Human Circulatory System: Definition, Organs and Functions

Circulatory System: Do you know that our heart is a part of a specialised system called the circulatory system. The circulatory system, also called the cardiovascular system or vascular system, comprises the heart, blood vessels, and blood. But what are the functions of this circulatory system? Why do so many parts or components are needed to function? Let us understand everything about the circulatory system through this article.

Circulatory System: Definition

The organ system responsible for the circulation of nutrients and transport of oxygen, carbon dioxide, amino acids, electrolytes, hormones, or other molecules and nutrients throughout the body is called the circulatory system.

Types of Circulatory System

The circulatory system can be classified into two main types based on the mode of transport of blood and the presence or absence of the blood vessels. The two systems are the open circulatory system and the closed circulatory system.

Open Circulatory System: In this type of circulatory system, the blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. It is found in arthropods and molluscs.

Closed Circulatory System: In this type of circulatory system, the blood pumped by the heart circulates through a closed network of blood vessels. It is found in annelids and chordates.

Human Circulatory System

1. The Human Circulatory system is an organ system that contains the heart and the blood vessels and moves blood throughout the body in a closed network of blood capillaries. 
2. Humans have a closed circulatory system.
3. The human circulatory system functions to transport blood and oxygen from the lungs to the various tissues of the body.
4. The human heart consists of four chambers – two ventricles and two auricles.

Organs or Parts of Circulatory System

The main parts of the human circulatory system include organs like blood vessels, the lymphatic system and the heart, and a fluid connective tissue called the blood.
Let us now learn about the organs of the circulatory system below:

Circulatory System: Blood

Blood is a fluid connective tissue that consists of blood cells, plasma, and platelets. It always keeps on circulating through blood vessels delivering oxygen and nutrients to various cells and tissues. It forms about \(8\) to \(10%\) of our body weight.

Blood consists of two major parts:
1. Plasma, which is nearly \(55\) to \(58%\).
2. Formed (cellular) elements or blood corpuscles are nearly \(42\) to \(45%\).
These are of three types, i.e.:
1. Red Blood Cells or RBCs – Red Blood Cells (RBCs) are also known as erythrocytes. They contain a complex chemical compound called haemoglobin which has iron.
2. White Blood Cells – White Blood Cells (WBCs) are also known as leukocytes. These blood cells fight against pathogens and other foreign bodies and thus protect our bodies from diseases.
3. Blood Platelets – Platelets are also known as Thrombocytes. These platelets help in preventing the loss of blood from our body as they cause clotting of blood at the site of injury.

Circulatory System: Blood Vessels

Blood vessels are the channels through which blood is distributed to body tissues. Blood flow in the blood vessels which are of the following three types:

1. Arteries – Arteries are vessels that carry blood away from the heart.
2. Veins – Veins bring blood back to the heart.
3. Capillaries – Capillaries are fine vessels that connect the arteries and veins.

Circulatory System: Lymphatic system

1. The lymphatic system is a network of tissues and organs that helps the body in getting rid of toxins, waste and other unwanted materials. 
2. The primary function of the lymphatic system is to transport lymph, a fluid containing infection-fighting white blood cells, throughout the body.
3. The lymphatic system comprises lymph, lymphatic capillaries, lymphatic vessels, lymphatic nodes and lymphatic ducts.

Circulatory System: Heart

The heart is a muscular organ that is made up of cardiac muscles that are located in the chest cavity, right between the lungs. It is positioned slightly towards the left in the thoracic region and is enveloped by the pericardium and it is involuntary in function.

The human heart is separated into four chambers, i.e., atria – the two upper chambers and ventricles – the two lower chambers of the heart.

Circulatory System: Double Circulation

The human heart performs a unique circulation called double circulation. In humans, the blood flows twice in the heart before it completes one full round of circulation, i.e., the pulmonary circulation and the systemic circulation. Hence, the blood circulation in the human body is also called ‘’Double Circulation”.

Pulmonary circulation – It starts in the pulmonary artery arising from the right ventricle which soon divides into two branches that enter the respective lungs. Pulmonary veins collect the oxygenated blood from the lungs and carry it back to the left auricle of the heart.

Systemic circulation – It starts with the aorta that arises from the left ventricle. The aorta arches back and continues behind as aorta. The aorta sends arteries to various body parts and their tissues. From there the blood is collected by veins and poured back into the heart.

Circulatory System: Portal System

A portal system is a network of blood capillaries that connect two organs or tissues, e.g., the hepatic portal system connects the small intestines to the liver via the hepatic portal vein.

Functions of Circulatory System

The functions of the Circulatory System are given below:

1. The circulatory system helps in transporting oxygen throughout the body.
2. It circulates oxygen and removes carbon dioxide from the body.
3. It transports blood, nutrients, hormones, etc., throughout the body.
4. It helps in the removal of the waste products of metabolism to the excretory organs for disposal.
5. It protects the body against disease and infection.
6. It acts as an interface for cell-to-cell interaction.

Diseases or Disorders of Circulatory System

Some of the disorders or diseases related to the circulatory system are as follows:
1. Hypertension – It is another name for high blood pressure.  It is an increased pressure, i.e. more than\(140{\rm{mmHg}}\) in the blood vessels. It can be caused due to stress, high cholesterol, etc., and this may increase the risk of heart attack or a stroke.
2. Hypotension – It is the medical term for low blood pressure. It is caused when the blood pressure falls below \(90/50{\rm{mmHg}}\) in adults.
3. Angina – It is also called angina pectoris or chest pain. In this disease, enough oxygen does not reach the heart muscles. The patient experiences pain in the chest.
4. Arteriosclerosis – It refers to the hardening and loss of elasticity of the arteries due to the deposition of cholesterol leading to the formation of plaque.
5. Coronary Artery Disease (CAD) or Atherosclerosis – It is the deposition of fatty substances especially cholesterol and triglycerides in the tunica interna and smooth muscles of arteries.
6. Fibrillation – It is a condition in which the heart muscles contract very rapidly but in an uncoordinated fashion. There is atrial and ventricular fibrillation. Ventricular fibrillation is life-threatening unless it can be stopped by defibrillation.
7. Heart attack (Myocardial infarction) – It is the death of a part of the heart muscle following the cessation of blood supply to it. It is an acute heart attack. The heart muscles suddenly get damaged by the inadequate blood supply.
8. Heart failure – It is the condition when the heart does not pump blood effectively enough to meet the needs of the body. It is sometimes called congestive heart failure because lung congestion is one of the main symptoms of this disease.

Summary

Through this article, we understood how your heart works like a pump that provides nutrients to every organ, tissue, and cell throughout your body. In turn, your cells dump waste products, like carbon dioxide, back into your blood to be returned to your heart. And also, cardio health is very important to maintain good health. The circulatory system helps in transporting oxygen throughout the body. It protects the body against disease and infection.

Frequently Asked Questions (FAQs) On Circulatory System

Let us look at some of the commonly asked questions about Circulatory system:

Q.1. What are the 4 main parts of the circulatory system
Ans: The 4 main parts of the circulatory system are the heart, blood, blood vessels, and lymphatic vessels. 

Q.2. Why is the circulatory system important?
Ans: The circulation system is essential because it supplies the body’s vital organs with enough oxygen and nutrients needed to operate.

Q.3. How does the circulatory system work?
Ans: The circulatory system includes the lymphatic system, which circulates lymph. The passage of lymph takes much longer than that of blood. Blood is a fluid consisting of plasma, red blood cells, white blood cells, and platelets that is circulated by the heart through the vertebrate vascular system, carrying oxygen and nutrients to and waste materials away from all body tissues. 

Q.4. What is the other name of the circulatory system?
Ans: The other name of the circulatory system is the cardiovascular system.

Q.5. What are the 33 circulatory systems?
Ans: The three types of circulation found within humans are systemic circulation, pulmonary circulation, and portal circulation.