Structure and Function of the Cardiovascular System

The cardiovascular system, also known as the circulatory system, is a complex network of organs and vessels responsible for circulating blood throughout the body. Its primary components include the heart, blood vessels, and blood. Understanding the structure and function of the cardiovascular system is essential for grasping its role in physical education and overall health.

Structure of the Heart:

The heart is a muscular organ located in the chest cavity between the lungs.

It is divided into four chambers: two atria (upper chambers) and two ventricles (lower chambers).

The heart is surrounded by a protective sac called the pericardium.

Valves within the heart ensure unidirectional blood flow: the atrioventricular valves (tricuspid and mitral valves) between atria and ventricles, and the semilunar valves (pulmonary and aortic valves) between the ventricles and major arteries.

This video explains the heart structure and function

Blood Vessels Leading Into and Out of the Heart:

Arteries carry oxygen-rich blood away from the heart to the body tissues.

Veins return oxygen-poor blood back to the heart.

The pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation.

The pulmonary veins return oxygenated blood from the lungs to the heart.

Functions of the Cardiovascular System:

Transportation of Oxygen and Nutrients: The cardiovascular system delivers oxygen and nutrients to body tissues via blood circulation.

Removal of Waste Products: It removes metabolic waste products, such as carbon dioxide and urea, from tissues for excretion.

Regulation of Body Temperature: Blood flow helps regulate body temperature by redistributing heat throughout the body.

Protection: The immune components in blood help defend against pathogens, and blood clotting mechanisms prevent excessive bleeding.

Blood Pressure:

Blood pressure is the force exerted by blood against the walls of blood vessels.

It is measured in millimetres of mercury (mmHg) and consists of two values: systolic pressure (during heart contraction) and diastolic pressure (during heart relaxation).

Normal blood pressure is typically around 120/80 mmHg.

The Heart's Performance as a Pump:

The heart pumps blood through the circulatory system, generating blood flow to supply oxygen and nutrients to tissues.

Its pumping action is coordinated by electrical impulses that regulate heart rate and rhythm.

Heart Rate:

Heart rate is the number of heart beats per minute (bpm).

It is regulated by the sinoatrial (SA) node, known as the heart's natural pacemaker.

Factors affecting heart rate include physical activity, stress, and hormonal influences.

Stroke Volume:

Stroke volume is the volume of blood ejected from the left ventricle with each heartbeat.

It is influenced by factors such as preload (amount of blood in the ventricles before contraction), afterload (resistance against which the heart pumps), and contractility (force of ventricular contraction).

Cardiac Valves:

Cardiac valves ensure one-way blood flow within the heart chambers.

Cardiac output (Q) is the amount of blood pumped from the heart every minute and can be calculated by multiplying heart rate (HR) by stroke volume (SV).

Q = HR × SV

SV is 70 to 90 millilitres at rest. The fitter you are, the larger your stroke volume.

We can calculate a typical cardiac output at rest and during exercise:

Q at rest = SV × HR

Q at rest = 70 × 70

Q at rest = 4900 ml/min

Q at rest = 4.9 l/min

Q during exercise = SV × HR

Q during exercise = 120 × 180

Q during exercise = 21600 ml/min

Q during exercise = 21.6 l/min

Understanding the structure and function of the cardiovascular system is vital for athletes to optimise performance, maintain cardiovascular health, and prevent cardiovascular diseases. Regular physical activity and proper nutrition contribute to the overall well-being of the cardiovascular system.