heart

Learning Outcomes of Chapter 20 The Heart

  • Describe the anatomy of the heart.

  • Describe the vascular supply of the heart muscle.

  • Describe the structure and function of the pericardium.

  • Compare and contrast the structure and location of the epicardium, myocardium, and endocardium layers of the heart wall.

  • Trace the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves.

  • Describe the conducting system of the heart, identify the location of its components, and trace the pathway of impulse initiation and conduction.

Introduction to the Heart

  • Components of the cardiovascular system:

    • Heart

    • Blood

    • Blood vessels

  • Key Facts about the Heart:

    • Beats approximately 100,000 times each day.

    • Pumps about 8,000 liters of blood per day.

Anatomy of the Heart

  • Circuits of blood flow:

    • Pulmonary circuit: Carries blood to and from gas exchange surfaces of lungs.

    • Systemic circuit: Carries blood to and from the rest of the body.

    • Each circuit begins and ends at the heart; Blood travels through these circuits in sequence.

Structure of Blood Vessels

  • Types of blood vessels:

    • Arteries: Carry blood away from the heart.

    • Veins: Return blood to the heart.

    • Capillaries (exchange vessels): Interconnect smallest arteries and smallest veins; Exchange dissolved gases, nutrients, and wastes between blood and surrounding tissues.

Four Chambers of the Heart

  • Right atrium: Receives blood from the systemic circuit.

  • Right ventricle: Pumps blood into the pulmonary circuit.

  • Left atrium: Receives blood from the pulmonary circuit.

  • Left ventricle: Pumps blood into the systemic circuit.

Orientation of the Heart in the Thoracic Cavity

  • The heart sits between two pleural cavities in the mediastinum; it has:

    • Base: Superior part where great vessels connect.

    • Apex: Inferior pointed tip.

Pericardium

  • Function: Surrounds the heart.

  • Layers:

    • Outer fibrous pericardium

    • Inner serous pericardium:

    • Outer parietal layer

    • Inner visceral layer (epicardium)

  • Pericardial cavity: Found between the parietal and visceral layers, contains pericardial fluid.

  • Pericarditis:

    • Caused by infections or pathogens in the pericardium.

    • Symptoms include a distinctive scratching sound and may cause cardiac tamponade (restricted heart movement due to excess fluid).

Superficial Anatomy of the Heart

  • Atria: Two thin-walled atria, each with an expandable outer auricle.

  • Sulci:

    • Coronary sulcus: Marks border between atria and ventricles.

    • Anterior and posterior interventricular sulcus: Mark boundaries between left and right ventricles.

Layers of the Heart Wall

  • Three distinct layers:

    • Epicardium (visceral layer of serous pericardium): Covers surface of heart.

    • Myocardium: Composed of cardiac muscle tissue.

    • Endocardium: Covers inner surfaces of heart; consists of simple squamous epithelium and areolar tissue.

Internal Anatomy of the Heart

  • Septa: Muscular partitions that separate the chambers:

    • Interatrial septum: Separates the atria.

    • Interventricular septum: Thicker than the interatrial septum, separates the ventricles.

Heart Valves

  • Atrioventricular (AV) valves:

    • Tricuspid valve: Between right atrium and right ventricle; prevents backflow into atrium.

    • Mitral valve (bicuspid valve): Between left atrium and left ventricle; prevents backflow into atrium.

  • Semilunar valves:

    • Pulmonary valve: Prevents backflow into right ventricle.

    • Aortic valve: Prevents backflow into left ventricle.

Blood Flow Through the Heart

  • Right atrium receives blood from:

    • Superior vena cava: Blood from head, neck, upper limbs, and chest.

    • Inferior vena cava: Blood from trunk, viscera, and lower limbs.

Foramen Ovale

  • An opening in the interatrial septum during fetal development connects the two atria.

  • Closes at birth and forms fossa ovalis.

Right Ventricle Anatomy

  • Trabeculae carneae: Muscular ridges on the internal surface of both ventricles.

  • Moderator band: Delivers stimulus for contraction to papillary muscles (prevents backward opening of valves).