CARDIOVASCULAR HEART

Heart

A four-chambered muscular organ that pumps blood through the blood vessels of the body.

Cardiovascular System (CVS)

Consists of the heart, blood vessels, and blood.

Right Side of the Heart

Pumps blood to the lungs and back to the left side of the heart through pulmonary circulation.

Left Side of the Heart

Pumps blood to all tissues of the body and back to the right side of the heart through systemic circulation.

4 Main Functions of the Heart

1. Generating blood pressure; 2. Routing blood; 3. Ensuring one-way blood flow; 4. Regulating blood supply.

Size of the Heart

Approximately the size of a clenched fist.

Location of the Heart

Mediastinum, protected by the thoracic cage.

Pericardium

A sac surrounding the heart that consists of fibrous and serous pericardium.

Fibrous Pericardium

The tough outer layer of the pericardium.

Parietal Layer of Serous Pericardium

Lines the inner surface of the fibrous pericardium.

Visceral Layer of Serous Pericardium

The layer covering the outer surface of the heart; also called the epicardium.

Epicardium

The outermost layer of the heart wall; also called the visceral pericardium.

Pericardial Cavity

The space between the parietal and visceral layers of the serous pericardium.

Pericardial Fluid

Fluid within the pericardial cavity that reduces friction as the heart beats.

Base of the Heart

Primarily formed by the atria.

Apex of the Heart

The pointed inferior end of the heart, formed mainly by the left ventricle.

Coronary Sulcus

A groove that separates the atria from the ventricles.

Interventricular Sulci

Grooves on the anterior and posterior surfaces that mark the separation between the right and left ventricles.

Superior Vena Cava (SVC)

Returns blood from the upper body to the right atrium.

Inferior Vena Cava (IVC)

Returns blood from the lower body to the right atrium.

Pulmonary Veins

Usually four veins that carry oxygenated blood from the lungs to the left atrium.

Pulmonary Trunk

Carries deoxygenated blood from the right ventricle toward the pulmonary arteries.

Aorta

The largest artery; carries oxygenated blood from the left ventricle to systemic circulation.

Right atrium; Left atrium; Right ventricle; Left ventricle.

4 Chambers of the Heart

Right Atrium (RA)

Receives deoxygenated blood from the SVC, IVC, and coronary sinus.

Left Atrium (LA)

Receives oxygenated blood from the four pulmonary veins.

Atria

The upper chambers of the heart that receive blood.

Interatrial Septum

Separates the right and left atria.

Ventricles

The lower chambers of the heart and the main pumping chambers.

Interventricular Septum

Separates the right and left ventricles.

Right Ventricle (RV)

Pumps deoxygenated blood into the pulmonary trunk.

Left Ventricle (LV)

Pumps oxygenated blood into the aorta.

Heart Valves

Structures that ensure one-way blood flow through the heart.

Atrioventricular valves; Semilunar valves.

2 Main Types of Heart Valves

Atrioventricular (AV) Valves

Valves located between the atria and ventricles.

Tricuspid Valve

Located between the right atrium and right ventricle.

Bicuspid (Mitral) Valve

Located between the left atrium and left ventricle.

Papillary Muscles

Muscles in the ventricles that attach to the AV valve cusps through the chordae tendineae and prevent valve prolapse during ventricular contraction.

Chordae Tendineae

Fibrous cords connecting AV valve cusps to papillary muscles.

Semilunar Valves

Valves with three pocket-shaped, half-moon-shaped cusps that prevent blood from flowing back into the ventricles.

Pulmonary semilunar valve; Aortic semilunar valve.

2 Semilunar Valves

Pulmonary Semilunar Valve

Located between the right ventricle and pulmonary trunk.

Aortic Semilunar Valve

Located between the left ventricle and aorta.

Correct Order of Blood Flow Through the Heart

1. SVC, IVC, and coronary sinus; 2. Right atrium; 3. Tricuspid valve; 4. Right ventricle; 5. Pulmonary semilunar valve; 6. Pulmonary trunk; 7. Right and left pulmonary arteries; 8. Lungs; 9. Pulmonary veins; 10. Left atrium; 11. Bicuspid/mitral valve; 12. Left ventricle; 13. Aortic semilunar valve; 14. Aorta; 15. Systemic circulation.

What Happens in the Lungs During Pulmonary Circulation?

Gas exchange occurs: blood releases carbon dioxide and takes up oxygen.

Pulmonary Circulation

The pathway of blood from the right ventricle to the lungs and back to the left atrium.

Systemic Circulation

The pathway of blood from the left ventricle to body tissues and back to the right atrium.

Oxygenation of Blood

Pulmonary circulation oxygenates blood in the lungs before it returns to the left side of the heart.

Coronary Arteries

Arteries that supply oxygenated blood to the heart muscle; they originate near the base of the aorta.

2 Main Coronary Arteries

1. Left coronary artery; 2. Right coronary artery.

Anterior interventricular artery; Circumflex artery.

2 Major Branches of the Left Coronary Artery

Anterior Interventricular Artery

Also called the left anterior descending (LAD) artery; supplies the anterior ventricles and much of the interventricular septum.

Circumflex Artery

A branch of the left coronary artery that supplies the left atrium and lateral/posterior regions of the left ventricle.

Left Marginal Artery

A branch, commonly of the circumflex artery, that supplies the lateral wall of the left ventricle.

Right marginal artery; Posterior interventricular artery.

2 Major Branches of the Right Coronary Artery

Right Marginal Artery

A branch of the right coronary artery that supplies the right ventricle.

Posterior Interventricular Artery

Supplies the posterior regions of the ventricles and part of the interventricular septum; commonly arises from the right coronary artery.

What Does the Left Coronary Artery Mainly Supply?

Much of the left ventricle and the anterior region of the heart.

What Does the Right Coronary Artery Mainly Supply?

Much of the right ventricle and portions of the inferior/posterior heart, depending on coronary dominance.

Venous Return From the Heart Muscle

Cardiac veins drain blood into the coronary sinus, which empties into the right atrium.

Epicardium; Myocardium; Endocardium.

3 layers of heart wall

Epicardium

The outer layer of the heart wall.

Myocardium

The middle muscular layer responsible for heart contraction.

Endocardium

The smooth inner lining of the heart chambers and valves.

Cardiac Muscle

Striated, involuntary muscle tissue specialized for continuous rhythmic contraction.

Intercalated Discs

Connections between cardiac muscle cells that help them communicate and contract in a coordinated manner.

ATP in Cardiac Muscle

Provides the energy needed for cardiac muscle contraction and relaxation.

Aerobic Metabolism in Cardiac Muscle

Uses oxygen to produce ATP, supporting the heart's continuous activity.

Cardiac Muscle Stimulation and Contraction

Coordinated electrical stimulation triggers contraction; cardiac muscle then relaxes before the next cycle.

Conduction System of the Heart

A network of specialized cardiac cells that generates and conducts electrical impulses to coordinate heartbeats.

Main Components of the Cardiac Conduction System

1. SA node; 2. AV node; 3. AV bundle (bundle of His); 4. Right and left bundle branches; 5. Purkinje fibers.

Sinoatrial (SA) Node

The natural pacemaker of the heart; initiates electrical impulses that spread through the atria and cause atrial depolarization.

Atrioventricular (AV) Node

Receives the atrial impulse and delays its conduction so the ventricles can fill before ventricular contraction.

AV Bundle (Bundle of His)

Conducts electrical impulses from the AV node into the interventricular septum.

Right and Left Bundle Branches

Conduct impulses down the interventricular septum toward the apex of the heart.

Purkinje Fibers

Distribute electrical impulses through the ventricular myocardium, promoting coordinated ventricular contraction from the apex upward.

Electrocardiogram (ECG/EKG)

A recording of the electrical activity of the heart.

3 Main ECG Components

1. P wave; 2. QRS complex; 3. T wave.

P Wave Represents

Atrial depolarization.

QRS Complex Represents

Ventricular depolarization; atrial repolarization occurs at approximately the same time and is hidden by this complex.

T Wave Represents

Ventricular repolarization.

Atrial Repolarization

Usually hidden within the QRS complex on an ECG.

QT Interval

Extends from the beginning of ventricular depolarization to the end of ventricular repolarization; represents the total electrical activity of the ventricles.

Cardiac Output (CO)

The volume of blood pumped by one ventricle per minute.

Cardiac Output Formula

CO = Stroke Volume (SV) × Heart Rate (HR).

Stroke Volume (SV)

The amount of blood pumped by one ventricle with each heartbeat.

Heart Rate (HR)

The number of heartbeats per minute.

Intrinsic Regulation

Regulation arising within the heart itself, especially through changes in ventricular filling and contraction.

Venous Return

The amount of blood returning to the heart through the veins.

Preload

The degree of ventricular stretch at the end of diastole, largely influenced by venous return and ventricular filling.

Frank-Starling Law of the Heart

Within physiological limits, greater ventricular filling stretches cardiac muscle fibers and produces a stronger contraction, increasing stroke volume.

Effect of Increased Preload

Increased preload generally increases stroke volume and, consequently, cardiac output if other factors remain constant.

Afterload

The pressure or resistance the ventricle must overcome to eject blood.

Cardiac Cycle

The sequence of events during one complete heartbeat, including filling, contraction, and relaxation.

Passive Ventricular Filling

When the AV valves are open, blood flows from the atria into the ventricles; this accounts for most ventricular filling, approximately 70% under typical resting conditions.

Atrial Systole

The atria contract, completing ventricular filling; the AV valves are open and the semilunar valves are closed.

Ventricular Systole

The ventricles contract; the AV valves close, ventricular pressure rises, and the semilunar valves open when ventricular pressure exceeds arterial pressure.

First Heart Sound (S1)

Caused mainly by closure of the mitral and tricuspid valves at the beginning of ventricular systole.

Ventricular Diastole

The ventricles relax; when ventricular pressure falls below arterial pressure, the semilunar valves close.

Second Heart Sound (S2)

Caused mainly by closure of the aortic and pulmonary semilunar valves.