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Overview of Circulatory System

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  • Last Updated : 27 Jul, 2022
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The circulatory system is a network of organs that permit the circulation of blood. The circulatory system’s other name is the Cardiovascular system or the vascular system. The primary function of the circulatory system is to transport blood to each part of the body. It is necessary because it carries nutrients, oxygen, carbon dioxide, hormones, and blood cells that are necessary for the hydration and growth of each organ’s cell population.

The Blood circulatory systems are many of the most important processes of the body because they deliver required amounts of oxygen in every portion of the body. The arteries transport the oxygenated blood from the heart to the body parts. Oxygen is provided to the body through diffusion and the blood becomes deoxygenated. This deoxygenated blood is carried return to the heart for oxygenation. This process known as blood circulation occurs continuously in all vertebrates.

Biology is part of many competitive exams SSC CGL, UPSC, SSC CPO, and Railways. We have written depth notes on the circulatory System To help you understand the Human Circulatory System in a much better way. To know more about Circulatory System which is mentioned below.

Organs of the Circulatory System : 

The four primary organs that make up the human circulatory system each perform a unique function. The essential organs of the circulatory system are: Heart, Blood, Blood Vessels, Lymphatic system

1. Heart

The human heart is a primary organ in the circulatory system. The human heart is placed in the front of your chest. It sits slightly beyond and to the left of your sternum (breastbone).  the heart is a muscular organ. It is surrounded by the pericardium and is located in the thoracic region with a slight leftward tilt. The four chambers of the human heart are divided into two upper chambers termed atria (plural: atrium) and two lower chambers known as ventricles.

Deoxygenated blood is collected by the heart, recycled through the lungs, and then given to the body as oxygenated blood. As per Gray’s Anatomy, the heart measures 12 cm in length, 8.5 cm in width, and 6 cm in thickness. Additionally, the average weight of the heart is 230-280 g for women and 280-340 g for men.

2. Blood

Blood is the fluid connective tissue of the body and is an essential component of the circulatory system. Its major function is to transport nutrients, hormones, minerals, and other vital substances to various bodily areas. Blood travels via a specific network of passageways known as blood vessels. The heart is the organ responsible for pumping blood to various body parts. Human blood is made up of blood cells, blood plasma, proteins, and other mineral components like sodium, potassium, and calcium.

Plasma, which makes up 90% of the fluid portion of the blood, is what makes up blood The solid component of blood is made up of platelets, white blood cells, and red blood cells.

Types of Blood Cells

The human body consists of three types of blood cells, namely:

Red blood cells (RBC) / Erythrocytes
Red blood cells are primarily involved in carrying oxygen, nutrients, and other materials throughout the body. These blood cells also eliminate waste from the body.

White Blood Cells (WBC)/ leukocytes
White blood cells are specialized cells that serve as a body’s defense system. They provide immunity by preventing dangerous bacteria and harmful microorganisms.

Platelets / Thrombocytes
Cells called platelets aid in the formation of clots and stop bleeding. They take action at the wound or damaged site.

Blood vessels

Arteries and veins are the two primary types of blood vessels in the circulatory system of the body.

Veins :

Veins are one form of a blood vessel that returns deoxygenated blood from your organs back to your heart. Veins are each of the tubular branching vessels that transport blood from the capillaries toward the heart.

Arteries : 

The arteries are the blood vessels that transport oxygen-rich blood from the heart to the tissues of the human body. Each artery is a muscular tube lined by smooth tissue and consists of three layers: The intima, and the inner layer lined by a smooth tissue called the endothelium. Media is the middle layer that consists of elastic fibers that keep your blood flowing in one direction. Adventitia is the outer layer that consists of nerves and tiny vessels.

Capillaries :

Capillaries are tiny blood vessels that have thin walls. Organs and tissues can absorb oxygen and nutrients from the blood via the walls. The capillaries also play a role to keep waste products from your tissues.

Types of Circulatory System : 

Open Circulatory System :

In the open circulatory system, blood moves from lacunae, large open gaps, and by sinuses among the tissues. Blood comprises extremely low pressure in this system. They are typically found in higher invertebrates likely insects, prawns, etc. Blood is in intimate contact with the tissues. The exchange of nutrients and gases occurs between the tissue and the blood. Since blood circulates in a free environment, it cannot be prevented. Plasma contains dissolved respiratory pigment from the blood that is passing through this system. There are no red blood cells.

Closed Circulatory System :

A closed circulatory system is more efficient because the volume of blood can be controlled by the contraction and relaxation of the smooth muscles of the blood vessels. The flow of blood in this system is very fast. In a closed circulatory system, blood flows through a closed system of chambers of the heart and blood vessels. Nutrients and gases move from the capillary wall into the tissue fluid.

Features of Circulatory System :

The following are the key components of the human circulatory system:

  • The components of the human circulatory system are blood, the heart, blood vessels, and lymph.
  • Blood is circulated twice by the human circulatory system (double circulation), once for oxygenated blood and once for deoxygenated blood.
  • Two ventricles and two atrium chambers make up the four chambers of the human heart.
  • Blood vessels can be found throughout the human body, which is home to the circulatory system. These are made up of capillaries, veins, and arteries.
  • Transporting oxygenated blood and nutrients to every region of the body is the main purpose of blood vessels. It is also responsible for gathering metabolic wastes that must be eliminated from the body.
  • The vast majority of circulatory system diagrams do not visually convey their length. Theoretically, a human’s arteries, veins, and capillaries, if laid end to end, would theoretically equal 100000 kilometers.


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