Circulatory System

The circulatory system consists of the heart and blood vessels including arteries, arterioles, veins, and capillaries. Cardiac volumes, blood and blood pressure is also covered.

Circulatory System Anatomy

What is the human circulatory system? We explain an overview of the circulatory system including its functions, how it transports oxygen and other nutrients around the body as well as the differences between systemic and circulatory elements. The main organ of the circulatory system is the Human Heart.


Arteries are blood vessels that carry blood away from the heart. All of which, with the exception of the pulmonary artery, carry oxygenated blood. The most widely known artery within the human body is the Aorta. This is the largest of all blood vessels.


Capillaries are the smallest of all blood vessels and form the connection between veins and arteries. As arteries branch and divide into arterioles and continue to reduce in size as they reach the muscle they become capillaries.


Veins are blood vessels that carry deoxygenated (or very low levels of oxygen) blood back to the heart. The exception to this rule is the pulmonary vein, which carries oxygenated blood, from the lungs, back to the heart, ready to be pumped around the rest of the body.

Heartbeat & Cardiac Volumes

The heartbeat is caused by impulses arising from two specialised groups of cells within the heart muscle. The Sino-Atrial (SA) node, situated in the wall of the right atrium initiates the beat and the Atrioventricular (AV) node which is positioned between the ventricles and continues to distribute the wave of impulses.

The Heart Conduction System

The conduction system of the heart refers to how the heart contracts. Here we explain how electrical impulses ensure it beats regularly including specific parts of the heart involved such as the Bundle of His, Synoartial node as well as exam-type questions and quizzes.

The Human Heart

The heart is a strong, powerful organ, consisting of cardiac muscle. The heart pumps continuously, without resting and without becoming fatigued. Its function is to pump blood to the lungs and around the body. The heart is one of the key organs in the Circulatory System.

Understanding Blood Pressure

The rate and distribution of blood flow through the circulatory system are variable and related to several factors including physical activity, cardiac output (the amount of blood pumped out of the heart) and venous return or the blood returning to the heart through the veins. What is blood pressure?

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