Why is the Circulatory System Essential for Survival? 

The circulatory system serves to deliver oxygen to different regions of the body. The oxygen that is inhaled diffuses through the air sacs into the blood where it binds to the hemoglobin component of the blood and transmitted to different regions of the body. This system is also responsible for the elimination of metabolic wastes like carbon dioxide. Without the circulatory system, the blood would remain static and there will not be a closed system of oxygen transport within the human body and the person will not be alive. 

Circulatory System 

The circulatory system is also known as the cardiovascular system as the heart is the core organ that functions as the start and the endpoint of circulation. However, this is also named as the vascular system as it helps in the transport of other substances such as respiratory gases, nutrients, amino acids, or hormones. The circulatory system and its proper regulation are mandatory to tackle disease and maintain homeostasis. Homeostasis is a balanced state within the body involving pH and temperature. 

What are the Major Components of the Circulatory System? 

The circulatory system is composed of four important components which are interconnected to each other and work in collaboration to perform the function. 

• The heart is the core circulatory organ which is made of cardiac muscle that can contract and expand based on the flow of blood. Due to this pumping action, the blood flows to different parts of the body and delivers oxygen for the functioning of other organs. In humans, the heart is a four-chambered structure consisting of left and right atria and left and right ventricle. The right atrium and ventricle receive deoxygenated blood which is transported to the lungs for oxygenation whereas the left atrium and ventricle receive oxygenated blood. 
• Veins are the major portion of blood vessels and the majority of the veins transports deoxygenated blood to the heart and from there it takes it to the lungs for oxygenation. 
• Arteries carry the oxygen-containing blood from the heart to other regions of the body which require oxygen for their functioning. 
• Blood is an important transport medium. The blood keeps traveling up and down throughout the body carrying its antibodies, nutrients, immune cells, oxygen, carbon dioxide, and hormones. 

Types of Circulation in the Human body 

In the human body, there are three types of blood circulation system which occur sin the body all the time. 

• Pulmonary circulation: This is a portion of the circulatory system which carries blood that does not contain oxygen (deoxygenated blood) from the heart to the lungs. Hence, the term “pulmonary”. However, this system also carries the blood back to the heart after the blood is oxygenated. 
• Systemic circulation: This portion of the circulation takes the oxygenated blood from the heart to different regions of the body but not to the lungs. 
• Coronary circulation is the part of the systemic circulation that supplies oxygenated blood to the muscles and tissues of the heart to ensure proper functioning. 

How does the Circulatory System Work to Ensure Blood Flow? 

The successful working of the circulatory system every day is what keeps us alive. It acts as a medium and supplies oxygen, nutrients, and hormones to appropriate organs inside the body to regulate different metabolic activities. Besides, the veins and arteries, there is yet another small component branching from the arteries called capillaries which regulates the nutrients and oxygen supply even to the nook and corner of the body. Capillaries are also necessary for the exchange of waste products such as carbon dioxide after metabolism. The steps by which circulation takes place are mentioned as follows: 

• When the blood does not contain oxygen or is deoxygenated, it enters into the heart on the right side (right atrium and then to the right ventricle) through the veins. 
• The heart takes up this blood and transports it to the lungs for oxygenation. The carbon dioxide in the blood gets exchanged with the oxygen inside the lungs through the process of diffusion. 
• Now, the blood containing fresh oxygen enters the heart, in the left atrium and then into the left ventricle. The oxygenated blood is brought back to the heart through pulmonary veins. 
• The oxygenated blood is pumped to different tissues through the aorta (the main and the largest artery) which transports the blood to the capillaries through arteries and arterioles (branch of the artery which connects it to capillaries). Capillaries are connected to all the major and minor organs and serve to distribute the oxygen, hormones, or nutrients and also pick up the metabolic waste from the cells. 
• Later, the blood depleted of the oxygen enters the heart. This cycle keeps continuing for a constant supply of oxygen and maintenance of homeostasis. In response to the change in blood volume, hormones, and electrolytes, the circulatory system acts accordingly to maintain homeostasis. 

Conditions Related to Circulatory System 

Any modification in the circulatory system or its components, can hinder the proper working and can damage the human body in a plethora of ways. The following are a few of the conditions resulting from the malfunctioning of the circulatory system. 

• Atherosclerosis: When the circulatory system has too much cholesterol, it starts to deposit in the form of plaque in the walls of the arteries. It can occur due to high blood pressure, use of tobacco, smoking, and an unhealthy diet. Atherosclerosis can cause the arteries to shrink in diameter which restricts the blood supply to the organs, especially the heart. This causes the organs to starve for oxygen. When this happens in the cardiac arteries, it is called coronary artery disease which results in cardiac arrest or stroke. 
• High Blood pressure: When the blood exerts too much force on the walls of the artery, it can lead to problems in the pumping of the heart. This condition can gradually affect your heart as well as other organs such as the eye. 
• Angina: Angina is a form of chest pain that happens when the heart receives limited blood supply (or has depletion in oxygen supply). This is known to be caused by coronary artery disease that causes the walls of the artery to become narrow. 
• Varicose veins: There are valves present inside the veins which result in the unidirectional flow of the deoxygenated blood to the heart. When there is a failure in the valves of the veins, it either leads to the blood getting collected in the veins which results in them becoming bulges and inflamed, or it leads to blood flow in the wrong direction. Swollen veins in the legs, arms, or other parts of the body due to faulty valves of the veins are painful and are called varicose veins. 

Context and Applications

Circulatory system in human body is very essential in professional coursework of both undergraduate and graduate programs such as  

• Bachelor of Science in Biology 
• Bachelor of Science in Zoology 
• Bachelor of Science in Medicine 
• Master of Science in Biological science 
• Master of Science in Human anatomy and physiology 
• Masters in Biotechnology