Anatomy of the Heart PDF

Anatomy of the Heart Dr. Sara Yousif Alshreef Objectives At the end of the lecture, the student should be able to :  Describe the shape of heart regarding : apex, base, sternocostal and diaphragmatic surfaces.  Describe the interior of heart chambers : right atrium, right ventricle, left atrium...

Anatomy of the Heart Dr. Sara Yousif Alshreef Objectives At the end of the lecture, the student should be able to :  Describe the shape of heart regarding : apex, base, sternocostal and diaphragmatic surfaces.  Describe the interior of heart chambers : right atrium, right ventricle, left atrium and left ventricle.  List the orifices of the heart : Right atrioventricular (Tricuspid) orifice. Pulmonary orifice. Left atrioventricular (Mitral) orifice. Aortic orifice.  Describe the innervation of the heart.  Briefly describe the conduction system of the Heart.  The Heart o It lies in the middle mediastinum. o It consists of 4 chambers: 2 atria (right& left) that receive blood & 2 ventricles (right& left) that pump blood. o The Heart is somewhat pyramidal in shape, having: 1. Apex Extra 2. Sterno-costal (anterior surface) 3. Diaphragmatic (inferior surface) 4. Base (posterior surface). o It is surrounded by a fibroserous sac called pericardium which is differentiated into: an outer fibrous layer inner serous sac (Fibrous pericardium) (Serous pericardium). further divided into Parietal Visceral (Epicardium) Pericardial Sinuses Transverse Sinus: Oblique Sinus: It is a recess (small space) of serous pericardium It lies posterior to the heart. It is a recess (small space) between ascending aorta & pulmonary trunk of serous pericardium behind the base of heart (left anteriorly , and upper parts of 2 atria & S.V.C atrium), separates base from descending aorta & (superior vena cava) posteriorly. esophagus. The pericardial sinuses are clinically important as in cases of pericardial effusion. Also in surgery as blood may accumulate there and they provide the surgeon with access to structures related to them (such as the aorta/pulmonary trunk). Extra Oblique Sinus Transverse Sinus The Heart Extra Extra  The Heart 1- Apex o Directed downwards, forwards and to the left. o It is formed by the left ventricle. o Lies at the level of left 5th intercostal space (the same level of the nipple) 3.5 inch from midline. Note that the base of the heart is called the base because the heart is pyramid shaped; the base lies opposite to the apex. The heart does not rest on its base; it rests on its diaphragmatic (inferior) surface. Extra The Heart 2- Sterno-Costal (Anterior) Surface o This surface is formed mainly by the right atrium and the right ventricle (we said mainly because there is also a little part by of the left ventricle). o Divided by coronary (atrio-ventricular) groove (which lodges the right coronary artery) into : 1. Atrial part: formed mainly by right atrium. 2. Ventricular part : the right 2/3 is formed by right ventricle, while the left 1/3 is formed by left ventricle. So, it is also formed of some of the left ventricle. o The 2 ventricles are separated by anterior interventricular groove, which lodges: Anterior interventricular artery (branch of left coronary) Great cardiac vein. The Heart 2- Sterno-Costal (Anterior) Surface It is formed mainly by the right atrium & the right ventricle, which are separated from each other by the vertical atrioventricular groove. superior and inferior borders of the heart. The right ventricle is separated from the left ventricle by an anterior interventricular groove. Between the atrium and ventricle  atrioventricular groove (coronary sulcus) Between the 2 ventricles  interventricular groove (anterior / posterior) Extra The Heart 3- Diaphragmatic (Inferior) Surface o Formed by the 2-ventricles, mainly left ventricle (left 2/3). o Slightly concave as it rests on diaphragm. o Directed inferiorly & backward. o Separated from base of heart by posterior part of coronary sulcus. o The 2-ventricles are separated by posterior interventricular groove which lodges: Posterior interventricular artery Middle cardiac vein. The Heart 4- Base of the Heart (posterior surface) o It is formed by the 2 atria, mainly left atrium, into which open the 4 pulmonary veins (2 right and 2 left). o It is directed backwards. o Lies opposite middle thoracic vertebrae (5-7) (T5, T6, T7). o Is separated from the vertebral column by: descending aorta, esophagus and oblique sinus of pericardium Bounded inferiorly by posterior part of coronary sulcus , which lodges the coronary sinus Extra  Upper border: Borders of the Heart Is formed by the 2 atria. It is concealed by ascending aorta & pulmonary trunk. Right border: Left border: Is formed by right atrium. Is formed mainly by left ventricle + auricle of left atrium. Lower border: Is formed mainly by right ventricle + apical part of left ventricle. Chambers of the Heart o The heart is divided by vertical septa into four chambers: the right and left atria the right and left ventricles. o The right atrium lies anterior to the left atrium, and the right ventricle lies anterior to the left ventricle. Extra Extra Extra  Chambers of the Heart Right Atrium o The right atrium consists of a main cavity and a small out pouching, the auricle (upward protrusion resembling ear). o 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. Extra Cavity of Right Atrium o Crista terminalis divides right atrium into: 1. Anterior part: rough (because of muscles) and trabeculated by bundles of muscle fibres (musculi pectinati or pectinate muscle). 2. Posterior part (sinus venarum) is smooth. o The interatrial septum carries an oval depression called Fossa ovalis. c o The margin of this depression is called Anulus ovalis o The blood leaves right atrium to right ventricle via tricuspid valve. Chambers of the Heart Right Atrium (openings) very important 1- SVC (superior vena cava)  has no valve 2- IVC (inferior vena cave)  guarded by a valve 3- Coronary sinus  has a well-defined 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 Extra Chambers of the Heart Cavity of right ventricle o Its wall is thinner than that of the left ventricle. o Its wall contains projections called trabeculae carnae (irregular bands and bundles of muscle projecting from the inner surface). o The right ventricle communicates with right atrium through right atrioventricular orifice & with pulmonary trunk through pulmonary orifice. o As the cavity approaches the pulmonary orifice it becomes funnel shaped, at which point it is referred to as the infundibulum.(also known as conus arteriosus) o Large projections arise from the walls called papillary muscles : Anterior papillary muscle Posterior papillary muscle Septal papillary muscle. Trabeculae carnae Chambers of the Heart Cavity of right ventricle o Each papillary muscle is attached to the cusps of tricuspid valve by tendinous threads called chordae tendinae*. o Blood leaves the right ventricle to pulmonary trunk through pulmonary orifice. o The wall of infundibulum (conus arteriosus) is smooth and contains no trabeculae. o Interventricular septum is connected to anterior papillary muscle by a muscular band called moderator band (the moderator band connects the anterior wall and the interventricular septum).  Extra explanation of the coming slides (orifices): Orifice means opening and there are 4 main orifices in the heart: Between the atrium and Between the ventricle and ventricle (atrio-ventricular) the major arteries Right Left Right ventricle Left and pulmonary ventricle Extra Tricuspid Bicuspid trunk (arteries) and aorta valve or Mitral valve Pulmonary Aortic valve valve Called tri/bicuspid based on the number of cusps or leaflets Also called semilunar valves In order to make sure the blood travels in one direction the orifices are surrounded by a fibrous ring which helps to maintain the shape of the opening. Attached to this ring are cusps. Two or three cusps make a valve. The valves guard the orifice. Extra Right Atrio-Ventricular (Tricuspid) Orifice o About one inch wide, admitting tips of 3 fingers. (wider than left atrio-ventricular orifice) o It is guarded by a fibrous ring which gives attachment to the cusps of tricuspid valve. o It has 3-cusps (anterior – posterior - septal or medial). o The atrial surface (superior) of the cusps are smooth, while their ventricular surfaces (inferior) give attachment to the chordae tendinae. Extra Extra Pulmonary Orifice o Surrounded by a fibrous ring which gives attachment to the cusps of the pulmonary valve. o The valve is formed of 3 semilunar cusps : 2 anterior and one posterior which are concave superiorly and SUPERIORLY convex inferiorly (like this ). INFERIORLY o No chordae tendineae or papillary muscles are attached to these cusps Extra Chambers of the Heart Left Atrium o The left atrium communicates with the left ventricle through the left atrioventricular orifice. o It forms the greater part of the base of heart. o Its wall is smooth except for small musculi pectinati in the left auricle. o Recieves 4 pulmonary veins (2 left & 2 right) which have no valves. o Sends blood to left ventricle through the left atrioventricular orifice which is guarded by mitral valve (Bicuspid valve). L. Atrium Chambers of the Heart Left Ventricle o Its wall is thicker than that of right ventricle. o It receives blood from left atrium through left atrio-ventricular orifice which is guarded by mitral valve (bicuspid) o The blood leaves the left ventricle to the ascending aorta through the aortic orifice. o The part of left ventricle leading to ascending aorta is called aortic vestibule. o The wall of this part is fibrous and smooth. o The wall of the left ventricle contains trabeculae carnae. o It also contains 2 large papillary muscles (anterior & posterior). o They are attached by chordae tendinae to cusps of mitral valve. Left Atrio-Ventricular (Mitral) Orifice o Smaller than the right, admitting only tips of 2 fingers. o Guarded by a mitral valve. o Surrounded by a fibrous ring which gives attachment to the cusps of mitral valve. o Mitral valve is composed of 2 cusps: Anterior cusp : lies anteriorly and to right. Posterior cusp : lies posteriorly and to left. o The atrial surfaces of the cusps are smooth, while ventricular surfaces give attachment to chordae tendinae. Aortic Orifice o Surrounded by a fibrous ring which gives attachment to the cusps of aortic valve. o Aortic valve is formed of 3 semilunar cusps which are similar to those of pulmonary valve, but the position of the cusps differs being one anterior and 2 posterior. Extra Nerve supply of the heart o Autonomic Supply: by sympathetic & parasympathetic fibers via the cardiac plexus situated below arch of aorta. o The sympathetic fibres arise from the cervical & upper thoracic (1, 2, 3, 4) ganglia of sympathetic trunks. o The parasympathetic fibres arise from the vagus nerves. o Sympathetic Fibers  accelerate heart rate but o Parasympathetic Fibers  slow heart rate (constriction of coronay arteries) Postganglionic fibres reach heart along – (1) SAN(SINOATRIAL NODE ) (2) AVN( ATRIOVENTICULAR NODE ) & (3) nerve plexus around coronary arteries. Conduction system of the heart o The beating of the heart is regulated by the intrinsic conduction (nodal) system. o Its function is to ensure that the chambers of the heart contract in the proper rhythm and sequence The main center is the sinoatrial (SA) node, located in the right atrium atrioventricular (AV) bundle (bundle of His) is located in the The atrioventricular interventricular septum (AV) node is located at the junction of the atria and the ventricles Purkinje fibers are located inside the walls of the ventricles The SA node is called the pacemaker of the heart, because it generates the impulse. Note: Like we studied in physiology all of the following are capable of generating impulses but because the SA node is the fastest it is the pacemaker. Thank You