Human Circulatory System

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Blood Circulation in The Human Body

Our body has a number of processes going on simultaneously. These processes are essential to keep the body alive. Transportation or circulation of blood throughout the body is essential for the oxygen to reach the cells. This oxygen is utilised by the cells for the purpose of respiration, which releases energy to carry out various life functions.

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The circulatory system of humans is made up of a complex network of veins, arteries and capillaries. The heart is a fist-sized organ located in the rib cage, slightly tilted towards the left. It is the organ that works like a motor and pumps blood from the body. 

Organs of The Circulatory System

Our circulatory system is made up of four important organs that have different functions and roles to perform.

These Important Organs Are As Follows:

Heart, blood, blood vessels and lymph. 

  • Heart

The heart is a four-chambered, fist-sized organ present inside the rib cage. It is made up of a special type of muscles called cardiac muscles. The upper two chambers are called auricles (or atria; singular- atrium) and the lower two chambers are called ventricles.

Humans have a very unique circulation which is also called double circulation. In this, the blood has to flow through the heart two times. This kind of mechanism is essential for the human body as it is quite large as compared to other animals. Every cell and organ of the body needs a continuous supply of oxygen-rich blood. Also, it has to be ensured that the pureblood does not get mixed with the carbon dioxide-rich blood. The heart is divided into four chambers by a division known as the septum. The left side of the heart has pure oxygenated blood flowing through it, while the right side of the heart has the deoxygenated or the carbon dioxide-rich blood flowing through it. 

Between the auricles and the ventricles, one valve is present on each side. These valves open, and the blood passes from the upper chambers to the lower chambers. The valves ensure a  unidirectional flow of blood. As soon as the blood flows to the ventricles, these valves close so as to prevent any backflow. The opening and closing of these valves produces a lubb-dubb sound which is heard as the heartbeat.

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  • Blood

Blood is technically not an organ but a tissue. It is a connective tissue. It is made up of blood cells, plasma, floating proteins and other minerals. Plasma is the fluid content of the blood. 90% of blood is made up of plasma. Various types of cells such as red blood cells, white blood cells and platelets float in the plasma. They are a solid part of the blood.

Red blood cells, also known as erythrocytes are responsible for transporting oxygen to the entire body. They contain a protein called haemoglobin which combines with oxygen to form a compound called oxyhaemoglobin. People who have a higher level of haemoglobin in their blood are usually active, because oxygen is able to reach their body cells quickly and hence more energy is produced.

White blood cells, also known as leukocytes, form a part of the body's defence mechanism. They help in fighting against foreign pathogens and building up the immunity.

Platelets, also known as thrombocytes, help in the clotting of the blood during an injury so that excess blood does not flow out of the body.

  • Blood Vessels

Blood vessels of tube-like structures through which the blood flows. There are primarily two kinds of blood vessels- arteries and veins.

Arteries are responsible for carrying oxygenated blood from the heart to the other organs of the body. Blood flows in arteries at a great pressure. This is why arteries have thick and elastic walls. They are located deep below the skin.

Veins are responsible for carrying deoxygenated blood from the cells of the body back to the heart. They are present near the surface of the skin. The pressure of blood flowing through veins is lesser as compared to blood flowing through arteries. 

  • Lymphatic System

Our circulatory system has one more kind of fluid, called lymph. Just like blood, lymph is also a tissue. It is a colourless liquid responsible for transporting absorbed food and fats to intracellular spaces. 

Functions of The Circulatory System

Circulatory system has the following functions:

  1. Maintaining the supply of blood to all the organs of the body.

  2. Transporting nutrients, oxygen-carbon dioxide, hormones to various cells and organs.

  3. Protecting the body from any foreign invasions and disease-causing microbes 

FAQ (Frequently Asked Questions)

1. Explain The Difference Between The Pulmonary Artery And Pulmonary Vein.

Arteries carry oxygenated blood, while veins carry deoxygenated blood. However, the functions of the pulmonary artery and pulmonary vein are entirely different. The pulmonary artery carries deoxygenated blood while the pulmonary vein carries oxygenated blood.

Pulmonary vein brings oxygenated blood from the lungs to the left auricle. The pulmonary artery takes the deoxygenated blood from the right ventricle of the heart back to the lungs.

2. Explain The Entire Process Of Circulation In The Human Body.

Process of circulation: We breathe in oxygen, which reaches the lungs. Inside every lung, tiny air sacs called alveoli are present. These alveoli are richly supplied with blood vessels. Here, the oxygen moves from the lungs to the blood. Through the pulmonary vein, the oxygen-rich blood enters the left auricle. The valve opens and this blood is pumped into the left ventricle. From here, the blood flows to the mother artery (aorta) after which, the blood is supplied to various organs of the body through a network of other arteries. 

Carbon dioxide formed as a product of respiration by the cells returns back to the heart. The carbon dioxide-rich blood enters the right auricle and is pushed into the right ventricle. The pulmonary artery takes this deoxygenated blood from the right ventricle to the lungs. Again, an exchange of gas takes place and carbon dioxide moves out of the blood into the lungs, after which it is exhaled through the nose.

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