The Cardiovascular System

Your body’s way of getting oxygen to where it’s needed.

Tricuspid, pulmonary, mitral, and aortic
Systole and diastole
Arteries, veins, and capillaries
Vessel diameter
High blood pressure

Overview of the Cardiovascular System

The cardiovascular system, also known as the circulatory system, is a vital component of human physiology, responsible for the transportation of nutrients, oxygen, and waste products throughout the body. It consists of three main components: the heart, blood vessels, and blood. The heart acts as a pump, propelling blood through a network of blood vessels, which include arteries, veins, and capillaries. The circulatory system is divided into three circuits: pulmonary, systemic, and coronary.


The pulmonary circuit transports deoxygenated blood from the heart to the lungs, where it picks up oxygen and releases carbon dioxide. The systemic circuit carries oxygenated blood from the heart to the rest of the body, delivering oxygen and nutrients to cells and tissues, and collecting waste products for elimination.

The coronary circuit supplies the heart itself with oxygen and nutrients. Arteries carry blood away from the heart, while veins return blood to the heart. Capillaries are the smallest blood vessels, facilitating the exchange of substances between blood and tissues. The cardiovascular system works in harmony to maintain homeostasis and support the body’s various functions.

Heart Anatomy

Building upon the overview of the cardiovascular system, let’s delve into the structure of the heart. The heart is a muscular organ with four chambers: two atria and two ventricles. The atria receive blood from the veins, while the ventricles pump blood into the arteries. The heart also contains four valves that ensure one-way blood flow: the tricuspid, pulmonary, mitral, and aortic valves.


The heart’s blood vessels include the superior and inferior vena cava, which bring deoxygenated blood from the body to the right atrium; the pulmonary arteries, which carry blood from the right ventricle to the lungs; the pulmonary veins, which return oxygenated blood from the lungs to the left atrium; and the aorta, which transports oxygenated blood from the left ventricle to the rest of the body. The coronary arteries supply the heart muscle with oxygen and nutrients, while the coronary veins remove waste products. Did you know that your heart beats 100,000 times per day and pumps 1.5 gallons of blood every minute?

Cardiac Cycle

The cardiac cycle is the sequence of events that occurs during one heartbeat, consisting of two main phases: systole and diastole. Systole is the contraction of the heart muscle, while diastole is the relaxation of the heart muscle . The cardiac cycle can be further divided into atrial diastole, atrial systole, ventricular diastole, and ventricular systole.


During atrial diastole, the atria are relaxed, and blood flows into them from the veins. Atrial systole follows, with the atria contracting and pushing blood into the ventricles. Ventricular diastole occurs simultaneously with atrial systole, allowing the ventricles to fill with blood. Finally, ventricular systole takes place, with the ventricles contracting and pumping blood into the arteries. The coordination of these phases ensures efficient blood circulation throughout the body.

Electrical Conduction System

The electrical conduction system of the heart plays a crucial role in coordinating heartbeats. The heart beats using an electrical stimulus generated by specialized cells within the sinoatrial (SA) node, located in the right atrium. The SA node is often referred to as the heart’s natural pacemaker, initiating electrical impulses that travel through the atria, causing them to contract.


The electrical signal then reaches the atrioventricular (AV) node, which delays the impulse before sending it to the bundle of His and subsequently to the ventricles, causing them to contract. An average human heart beats approximately 60 to 100 times per minute. The electrical conduction system is critical for maintaining a regular and synchronized heartbeat, ensuring efficient blood circulation.

Today, people can have a pacemaker to assist the heart. In 1958, Åke Senning, a thoracic surgeon at the Karolinska Hospital in Stockholm, implanted myocardial electrodes and a pulse generator with a rechargeable nickel-cadmium battery in a 40-year-old patient. It was the first implantable pacemaker.

Blood Vessels

Blood vessels are classified into three types: arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart and have thick, muscular walls to withstand the pressure of blood being pumped by the heart. Veins return deoxygenated blood to the heart and have thinner walls and valves to prevent backflow. Capillaries are the smallest blood vessels, connecting arteries and veins, and facilitating the exchange of nutrients, oxygen, and waste products between blood and tissues.


Each type of blood vessel plays a crucial role in the circulatory system. Arteries transport oxygen and nutrients to cells and tissues, veins collect waste products for elimination, and capillaries enable the exchange of substances between blood and tissues, ensuring efficient nutrient delivery and waste removal. Did you know that there are over 60 000 miles of blood vessels in the human body?

Blood Pressure


Blood pressure is the force exerted by blood against the walls of blood vessels and plays a vital role in the body. Factors affecting blood pressure include cardiac output , peripheral vascular resistance, volume of circulating blood, viscosity of blood, and elasticity of vessel walls. The nervous system, hormonal system, and renal system all play a role in regulating blood pressure.

Cardiac output is the volume of blood pumped by the heart per minute, while peripheral vascular resistance is the resistance blood encounters as it flows through blood vessels. An increase in either of these factors can lead to higher blood pressure. The volume of circulating blood, blood viscosity, and elasticity of vessel walls also influence blood pressure. The body constantly adjusts these factors to maintain optimal blood pressure and ensure adequate blood flow to tissues.

Blood Flow

Blood flow is the movement of blood through the circulatory system and is essential for delivering oxygen and nutrients to cells and removing waste products. Factors that affect blood flow include vessel diameter, blood viscosity, and vessel length.


Vessel diameter is a significant determinant of blood flow, as a larger diameter allows for more blood to flow through the vessel. Blood viscosity, or thickness, also affects blood flow, with thicker blood flowing more slowly. Vessel length plays a role as well, with longer vessels offering more resistance to blood flow. The body adjusts these factors to maintain optimal blood flow and meet the needs of tissues and organs.

Circulatory Pathways


Circulatory pathways are the routes blood takes through the body and can be divided into systemic, pulmonary, and coronary circulation. Systemic circulation carries oxygenated blood from the heart to the rest of the body, delivering oxygen and nutrients to cells and tissues. An example of systemic circulation is the blood flow from the aorta to the smaller arteries and capillaries throughout the body.

Pulmonary circulation transports deoxygenated blood from the heart to the lungs, where it picks up oxygen and releases carbon dioxide. This process occurs as blood flows from the pulmonary arteries to the capillaries in the lungs. Coronary circulation supplies the heart itself with oxygen and nutrients, with blood flowing through the coronary arteries and veins. Each of these circulatory pathways is essential for maintaining overall cardiovascular health and function.

Cardiovascular Disorders

Common cardiovascular disorders include hypertension, atherosclerosis, coronary heart disease, stroke, peripheral arterial disease, and aortic disease. Hypertension, or high blood pressure, can damage blood vessels and organs over time, increasing the risk of heart attack, stroke, and kidney disease. Atherosclerosis is the buildup of plaque in arteries, which can restrict blood flow and lead to coronary heart disease, the leading cause of death worldwide.


Stroke occurs when blood flow to a part of the brain is interrupted, resulting in brain cell damage and potential loss of function. Peripheral arterial disease involves the narrowing of peripheral arteries, often in the legs, leading to reduced blood flow and pain. Aortic disease encompasses conditions affecting the aorta, the body’s largest artery, such as aneurysms and dissections, which can be life-threatening if not treated promptly. Understanding and managing these cardiovascular disorders is crucial for maintaining overall health and preventing complications.

You will forget 90% of this article in 7 days.

Download Kinnu to have fun learning, broaden your horizons, and remember what you read. Forever.

You might also like

Introduction to Human Physiology;

What human physiology is - and why it matters.

The Endocrine System;

The system that governs all hormonal activity.

The Musculoskeletal System;

The interlinked system of muscles and skeletons that holds us all together.

The Respiratory System;

The system built around the exchange of gases.

The Urinary System;

How your body disposes of liquid waste.

The Nervous System;

The system governing sensation and neural communications.

Leave a Reply

Your email address will not be published. Required fields are marked *