Anatomy of The Heart

Heart

A muscular pump located in the mediastinum between the lungs. Weighs about 300–450 grams and is roughly the size of an adult fist.

Location of the Heart

Lies in the thoracic cavity behind the breastbone in the mediastinum.

Four Chambers of the Heart

Two upper atria and two lower ventricles.

Atria

The two upper chambers of the heart that receive blood.

Ventricles

The two lower chambers of the heart that pump blood out of the heart.

Double Pump of the Heart

The right side pumps oxygen-poor blood to the lungs, while the left side pumps oxygen-rich blood to the body.

Right Side of the Heart

Pumps oxygen-poor blood to the lungs.

Left Side of the Heart

Pumps oxygen-rich blood to the body.

Venae Cavae

The two largest veins in the body that carry oxygen-poor blood to the heart.

Superior Vena Cava

Drains blood from the upper portion of the body into the right atrium.

Inferior Vena Cava

Carries blood from the lower portion of the body into the right atrium.

Right Atrium

The upper right chamber that receives oxygen-poor blood from the venae cavae.

Function of the Right Atrium

Contracts to force blood through the tricuspid valve into the right ventricle.

Tricuspid Valve

Valve located between the right atrium and right ventricle.

Function of the Tricuspid Valve

Prevents blood from flowing back into the right atrium.

Right Ventricle

The lower right chamber that pumps oxygen-poor blood to the lungs.

Function of the Right Ventricle

Pumps blood through the pulmonary valve into the pulmonary artery.

Pulmonary Valve

Valve between the right ventricle and pulmonary artery.

Pulmonary Artery

Carries oxygen-poor blood from the heart to the lungs.

Function of the Lungs

Add oxygen to the blood and remove carbon dioxide.

Pulmonary Veins

Carry oxygen-rich blood from the lungs to the left atrium.

Left Atrium

The upper left chamber that receives oxygen-rich blood from the pulmonary veins.

Function of the Left Atrium

Contracts to force blood through the mitral valve into the left ventricle.

Mitral Valve

Valve between the left atrium and left ventricle.

Left Ventricle

The lower left chamber of the heart.

Function of the Left Ventricle

Pumps oxygen-rich blood through the aortic valve into the aorta.

Thickest Heart Chamber

The left ventricle has the thickest walls.

Why the Left Ventricle Is Thick

It must generate enough force to pump blood throughout the body.

Aortic Valve

Valve between the left ventricle and aorta.

Function of the Aortic Valve

Prevents blood from flowing back into the left ventricle.

Aorta

The largest artery in the body that distributes oxygen-rich blood to all body tissues.

Septa

Partitions that separate the chambers of the heart.

Interatrial Septum

Partition that separates the right and left atria.

Interventricular Septum

Muscular wall that separates the right and left ventricles.

Endocardium

Smooth inner layer of endothelial cells lining the heart chambers and valves.

Myocardium

The thick muscular middle layer of the heart wall.

Pericardium

Fibrous and membranous sac surrounding the heart.

Visceral Pericardium

Inner layer of the pericardium that adheres directly to the heart.

Parietal Pericardium

Outer layer of the pericardium that lines the fibrous sac.

Pericardial Cavity

Space between the visceral and parietal pericardium.

Pericardial Fluid

Fluid within the pericardial cavity that lubricates the heart as it beats.

Amount of Pericardial Fluid

Normally contains 10 to 15 mL of fluid.

Pathway of Blood Through the Heart

Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Artery → Lungs → Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta.