Circulatory System

Circulatory System

High School

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Learning Objectives

• Discuss why a circulatory system is essential for the survival of complex organisms.

• Compare and contrast the features of single and double circulatory systems.

• Explain the main advantages of having a double circulatory system.

• Label the different parts of the human heart and trace the path of blood.

Key Vocabulary

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Circulatory System

The circulatory system is a network that transports blood, oxygen, and nutrients throughout the body.

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Double Circulation

A system where blood passes through the heart twice for each complete circuit of the body.

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Arteries

Arteries are thick-walled vessels carrying oxygen-rich blood away from the heart under high pressure.

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Veins

Veins are thin-walled blood vessels with valves that carry deoxygenated blood back to the heart.

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Septum

The septum is the muscular wall that divides the heart's left and right sides.

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Capillaries

Capillaries are the smallest blood vessels with thin walls, allowing easy diffusion of oxygen to cells.

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The Circulatory System

• The circulatory system is the body's essential transport and delivery network.

• ​It delivers oxygen and nutrients to cells and removes carbon dioxide waste.

• This system also plays a crucial role in regulating your body temperature.

• Its main components are the heart, blood vessels, and the blood.

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Multiple Choice

What are the three main components of the circulatory system?

• Brain, Spinal Cord, and Nerves

• Heart, Blood Vessels, and Blood

• Heart, Lungs, and Blood

• Lungs, Arteries, and Veins

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Double Circulatory System: An Efficient Design

Pulmonary Circulation

• This circuit carries deoxygenated blood from the heart to the lungs.

• In the lungs, the blood releases carbon dioxide and collects oxygen.

• The newly oxygen-rich blood then travels back to the heart.

Systemic Circulation

• This circuit pumps oxygenated blood from the heart to the entire body.

• It delivers oxygen and essential nutrients to every organ and tissue.

• Deoxygenated blood from the body returns to the heart to be sent to the lungs.

Multiple Choice

Which circuit in the double circulatory system is responsible for sending blood to the lungs to pick up oxygen?

• Pulmonary Circulation

• Single Circulation

• Systemic Circulation

• Coronary Circulation

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The Chambers of the Heart

Atria

• ​These are the two upper chambers of the heart that receive incoming blood.

• ​​They have thin muscular walls because they only pass blood to the ventricles below.

• ​The atria collect blood returning to the heart from the lungs and other body parts.

Ventricles & Septum

• ​These are the two lower chambers with thick walls for pumping blood out.

• ​​The left ventricle's wall is thicker because it pumps blood to the entire body.

• ​The septum is a wall that divides the heart and prevents blood from mixing.

Multiple Choice

Why is the wall of the left ventricle thicker and more muscular than the right ventricle?

• It needs to hold a larger volume of blood.

• It has to pump blood to the entire body at high pressure.

• It is where the pacemaker is located.

• It receives blood directly from the lungs.

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The Heart's Controls: Valves and Pacemaker

Heart Valves

• The heart has four valves that act like one-way doors, controlling the direction of blood flow.

• Their main job is to ensure blood flows in the correct direction and to prevent it from flowing backward.

• These valves are the tricuspid, bicuspid (mitral), pulmonary, and aortic valves.

Pacemaker

• The pacemaker is a small patch of muscle tissue located in the wall of the right atrium.

• It controls the heart's rhythm by generating electrical impulses that cause the heart muscle to contract.

• This contraction pumps blood from the heart to the rest of the body, creating your heartbeat.

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Solved Example 1
A patient's heart pumps 2,000 gallons of blood daily. If their heart beats 70 times per minute, what is the volume of blood pumped with each beat (stroke volume) in gallons? (1 day = 1440 minutes)

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Step 1: Analyze and Sketch the Problem

• Goal: Calculate the stroke volume in gallons per beat.

• Knowns: Total volume per day = 2,000 gallons, Heart rate = 70 beats/minute, 1 day = 1440 minutes.

• Unknown: Stroke volume (gallons/beat) = ?

• Formula: Stroke Volume = Total Volume / Total Beats

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Solved Example 1
A patient's heart pumps 2,000 gallons of blood daily. If their heart beats 70 times per minute, what is the volume of blood pumped with each beat (stroke volume) in gallons? (1 day = 1440 minutes)

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Step 2: Solve for the Unknown

• First, find the total number of heartbeats in a day: 70 beats/minute × 1440 minutes/day = 100,800 beats/day.

• Next, calculate the stroke volume by dividing the total volume by the total beats: Stroke Volume = 2,000 gallons / 100,800 beats ≈ 0.0198 gallons/beat.

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Solved Example 1
A patient's heart pumps 2,000 gallons of blood daily. If their heart beats 70 times per minute, what is the volume of blood pumped with each beat (stroke volume) in gallons? (1 day = 1440 minutes)

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Step 3: Evaluate the Answer

• To verify, multiply the stroke volume by the total daily beats: 0.0198 gallons/beat × 100,800 beats/day ≈ 1995.84 gallons.

• This value is approximately 2,000 gallons, confirming the answer is reasonable.

Multiple Choice

What is the primary function of the heart's valves?

• To control the heart's rhythm

• To separate oxygenated and deoxygenated blood

• To prevent the backflow of blood

• To pump blood out of the heart

Types of Blood Vessels

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Arteries

• Carry oxygen-rich blood away from the heart under high pressure.

• They have thick, muscular walls to withstand this high pressure.

• The pulmonary artery is an exception, carrying deoxygenated blood to the lungs.

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Veins

• Carry deoxygenated blood from the body back toward the heart.

• They have thinner walls and operate under much lower blood pressure.

• Valves prevent backflow; the pulmonary vein is an exception.

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Capillaries

• These are the smallest and most numerous blood vessels in the body.

• Their walls are extremely thin, often only a single cell thick.

• This allows for easy diffusion of oxygen and nutrients into cells.

Multiple Choice

Which feature is unique to veins compared to arteries?

• They have thick, elastic walls.

• They contain valves to prevent backflow.

• They carry blood away from the heart.

• They operate under high pressure.

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The Path of Blood Flow

Deoxygenated Blood

• ​Blood that is low in oxygen comes from the body into the right atrium.

• ​​The right ventricle pumps this blood to the lungs through the pulmonary artery.

• In the lungs, carbon dioxide is removed, and the blood picks up fresh oxygen.

Oxygenated Blood

• ​Blood rich with oxygen returns from the lungs and enters the left atrium.

• ​​The left ventricle then pumps this blood into the aorta for body-wide distribution.

• ​This process ensures all organs and tissues receive the oxygen they need to function.

Multiple Choice

After leaving the lungs, where does oxygenated blood travel to next?

• Right Atrium

• Aorta

• Left Atrium

• Right Ventricle

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What Makes Up Our Blood?

• Plasma is the liquid that transports nutrients, sugars, hormones, and waste products.

• Red blood cells use hemoglobin to carry oxygen to all your body’s cells.

• White blood cells fight infections by destroying pathogens, sometimes using antibodies.

• Platelets are small cell fragments that form a plug or scab to clot blood.

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Solved Example 3
If a person has 5 liters of blood, and plasma makes up 55% of the total blood volume, how many liters of plasma do they have in their body?

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Step 1: Analyze and Sketch the Problem

• Goal: Calculate the volume of plasma in liters.

• Knowns: Total blood volume = 5 L; Plasma percentage = 55%.

• Unknown: Volume of plasma = ?

• Formula: Volume of Plasma = Total Blood Volume × (Plasma Percentage / 100)

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Solved Example 3
If a person has 5 liters of blood, and plasma makes up 55% of the total blood volume, how many liters of plasma do they have in their body?

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Step 2: Solve for the Unknown

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Solved Example 3
If a person has 5 liters of blood, and plasma makes up 55% of the total blood volume, how many liters of plasma do they have in their body?

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Step 3: Evaluate the Answer

• The calculated plasma volume is 2.75 L, which is 55% of the total 5 L blood volume.

• The answer is reasonable and correctly calculated.

Multiple Choice

Which component of blood is primarily responsible for fighting infections?

• Red Blood Cells

• Platelets

• White Blood Cells

• Plasma

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Heart Health: Artery Conditions

• Arteriosclerosis is when arteries become hard and narrow, restricting blood flow.

• This condition is often referred to as the 'hardening of the arteries'.

• Atherosclerosis is a type of arteriosclerosis caused by plaque build-up in arteries.

• Plaque is a sticky material made of fat, cholesterol, and other substances.

Multiple Choice

What is the key difference between arteriosclerosis and atherosclerosis?

• Arteriosclerosis affects veins, while atherosclerosis affects arteries.

• Atherosclerosis is a specific type of arteriosclerosis caused by plaque buildup.

• They are two terms for the exact same condition.

• Atherosclerosis is the hardening of arteries, while arteriosclerosis is the narrowing.

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Common Misconceptions About the Circulatory System

Misconception	Correction
Arteries carry oxygenated blood, and veins carry deoxygenated blood.	The pulmonary artery carries deoxygenated blood; pulmonary veins carry oxygenated blood.
Blood is blue when it does not have oxygen.	Deoxygenated blood is dark red. Veins appear blue due to light reflection.
The heart is located on the left side of the chest.	The heart is in the center of the chest, tilted slightly to the left.

Multiple Choice

Why is the human circulatory system referred to as a 'double circulatory system'?

• Because it serves two functions: transport and temperature regulation.

• Because there are two types of blood, oxygenated and deoxygenated.

• Because it has two hearts, one for each side of the body.

• Because blood passes through the heart twice for every one full circuit of the body.

Multiple Choice

What is the functional difference between the heart's septum and its valves?

• The septum pumps blood, while valves receive it.

• The septum separates blood types, while valves prevent backflow.

• The septum carries blood to the lungs, while valves carry it to the body.

• The septum controls heart rhythm, while valves filter blood.

Multiple Choice

A venomous snake bites a person on their left leg. Analyze the path the venom would take to first reach the heart.

• It would travel through the pulmonary vein to the left atrium.

• It would travel up through the inferior vena cava to the right atrium.

• It would enter the aorta and be pumped directly to the heart muscle.

• It would travel up through the superior vena cava to the left atrium.

Multiple Choice

If a blood clot completely blocks the pulmonary artery, predict the immediate effect on the blood composition in the aorta.

• The blood would become severely deoxygenated.

• There would be no change in the blood composition.

• The platelet count in the blood would increase.

• The blood would become overly oxygenated.

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Summary

• The circulatory system transports substances through a double loop pulmonary and systemic circuit.

• The heart's four chambers and valves ensure that blood flows in one direction.

• Arteries, veins, and capillaries transport blood, which has several vital components.

• Understanding the path of blood flow reveals how the entire system functions together.

Poll

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