Diagram of a Human heart and its structure and function

 Diagram of a Human heart and its structure and function

Heart diagram
Heart diagram


Hear is one of the most vital organs of the human body. It is impossible for any human being to survive without a heart as it pumps and circulates blood throughout the human body.


1.  Definition of Heart

2.  Position of Heart in the human body

3.  Shape and size of Heart

4.  Structure of Heart

5.  Function of heart

6.  Circulatory system

7.  Cardiac cycle

8.  Heart rate 

9.  Facts about heart

Simple heart diagram
Simple heart diagram


Definition of Heart

The human heart is a muscular organ that controls the circulatory system by pumps blood throughout the body by repeated rhythmic contraction. It also supplies oxygen and nutrients to the tissues and removes carbon dioxide and other wastes.

Anatomy of the heart

The anatomy of a heart includes its position in body, shape, size, etc. 

Position of Heart in the human body

position of heart in human body
position of heart in human body

The exact location of the heart in the human body is in the thoracic cavity, between the lungs. It is placed towards the left of the sternum or breastbone. 

Shape and size of Heart

The human heart is a cone-shaped hollow organ.  It is  10 cm in length. It is approximately the size of the owner’s fist. In females heart weight about 250-300 gm and in males 300-350gm.  

Structure of Heart

human heart diagram with label
human heart diagram with label

Heart is a four-chambered muscular organ situated in the pericardial sac. It is divided into 4 chambers, 2 ventricles and 2 atria. The ventricles are pump blood and atriums receive blood. The heart is also divided into the right heart and left heart. Each part consists of one ventricle and one atrium. Right and left heart are divided by septum, a muscular wall. 

external structure of Heart
external structure of Heart

The external structure of Heart

The heart is situated in the fluid-filled pericardial cavity. The membrane which constructs the walls and lining of the pericardial cavity called the pericardium. 

The pericardium builds an external cover around the heart. It protects the heart by lubricating the heart and preventing friction with surrounding organs. The pericardium also keeps the heart holding in its position and gives it a hollow space to expand itself when it is full.

The pericardium is constructed by two layers

  1. Visceral Layer: It forms the outer cover of the heart.

  1. Parietal Layer: It forms the pericardial sac.

The Heart Wall -

The heart wall is made up of three layers of tissue. 

  1. Epicardium – The outermost layer of the heart is Epicardium. It is composed of a thin-layered membrane.  This layer lubricates and protects the outer section of the heart.

  1. Myocardium – The middle layer of the Heart-Wall is made of a layer of special cardiac tissue called the Myocardium. 

It contributes to the thickness of the heart. It helps in the pumping action. This layer is supported by the network of fine fiber, called the fibrous skeleton of the heart. 

  1. Endocardium – Endocardiumis the innermost layer. It lines the chambers of the heart and covers valves of the heart. It is a thin and smooth membrane. it prevents the blood from sticking to the inner walls of blood vessels and allows smooth flow of blood.

Cross section of heart
Cross section of heart

Lateral section of heart
Lateral section of heart

The internal structure of the heart

The internal structure of the heart is construed by 4 chembers of the Heart, valves of the heart and blood vessels. 

Chambers of heart -

The heart is divided into 4 chembers.

  1. Left atrium

  2. Right atrium

  3. Left ventricle

  4. Right ventricle

Atria are blood receiving chembers. They are thin-walled and less muscular in nature. 

Ventricles are blood-pumping chembers. They push blood out of the heart for circulation. They are thick muscular walled large chambers. The right atrium receives corban dioxidized blood from the body through superior and inferior vena cava. 

The left atrium receives oxygenated blood from the lungs through the pulmonary vein. 

The left atrium and left ventricle make the left heart and the right atrium and right ventricle make the right heart. The right and left heart is separated by the septum. 

The wall of the ventricle has been made by a muscular ridge or projection that is known as columnae cornea. 

The cavity of ventricles is divided into smaller spaces by the Columnae cornea. These spaces are called fissures. 

Right heart chembers are comparatively smaller than chembers of the left heart. This size difference is based on their function. The right side supplies blood to pulmonary circulation while the left side supplies control blood circulation of the whole body. 

Valves of Heart

Valves are flap-like organs present between the veins in the cardiac chambers. They are made up of fibrous tissues. They make sure that the blood flows in a single direction and there is no backward flow of blood. 

There are two types of valves. This division is based on their function.

  1.  Atrioventricular valves- atrioventricular valves are situated between ventricles and atria. There are two atrioventricular valves present in the heart. The atrioventricular valve between the right ventricle and right atrium has three flaps because of that it is known as tricuspid valve. The other atrioventricular valve situated between the left ventricle and left atrium is known as the mitral valve. these valves open towards only one direction and prevent the backward flow of blood. These two valves are attached to the ventricle wall by chordae tendinae. 

  1. Semilunar valves- Semilunar valves are situated between vertical and artery. It is semilunar in shape. The left semilunar valve is known as the aortic valve and the right semilunar valve is known as the pulmonary valve.

Blood vessels

In humans, blood flows through a pipe-like hollow structure and that is called as blood vessels. These blood vessels make a closed circulation system in humans. 

There are mainly 3 types of blood vessels found in the human body. 

  1. Veins- Veins carry deoxygenated blood to the heart via inferior and superior vena cava.  and it eventually drains into the right atrium.

  2. Capillaries- these are tiny blood vessels that form a network between the arteries and veins.

  3. Arteries- arteries carry oxygenated blood from the heart to various body parts. Aorta is the largest artery. it divides into various smaller arteries throughout the body.

Function of heart

  1. The main function of the Heart is to pump blood throughout the body. 

  2. Receives deoxygenated blood from other parts of the body and sends it to the lungs. 

  3. Receive oxygenated blood from the lungs and send it to other parts of the body. 

  4. Maintain blood pressure in the body. 

  5. Pump hormones, nutrients and other necessary components to the whole body through blood. 

Circulatory system

circulatory system diagram
circulatory system diagram

Blood circulation in body
Blood circulation in body

Dual Circulatory system diagram
Dual Circulatory system diagram

simple circulatory system diagram
simple circulatory system diagram

The circulatory system is a system that consists of a network of arteries, veins, capillaries. The circulatory system permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and other vital components in the body to provide nourishment, develop immunity, stabilize temperature, maintain pH level, and homeostasis.

There are two types of circulation systems found in the human body. 

  1. Pulmonary circulation 

This circulation happens between the lungs and the heart. 

The heart receives the deoxygenated blood from the body in the right atrium. Through the tricuspid valve, this blood enters the right ventricle. From the ventricle, this blood flows to the pulmonary artery through the pulmonary valve.

And pulmonary artery carries this blood to the lungs. In the Lungs, the blood leaves carbon dioxide and gets oxygenated.

Then Pulmonary veins carry oxygenated blood to the left atrium of the heart.

  1. Systemic circulation

This circulation system happens between the heart and other parts of the body. From the aorta, blood flows into the branches of arteries that lead to all parts of the body. Then blood flows into Capillaries where exchange functions of cells take place.

  1. Coronary System

This circulation system happens within the heart. It supplies blood and other vital components of the heart itself. 

Cardiac cycle

Cardiac cycle
Cardiac cycle

Cardiac cycle systol diastole diagram
Cardiac cycle systol diastole diagram

The sequence of alternate contraction and relaxation of the atria and ventricles is known as the Cardiac cycle. This cardiac cycle is responsible for pumping blood. 

The period of contraction is called systole and the period of relaxation is called diastole. Systole and diastole happen in both the atria and ventricles. 

Heart rate 

Heart rate is one of the vital signs or factors of human health. It measures how many times the heart beats or contracts in 1 minute. 

Heart rate varies from person to person. It depends on various factors such as age, fitness, activity levels, another disease ( cardiovascular disease, high cholesterol, diabetes etc), air temperature, emotions, size of body, medications, etc. 

Facts about heart

Here are some amazing facts about the heart. 

  1. Human Arteries’ diameter is about 4 millimeters.

  2. The human Heartbeats nearly 100,000 times a day. 

  3. The heart pumps about two thousand gallons of blood every day. 

  4. Heart rate varies from person to person. 

  5. Heartbeat in females is slightly more than in males. 

  6. The opening and closing of valves make the sound of the heart. 

Hopefully, we provided the maximum of your queries about the heart and diagrams of the heart. We covered the human heart diagram and function, heart diagram labeled, structure and function of heart, human circulatory system diagram, heart cross-section diagram, etc. 

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