Cardiovascular System

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What is Human Circulatory System?

The human body consists of complex organs and organ systems. Hence there exists complex functional systems and these systems should be performed without any distractions or problems. In order to function properly the supply of the required amount of essential nutrients is required. This role is taken by the human cardiovascular system. 

Let’s gain knowledge on this vascular system, its definition, its anatomy, cardiovascular system function, and how to protect it. We will start by learning the definition of it. A type of organ system that allows the blood to transport essential substances by circulating all over the body. The essential substances include nutrients, oxygen, carbon dioxide, waste products, and hormones.


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Cardiovascular System Anatomy

There are several organs, tissues, and systems that are combined to work together to take place the circulation in the body. Let us see what is the cardiovascular system made of? It consists of the heart, circulatory system, blood vessels, and blood. The blood is transported to all the organs that carry oxygen and nutrients. This vascular system is powered by a specialized organ called the heart. 

  1. Heart: The muscular pumping organ that is situated in the thoracic region is called the heart. It consists of four chambers namely the atrium and ventricles. Even though the heart is found in other animals, the human heart is found to be advanced in both structure and function. 


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  1. Circulatory systems: It can further be divided into two parts

  1. Pulmonary Circulation: In this circulation, the transportation of deoxygenated blood takes place from the right side of the heart to the lungs. Later the oxygenated blood is carried into the heart from the left side of the heart. The chambers of the heart that is involved in the pulmonary circulation are the right atrium and right ventricle.

  2. Systemic Circulation: In this circulation, the transportation of the oxygenated blood takes place from the left side of the heart to all the other parts of the body. Systemic circulation aims at removing the waste material from the tissues. It also returns the deoxygenated blood from the body to the right side of the heart. The chambers of the heart that is involved in the systemic circulation are the left atrium and left ventricle.

  1. Blood Vessels: The highways of the body where the transportation of the blood takes place are called blood vessels. The amount of the flow of blood is correspondent to the size of the blood vessels. The blood vessels consist of a hollow region known as the lumen through which the blood passes. They are lined with the endothelium which is a thin layer of the simple squamous epithelium. It aims at preventing the formation of clots inside the vessels. 


There are Three kinds of Blood Vessels:

  1. Arteries: This type of blood vessel carries the oxygenated blood away from the heart. They face high pressure as the blood is to be taken away from the heart, the blood is pushed at greater force thus increasing the pressure. Hence they are more elastic, thick, and more muscular in nature. A more percentage of the elastic tissues in the human body is present in arteries that helps to stretch and accommodate the pressure. The smaller arteries are more muscular and thus contract or regulate the flow of blood. Thereby controlling the amount of blood travelling to each organ. The branches that arrive at the end of the arteries are called arterioles. These are narrower in nature and greater in number hence facing lower levels of blood pressure. They act as bridges between arteries and capillaries. 

  2. Capillaries: The smallest and thinnest type of blood vessels are capillaries. It can be found running in every tissue of the body. They act as a bridge between venules and arterioles. They carry the blood very close to the cells in order to exchange nutrients, gases, and waste materials.

  3. Veins: They are the return parts of the arteries. During the contraction the arteries, arterioles, and capillaries absorb more force, veins have low blood pressure. Since they need to push the blood back to the heart they rely on inertia, gravity, and force of the skeletal muscles. Thus the walls of veins are less elastic, less muscular and thinner in nature. 

The veins contain one-way valves in order to facilitate the movement of blood and stop blood flow away from the heart. When the muscles get contracted they push the blood closer to the heart. When the muscles relax the blood gets trapped until the next contraction. 

Venules are the same as arterioles instead of connecting to capillaries they collect the blood and send it to the veins for transporting back to the heart.

Blood: The human body consists of about four to five litres of blood. It is a liquid connective tissue. It can maintain homeostasis of the nutrients, gases, and waste by travelling throughout the body. It is made up of blood cells, platelets, and liquid plasma. The blood cells are of two types: red blood cells and white blood cells. Let us look at each of the blood constituents.

  1. Red Blood Cells: Red blood cells or RBC are also called erythrocytes. They are the most common type of blood component. About 45% of it make up the blood. They are produced inside the bone marrow. They are disk-like structures that are biconcave in shape. Where the centre of the disk is thinner when compared to the edges. This unique feature of erythrocytes makes them acquire more volume thereby increasing the ratio of surface area to volume. They lack in nucleus hence there is no DNA content. They consist of a specialized pigment called haemoglobin that supplies oxygen to the blood. The pigment is made up of iron and proteins thereby increasing the oxygen-carrying capacity. The high surface area to volume ratio helps to transfer oxygen into the cell in the lungs and out of the cell in capillaries.

  2. White Blood Cells: The white blood cells or WBC are called leukocytes. They are in very small amounts in the bloodstream but perform important functions. They can further be divided into granular leukocytes and agranular leukocytes.

  • Granular Leukocytes: Depending on the presence of chemical-filled vesicles. It can further be subdivided into three types, neutrophils, basophils, and eosinophils. Neutrophils consist of digestive enzymes that can neutralize body invading bacteria. Basophil releases a chemical called histamine that helps and protect the body from infections. Eosinophils consists of specialized digestive enzymes that can digest the viruses bound by antibodies. 

  • Agranular Leukocytes: They include lymphocytes and monocytes. Lymphocytes are a combination of t-cells and natural killer cells and b-cells. T-cells and natural killer cells aim at fighting off viral infections. B-cells produce antibodies against pathogens. Monocytes develop themselves in the form of macrophages. These macrophages ingest the pathogens or the dead cells around the wound.

  1. Platelets: They are also called thrombocytes. These are responsible for the clotting of blood and the formation of the protective tissue called scab. The large megakaryocyte cells in the bone marrow that rupture periodically. These ruptured pieces are converted to form platelets. They lack in the nucleus. 

  2. Plasma: The liquid portion of the blood that makes up about 55% of the volume. The mixture of proteins, water and dissolved substances are combined to form plasma. The water content in the plasma varies depending upon the hydration level of an individual. The proteins in the plasma are made of albumin and antibodies. Albumins provide an isotonic solution to the body hence maintaining the osmotic balance of the body. Plasma acts as a transport medium to move substances throughout the body.


Cardiovascular System Function

The main functions of the cardiovascular system can be divided into three subcategories:

  1. Transportation: As the name implies it transfers oxygenated and deoxygenated blood heart to other parts and back from other parts of the body to heart. It transports oxygen and essential nutrients and removes waste products and carbon dioxide from the body. Whereas the plasma helps to transport the hormones in the body.

  2. Protection: The white blood cells present in the human circulatory system helps to protect the body from infections. They clean the debris and fight against pathogens. They can also form scabs in order to seal the wounds. Thus the entry of pathogens into the body is restricted. 

  3. Regulation: The vascular system acts as a tool to monitor the ability of the body to maintain hemostasis. They are also responsible for maintaining a stable body temperature. When the blood is overheated the blood vessels that are present near the surface of the skin open up to dump the excess heat to the surroundings. This condition is called hyperthermia. Whereas hypothermia refers to the constriction of the blood vessels. 


Effect of exercise on Cardiovascular System

The key benefits of exercising on a regular routine can control or modify heart-related problems. The key benefits are:

  • It lowers blood pressure.

  • Reduces the risk of developing diabetes.

  • Improves the ability of the muscles to pull oxygen out of the blood. Hence the pressure on the heart to supply oxygen to the body could be reduced.

  • It can keep an eye on reducing the dress causing hormones hence relieving the extra burden on the heart.

  • It can improve the amount of good cholesterol in the body.

FAQs (Frequently Asked Questions)

1. What is cardiovascular system? Write down cardiovascular system organs.

Ans: The circulation of the blood takes place in order to transport essential substances such as oxygen, nutrients, and hormones to the cells. And removes the waste materials from the body. This process is called the circulatory system or cardiovascular system or vascular system. 


It takes place with the help of a heart, the powered organ that looks after all the functions. The blood vessels, which help in transportation. The circulatory systems, that follow the pattern of the process of circulation. And the blood, which flows through all these organs to supply essential substances.

2. What is hemostasis?

Ans: Hemostasis is also known as clotting of blood and formation of scabs. The platelets in the human body remain inactive until they reach any wound or damage. Then they become active and turn in the form of a spiny ball and thick in texture. Hence they release the chemical clotting factors and produces fibrin. It is a protein that acts as a structure for blood clots. Then the platelets start combining to form a platelet plug. It acts as a seal temporarily to prevent the blood from flowing out of the blood tissue and germs entering the body.

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