirds of the ventricular septum, most of the left atrium, the RBB, and the LBB.• Arterial Supply to the Conducting System• The sinuatrial node is usually supplied by the right but sometimes by the left coronary artery. The atrioventricular node and the atrioventricular bundle are supplied by the right coronary artery. The RBB of the atrioventricular bundle is supplied by the left coronary artery; the LBB is supplied by the right and left coronary arteries.• Venous Drainage of the Heart• Most blood from the heart wall drains into the right atrium through the coronary sinus, which lies in the posterior part of the atrioventricular groove and is a continuation of the great cardiac vein. It opens into the right atrium to the left of the inferior vena cava. The small and middle cardiac veins are tributaries of the coronary sinus. The remainder of the blood is returned to the right atrium by the anterior cardiac vein and by small veins that open directly into the heart chambers.
The anterior surface of the heart and the great blood vessels. Note the course of the coronary arteries and the cardiac veins .
A. Posterior view of the heart showing the origin and distribution of the posterior interventricular artery in the rightdominance .B .Posterior view of the heart showing the origin and distribution of the posterior interventricular arteryin the left dominance .C .Anterior view of the heart showing the relationship of the blood supply to the conductingsystem .
Nerve Supply of the Heart• The heart is innervated by sympathetic and parasympathetic fibers of the autonomic nervous system via the cardiac plexuses situated below the arch of the aorta. The sympathetic supply arises from the cervical and upper thoracic portions of the sympathetic trunks, and the parasympathetic supply comes from the vagus nerves.• The postganglionic sympathetic fibers terminate on the sinuatrial and atrioventricular nodes, on cardiac muscle fibers, and on the coronary arteries. Activation of these nerves results in cardiac acceleration, increased force of contraction of the cardiac muscle, and dilatation of the coronary arteries.• The postganglionic parasympathetic fibers terminate on the sinuatrial and atrioventricular nodes and on the coronary arteries. Activation of the parasympathetic nerves results in a reduction in the rate and force of contraction of the heart and a constriction of the coronary arteries.• Afferent fibers running with the sympathetic nerves carry nervous impulses that normally do not reach consciousness. However, should the blood supply to the myocardium become impaired, pain impulses reach consciousness via this pathway. Afferent fibers running with the vagus nerves take part in cardiovascular reflexes.
Surface anatomy of the heart• For practical purposes, the heart may be considered to have both an apex and four borders.• The apex ,formed by the left ventricle, corresponds to the apex beat and is found in the fifth left intercostal space 3.5 inch (9 cm) from the midline• .• The superior border ,formed by the roots of the great blood vessels, extends from a point on the second left costal cartilage (remember sternal angle) 0.5 inch. (1.3 cm) from the edge of the sternum to a point on the third right costal cartilage 0.5 inch. (1.3 cm) from the edge of the sternum• The right border ,formed by the right atrium, extends from a point on the third right costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum downward to a point on the sixth right costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum• The left border ,formed by the left ventricle, extends from a point on the second left costal cartilage 0.5 in. (1.3 cm) from the edge of the sternum to the apex beat of the heart• The inferior border ,formed by the right ventricle and the apical part of the left ventricle, extends from the sixth right costal cartilage 0.5 in. (1.3 cm) from the sternum to the apex beat
Surface Anatomy of the Heart Valves• . The surface markings of the heart valves are as follows:• The tricuspid valve lies behind the right half of the sternum opposite the fourth intercostal space.• The mitral valve lies behind the left half of the sternum opposite the fourth costal cartilage.• The pulmonary valve lies behind the medial end of the third left costal cartilage and the adjoining part of the sternum.• The aortic valve lies behind the left half of the sternum opposite the third intercostal space.• Where to listen for heart sounds??• To listen for valve sounds, position the stethoscope downstream from the flow of blood through the valves• The tricuspid valve is heard just to the left of the lower part of the sternum near the fifth intercostal space.• The mitral valve is heard over the apex of the heart in the left fifth intercostal space at the midclavicular line.• The pulmonary valve is heard over the medial end of the left second intercostal space.• The aortic valve is heard over the medial end of the right second intercostal space.
Cross Section of the Thorax at eighth Thoracic Vertebra
Questions1. Give a short account on the anatomy of the followings: - - Right atrium (relations, exterior, interior & blood supply) -- Left ventricle (relations, exterior, interior& blood supply) - -- Conducting system of the heart ---- Fibrous skeleton of the heart --- Blood supply of the heart2. What is the surface anatomy of the heart &its valves3. Complete the following statements: --- The distribution of the right coronary artery include: 1. …………. 2. ………………… … 3…………….. 4………… --- The distribution of the left coronary artery include: 1……………… 2……………. 3……………… 4……… ----- Sinoatrial node is ………………… & is usually supplied by a branch from ………… artery ---- the coronary sinus opens into………………... Its tributaries are : 1…………………... 2 …………… 3… …. …… 4………………5……………..