Human Circulatory System | Parts, Functions, Types

The heart and brain are the most complex part of the human body. The heart is the circulatory system and regulates the circulation of blood to different parts of the body. Here we are discussing different parts of the Circulatory System, their functions, and types of circulation.

The cardiovascular system means the system of the heart and blood vessels of the human body. The term “cardiovascular” is a combination of two words; “Cardio” and “vascular”. The term “cardio” is derived from “cardiac” meaning Heart and the term “vascular” means blood vessels. So the name itself indicates’ that Cardiovascular System is the system of heart and blood vessels. The cardiovascular system is also known as the “Circulatory System”.

Human heart
Human Heart with parts label

The circulatory system is a network that carries blood throughout the body. The human circulatory system supplies the food and oxygen that is necessary for the body to survive. At the same time, it carries carbon dioxide and other waste materials away from the cells. The circulatory system also helps to regulate body temperature and carries substances that protect the body from disease. The circulatory system transports chemical substances called hormones, which help to regulate the activities of various parts of the body.

Parts of Circulatory System

1. The Heart

The heart is a hollow, muscular organ that pumps blood. It consists of two pumPs that lie side by side, These pumps relax when taking in blood and contract as they send out blood. The left side of the heart is a stronger pump than the right side. The stronger pump receives blood from the lungs and sends it to cells throughout the body. The weaker pump receives blood from the cells throughout the body and sends the blood to the lungs.

2. The Blood Vessels

Blood Vellsels are tubes that transport blood throughout the entire body. This is an essential’ function because blood delivers valuable nutrients to and removes wastes from our cells. The blood vessels form a complicated system of connecting tubes throughout the body. The three major types of blood vessels are:

a) Arteries: Arteries carry blood from the heart. Arteries are elastic vessels that transport blood away from the heart. Pulmonary arteries carry blood from the heart to the lungs, where oxygen is collected by red blood cells, Systemic arteries deliver blood to the rest of the body.

b) Veins: Veins are elastic vessels that transport blood to the heart.

c) Capillaries: Capillaries are extremely’ small vessels. They are located within the tissues of the body that transport blood from the arteries to the veins. The nutrients and oxygen exchange usually occurs in the capillaries

3. The Blood

The blood consists mainly of a liquid called plasma. Plasma is made mostly of water. It also contains proteins, minerals, and other substances. There are three types of elements in the blood. They are red blood cells, white blood cells, and platelets. Red blood cells carry oxygen and carbon dioxide throughout the body. White blood cells help to protect the body from disease. Platelets release substances that help to enable blood to clot’. Platelets help to prevent the loss of blood from injured vessels.

Functions Of Circulatory System

The circulatory system performs many vital functions. The circulatory system Is important to remove the wastes and toxins and many other processes, It also plays an important role in respiration by delivering oxygen to cells and removing carbon dioxide from them. During this process, the blood follows two routes. They are called

  • Pulmonary Circulation
  • Systemic Circulation.

We have two-circuit circulatory systems: one circuit is for pulmonary circulation (circulation to the lungs; Pulmo = lungs) and the other circuit is for systemic circulation (the rest of the body).Pulmonary Circulation

human heart internal
Human Heart Internal
human heart
Human Heart External

1. Pulmonary Circulation

Blood that has a low amount of oxygen is said to be deoxygenated. This blood has just exchanged oxygen for carbon dioxide across cell membranes and now it contains mostly carbon dioxide. Deoxygenated blood enters the right atrium through the superior vena cava and the inferior vena cava.

Superior means higher and inferior means lower. So the superior vena cava Is at the top of the right atrium and the inferior vena cava enters the bottom of the right atrium.

From the right atrium, the deoxygenated blood drains into the right ventricle through the right atrioventricular (AV) valve. It is called the atrioventricular because it is between the atrium and the ventricle. This valve is also referred to as the tricuspid valve because It has three naps in its structure. When the ventricles contract, the atrioventricular valve closes off the opening between the verticle and the atrium, so that blood does not flow back up Into the atrium.

As the right ventricle contracts, it forces the deoxygenated blood through the pulmonary semilunar valve and into the pulmonary artery. Semilunar means half-moon and refers to the shape of the valves. This is the only artery in the blood that contains deoxygenated blood. All other arteries contain oxygenated blood. The semilunar valve keeps blood from flowing back into the right ventricle once it is in the pulmonary artery. The pulmonary artery carries the blood that is very low in oxygen to the lungs, where it becomes oxygenated.

2. Systemic Circulation

Freshly oxygenated blood returns to the heart from the pulmonary veins. These are the only veins in the body that contains oxygenated blood. All other veins contain deoxygenated blood.

The pulmonary veins enter the left atrium. When the left atrium relaxes, the oxygenated blood drains into the left ventricle through the left atrioventricular valve. This valve is also called the bicuspid valve because it has only two flaps in its structure.

Now the heart really squeezes. As the left ventricle contracts, the oxygenated blood is pumped into the main artery of the body. This is the aorta, which is also the biggest artery. Blood passes through the aortic semilunar valve to reach the aorta, which serves to keep blood flowing from the aorta back into the left ventricle.

The aorta branches into other arteries and then they branch into smaller arterioles. The arterioles meet up with capillaries, which are the blood vessels where oxygen is exchanged for carbon dioxide.

Circulatory Process

  • Blood enters the right atrium.
  • Blood passes through valves (tricuspid) to the right ventricle.
  • The ventricle propels blood through the pulmonary vein to the lung where it drops off carbon dioxide and picks up oxygen.
  • Oxygenated blood enters the pulmonary artery empties into the left atrium.
  • Blood passes through valves (mitral valves) to the left ventricle.
  • The left ventricle pushes blood to the aorta.

Function Of Blood

  • It transports nutrients to the dissues of all the organs.
  • It carries the waste priducts away.
  • It transports oxygen to the tissues and carries carbon dioxide away.
  • It transports various substances around the body.
  • It provides antibodies body temperature.
  • It helps in healing of wounds.

Hope you have now a better understanding of how the human circulatory system works, functions, and types of the circulatory system of the human body. If you have any confusions and queries please comment down.


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