The Heart

Primary Function of the Heart

Pumps blood through arteries and veins to deliver oxygen/nutrients and remove CO₂ and wastes.

Right Side of Heart

Receives deoxygenated blood and pumps it to the lungs.

Left Side of Heart

Receives oxygenated blood and pumps it to the body.

Four Chambers

Right atrium, right ventricle, left atrium, left ventricle.

Atria

Thin‑walled chambers that receive blood returning to the heart.

Ventricles

Thick‑walled chambers that pump blood out of the heart.

Right Atrium

Receives deoxygenated blood from systemic veins.

Right Ventricle

Pumps blood to the lungs for gas exchange.

Left Atrium

Receives oxygenated blood from the lungs.

Left Ventricle

Pumps oxygenated blood to the entire body; thickest myocardium.

Fibrous Pericardium

Tough outer layer that protects and anchors the heart.

Serous Pericardium

Double membrane with parietal and visceral layers.

Parietal Layer

Outer serous layer lining the fibrous pericardium.

Visceral Layer (Epicardium)

Inner serous layer covering the heart surface.

Pericardial Cavity

Space between layers containing lubricating fluid.

Myocardium

Thick middle layer of cardiac muscle responsible for contraction.

Endocardium

Smooth inner lining of chambers and valves.

Conducting System

Specialized cardiac cells that initiate and distribute electrical impulses.

Autorhythmicity

Heart contracts without neural or hormonal input.

SA Node

Primary pacemaker in right atrium; initiates heartbeat.

AV Node

Delays impulse to allow atrial contraction before ventricles contract.

AV Bundle (Bundle of His)

Conducts impulse from AV node into ventricles.

Bundle Branches

Carry impulses through interventricular septum.

Purkinje Fibers

Distribute impulses through ventricular myocardium for coordinated contraction.

Impulse Conduction Sequence

Step 1: SA Node Fires → Atrial depolarization begins.
Step 2: Impulse Spreads → Travels across atria to AV node.
Step 3: AV Node Delay → 100 ms pause allows atrial contraction.
Step 4: AV Bundle to Branches → Impulse travels down septum to Purkinje fibers.
Step 5: Ventricular Activation → Ventricles depolarize and contract.

Coronary Arteries

Right and left coronary arteries supply oxygenated blood to the heart muscle.

Right Coronary Artery

Supplies right atrium, right ventricle, SA and AV nodes.

Left Coronary Artery

Branches into LAD and circumflex; supplies left heart.

Coronary Veins

Return deoxygenated blood from myocardium to right atrium.