The Heart - Cardiovascular System

THE HEART

CARDIOVASCULAR SYSTEM - LESSON 1
OVERVIEW OF LESSON OBJECTIVES

  • Describe the location of the heart.

  • Explain some benefits of that location.

  • Describe the micro-anatomy of heart tissues.

LOCATION OF THE HEART
GENERAL LOCATION

  • The heart is situated almost dead-center laterally in the chest cavity.

  • It is on the anterior side of the chest cavity and is contained within its own membrane sac called the pericardium.

  • The pericardium is a fluid and fat-filled sac that lubricates the heart, minimizing damage during the heart's pumping action.

PROTECTION AND FUNCTIONALITY

  • The heart is protected by the sternum and spine, which provides physical support and protection.

  • The centralized location of the heart has critical implications for Cardiopulmonary Resuscitation (CPR). This positioning facilitates the process of squeezing the heart via pushing on the sternum during CPR.

  • Before performing CPR, it is necessary to open up the patient below the xiphoid process and pump with the hand to effectively compress the heart.

HEART MICROANATOMY
STRUCTURAL COMPONENTS

  1. Visceral Pericardium: This is the inner layer of the pericardium that is attached to the heart muscle itself.

  2. Parietal Pericardium: This is the outer layer that forms the outer wall of the pericardial sac.

  3. Pericardial Cavity: This is the space filled with lubricating fluid that reduces friction between the heart and the pericardium during heartbeats.

  4. Myocardium: This is the muscular layer of the heart, responsible for the contraction and pumping action.

  5. Endocardium: This is the innermost layer of tissue that lines the chambers of the heart.

  6. Normal Myocyte: This is a heart cell, specifically referring to cardiac muscle cells that contract to pump blood.

HEART FUNCTIONALITY
PUMPING CAPACITY

  • The heart pumps approximately 1.3 gallons per minute.

  • Annually, this totals approximately 700,000 gallons.

  • The heart can effectively operate for 100+ years, which is calculated based on an average heart rate of 60 BPM (beats per minute), across 525,960 minutes in 100 years. This leads to roughly 3.16 billion beats throughout a lifetime.

  • The total length of blood vessels in the human body is approximately 50,000 miles, which is about twice the circumference of the earth.

HEART STRUCTURES AND FLOW
HEART CYCLE

  1. Systole: This is the phase of contraction of the ventricles, during which pressure increases in the heart chambers.

  2. Diastole: This is the relaxation phase of the ventricles, during which the pressure decreases.

  3. Atrial Systole/Diastole: Measuring the pressures during atrial contraction and relaxation can be challenging due to their rapid and less pronounced changes compared to the ventricles.

ELECTRICAL SYSTEM OF THE HEART
COMPONENTS

  • Sinoatrial (SA) Node: This is the primary pacemaker of the heart, located in the right atrium.

  • Bachmann’s Bundle: This helps in the conduction of electrical impulses from the right atrium to the left atrium.

  • Atrioventricular (AV) Node: Located between the atria and ventricles, it serves as a gatekeeper for electrical signals.

  • Bundle of His: This pathway carries the electrical impulses from the AV node into the ventricles.

  • L and R Bundle Branches: These branches transmit impulses to the left and right ventricles, respectively.

  • Purkinje Fibers: These fibers spread the electrical signals throughout the ventricles, leading to coordinated contraction.

COMMON ELECTRICAL CONDITIONS

  • Bradycardia: A condition where the heart beats too slowly.

  • Tachycardia: A condition where the heart beats too quickly.

  • Fibrillation:

    • Atrial Fibrillation: Irregular and rapid heart rate.

    • Ventricular Fibrillation: Erratic heart rhythm that can lead to cardiac arrest.

  • Heart Block: A condition that disrupts the normal electrical conduction within the heart.

VALVE ANATOMY AND PATHOLOGY
VALVE ISSUES

  1. Heart Valve Stenosis: A condition where the valve does not open fully, which can be caused by:

    • Congenital heart defects.

    • Calcification of valve tissue.

    • Severity classification:

      • Normal: Greater than 3.0 cm².

      • Mild: Between 1.5 cm² and 3.0 cm².

      • Moderate: Between 1.0 cm² and 1.5 cm².

  2. Heart Valve Prolapse: Occurs when a valve does not close fully, which may also arise from:

    • Congenital heart defects.

    • Calcification of valve tissue.

    • Example of physiological structure observed: The left atrium, left ventricle, and the mitral valve.

HEART DEVELOPMENT

  • The heart undergoes critical development stages:

    • Developments between 15 days and 50 days after conception.

ATHEROSCLEROSIS AND RELATED PATHOLOGY

  • Atherosclerosis is a condition characterized by the thickening and hardening of arteries.

  • It plays a significant role in coronary blockage and heart disease.

MISCELLANEOUS

  • Graphical examples and diagrams were likely included to elaborate on the concepts of flow and functionalities, but are not transcribed here.

  • Ongoing developments in medical training and simulations were noted throughout the study materials published by Medical Training and Simulation LLC.