Cardiovascular System

Cardiovascular System

Middle School

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Learning Objectives

• Describe the heart's main functions and its role in the circulatory system.

• Explain the differences in structure and function between arteries and veins.

• Identify the main components of blood and describe their specific purposes.

• Explain the pulmonary and systemic circulation loops in the human body.

• List key practices for maintaining a healthy cardiovascular system.

Key Vocabulary

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Cardiovascular

Relating to the heart and the network of blood vessels that transport blood throughout the body.

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Atrium

An upper chamber of the heart that receives blood from the veins and pumps it to a ventricle.

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Ventricle

A lower chamber of the heart that receives blood from an atrium and pumps it into the arteries.

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Artery

A vessel that carries oxygenated blood away from the heart to the rest of the body.

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Vein

A vessel that carries deoxygenated blood from the body back towards the heart.

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Plasma

The yellowish fluid part of blood that holds the blood cells in suspension for transport.

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The Heart: Our Body's Engine

• The heart is the center of the cardiovascular system.

• It is made of a special cardiac muscle that beats automatically.

• It pumps blood with oxygen and nutrients to all of your cells.

• The pumped blood eliminates waste like carbon dioxide from your cells.

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Multiple Choice

What is the primary role of the heart in the cardiovascular system?

• To pump blood, delivering oxygen and nutrients to the body.

• To create the carbon dioxide that we exhale.

• To digest food and absorb nutrients into the blood.

• To store blood until the body needs it.

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Inside the Heart: Chambers and Valves

• Your heart is a fist-sized organ with four sections called chambers.

• The two upper chambers, the atria, receive blood coming into the heart.

• The two lower, muscular chambers, the ventricles, pump blood out.

• Four valves act like one-way doors to control blood flow direction.

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Multiple Choice

What is the function of the valves in the heart?

• To prevent blood from flowing backward.

• To pump blood out of the heart.

• To receive blood from the veins.

• To enrich the blood with oxygen.

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The Body's Highways: Arteries and Veins

Arteries

• ​Arteries are vessels responsible for carrying blood away from the heart to other parts of the body.

• ​​Their walls are thick, muscular, and elastic to handle blood that is under high pressure from the heart's pumping.

• ​The push of blood from muscular arteries creates the pulse that you can feel on your wrist or neck.

Veins

• ​Veins are the vessels that do the opposite of arteries, returning blood from the body to the heart.

• ​​Since blood pressure in veins is much lower, their walls are not as thick or muscular as artery walls.

• ​Superficial veins, found just under the skin, help release body heat, which helps to cool you down.

Multiple Choice

Which statement correctly compares arteries and veins?

• Arteries are thicker and more muscular than veins because they handle higher blood pressure.

• Veins carry blood away from the heart, while arteries carry blood to the heart.

• Arteries have valves to prevent backflow, while veins do not.

• Veins are always deep in the body, while arteries are superficial.

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Blood Composition and Circulation

Blood Composition

• ​About 55% of blood is a fluid called plasma, which carries all the blood components.

• ​​The other 45% consists of red blood cells, white blood cells, and platelets suspended in plasma.

• ​Red cells carry oxygen, white cells fight germs, and platelets help stop bleeding by forming clots.

Blood Circulation

• ​The Pulmonary Loop carries blood between the heart and lungs to pick up fresh oxygen (O₂).

• ​​This loop also helps the blood get rid of waste like carbon dioxide (CO₂) in the lungs.

• ​The Systemic Loop sends this oxygen-rich blood from the heart to the entire rest of the body.

Multiple Choice

What is the main function of the Pulmonary Loop?

• To take blood to the lungs to reload with oxygen.

• To send oxygen-rich blood to the entire body.

• To filter waste products out of the blood plasma.

• To deliver nutrients from food to the body's cells.

Keeping Your Heart Healthy

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Cardiovascular Exercise

• Get your heart rate up and breathe more heavily during exercise.

• Aim for at least 20 minutes of activity, four times a week.

• Good activities include walking, running, or playing sports with friends.

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Heart-Healthy Diet

• Focus on eating plenty of fruits, veggies, and whole grains daily.

• Include lean protein sources in your meals for muscle health benefits.

• It is very important to limit your sweets and sugary drinks.

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Proper Hydration

• Your body needs plenty of fluids, especially water, to work correctly.

• Drink water before, during, and after any physical activity you do.

• Staying hydrated prevents energy loss and improves your overall physical performance.

Multiple Choice

According to the recommendations for heart health, what should you do?

• Engage in at least 20 minutes of cardiovascular exercise four times a week.

• Avoid all sweets and fats entirely from your diet.

• Only drink water when you begin to feel thirsty.

• Focus on eating red meat and dairy products for protein.

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Common Misconceptions

Misconception	Correction
Arteries always carry oxygen-rich blood.	The pulmonary artery carries oxygen-poor blood from the heart to the lungs.
You only need to drink water when you feel thirsty.	Thirst is not a reliable sign of dehydration, so drink fluids regularly.
All veins are located deep within the body.	Superficial veins are located just under your skin and are often visible.
A healthy diet means you can never eat sweets.	A healthy diet is about balance. It is best to eat sweets in moderation.

Multiple Choice

Why do arteries need to be thicker and more elastic than veins?

• Because they must handle blood under high pressure from the heart's pumping action.

• Because they have to carry blood a longer distance throughout the body.

• Because they are responsible for helping the body to regulate its temperature.

• Because they contain valves that stop the flow of blood periodically.

Multiple Choice

How does the primary function of the pulmonary loop differ from the systemic loop?

• The pulmonary loop oxygenates blood, while the systemic loop delivers that oxygenated blood to the body.

• The pulmonary loop sends blood to the brain, while the systemic loop sends it everywhere else.

• The pulmonary loop carries nutrients, while the systemic loop carries oxygen.

• The pulmonary loop uses veins, while the systemic loop uses arteries.

Multiple Choice

A person's pulse is felt in the wrist, an area far from the heart. Based on this, what type of vessel is being felt and what does this imply about its structure?

• It is a muscular artery, which has a thick muscular layer to "push" blood along.

• It is a superficial vein, which is close to the skin to help regulate heat.

• It is an elastic artery, which needs to stretch to slow down the blood.

• It is a deep vein, which runs parallel to a major bone in the arm.

Multiple Choice

A doctor needs to draw a blood sample and chooses to use the superficial cubital vein in the elbow. Predict the most likely reason for choosing this vein instead of a nearby artery.

• Veins are under much lower pressure, making them safer and easier to draw blood from.

• Arteries in the arm do not contain red blood cells, which are needed for tests.

• Veins are more muscular, so they do not collapse when a needle is inserted.

• The blood in veins is always cleaner and free of waste products.

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Summary

• The heart's four chambers pump blood, oxygen, and nutrients through the body.

• Arteries carry blood from the heart, while veins return blood to it.

• Blood circulates in two loops and contains plasma, cells, and platelets.

• A balanced diet, exercise, and hydration keep your heart healthy.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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