heart power point 2022-1

Cardiovascular System: Heart

Time Frame: 75 Minutes

Course Code: ALHL2021

Faculty: Health Sciences – Patricia Lopez

Objectives

• Structure of the Heart: Describe the wall, chambers, great vessels, and valves of the heart in detail.

• Pathway of Blood: Trace the journey of blood flow through the heart's chambers and vessels accurately.

• Circulations: Describe the functions and pathway of pulmonary and systemic circulations thoroughly.

• Conduction System: Identify all components of the heart's conduction system and trace the conduction pathway comprehensively.

• Cardiac Cycle: Describe the detailed events and phases involved in the cardiac cycle.

Heart Anatomy

• Size: The heart is approximately the size of a human fist, averaging around 12 cm in length.

• Location:

  • Positioned on the superior surface of the diaphragm.

  • Located slightly left of the midline.

  • Anterior to the vertebral column and posterior to the sternum.

Coverings of the Heart

• Pericardium:

  • Protects and anchors the heart within the thoracic cavity.

  • Prevents overfilling of the heart with blood, acting as a barrier against excessive pressure.

  • Provides a friction-free environment to facilitate smooth heart function.

Pericardial Layers

1. Fibrous Pericardium: The tough, outer layer that provides structural support and protection against physical trauma.

2. Serous Pericardium: Divided into:

   • Parietal Layer: Lines the fibrous pericardium.

   • Visceral Layer (Epicardium): Directly covers the heart's surface.

   • Pericardial Cavity: Contains serous fluid that reduces friction during heart contractions.

Heart Wall Layers

1. Epicardium: The visceral layer of the serous pericardium and the outermost layer of the heart.

2. Myocardium: Thick muscular layer responsible for the heart's contractile force. Composed of cardiac muscle cells, it forms the bulk of the heart wall.

3. Fibrous Skeleton: An intricate connective tissue network that provides structural integrity, facilitates electrical conduction, and supports the heart valves.

4. Endocardium: The innermost layer composed of endothelial cells that line the heart chambers and valves, providing a smooth surface for blood flow.

Major Vessels of the Heart

• Returning Blood:

  • Superior Vena Cava: Returns deoxygenated blood from the upper body to the right atrium.

  • Inferior Vena Cava: Returns deoxygenated blood from the lower body to the right atrium.

  • Right and Left Pulmonary Veins: Transports oxygenated blood from the lungs to the left atrium.

• Conveying Blood Away:

  • Pulmonary Trunk: Divides into right and left pulmonary arteries, carrying deoxygenated blood to the lungs for oxygenation.

  • Ascending Aorta: Distributes oxygenated blood to the body; branches include the brachiocephalic artery, left common carotid artery, and left subclavian artery.

Blood Supply to the Heart

• Arteries:

  • Right and Left Coronary Arteries: Supply blood to the heart muscle; originate from the aorta.

  • Marginal Artery: Provides collateral circulation along the heart's surface.

  • Circumflex Artery: Supplies the left atrium and the lateral and posterior walls of the left ventricle.

  • Anterior Interventricular Artery (LAD): Supplies blood to the anterior portion of the interventricular septum and parts of both ventricles.

• Veins:

  • Small Cardiac Vein: Drains the right atrium and ventricle.

  • Anterior Cardiac Vein: Drains blood from the anterior surface of the right ventricle into the right atrium.

  • Great Cardiac Vein: Drains the blood from the anterior heart wall and empties into the coronary sinus.

External Heart Anatomy (Anterior View)

• Key Structures:

  • Brachiocephalic Artery: Supplies the head, neck, and arms.

  • Right Pulmonary Artery: Transports deoxygenated blood to the right lung.

  • Ascending Aorta: The main artery carrying blood from the heart.

  • Right and Left Atria: The two upper chambers of the heart that receive blood.

  • Left and Right Ventricles: The two lower chambers responsible for pumping blood out of the heart.

• Key Functions: Visualize flow directions and connections to understand the overall circulatory patterns.

External Heart Anatomy (Posterior View)

• Key Structures:

  • Aorta: The largest artery in the body, carrying oxygenated blood to the systemic circulation.

  • Left and Right Pulmonary Veins: Return oxygenated blood from the lungs to the heart.

  • Coronary Sinus: Collects deoxygenated blood from the heart muscle and drains into the right atrium.

  • Right Coronary Artery: Supplies blood to the right atrium and right ventricle.

  • Posterior Interventricular Artery: Supplies the posterior portion of the interventricular septum.

Coronary Circulation

• Definition: The network of blood vessels supplying blood to the heart muscle, vital for its metabolic needs.

• Collateral Routes: Develops to ensure that the heart muscle still receives blood supply even if major vessels become occluded.

Heart Valves

• Function: Ensure unidirectional blood flow through the heart, preventing backflow and maintaining efficient circulation.

• Types:

  • Atrioventricular (AV) Valves:

    • Tricuspid Valve: Separates the right atrium and right ventricle.

    • Bicuspid (Mitral) Valve: Separates the left atrium and left ventricle.

  • Semilunar Valves:

    • Aortic Valve: Located between the left ventricle and the aorta.

    • Pulmonary Valve: Located between the right ventricle and the pulmonary trunk.

Phases of the Cardiac Cycle

1. Ventricular Filling (Diastole):

   • Heart pressure is low, allowing blood to flow from the atria into the ventricles.

   • Atrioventricular (AV) valves are open; atrial systole occurs, pushing blood into the ventricles.

2. Ventricular Systole:

   • AV valves close to prevent backflow as ventricles contract.

   • Semilunar valves open, allowing blood to enter the aorta and pulmonary trunk.

3. Isovolumetric Relaxation:

   • Ventricle relaxes, leading to decreased pressure.

   • Semilunar valves close to prevent backflow into the heart.

Heart Physiology - Conduction System

• Components:

  • Sinoatrial (SA) Node: The natural pacemaker located in the right atrium that initiates electrical impulses.

  • Atrioventricular (AV) Node: Delays the signal to ensure the atria contract before the ventricles.

  • AV Bundle (HIS): Transmits impulses from the AV node to the ventricles.

  • Bundle Branches: Conduct impulses to the left and right ventricles.

  • Purkinje Fibers: Spread throughout the ventricles to coordinate their contraction.

• Function: Coordinates the heartbeat through precise impulse generation and conduction, leading to synchronized heart contractions.

Electrocardiography (ECG)

• Components:

  • P wave: Represents atrial depolarization.

  • QRS Complex: Represents rapid ventricular depolarization.

  • T wave: Reflects ventricular repolarization.

• Importance: Facilitates the detection of cardiac abnormalities and the assessment of heart health.

Cardiac Output and Regulation

• Cardiac Output (CO): The volume of blood pumped by the heart per minute; a key indicator of heart efficiency and function.

• Components:

  • Formula: CO = Heart Rate (HR) x Stroke Volume (SV), whereby HR is the number of beats per minute and SV is the amount of blood ejected with each beat.

• Regulators: Influenced by hormones (e.g., epinephrine) and variations in ion concentrations (like calcium).

Homeostatic Imbalance

• Consider discussing common heart-related conditions, such as hypertension, coronary artery disease, heart failure, and arrhythmias, highlighting their causes, symptoms, and implications for overall health.