What is human heart and its function?

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 Introduction

              Heart is a muscular organ which is responsible for the pumping of blood from heart to each and every cell of the body. It also transport oxygen, hormones, nutrients and immune cells to tissue and also it remove carbon dioxide and metabolic wastes.

The heart become functional before birth and it will stay active and functional till death. It perform its function by combining with the blood vessels that why there combine system is called cardiovascular system for more about blood vessels https://healthduhs.blogspot.com/2026/05/what-is-circulatory-system-and-human.html It is the  indirect  control center of the body because brain directly control the whole body through their nervous system but for the purpose of their controlling it require energy that energy it will get from blood without blood brain its self is nothing for the transmission of blood to brain our blood vessel play a vital and the heart which is most important they pump the blood to brain through their blood vessels that’s why we called it’s the indirect control center of the body.

Location   

              Heart is located in the thoracic cavity, inside the mediastinum between the lungs.

One third of the heart is located in the right side of the chest and two third is located in the left side and it rest on diaphragm..

The upper portion of the heart is called base and lower portion of the heart is called apex that is toward left side.

The position of heart start from the second number of ribs and its end in 5th number of ribs where its apex located.

Weight and size of heart

The size and weight of heart is different in male and female.

In male

              280-340 g

              12-13cm

In female

              230-280g

              11-12cm

Protective layers of the heart

There is a protective layer around the heart that is called pericardium which has further two layers

1.      Fibrous pericardium

It is the tough outer layer  which prevent the heart from overexpansion

2.      Serous pericardium

It further divide into two layers

·       Parietal layer

·       Visceral layer

Between these two layers there is a fluid called pericardial fluid

This reduce the friction between heart and outer layer  and also maintain the position of heart and it also prevent sudden dilation of heart.

 Walls of the heart

When move inward from protective layer the wall of heart start it has further three layers.

1-      Epicardium

It is the outermost layer of heart which is also called visceral layer of serous pericardium they contain blood vessels, fats and nerves.

2-      Myocardium

It is the middle layer of heart which is made up of cardiac muscle fibers which is responsible for the contraction and  pumping of blood and it is the thickest layer of heart

3-      Endocardium

It is the inner most layer of heart which is made up of endothelial tissues which helps the flow of blood smoothly.

              Heart chambers

 There are four chambers of heart

1-      RIGHT ATRIUM

It receive the superior and inferior vena cava which contain deoxygenated blood after receiving  transfer it into right ventricle

2-      LEFT ATRIUM

It receive oxygenated from heart through four pulmonary vein which drain that blood into the left atrium it pass the blood into the left ventricle

3-      RIGHT VENTRICLE

Right ventricle transfer deoxygenated blood to the lung for the purpose of oxygenation  through two pulmonary artery 

4-      LEFT VENTRICLE

It receive oxygenated blood from left atrium and transfer the blood to each and every cell of the body.

Valves of the heart

There are two valves in the  heart between the chamber which help in the flow of blood in one direction

1-      Atrioventricular valve

·       Tricuspid valve

It is present between right atrium and right ventricle which the backflow of blood from right ventricle into right atrium and also prevent the leakage of blood into right ventricle from right atrium.

·       Bicuspid valve

It is present between left atrium and left ventricle which the backflow of blood from left ventricle into left atrium and also prevent the leakage of blood into left ventricle from left atrium

2-      Semilunar valve

·       Pulmonary valve

It is present between right ventricle and two pulmonary artery which prevent the backflow of blood from pulmonary artery  into right ventricle

·       Aortic valve

It is located between left ventricle and aorta it prevent the backflow of blood from aorta into the left ventricle.

Conducting system of the heart

Conducting system of the heart is the system which control the process of beating of heart in these beating heart pumps blood from heart to the body  that beating is controlled by its own system that is called conducting system of the heart.

It has further division

1-      SA node ( Sinoatrial Node )

It is located in the right atrium of the heart which generate electrical impulse In normally 60-100 beat/min. it is also called the natural pacemaker of the heart.

2-      AV node ( Atrioventricular Node )

It allows atrial contraction before ventricle contraction

3-      Bundle of his

It distribute impulse to interventricular septum

4-      Right and left bundle branches

transmit impulses through ventricle

5-      Purkinjie fiber

  Distribute impulse to ventricular myocardium

 

Pattern of blood flow in heart

1-      From throughout the body it received by superior and inferior vena cava

2-   1-       Right atrium

3-     2-     Right ventricle

4-     3-     Two pulmonary artery

5-   4-       Lung for oxygenation

6-    5-      Through four pulmonary vein oxygenated blood into the heart

7-   6-       Left atrium receive oxygenated blood

8-    7-      Left ventricle

9-    8-      Aorta which supply to whole body

   Nervous system which control the heart

Sympathetic system

It increase heart beat and conduction rate of heart. Here two  neurotransmitter epinephrine and nore-epinephrine play a vital role

Parasympathetic system

It decrease heart rate and conduction speed of heart. Here a  neurotransmitter acetylcholine play its function

for more about nervous system https://healthduhs.blogspot.com/2026/05/what-is-nervous-system-and-how-it-is.html

What is cardiac cycle?

The whole process which happen inside  the heart during one heart beat is called cardiac cycle.

There are four phases

1-        Atrial systole

In this phase atria contract and transfer its blood into ventricle

2-      Ventricle systole  

in this phase ventricle contract and eject blood out from the  heart

3-      Atrial diastole

In this phase atria relax and it is the refectory period.

4-      Ventricle diastole

It is the phase where ventricle relax and that is its refectory phase.

 reference

WHO -World Health Organization

NIH- National Institute Of Health)

 CDC- Centre for Disease Control and prevention


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