The Cardio-Respiratory System – The Heart

Heart

The organ that sits within the thoracic cavity, between the lungs, and is protected by the pericardium.

Mediastinum

The area in the thoracic cavity where the heart is located, between the lungs.

Pericardium

A fluid-filled sac that surrounds and protects the heart.

Base

The top part of the heart.

Apex

The bottom part of the heart.

Left Heart

The part of the heart that supplies systemic circulation, receiving blood from the lungs and sending it to the body.

Right Heart

The part of the heart that receives deoxygenated blood from the body and pumps it to the lungs for oxygenation.

Pulmonary Veins

The veins that carry oxygenated blood from the lungs to the left atrium; there are four pulmonary veins.

Mitral Valve

The valve that allows blood to flow from the left atrium to the left ventricle.

Aortic Valve

The valve that allows blood to flow from the left ventricle into the aorta.

Ascending Aorta

The section of the aorta that rises from the heart and supplies blood to the body.

Superior Vena Cava

The vein that brings deoxygenated blood from the upper body back to the heart.

Inferior Vena Cava

The vein that brings deoxygenated blood from the lower body back to the heart.

Ventricular Septum

The muscular wall that separates the left and right ventricles.

Atrial Septum

The thin wall that separates the left and right atria.

Diastole

The phase of the cardiac cycle when the heart relaxes and fills with blood.

Systole

The phase of the cardiac cycle when the heart contracts and pumps blood.

End Diastolic Volume (EDV)

The volume of blood in the ventricles at the end of diastole.

End Systolic Volume (ESV)

The volume of blood remaining in the ventricles at the end of systole.

Stroke Volume (SV)

The amount of blood ejected from the heart with each beat, calculated as SV = EDV - ESV.

Endocardium

The innermost lining of the heart that is in direct contact with blood. Layer of endothelium cells

Myocardium

The muscular layer of the heart responsible for contraction and relaxation. Made up of specialized cells called cardiomyocytes.

Epicardium

The outer layer of the heart that provides protection. Are mesothelium cells.

Coronary Arteries

The arteries that supply blood to the heart muscle itself.

Sinoatrial Node (SA Node)

The natural pacemaker of the heart located in the upper right atrium.

Atrioventricular Node (AV Node)

The node that delays the electrical signal to allow the atria to finish contracting before the ventricles contract.

Bundle of His

The pathway that carries electrical impulses from the AV node to the ventricles.

Purkinje Fibres

Fibres that distribute electrical impulses throughout the myocardium to ensure coordinated contraction.

P-wave

The part of an electrocardiogram that indicates depolarization of the SA node and contraction of the atria.

QRS Complex

The part of an electrocardiogram that indicates contraction of the ventricles.