Corazón, Anatomía y Fisiología

Heart Anatomy and Function

Structure of the Heart

• The heart consists of four chambers: right atrium, right ventricle, left atrium, and left ventricle.

• It is located in the thorax between the two lungs; the right and left chambers function simultaneously as two pumps.

Blood Circulation Processes

• Pulmonary Circulation: Right cavities pump deoxygenated blood to the lungs via the pulmonary artery for oxygenation.

• Systemic Circulation: Left cavities pump oxygenated blood through the aorta to body organs for nutrient exchange and waste removal.

Blood Vessels and Oxygen Content

• All vessels leaving the heart are arteries (e.g., aorta, pulmonary artery) with varying oxygen content; returning vessels are veins (e.g., superior/inferior vena cavae).

• The vena cavae carry blood with lower oxygen concentration while pulmonary veins transport more oxygen-rich blood back to the heart.

Cardiac Wall Structure

Layers of Cardiac Tissue

• The cardiac wall has three layers: endocardium (inner), myocardium (middle), and epicardium (outer). The thickness of myocardium varies based on pumping pressure needs.

Chamber Communication

• Atrioventricular openings connect atria to ventricles, covered by valves that ensure unidirectional blood flow:

• Tricuspid valve separates right atrium from right ventricle.

• Mitral valve separates left atrium from left ventricle.

Valves and Their Functions

Valve Mechanisms

• Semilunar valves regulate flow from ventricles into major vessels:

• Pulmonary valve controls outflow from the right ventricle.

• Aortic valve controls outflow from the left ventricle.

Preventing Backflow

• Tendinous cords connect valves to papillary muscles in ventricles, preventing backflow during contraction by keeping valves closed when necessary. The tricuspid valve has three cusps compared to two in other valves for similar functions.

Right Heart Pump Mechanics

Right Atrium Functionality

• The right atrium receives deoxygenated blood from systemic circulation via superior/inferior vena cavae and coronary sinus before passing it to the right ventricle through tricuspid valve opening.

Ventricular Pressure Dynamics

• During systole, the right ventricle pumps blood into pulmonary arteries at a systolic pressure of 25–30 mmHg; its wall is thinner than that of the left due to shorter distance to lungs.

Left Heart Pump Mechanics

Left Atrium Functionality

• The left atrium receives oxygenated blood from lungs via four pulmonary veins before transferring it through mitral valve into left ventricle.

Systolic Pressure Comparison

• Left ventricular systolic pressure reaches approximately 120 mmHg; thus, its muscular wall is thicker than that of the right ventricle due to higher resistance encountered when pumping throughout body organs.

Cardiac Electrical System

Coronary Arteries Role

• Coronary arteries supply essential nutrients and oxygen directly to cardiac tissue; they branch off above semilunar aortic valve ensuring proper myocardial function during contractions.

Ischemia Risks

• Reduced coronary circulation can lead to ischemia or myocardial infarction if vascular obstruction occurs, highlighting importance of adequate arterial health for heart function.

Pacemaker Cells

Cardiac Electrical Activity and Diagnostic Techniques

Cardiac Conduction System

• The cardiac impulse begins at the sinoatrial (SA) node and propagates to the atrioventricular (AV) node, then to the bundle of His where the signal slows down, allowing the atria to contract before the ventricles.

• The conduction continues through the branches of the bundle of His and into Purkinje fibers, exciting 99% of remaining muscle fibers known as contractile fibers.

Electrocardiogram (ECG) Analysis

• An electrocardiogram evaluates electrical activity by placing electrodes on limbs and around the heart in predefined locations. This analysis captures electrical traces such as:

• P wave representing atrial depolarization.

• QRS complex indicating ventricular depolarization.

• T wave reflecting ventricular repolarization.

• These traces provide insights into heart rhythm, chamber sizes, potential damage (e.g., myocardial infarction), drug effects on cardiac transmission or contraction, and functionality of implanted devices within the heart.

Echocardiogram Overview