Circulatory System [Parts and Functions] for kids

The Circulatory System for Primary school
Circulatory System Parts and Functions for Primary School
Circulatory System for kids

The Circulatory System Parts and Functions

What is the circulatory system? The circulatory system is one of the most important in our body. Nutrients must reach every cell in the body. For this, they use the circulatory system as a “means of transport”. It is responsible for distributing the blood throughout the body in order to feed it and collect waste. In this article you will find a summary of: The circulatory system for Elementary-level children.

The circulatory system never rests, and there are many substances that travel through the blood. The body needs to constantly distribute the nutrients obtained through the process of digestion. It also transports any waste that is created to the places where it will be disposed of.

What does the circulatory system do for the body?

The circulatory system connects all the cells of our body carrying oxygen, nutrients, water and eliminating the waste they produce.

What does the circulatory system do for the digestive system?

The circulatory system is closely related to the digestive system. Nutrients are absorbed through the digestive system. When the body needs proteins for the hair or your nails to continue growing, it conducts them through a red liquid that we call blood. It is the “means of transport” that the body uses to get nutrients to the exact place where they are needed. Substances that are not used are eliminated from the body through the circulatory system. Without the circulatory system, the digestive system would not be able to move the nutrients it absorbs.

Circulatory System: Parts and Functions

To fulfill its function and for the blood to circulate throughout your body, the circulatory system contains an “engine” (this is the heart, that works like a pump) and a set of tubes that run throughout the body.

Circulatory System: Organs

  • Heart.
  • Arteries.
  • Veins.
  • Capillaries.

We will explain each of them.

Circulatory System for 5th Grade

Circulatory System Diagram for kids
Circulatory System Diagram for kids

Parts of the Heart for Primary School

The heart is central to the human circulatory system, as it pumps blood throughout the body. It works like an “engine” driving blood through tubes called blood vessels. The heart is a muscle whose job it is to constantly “pump” to keep blood moving throughout the body. Blood circulates around a complex network of blood vessels that extends to all parts of the body.

Heart Function for Kids

The heart is shaped like an inverted cone and is the size of a fist. It is lined by a membrane called the pericardium. It is located between the two lungs, slightly inclined to the left of the mid-line of the body.

Human Heart Coloring Page for Kids

Human Heart coloring page for kids
Human Heart: Coloring page for kids

The heart is divided into four chambers: Two atria in the upper part and two ventricles in the lower part. Each atrium communicates with the ventricle on its same side through a valve. Blood passing through the left side carries oxygen and turns red. The one that circulates on the left is colored blue because it carries carbon dioxide. And they never mix!

  • Arteries: They are the blood vessels that carry blood from the heart to the organs.
  • Veins: They are the blood vessels that carry blood from the organs to the heart.
  • Capillaries: They are small vessels that connect arteries and veins.

What is Plasma?

Plasma is the largest part of your blood. It, makes up more than half of its overall content. When separated from the rest of the blood, plasma is a light yellow liquid. Plasma carries water, salts and enzymes. The main role of plasma is to take nutrients, hormones, and proteins to the parts of the body that need it. Blood contains a liquid part called plasma made up largely of water in which different types of cells float:

  • Red blood cells.
  • White blood cells.
  • Platelets.
What is Plasma? The Composition of blood for kids
What is Plasma? The Composition of Blood

Plasma is the often forgotten part of blood. White blood cells, red blood cells, and platelets are important to body function. This fluid carries the blood components throughout the body.

What are the organs and functions of the circulatory system?

Vessels that carry blood with oxygen are represented in red. The vessels that carry blood with carbon dioxide are represented in blue. Color the blood in the arteries red and the blood in the veins blue.

The Arteries

The arteries are tubes with elastic walls whose function is to expel blood from the heart. They leave the left ventricle conducting blood to all the organs of the body.

What are the Major Arteries of the Heart?

The main arteries are:

Pulmonary Artery: Comes out of the right ventricle and carrying blood to the lungs.

Artery Aorta: Comes out of the left ventricle and branches throughout the body.

Vein Characteristics

Veins are thin-walled tubes and not very elastic. Their function is to collect blood from the body to take it back to the heart.

What are the Main Veins of the Heart

  • Pulmonary Veins: There are four (4), two for each lung. They carry the purified blood to the left atrium and they are the only ones that carry arterial blood.
  • Coronary Veins: They bring blood from the walls of the heart.
  • Superior Vena Cava: Carries blood from the head, neck, upper limbs and thorax to the right atrium of the heart.
  • Inferior Vena Cava: Collects blood from the lower limbs, the pelvis and the abdomen.


Capillaries are very thin vessels that bathe the organs throughout the body and connect the arteries with the veins. The arteries divide and subdivide to form these fine vessels that penetrate all organs of the body. Capillaries, when rejoined, form veins and surround cells.

Blood Circulation Process in the Heart

The heart pushes the blood and the goal is to circulate the blood throughout the body. It is responsible for receiving it and through its movements, pumping blood throughout the body through the arteries and capillaries.

Heart function in Circulatory System: Heart's valves
Heart function in Circulatory System

What does Diastole and Systole mean?

The muscles of the heart constantly perform two movements called: diastole and systole.

  • In diastole, the heart widens and causes blood to enter the atria through the veins (vena cava and pulmonary) and pass to each ventricle on the same side.
  • In systole there is a contraction that causes blood to leave the ventricles through the two arteries (aorta and pulmonary).

Learn how the heart and blood vessels help the circulatory system move blood through the body.

The main parts of the heart are the atria, ventricles, and valves. Close your eyes and imagine yourself standing in your bedroom. Now imagine that you walk to the bathroom. Did you go through a door? Believe it or not, your heart is made up of parts much like the rooms and doors of your house.

The heart has four chambers, which are like rooms. Two cameras located above the other two. The upper chambers are known as the atria and the lower chambers are known as the ventricles. The atria and ventricles are located next to each other, so there is a right atrium and ventricle, as well as a left atrium and ventricle.

The heart has two atria and two ventricles communicated by valves.

Heart’s Valves

Like the doors of your house, valves open and close, controlling the flow of blood from one chamber to another and to the rest of the body. When a real door closes, there is a ‘thud’. Similarly, when the valves open and close, they make a noise similar to “lub-dub”. The sound of the heartbeat is really the sound of the valves opening and closing. Like most doors in your home, heart valves only open in one direction. These valves open in one direction and help direct the flow of blood.

What are the function of heart valves?

The atria are separated from the ventricles by the atrioventricular valves:

  • The tricuspid valve separates the right atrium from the right ventricle.
  • The mitral valve separates the left atrium from the left ventricle.

Two valves also separate the ventricles from the large blood vessels that carry blood leaving the heart:

  • The pulmonic valve is between the right ventricle and the pulmonary artery, which carries blood to the lungs.
  • The aortic valve is between the left ventricle and the aorta, which carries blood to the body.

So, let’s take a closer look at the exact path in which blood travels through the heart.

Read also: Respiratory System: Parts and Functions for Kids

Heart function in Circulatory System

To understand the path that blood travels, you must know that blood has two forms:

Oxygen -rich blood.

Oxygen- poor blood.

One of the purposes of the blood that circulates through your body is to supply oxygen to your tissues. For this reason, oxygen-poor blood must be converted to oxygen-rich blood.

Then, the oxygen-poor blood from the body flows into the right atrium. It passes through a valve into the right ventricle. The right ventricle pumps blood through another valve to the lungs. Like a car stopping to refuel on a road trip, your blood passes through your lungs to pick up oxygen.

Process of Blood Circulation: Major and Minor Circuit

In the human body, the blood circulation is closed, double and complete. It is carried out by means of two circulatory routes known as Major Circulation (systemic circulation) and Minor Circulation (pulmonary circulation)

The blood circulation for teens: Human Circulatory System
Human Circulatory System: The blood circulation

Characteristics of Human Circulation

Why is the Human Circulation Complete, Closed and Double?

Complete: Because oxygenated blood does not mix with blood containing carbon dioxide.

Closed: Because the blood never leaves the blood vessels.

Double: Because you can see two circuits: a minor or pulmonary one that goes from the heart to the lungs and back to the heart; and a major or systemic one that goes from the heart to the rest of the body and then to the heart.

Closed and open circulatory systems:

  • In closed circulatory systems, the heart pumps blood through vessels that are separate from the interstitial fluid of the body.
  • In an open circulatory system, the blood is not enclosed in the blood vessels, but is pumped into a cavity called a hemocoel.

Also read: The 5 Basic Food Groups

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