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Heart: Structure & Its Functions

Raina Rahul Agarwal 5 Jan, 2023 Health & Fitness No Comments


The heart is one of the essential organs of the body. It plays a vital role in the cardiovascular system- a network of blood vessels that pumps blood throughout the human body. The heart is a muscular organ and its size is about an adult’s clenched fist. The heart is a mesodermally derived organ located in the thoracic (chest) cavity in between the two lungs. It is slightly tilted to the left lung. The human heart functions throughout a person’s life span and it is one of the most robust and hard-working muscles in the human body. Besides human animal also possesses a heart.

What Is Heart?

Structure Of Heart:

The heart is divided into four chambers namely: Two Ventricles and Two Atriums. The heart has a right and left side separated by a wall called the septum.  Among these, both the right atrium and ventricle make up the “right heart” and the left atrium and ventricles make up the “left heart”. The left atrium and right atrium are the upper chambers. The left ventricle and right atrium comprise the lower chamber. The ventricles are the chambers that pump blood and the atrium are the chambers that receive blood.

  • The right atrium receives blood from the veins and pumps it to the right ventricles.
  • The right ventricle receives blood from the right atrium and pumps it to the lungs.
  • The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricles.
  • The left ventricle pumps oxygenated blood to the rest of the body.

External Structure Of Heart:

The heart is enclosed within a fluid-filled cavity called a pericardial cavity and the membrane of the pericardial cavity is known as the pericardium. The pericardium has two layers:

Visceral Layer: Visceral Layer directly covers the outside of the heart.

Parietal Layer: Parietal layer forms a sac around the outer region of the heart.

The heart wall is made up of 3 layers:

Epicardium: It is the outermost layer of the heart composed of the thin layered membrane that serves to lubricate and protect the outer section.

Myocardium: This is a layer of muscle or tissue and constitutes the heart’s middle layer wall. It contributes to the thickness and is responsible for the pumping action.

Endocardium: The endocardium is the innermost layer of the heart chambers and covers the heart valves. It prevents the blood from sticking to the inner wall.

Internal Structure Of The Heart:

Chambers Of The Heart:

Mammalian hearts consist of four chambers:

  1. Right Atrium
  2. Left Atrium
  3. Right Ventricle
  4. Left Ventricle
Heart chamber of the heart
SOURCE: Donna Van Wynsberghe, et al (1995). Human Anatomy & Physiology, 3rd Ed. “Anatomy of the Heart,” Ch. 20, page 620, Fig 20.5A.

Atria: Atria are thin and have less muscular walls. Atria are smaller than the ventricle. Atria are the blood-receiving chambers.

Ventricles: Ventricles are thick and more muscular chambers. It is responsible for pumping and pushing blood out into circulation.

  • A thin, muscular wall called the interatrial septum separates the right and the left atria.
  • A thick-walled, inter-ventricular septum, separates the left and the right ventricles.
  • The atrium and the ventricle on the same side are also separated by a thick fibrous tissue called the atrioventricular septum.
  • The atrioventricular valves maintain unidirectional blood flow between the atria and ventricles.
  • Tricuspid Valve: The opening between the right atrium and the right ventricle is guarded by a valve formed of three muscular flaps or cusps, the tricuspid valve.
  • Mitral Valve: The AV valve on the left is the bicuspid or mitral valve.
  • A bicuspid or mitral valve guards the opening between the left atrium and the left ventricle.
  • A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN).
  • Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrioventricular septum called the atrioventricular node (AVN).
  • The pulmonary valve is located at the exit of the right ventricle.
  • The Aorta valve is located at the exit of the left ventricle.

Blood Vessels: 

Following blood vessels found in the circulatory system:

Veins: Veins carry deoxygenated blood and supply it to the heart via the superior and inferior vena cava.

Capillaries: Capillaries are tiny, tube-like vessels. It forms a network between the arteries to veins.

Arteries: These are muscular wall tube-like structures responsible for the transportation of blood to and from every organ in the body.

Disclaimer: All the content of this article is for information purposes only.


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Raina Rahul Agarwal
My name is Raina Agarwal, and I am a seasoned content writer with three years of experience in the field. Holding a master's degree in microbiology. I have also garnered valuable experience as a microbiologist, with a career spanning over a decade since 2011. My diverse professional background enables me to offer unique insights and perspectives in my content creation endeavours.

Raina Rahul Agarwal

A Non-Medical Scientist, BSL-2 Lab, Mirzapur

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