Chapter 18 THE HEART

Approximately the size of the fist Extends: Heart Anatomy Approximately the size of the fist Extends: From 2nd rib to 5th intercostal space Location: Rests on superior surface of diaphragm Anterior to the vertebral column Posterior to the sternum 2/3 lies left to the midsternal line Flanked by left & right lungs

Heart Anatomy & Location Figure 18.1

Coverings of the Heart: Anatomy Pericardium: A double-walled sac around the heart Composed of: A superficial fibrous pericardium A deep two-layer serous pericardium with: A parietal layer lining the internal surface of the fibrous pericardium A visceral layer (epicardium) lining the surface of the heart A fluid-filled pericardial cavity between the two layers

Coverings of the Heart: Physiology The pericardium: Protects the heart Anchors the heart to its surrounding structures Prevents overfilling of the heart with blood Allows for a relatively friction-free working environment for the heart

Pericardial Layers of the Heart Figure 18.2

Fibrous skeleton of the heart: Heart Wall Layers Epicardium: Visceral layer of the serous pericardium Myocardium: Cardiac muscle layer forming the bulk of the heart Arranged in circular or spiral bundles Fibrous skeleton of the heart: Crisscrossing, interlacing layer of connective tissue A network of collagen & elastic fibers (reinforcement) Endocardium: Thin endothelial layer of the inner myocardial surface

Cardiac Muscle Bundles Figure 18.3

Major Vessels of the Heart (Anterior View) Vessels returning blood to the heart include: Superior vena cava: Returns venous blood from upper region (above diaphrag.) Inferior vena cava: Returns venous blood from lower region (below diaphrag.) Coronary sinus: Returns venous blood from the myocardium Right pulmonary veins: Returns venous blood from the right lung Left pulmonary veins: Returns venous blood from the left lung

interventricular artery (in anterior interventricular sulcus) Inferior Left common carotid artery Brachiocephalic trunk Left subclavian artery Superior vena cava Aortic arch Right pulmonary artery Ligamentum arteriosum Ascending aorta Left pulmonary artery Left pulmonary veins Pulmonary trunk Left atrium Right pulmonary veins Auricle Right atrium Circumflex artery Right coronary artery (in coronary sulcus) Left coronary artery (in coronary sulcus) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Marginal artery Small cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Inferior vena cava (b) Apex Figure 18.4b

Major Vessels of the Heart (Anterior View) Vessels conveying blood away from the heart: Pulmonary trunk: splits into two branches: Right pulmonary artery Left pulmonary artery Ascending aorta: gives three branches: Brachiocephalic artery Left common carotid artery Subclavian artery

interventricular artery (in anterior interventricular sulcus) Inferior Left common carotid artery Brachiocephalic trunk Left subclavian artery Superior vena cava Aortic arch Right pulmonary artery Ligamentum arteriosum Ascending aorta Left pulmonary artery Left pulmonary veins Pulmonary trunk Left atrium Right pulmonary veins Auricle Right atrium Circumflex artery Right coronary artery (in coronary sulcus) Left coronary artery (in coronary sulcus) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Marginal artery Small cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Inferior vena cava (b) Apex Figure 18.4b

Vessels that Supply/Drain the Heart (Anterior View) Arteries: (located in the atrioventricular groove): Left coronary artery: its major branches: Anterior interventricular artery Circumflex artery Right coronary artery: its major branches: Posterior interventricular artery Marginal, artery

interventricular artery (in anterior interventricular sulcus) Inferior Left common carotid artery Brachiocephalic trunk Left subclavian artery Superior vena cava Aortic arch Right pulmonary artery Ligamentum arteriosum Ascending aorta Left pulmonary artery Left pulmonary veins Pulmonary trunk Left atrium Right pulmonary veins Auricle Right atrium Circumflex artery Right coronary artery (in coronary sulcus) Left coronary artery (in coronary sulcus) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Marginal artery Small cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Inferior vena cava (b) Apex Figure 18.4b

Vessels that Supply/Drain the Heart (Anterior View) Veins: (all empty in the coronary sinus): Great cardiac Middle cardiac Small cardiac Anterior cardiac veins Posterior vein of the left ventricle

interventricular artery (in posterior interventricular sulcus) (d) Superior vena cava Right pulmonary artery pulmonary veins Right atrium Right coronary artery (in coronary sulcus) Right ventricle Coronary sinus Middle cardiac vein Left Left atrium Auricle of left atrium Left ventricle Posterior vein of left ventricle Posterior interventricular artery (in posterior interventricular sulcus) Great cardiac vein Apex Inferior Aorta Figure 18.4d

Aorta Superior vena cava Left Right pulmonary artery pulmonary artery Left atrium Pulmonary trunk Left pulmonary veins Right atrium Right pulmonary veins Mitral (bicuspid) valve Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Left ventricle Papillary muscle Right ventricle Chordae tendineae Interventricular septum Myocardium Trabeculae carneae Visceral pericardium Inferior vena cava Endocardium (e) Figure 18.4e

Atria are the receiving chambers of the heart Atria of the Heart Atria are the receiving chambers of the heart Each atrium has a protruding auricle (volume increase ) Pectinate muscles mark right atrial anterior walls Right atria receive blood from: Superior vena cava Inferior vena cava Coronary sinus Left atria receive blood from: pulmonary veins (four)

Ventricles of the Heart Ventricles are the discharging chambers of the heart Papillary muscles and trabeculae carneae muscles mark ventricular walls Right ventricle pumps blood into the pulmonary trunk Left ventricle pumps blood into the aorta

Right and Left Ventricles Figure 18.6

Pathway of Blood Through the Heart & Lungs Right atrium  tricuspid valve  right ventricle Right ventricle  pulmonary semilunar valve  pulmonary arteries  lungs Lungs  pulmonary veins  left atrium Left atrium  bicuspid valve  left ventricle Left ventricle  aortic semilunar valve  aorta Aorta  systemic circulation Aorta  coronary artery  coronary circulation

Figure 18.5

Coronary circulation: The functional blood supply to the heart muscle itself Collateral routes: Ensure blood delivery to heart Even if major vessels are occluded Ex. Bypass surgery

Coronary Circulation: Arterial Supply Figure 18.7a

Coronary Circulation: Venous Supply Figure 18.7b

Atrioventricular (AV) valves: Heart Valves Heart valves: Ensure unidirectional blood flow through the heart Atrioventricular (AV) valves: Lie between atria and ventricles Prevent backflow into atria when ventricles contract Tricuspid (between right atrium & right ventricle) Bicuspid /Mitral (between leftt atrium & left ventricle) Chordae tendineae: Collagenous fibers Anchor AV valves to papillary muscles

Aortic semilunar valve: Heart Valves Semilunar valves: lie between ventricles and major vessels prevent backflow of blood into the ventricles Aortic semilunar valve: lies between the left ventricle and the aorta Pulmonary semilunar valve: lies between the right ventricle and pulmonary trunk No valves in superior & inferior venae cavae

Heart Valves Figure 18.8a, b

Heart Valves Figure 18.8c, d

Atrioventricular Valve Function Figure 18.9

Semilunar Valve Function Figure 18.10

Microscopic Anatomy of Heart Muscle Cardiac muscle is: Striated, uninucleate Short & fat Branched & interconnected The connective tissue endomysium acts as both tendon and insertion Intercalated discs: Anchor cardiac cells together Allow free passage of ions Heart muscle behaves as a functional syncytium (unit) PLAY

Microscopic Anatomy of Cardiac Muscle Figure 18.11