Human Circulatory System

The human circulatory system is a complex system consisting of different types of tissues. The main organ of the human circulatory system is the heart which pumps blood throughout the body. The human circulatory system also consists of a vast network of vessels or pipelines that carry blood throughout the body. The main purpose of the human circulatory system is to transport various essential substances that are required for the survival of the body.

Human Circulatory System

The human circulatory system also known as the cardiovascular system (cardio means heart, and vascular means blood vessels) is one of the very important organ systems of the human body that is responsible for transporting essential substances throughout the body and connecting all the systems.

The human circulatory system consists of the heart, blood vessels, blood, and lymphatic system. The heart is the main organ that pumps the blood throughout the circulatory system. Throughout the body, the blood travels with the help of the blood vessels whereas the lymphatic system is responsible for the transport of the lymph throughout the body. The human circulatory system consists of three different pathways; the systemic pathway, the pulmonary pathway, and the coronary pathway.

Human Circulatory System Diagram

The diagram of human circulatory system is shown below:

Features of the Human Circulatory System

The main features of the human circulatory system are;

1. The system consists of the heart, blood vessels, blood, and lymphatic system.
2. The blood is a fluid connective tissue that flows through the system.
3. The heart is the main blood-pumping organ of the system.
4. The thickness and elasticity of blood vessels depend on the blood pressure exerted on them.
5. Blood is responsible for the transport of nutrients, wastes, hormones, oxygen, carbon dioxide, etc.
6. The network of blood vessels extensively spreads throughout the body.
7. There are three types of blood vessels; arteries, veins, and capillaries.
8. The circulatory system circulates the blood in two loops; oxygenated blood flows in one loop and deoxygenated blood flows in another loop.
9. The human heart has four chambers; two on each side that are connected.
10. The approximate length of the blood vessel is around 10⁵ kilometers in length.

Organs of Human Circulatory System

The human circulatory system consists of the; heart, blood, blood vessels, and the lymphatic system.

Heart

The heart is the main blood-pumping organ of the circulatory system. It is a muscular organ made of cardiac tissues. It is almost the size of a closed fist. It is located in the thoracic cavity between the right and left lungs with its apex slightly tilted towards the left side. The human heart has four chambers. It is covered by a protective covering called the pericardium. The chambers of the right side and left side are separated by the septum whereas the atrium and ventricle are separated by the atrioventricular septum that has valves in them. The left side of the heart deals with the oxygenated blood whereas the right side of the heart deals with the deoxygenated blood.

Blood

Blood is a fluid connective tissue that acts as the medium of transport in the body. Blood consists of blood cells and fluid plasma. Blood cells include; red blood cells, white blood cells, and platelets. Blood plasma is a straw-colored fluid that consists of water and other substances.

• Red Blood Cells: They are also known as erythrocytes that lack a nucleus. These cells consist of hemoglobin which is responsible for the transport of oxygen in the body and gives the red color of the blood. These cells also consist of antigens that determine the blood group of the person.
• White Blood Cells: They are also known as leukocytes which are responsible for the body’s immune system. They are of the following types; lymphocytes, monocytes, neutrophils, eosinophils, and basophils.
• Platelets: They are also known as thrombocytes which are small disk-shaped fragments produced in the bone marrow. They help in the clotting of blood during any injury.

Blood Vessels

Blood vessels are a network of pipelines that spreads throughout the body. These pipelines are responsible for the transport of blood throughout the body. Blood vessels consist of; arteries, veins, and capillaries.

• Arteries: These are thick and elastic blood vessels that are responsible for transporting high-pressure blood that is pumped by the heart. It is responsible for transporting oxygenated blood to the tissues of the body and deoxygenated blood to the lungs.
• Veins: These are thin and less elastic blood vessels that are responsible for the transport of low-pressure blood to the heart. It is responsible for transporting deoxygenated blood to the heart and oxygenated blood to the lungs.
• Blood Capillaries: These are very delicate one-celled thick blood vessels that are found deeply embedded in the tissues and are responsible for the exchange of materials between the blood and tissue (cells).

Lymphatic System

Lymph is a body fluid derived from blood that appears pale yellow. It connects the blood circulatory system to tissues and acts as a transport medium between the two. It lacks red blood cells as it seeps out of the blood circulatory system and requires the help of lymphatic vessels to return to the blood circulatory system. Lymph nodes (components of the lymphatic system) help in detecting pathogens or antigens present in the body’s tissue system.

Working of the Human Circulatory System

The human circulatory system works in two loops one for the oxygenated blood and the other for the deoxygenated blood.

For deoxygenated blood; the blood from tissue capillaries reaches the veins and then into the superior and inferior vena cava and flows into the right atrium, then to the right ventricle through the tricuspid valve. Then through the pulmonary valve, it gets pumped into the pulmonary artery. Through the pulmonary artery, it reaches the capillaries of the lungs where deoxygenated blood becomes oxygenated.

For oxygenated blood; the blood from the lungs flows into the left atrium through the pulmonary veins, then into the left ventricle through the mitral valve. Then through the aortal valve, it gets pumped into the aorta. Some amount of blood goes into the coronary circulation and the rest reaches the tissue capillaries through the arteries where the oxygenated blood becomes deoxygenated.

Types of Blood Circulation

There are mainly two types of blood circulation that occur in the human body;

• Double circulation
• Coronary circulation

Double Circulation

The flow of blood in two different circuits for oxygenated and deoxygenated blood is explained by double circulation. It includes;

• The Systemic Circuit: It is the circuit of blood transport that occurs between the heart and the different tissues of the body. In this circuit, the oxygenated blood leaves the left ventricle and then with the help of the aorta and arteries reaches the capillaries where an exchange of gases takes place and then the deoxygenated blood by the help of the vein and vena cava reaches the right atrium of the heart.
• The Pulmonary Circuit: It is the circuit of blood transport that occurs between the heart and the lungs. In this circuit, the deoxygenated blood leaves the right ventricle and then with the help of the pulmonary artery reaches the capillaries near the alveoli of the lungs for gaseous exchange, after which the oxygenated blood with the help of pulmonary veins will reach the left atrium of the heart.

Coronary Circulation

The flow of blood between the double circulatory system and the heart muscle (myocardium) is called coronary circulation. In this circulation, the coronary arteries from the aorta supply oxygenated blood to the heart muscle tissues where the exchange of gases and other substances takes place. Then the deoxygenated blood is transported to the vena cava with the help of coronary veins. This system ensures an uninterrupted supply of blood to the heart muscles.

Functions of the Circulatory System

Following are some of the functions of the circulatory system;

1. Transport of oxygen and carbon dioxide.
2. Transport of nutrients, waste, hormones, and other substances.
3. Regulation of the body temperature.
4. Regulation of the body’s pH.
5. Provides immunity to the body.
6. Helps in blood clotting during injury.
7. Helps in the conduction of information between cells.

FAQs on Human Circulatory System

1. What Is The Blood Circulatory System?

The blood circulatory system is the process by which blood carrying various substances is circulated throughout the body through the network of blood vessels.

2. How does the Human Circulatory System Function?

The human circulatory system functions by the help of pumping action of heart that pumps the blood to the network of arteries, veins, and capillaries. This mechanism ensures the continuous circulation of blood throughout the body.

3. What Are The Main Functions Of The Circulatory System?

The main function of the circulatory system is to circulate the fluid connective tissue i.e. the blood and the lymph throughout the body with the help of the heart and the network of blood vessels. It also helps in the exchange of gases, supply of nutrients, removal of waste, transport of hormones, etc.

4. What Are The Types Of Circulation?

The types of circulation are; systemic circulation which occurs between the heart and body tissues, pulmonary circulation which occurs between the heart and the lungs, and coronary circulation which occurs between the major blood vessels of the heart and the myocardium.

5. What is the Advantage of Double Circulation?

The advantage of double circulation is that two seperate circulation works for oxygenated and deoxygenated blood in alternate and continuous manner without letting the oxygenated and deoxygenated blood to get mixed.