Circulatory System

All living organisms require a few fundamental elements like food, water, and air to support their life. On a daily basis, we ensure these elements by eating, drinking and breathing. In order to utilize these elements in our body cells, they need to be transported to them. Let’s learn about the human circulatory system and its components which serve as the transportation system in our body.

Circulatory system

A network of organs that allow the circulation of blood throughout the body is also known as the cardiovascular system or vascular system. The vital function of the circulatory system is to transport blood to all parts of the body, which is extremely important because it carries nutrients, oxygen, carbon dioxide, hormones and blood cells which are required for the nourishment and growth the cells of every organ.
It is a closed network consisting of four major components:

  • The heart
  • Blood
  • Blood vessels

These four, with the help of certain other organs such as the lungs, are responsible for the circulation of blood in the human body.
Circulatory System
Major Components of the human circulatory system are mentioned below.

  • The Heart

The heart is a muscular organ, located roughly at the body’s midline in the thoracic region, and responsible for the pumping of blood in the body. The heart is divided into four chambers: Right atrium, right ventricle, left atrium and left ventricles. The atriums collect the blood in the heart and the ventricles pump it to different organs.

The Heart

  • Blood

Blood is a fluid connective tissue which plays an essential role in the circulatory system. It carries oxygen and nutrients to all parts of the body. It also regulates the temperature and acidic balance of the body.
Types of blood circulation

  1. The systemic circulation:

It carries oxygenated blood from the heart to all parts of the body through a complex system of arteries and capillaries. It also carries deoxygenated blood from these organs back to the heart through veins.

  1. The pulmonary circulation:

After the heart receives the deoxygenated blood from different parts of the body, it pumps those to the lungs for expelling the carbon dioxide and other impurities and collect oxygen, after which the oxygenated blood is sent back to the heart for systemic circulation.

  • Blood Vessels

Blood Vessels
There are three types of blood vessels in the human body:

  1. Artilleries– They carry blood away from the heart. The arteries in the systemic loop carry oxygenated blood to different parts of the body while the ones in the pulmonary loop carry deoxygenated blood to the lungs.
  2. Veins– They carry deoxygenated blood from the body and oxygenated blood from the lungs into the heart.
  3. Capillaries– Arteries break down into a minuscule network of capillaries, which are the smallest blood vessels and present in the lungs and muscles.


Types of Circulatory System

Open Circulatory System
In the open circulatory system, blood flows from lacunae, large open spaces and through sinuses among the tissues. Blood comprises very low pressure in this system. They are usually found in higher invertebrates namely insects, prawns, etc. Tissues are in direct contact with the blood. Exchange of nutrients and gasses takes place between the tissue and the blood directly. The flow of blood cannot be stopped as it flows in open space. The respiratory pigment is present in the blood flowing through this system is dissolved in plasma. Red Blood Cells are not present.

Closed Circulatory System
The blood does not come in direct contact with tissue. Blood comprises very high pressure in this system. This circulatory system is found in molluscs, echinoderms and in all vertebrates. The respiratory pigment is present in the blood flowing through this system is found in Red Blood Cells. Closed Circulatory System is more efficient as the volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels.
The flow of blood is quite rapid in this system. In the closed circulatory system, blood flows through a closed system of chambers the heart and blood vessels. Nutrients and gasses pass through the capillary wall to the tissue fluid.   Lymphatic System comprises a fluid known as lymph, lymph capillaries and lymph ducts. It is an extension of the circulatory system.

  1. Lymphatic Ducts or Vessels: They are present in various parts of the body. They consist of all the three layers namely tunica internal, tunica media and tunica external. These vessels are like veins.
  2. Lymph: All vertebrate possess a lymphatic system. It can be defined as blood minus RBC’s. It is a yellowish fluid present in the lymph vessels.
  3. Lymph capillaries: Small, thin, lined by endothelium resting on a basement membrane. One end unites to form lymphatic ducts and one end is blind.

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