Cardiovascular System- The Heart Anatomy Chap. 21

The Cardiovascular system is comprised of the heart, blood vessels, & blood The heart acts as a “pump”, creating pressure which causes blood to move through the blood vessels of the body, allowing O2 & nutrients to be distributed to, & wastes removed from, body tissues

Heart Anatomy Overview Play Heart Anatomy video

Anatomical Features of the Heart The heart lies within the mediastinum of the thoracic cavity Hollow muscular organ with four internal chambers (2) atria (lt. atrium & rt. atrium)- receive blood from veins (2) ventricles (lt. ventricle & rt. ventricle)- pump blood into arteries Superior aspect of heart is the “base” (3rd intercostal space/sternal angle), where the blood vessels attach; Inferior is the “apex” (5th intercostal space), which rests on the relaxed diaphragm

Pericardium The heart lies enclosed within pericardial membranes Fibrous pericardium (pericardial sac) – outer layer of dense CT that protects & anchors Serous pericardium – double layered membrane with “pericardial fluid” between Parietal pericardium – lines the pericardial sac Visceral pericardium – covers the heart; also known as the “epicardium”

Layers of Heart Wall Epicardium (a.k.a. visceral pericardium) Myocardium Endocardium

Cardiac muscle tissue

Because of the characteristics of cardiac muscle tissue & the arrangement of connective tissue (fibrous skeleton) within the heart, the heart basically has two functional units: the myocardium of the atria (upper chambers) act as one functional unit the myocardium of the ventricles (lower chambers) act as the other

This allows the atria to contract simultaneously while the ventricles are relaxed; then the ventricles contract simultaneously while the atria relax

External Features Auricles Coronary sulcus – contains the coronary sinus Anterior interventricular sulcus – contains coronary vessels Posterior interventricular sulcus – contains coronary vessels

Lt Atrium Rt Atrium SVC IVC Deoxygenated blood Interatrial septum Coronary sinus (opening) Deoxygenated blood Interatrial septum Fossa ovalis Pulmonary veins Oxygenated blood Rt Atrium Lt Atrium Pectinate muscles Tricuspid valve Bicuspid (mitral) valve Chordae tendineae Papillary muscle

Atrioventricular (AV) valves Tricuspid Bicuspid

Lt ventricle Rt ventricle Aorta (ascending) Pulmonary artery Aortic semilunar valve Pulmonary semilunar valve Pulmonary trunk Pulmonary artery Trabeculae carneae Rt ventricle Lt ventricle Interventricular septum

Semilunar valves

Lt ventricle Rt ventricle Ligamentum arteriosum Aortic Arch Brachiocephalic trunk Left common carotid artery Left subclavian artery Ligamentum arteriosum Aortic Arch Aortic semilunar valve Pulmonary semilunar valve Pulmonary trunk Pulmonary artery Trabeculae carneae Rt ventricle Lt ventricle Interventricular septum

Anatomy

Coronary Circulation Myocardium receives oxygenated blood from the left & right Coronary arteries – branches off the ascending aorta left coronary artery  anterior interventricular branch & circumflex branch right coronary artery  marginal branch & posterior interventricular branch Deoxygenated blood is drained through Cardiac veins (Great, posterior, middle & small cardiac veins), which all eventually merge and drain into the coronary sinus

Conducting System Intrinsic regulating system that generates “heartbeat” comprised of functionally specialized “autorhythmic (conducting) cells” – which can spontaneously generate action potentials SA node (“pacemaker”)  AV node  AV bundle (of His)  Bundle branches  Purkinje fibers

Movement of blood through heart & heart sounds The activity of the conduction system results in the contraction (systole) & relaxation (diastole) of the heart chambers atria will contract as ventricles remain relaxed (atrial systole/ventricular diastole). Blood moves from atria to ventricles as atria relax, ventricles begin to contract (atrial diastole/ventricular systole). The AV valves (tricuspid & bicuspid/mitral) snap shut to prevent backflow of blood into atria. The closing of the valves makes a sound – “Lub” as blood moves from ventricles to arteries (pulmonary trunk & aorta), pressure will increase in the arteries and decrease in the ventricles. Semilunar valves will then shut  “Dupp” as ventricles relax all 4 chambers will be in diastole, and then cycle begins again