CHAPTER 1 The Anatomy of the Heart { Structure }

Understanding 12 Lead EKGsA Practical ApproachBrenda M. Beasley, RN, BS, EMT-Paramedic Michael C. West, RN, MS, EMT- Paramedic CHAPTER 1 The Anatomy of the Heart { Structure }

Anatomy of the Heart • Objectives: • Describe the chambers of the heart • Atria • Ventricles • Identify the location, shape, and size of the heart • Name the layers of the heart • Name the valves of the heart BRADY : Understanding 12 leads Ch. 1

Anatomy of the Heart • Objectives [ continued ] • Describe the structure and function of the blood vessels • Arteries • Veins • Capillaries BRADY : Understanding 12 leads Ch. 1

Anatomy of the Heart • The Heart is Muscle • Myocardium - heart muscle • “Two-sided pump” • Atrium [ atria ] Upper chambers • separated by interatrial septum • Ventricles - Lower Chambers • separated by interventricular septum BRADY : Understanding 12 leads Ch. 1

Location, size, and shape of the Heart BRADY : Understanding 12 leads Ch. 1

Location, Size, and Shape of the Heart • Located in Mediastinum • Lying in front of spinal column, behind sternum, and between lungs • 2/3 lies to left of midline • Apex lies just above diaphragm • Base lies at level of the third rib • Size of owner’s closed fist BRADY : Understanding 12 leads Ch. 1

Layers of the Heart • Pericardium - closed, two layered sac • Parietal Pericardium - tough, nonelastic, fibrous connective tissue • Visceral Pericardium - thin, serous inner layer of pericardium BRADY : Understanding 12 leads Ch. 1

The Heart Wall • Epicardium- smooth outer surface • Myocardium- thick, middle layer of the heart, composed of cardiac muscle cells , responsible for ability to contract • Endocardium -innermost layer, composed of connective tissue BRADY : Understanding 12 leads Ch. 1

Valves of the Heart • Four valves allow blood to flow in one direction • Two Sets • Atrioventricular Valves • Semilunar Valves BRADY : Understanding 12 leads Ch. 1

Atrioventricular Valves • Located between atria and the ventricles • Allow flow from atria into ventricles • Prevent flow backward from ventricles • Tricuspid Valve - three cusps - located between right atrium / right ventricle • Mitral / bicuspid Valve- has two cusps - located between left atrium / left ventricle BRADY : Understanding 12 leads Ch. 1

Semilunar Valves • Prevent backflow of blood into the Ventricles. Each valve contains threesemilunar, or moon-shaped, cusps. • Pulmonic Valve- located between right ventricle and pulmonary artery • Aortic Valve - located between left ventricle and trunk of aorta BRADY : Understanding 12 leads Ch. 1

Heart Valves Function • Chamber pressure governs opening and closing of heart valves • Ventricular Systole [ contraction ofventricles ] atrioventricular valves close and semilunar valves open • Ventricular Diastole [ relaxation ofventricles ] atrioventricular valves are open and semilunar valves are closed BRADY : Understanding 12 leads Ch. 1

Blood Vessels • Blood Vessels are the “container” for fluid or blood • Arteries • Veins • Capillaries BRADY : Understanding 12 leads Ch. 1

ARTERIES • Thick wall and muscular • Function under high pressure • Carry blood AWAY FROM heart • Regulate blood pressure by changes in peripheral vascular resistance • Arteries - larger vessels • Arterioles - smaller vessels BRADY : Understanding 12 leads Ch. 1

Arterial Wall Layers BRADY : Understanding 12 leads Ch. 1

VEINS • Vessels that carry blood back to the heart • Venules - smaller vessels • Operate under low pressure BRADY : Understanding 12 leads Ch. 1

CAPILLARIES • Tiny blood vessels whose walls are thinnest of all • Vast majority of gas exchange occurs • Circulation - movement through a course [ body ] that leads back to initial point [ heart ] BRADY : Understanding 12 leads Ch. 1

12 Lead EKG Chapter 1 • ANY QUESTIONS? BRADY : Understanding 12 leads Ch. 1

CHAPTER 1 The Anatomy of the Heart { Structure }