The Human Heart

Your heart is really a muscle. It’s located a little to the left of the middle of your chest, and it’s about the size of your fist.

The heart muscle is special because of what it does. The heart sends blood around your body. The blood provides your body with the oxygen and nutrients it needs. It also carries away waste.

Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.

Study the diagram below, and take the Quiz at the bottom of the page when you’re ready:

Videos to Watch:

Study Resources:

Facts About the Heart for Kids

Duckster: Blood and the Heart

New World Encyclopedia: Human Heart

Wikipedia: The Human Heart

The Circulatory System

About the Cardiovascular System

The human heart is one of the most important organs responsible for sustaining life. It is a muscular organ with four chambers. The size of the heart is the size of about a clenched fist.

The human heart functions throughout a person’s lifespan and is one of the most robust and hardest working muscles in the human body.

Besides humans, most other animals also possess a heart that pumps blood throughout their bodies. Even invertebrates such as grasshoppers possess a heart like pumping organ, though they do not function the same way a human heart does.

Did you know?!

  • The heart pumps around 6,000-7,500 litres of blood in a day throughout the body.
  • The heart is situated at the centre of the chest and points slightly towards the left.
  • On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
  • The average male heart weighs around 280 to 340 grams (10 to 12 ounces). In females, it weighs around 230 to 280 grams (8 to 10 ounces).
  • An adult’s heart beats about 60 to 100 times per minute, and a newborn baby’s heart beats at a faster pace than an adult which is about 90 to 190 beats per minute.
human-heart

1. What is pulmonary circulation?

Pulmonary circulation is a type of blood circulation responsible for carrying deoxygenated blood away from the heart, and to the lungs, where it is oxygenated. The system then brings oxygenated blood back to the heart to be pumped throughout the body.

2. Define systemic circulation.

In systemic circulation, the heart pumps the oxygenated blood through the arteries to every organ and tissue in the body, and then back again to the heart through a system of veins.

3. Elaborate on coronary circulation and its significance.

The heart is a muscle, and it needs a constant supply of oxygenated blood to survive and work effectively. This is where coronary circulation fulfils this function through a network of arteries and veins in the heart. The coronary arteries supply oxygenated blood to the heart, and the cardiac veins drain the blood once it has been deoxygenated by the tissues of the heart.

4. Briefly explain the structure of the human heart.

The human heart is divided into four chambers, namely two ventricles and two atria. The ventricles are the chambers that pump blood and atrium are the chambers that receive the blood. Among which, the right atrium and ventricle make up the “right portion of the heart”, and the left atrium and ventricle make up the “left portion of the heart.”

5. Name the chambers of the heart.

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle

6. What is pericardium? Explain its function.

The pericardium is a fibrous membrane that envelops the heart. It also serves a protective function by producing a serous fluid, which lubricates the heart and prevents friction between the surrounding organs. Furthermore, the pericardium also holds the heart in its position and provides a hollow space for the heart to expand and contract.

7. Explain the three layers of the heart wall.

The heart wall is made up of 3 layers, namely:

  • Epicardium – This is the outermost layer of the heart. It is composed of a thin layer of membrane that protects and lubricates the outer section.
  • Myocardium – This is a layer of muscle tissue that constitutes the middle layer wall of the heart. It is responsible for the heart’s “pumping” action.
  • Endocardium – The innermost layer that lines the inner heart chambers and covers the heart valves. Prevents blood from sticking, thereby avoiding the formation of fatal blood clots.

8. Explain the three major blood vessels of the human body.

The  blood vessels comprise:

  • Veins – It supplies deoxygenated blood to the heart via inferior and superior vena cava, eventually draining into the right atrium.
  • Capillaries – They are minuscule, tube-like vessels which form a network between the arteries and veins.
  • Arteries – These are muscular-walled tubes responsible for supplying oxygenated blood away from the heart to all other parts of the body.

9. What is the function of the heart valves? Provide examples of various valves.

Valves are flaps of tissues that are present in cardiac chambers between the veins. They prevent the backflow of blood. Examples include the atrioventricular valves, tricuspid valves, mitral valves and the semilunar valves.

10. What is meant by myocardial infarction?

Myocardial infarction is a serious medical condition where the blood flow to the heart is reduced or entirely stopped. This causes oxygen deprivation in the heart muscles, and prolonged deprivation can cause tissues to die.

Activities:
1. Can you identify the parts to the human heart? Take the Quiz
2. The Human Heart Word Search – Printable
3. Print, label the parts of the heart, and color: Heart Worksheet Page
4. Learn how to check your pulse (your heart rate)