ekg unit 1.1

Electrocardiogram (ECG or EKG)

A non-invasive, safe, and painless test that records the electrical activity of the heart and gives the physician vital data about a patient’s heart health.

Heart location and size

The heart is a two-sided, hollow organ about the size of a fist, located between the lungs in the thoracic cavity, behind the sternum, and slightly to the left.

Pericardium

The outer double membrane (sac) that covers the heart and contains lubricating fluid to reduce friction during heartbeats.

Myocardium

The thick, middle layer of the heart made of muscle tissue; responsible for pumping blood through the circulatory system.

Endocardium

The smooth inner layer of cells lining the heart and blood vessels; allows smooth blood flow through the heart.

Septum

A thick, muscular wall that separates the right and left sides of the heart.

Atria (plural of atrium)

The top two chambers of the heart that receive blood entering the heart.

Ventricles

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

Heart valves

Structures that keep blood flowing in only one direction through the heart.

Atrioventricular (AV) valves

Valves located between the atria and ventricles; include the tricuspid valve (right side) and bicuspid/mitral valve (left side).

Semilunar valves

Valves located between the ventricles and blood vessels leaving the heart; include the pulmonary valve and aortic valve.

Pulmonary circulation

The flow of blood between the heart and lungs; the right side of the heart pumps oxygen-poor blood to the lungs, where it becomes oxygen-rich before returning to the left side of the heart.

Systemic circulation

The flow of blood between the heart and the rest of the body; the left side of the heart pumps oxygen-rich blood to the body, and oxygen-poor blood returns to the right side.

Path of blood – Step 1

The right atrium receives deoxygenated blood from the body through the inferior and superior vena cava.

Path of blood – Step 2

Blood moves through the tricuspid valve into the right ventricle; the valve prevents backflow into the atrium.

Path of blood – Step 3

The right ventricle fills with blood.

Path of blood – Step 4

The right ventricle contracts, sending blood through the pulmonary valve into the pulmonary artery and to the lungs; the valve prevents backflow.

Path of blood – Step 5

The left atrium receives oxygenated blood from the lungs through the pulmonary veins.

Path of blood – Step 6

Blood moves through the bicuspid (mitral) valve into the left ventricle; the valve prevents backflow into the atrium.

Path of blood – Step 7

The left ventricle fills with blood.

Path of blood – Step 8

Blood leaves the heart through the aortic valve into the aorta, which sends oxygen-rich blood throughout the body; the valve prevents backflow into the ventricle.