The Cardiovascular System

The Cardiovascular System

High School

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Learning Objectives

• Describe the function and primary organs of the cardiovascular system.

• Trace the path of blood through the heart’s chambers and valves.

• Compare the structure and function of arteries, veins, and capillaries.

• Identify the key components of blood and their primary roles.

• Explain how heart activity is regulated and list common cardiovascular disorders.

Key Vocabulary

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Pericardium

The double-layered sac forming the heart's outer layer, providing it with vital protection and support.

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Septum

A muscular wall that divides the heart, preventing oxygen-rich and oxygen-poor blood from mixing.

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Arteries

These are blood vessels with thick walls that carry oxygenated blood away from the heart.

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Capillaries

Microscopic vessels where gases, nutrients, and waste are exchanged between the blood and body tissues.

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Plasma

The liquid part of blood, mostly water, that transports cells and many other important substances.

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Cardiac Cycle

The sequence of events in one heartbeat, involving the heart muscle's contraction and subsequent relaxation.

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The Heart's Structure and Layers

• The heart is a fist-sized organ located between the lungs.

• A protective double-layered sac called the pericardium surrounds the heart.

• The muscular myocardium pumps blood; the endocardium provides a smooth inner lining.

• The heart has four chambers: two atria and two ventricles.

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Solved Example 1
An adult has a stroke volume of 70 mL/beat and a resting heart rate of 75 beats/minute. What is their cardiac output in L/minute?

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Step 1: Analyze and Sketch the Problem

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Solved Example 1
An adult has a stroke volume of 70 mL/beat and a resting heart rate of 75 beats/minute. What is their cardiac output in L/minute?

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Step 2: Solve for the Unknown

• Substitute the known values into the formula: CO = 70 mL/beat × 75 beats/minute = 5250 mL/minute.

• Convert milliliters per minute to liters per minute by dividing by 1000, since 1 L = 1000 mL: 5250 mL/minute ÷ 1000 mL/L = 5.25 L/minute.

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Solved Example 1
An adult has a stroke volume of 70 mL/beat and a resting heart rate of 75 beats/minute. What is their cardiac output in L/minute?

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Step 3: Evaluate the Answer

• The units were correctly multiplied and converted, resulting in the desired unit of L/minute.

• The average adult body contains approximately 4-6 liters of blood. A cardiac output of 5.25 L/minute means the entire blood supply circulates through the heart each minute, which is physiologically accurate for a resting adult. The answer is reasonable.

Multiple Choice

What is the primary function of the septum in the heart?

• To prevent the mixing of oxygen-rich and oxygen-poor blood

• To receive blood returning to the heart

• To form the protective outer layer of the heart

• To pump blood to the lungs

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Function of Heart Valves and Blood Flow

Right Side of the Heart

• The tricuspid valve is between the right atrium and the right ventricle.

• The pulmonary valve separates the right ventricle from the pulmonary artery.

• Deoxygenated blood is pumped from the right side of the heart to the lungs.

Left Side of the Heart

• The mitral valve is found between the left atrium and the left ventricle.

• The aortic valve is located between the left ventricle and the aorta.

• Oxygenated blood is pumped from the left side of the heart to the body.

Multiple Choice

After leaving the right ventricle, where does deoxygenated blood go next?

• To the left atrium

• To the lungs via the pulmonary artery

• To the aorta

• To the right atrium

The Blood Vessels

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Arteries

• Carry oxygenated blood away from the heart to the body.

• Their walls are thick and elastic to withstand high pressure.

• The largest artery in the body is called the aorta.

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Veins

• Carry oxygen-poor blood from the body back to the heart.

• Their walls are thinner and less elastic than artery walls.

• They contain valves that prevent the backward flow of blood.

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Capillaries

• These are microscopic vessels connecting arteries and veins.

• Their very thin walls allow for efficient exchange with cells.

• Oxygen and nutrients are exchanged for CO₂ and waste products.

Multiple Choice

Which statement accurately compares arteries and veins?

• Gas exchange occurs in both arteries and veins.

• Arteries have thick, elastic walls to handle high pressure, while veins have thinner walls and contain valves.

• Arteries have thinner walls and carry blood to the heart.

• Veins carry oxygenated blood away from the heart under high pressure.

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Components of the Blood

• Plasma is the liquid part of blood, transporting cells, proteins, and waste.

• Red blood cells use a protein called hemoglobin to carry oxygen.

• White blood cells are part of the immune system and fight infections.

• Platelets are small cell fragments that form blood clots to stop bleeding.

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Multiple Choice

Which component of blood is primarily responsible for transporting oxygen?

• Platelets (Thrombocytes)

• Plasma

• White Blood Cells (Leukocytes)

• Red Blood Cells (Erythrocytes)

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Cardiac Cycle and Regulation

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Multiple Choice

What is the role of the sinoatrial (SA) node in the heart?

• To separate the ventricles from the atria

• To pump blood into the aorta

• To slow down the heart rate during rest

• To act as the heart's natural pacemaker, initiating the electrical impulse

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Cardiovascular Diseases and Disorders

Diseases of the Arteries

• Hypertension is the medical term for consistently high blood pressure inside of the arteries.

• Atherosclerosis is a dangerous buildup of fatty plaque on the inside of the artery walls.

• An aneurysm describes a bulge or a weakened area that can develop within an artery wall.

Heart Wall & Valve Disorders

• Cardiomyopathy involves the weakening or thinning of the heart's muscular wall, affecting its pumping ability.

• Valvular dysfunction occurs when heart valves are leaky or don't close properly between heartbeats.

• A heart murmur is an unusual sound that is often caused by dysfunctional heart valves.

Multiple Choice

What is atherosclerosis?

• A weakening of the heart muscle

• A condition of consistently high blood pressure

• The buildup of plaque within the artery walls

• A leaky or improperly closing heart valve

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Common Misconceptions

Misconception	Correction
All arteries carry oxygen-rich blood, and all veins carry oxygen-poor blood.	The pulmonary artery carries oxygen-poor blood; pulmonary veins carry oxygen-rich blood.
A heart attack and cardiac arrest are the same thing.	A heart attack is a circulation problem; cardiac arrest is an electrical problem.
Blood inside the body is blue.	Blood is always red; it just appears blue through your skin.
Cardiovascular disease only affects older adults.	Plaque buildup can begin at any age, even in childhood.

Multiple Choice

Why does the left ventricle have a thicker muscular wall (myocardium) than the right ventricle?

• Because it needs to pump blood to the nearby lungs, which requires less force.

• Because it receives deoxygenated blood from the body, which is heavier.

• Because it contains the SA node, which adds to its mass.

• Because it must pump oxygen-rich blood to the entire body, which requires much greater force.

Multiple Choice

Which statement best describes the structural and functional differences between major arteries and veins?

• Arteries have thick, muscular walls for high pressure, while veins have thinner walls and valves for low-pressure flow.

• Veins have thick, elastic walls to handle high pressure, while arteries have valves.

• Both have identical structures, but carry different types of blood.

• Arteries carry blood towards the heart, while veins carry blood away and have thinner walls.

Multiple Choice

If a person's sinoatrial (SA) node completely fails, what is the most likely immediate consequence for the heart's rhythm?

• The heart would stop beating immediately and permanently.

• The ventricles would start contracting at a much faster rate than normal.

• The heart's rhythm would become perfectly regular but very weak.

• The AV node would likely take over as the pacemaker, resulting in a slower heart rate.

Multiple Choice

How can atherosclerosis in the coronary arteries directly cause a myocardial infarction (heart attack)?

• A piece of plaque can rupture, leading to a blood clot that completely blocks blood flow to a section of heart muscle.

• The plaque buildup electrically insulates the heart muscle, stopping its contraction.

• The plaque absorbs all the oxygen from the blood before it can reach the heart muscle.

• The hardened arteries increase blood pressure, causing the heart to overwork and fail.

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Summary

• The cardiovascular system circulates blood using the heart, arteries, and veins.

• The four-chambered heart pumps blood through pulmonary and systemic circuits.

• Blood’s components transport oxygen, fight infections, and enable clotting.

• Electrical signals regulate heart function; common disorders include hypertension and atherosclerosis.

Poll

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