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Blood Blood is the fluid that circulates in the heart, arteries, veins and capillaries of the body. Blood carries nutrients, oxygen and hormones throughout the body using a vast network of blood vessels. Not only does blood carry nutrients to the body’s cells, it also transports waste products away from them. Blood also plays a crucial role in fighting infection.

Blood transport is dependent upon the cardiovascular system. The cardiovascular system is comprised of the heart (a muscular pump) and blood vessels—arteries, veins and capillaries. It is a closed circulatory system with two important “loops” through the body.

The first loop involves pulmonary circulation: blood leaves the heart to pick up oxygen from the lungs and then returns this oxygenated blood back to the heart. The heart then circulates this freshly oxygenated blood to the body’s organs, muscles and tissues. This second loop is referred to as systemic circulation.

Module 8—Disease Control and PreventionLESSON 8.5 — The Cardiovascular System

Essential HealthCopyright © Human Relations Media

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The Cardiovascular System LESSON 8.5

THE CARDIOVASCULAR SYSTEM12 page student lesson - 1 of 12

Did You Know?The cardiovascular system is comprised of the heart, arteries, veins and capil laries.

Cardiovascular System

There are three important types of blood cells—red blood cells, white blood cells and platelets—all suspended in plasma, the fluid part of blood.

Red blood cells get their bright red color from the oxygen they collect in the lungs. Each red blood cell can survive only a few months, but the body is constantly producing new ones. These cells are important because they deliver oxygen to our tissues and muscles.

White blood cells are known for their infection-fighting properties. There are far fewer white blood cells than red blood cells. However, when a person contracts an infection, the body increases its production of these infection fighters.

Platelets are cells that help with clotting. When a blood vessel gets torn or cut, platelets gather in the area and close up the wound. For larger injuries, other clotting factors—and sometimes stitches—are needed to help with healing.

Quick Notes

blood carries oxygen, important

nutrients and hormones

though a network of vessels

supported by the heart and

cardiovascular system

cardiovascular system a closed circulatory system

that includes the heart and

blood vessels (arteries, veins

and capillaries)

pulmonary circulation the route taken when blood

exits the heart, is oxygenated

in the lungs and returns back

to the heart

systemic circulation the route taken when freshly

oxygenated blood travels

from the heart to the body’s

organs, muscles and tissues

LESSON 8.5 The Cardiovascular System

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The Heart

The heart is a muscle composed of four hollow chambers—two atria at the top and two ventricles at the bottom—separated by different valves that open and shut as necessary. These compartments are used to collect and pump blood out to the body. The heart is about as big as a clenched fist and is located in the chest cavity between the lungs.

Continued on the next page



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THE HEART3 of 12

The Heart

Did You Know?Your heart beats about 100,000 times a day. By the time you reach your 70th birthday, your heart wil l have logged approximately

2.5 bil l ion beats!

Blood VesselsArteries, veins and capillaries are the three types of blood vessels in the cardiovascular system. Arteries carry blood away from the heart to the rest of the body. Arteries have thick, elastic walls that are strong enough to handle the heart’s pumping rate.

The main arteries are the aorta, which carries blood from the left ventricle to the body and the pulmonary artery, which carries deoxygenated blood from the right ventricle back to the lungs to receive fresh oxygen. As blood makes its way throughout the body, the arteries branch off into smaller vessels called arterioles. Healthy arteries and arterioles are crucial to proper blood circulation.

Veins carry blood from the body back to the heart. They are not as strong as arteries, but they contain special valves that prevent the blood from flowing back and pooling in the lower extremities due to gravity.

Arteries and veins are connected by tiny vessels called capillaries. Capillaries act as middlemen, distributing the nutrients and oxygen from arterioles to our tissues and then removing the deoxygenated blood and waste and passing it along to the veins to be returned to the heart and lungs. Although capillaries are microscopic, they play a big role in the circulatory system.


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Did You Know?If al l the blood vessels in your body were attached in a long l ine, they would

span 60,000 miles. That’s more than twice the circumference of the Earth!

Keeping the cardiovascular system in order and keeping the heart healthy is a lifetime task. Many cardiovascular diseases can begin to take form during the childhood and teenage years. At birth, a person’s blood vessels are strong, but as time goes on, certain factors can cause an accumulation of plaque, a loss of elasticity and a weakening of the heart muscle. A problem affecting one area of the cardiovascular system can set off many other reactions leading to an overall damaged system. Because the heart muscle, blood vessels and circulatory system all depend on each other, it is important for all components to remain healthy and strong.

There are many different types of cardiovascular diseases.

Coronary Artery Disease and AtherosclerosisCoronary artery disease is a condition caused by atherosclerosis, the narrowing of blood vessels due to an accumulation of plaque or fat deposits, that build up on the walls of blood vessels, narrowing and sometimes totally blocking the vessels. If a certain vessel becomes blocked, some of the heart cells will not be able to

receive proper nutrients and oxygen. Eating foods high in saturated fats, smoking tobacco and having high blood pressure are believed to contribute to plaque build-up. Eventually, atherosclerosis can cause serious health problems including heart attack, stroke and congestive heart failure—all of which can be fatal.




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HEART DISEASES5 of 12

Did You Know?Your heart has its own built-in

pacemaker. The sinoatrial node

(or SA node) in the right atrium

of the heart is in charge of

maintaining an electrical signal

that keeps your heart beating

at an appropriate rate.

Heart ArrhythmiasHeart arrhythmias or irregular heartbeats, are very common. The body depends on the heart muscle’s rhythm to pump blood to the organs, muscles and tissues. Sometimes the heart may beat too slowly, too quickly or skip a beat all together. Usually heart arrhythmias are not dangerous; however, in some cases they can lead to cardiac arrest, a condition in which the heart stops beating. Pacemakers are small, battery-powered implants that can maintain the heartbeat at a regular pace. They send electrical currents into the heart to stimulate a healthy muscle contraction.

l Tachycardia is a heart arrhythmia where the heart beats more than 100 times per minute.

l Bradycardia is a heart arrhythmia where the heart beats fewer than 60 times per minute.



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Implantable DefibrillatorDid You Know?

A fibrillation is an abnormal contraction of

your heart muscle causing an uncoordinated

movement. A defibrillator is used by

doctors to get a person’s heart pumping

again. A strong electric current is sent

through two metal plates placed on the

patient’s chest. Doctors calculate the

shock intensity required based on body

weight. Doctors can also surgical ly implant

a miniature version of this device cal led an

implantable cardioverter defibri l lator (ICD).

An ICD shocks the heart when it senses

potential ly deadly heart arrhythmias.

An ECG machine

StrokeStroke is a very serious condition caused by an interruption of blood flow to the brain. Similar to cardiovascular disease, stroke is usually caused by plaque build-up in the arteries of the brain. According to the American Stroke Association, strokes are the third leading cause of death in the United States. If there is a blood clot blockage in an artery leading to the brain or if a blood vessel bursts inside the brain, blood flow will be prevented and brain tissue will die.

Effects of stroke can include problems with vision, paralysis of the face or body, memory loss and speech impairment.

Heart AttackA heart attack, also known as a myocardial infarction, is a very common form of cardiovascular disease as well as the leading cause of sudden death. In the United States alone, more than one million people have heart attacks each year.

Heart attacks are a result of the heart muscle not receiving enough oxygen, usually due to plaque buildup in the coronary arteries. Without oxygen, the cells die off and are not able to pump normally. This leads to congestive heart failure (when the heart no longer pumps efficiently) and fluid build-up in the lungs.



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HEART DISEASES CONTINUED7 of 12

Did You Know?You may have heard people use the word “angina”

when discussing cardiovascular disease. Angina

means heart pain and not an actual disease

itself. Angina is usually described as a tightening

feeling in the chest when blood flow is lessened.

There are three main types of angina:

1. Stable angina is a result of the heart

working too hard. It can be treated

with medication and/or rest.

2. Unstable angina is the most dangerous

type. It usually indicates a heart attack

and cannot be relieved with medication.

3. Variant angina occurs at night, usually

while you’re sleeping. This pain can

be very severe, but may be treated

with medication.

Defibrillator

Quick Notes

hypertension or high blood pressure a disorder indicating that

the heart is overworking to

move blood through clogged

blood vessels and arteries.

Causes heart attack, stroke,

heart failure, kidney disease

and blindness

When blood is pumped out of the heart and through the blood vessels, it exerts a force against vessel walls. This force is recorded in two different numbers called the systolic and the diastolic blood pressure.

The systolic is the higher of the two measurements representing the moment when the heart beats. The diastolic is the lower number representing the pressure when the heart is at rest. Usually the two are recorded together in the following format: systolic/diastolic measured in millimeters of mercury.

Your blood pressure is constantly changing; stress, food, activity and illness can alter your blood pressure readings, but doctors consider 120/80 mm Hg as the normal level.

High blood pressure or hypertension is very dangerous and is often referred to as a “silent killer” since often there are no obvious symptoms or warning signs. That’s why it’s important to measure blood pressure on a regular basis. Most doctors take a blood pressure reading with every office visit.

High blood pressure is an indication that the heart is working harder than usual and increases the risk for many types of cardiovascular disease and other illnesses including heart attack, stroke, heart failure, kidney disease and even blindness.

The chart below outlines the different blood pressure categories according to the American Heart Association.


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American Heart Association Recommended Blood Pressure Levels

Blood Pressure Category

Systolic (mm Hg)

Diastolic (mm Hg)

Normal less than 120 and less than 80Prehypertension 120–139 or 80–89

HighStage 1 140–159 or 90–99Stage 2 160 or higher or 100 or

higher

Blood pressure is measured using a special

instrument called a sphygmomanometer .

The sphygmomanometer has a cuff that

wraps around your arm and, when inflated,

cuts off blood flow through your arteries.

When it is deflated, blood flow resumes and

the doctor or nurse is able to hear the return

of normal blood flow through the artery. He

or she can then determine your systolic and

diastolic pressure readings.

Normal Blood Pressure (BP)

is 120/80

Quick NotesThere are many easy ways to help lower the risk of developing cardiovascular disease. Eating right, exercising and avoiding tobacco are three fundamental keys to a healthy heart.

Choosing foods low in saturated and trans fat is very important in keeping the blood vessels plaque-free. Cholesterol is a fatty substance made by the liver. Cholesterol aids in food digestion and cell maintenance. Many foods high in saturated fat and trans fats (like animal products and processed junk foods) are loaded with cholesterol. Since the liver produces enough cholesterol for the body’s needs, it is not necessary to consume any extra cholesterol from food.

Eating too many cholesterol-laden foods clogs the arteries and can lead to atherosclerosis and coronary artery disease, while increasing an individual’s risk for heart attack and stroke. The American Heart Association suggests that people consume fewer than 300 mg of cholesterol a day.

The American Heart Association also suggests eating a diet high in fresh fruits, vegetables, whole grains and low-fat dairy products. Try to eat foods that can deliver proper nutrients, vitamins, minerals and fiber. Specific suggestions include:

l Eat lean meats and poultry (with the skin removed).

l Opt for low-fat dairy products.

l Limit partially hydrogenated vegetable oils.

l Avoid high cholesterol foods.

l Limit added sugars, especially in soda and sweets.

l Monitor sodium intake.

l Be aware of oversized food portions when eating at restaurants.

low-density lipoproteins (LDL) are considered the “bad

cholesterol.” This type of

cholesterol can lead to

increased plaque deposits

in the blood vessels

high-density lipoproteins (HDL) are considered the

“good cholesterol.” These

lipoproteins are like little

garbage trucks, collecting

the bad LDL cholesterol

and delivering it back to

the liver to be removed as

waste. Eating healthy fats

and exercising can increase

a person’s HDL levels



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EAT HEALTHY FOR HEART HEALTH9 of 12

Remember——avoid saturated and trans fats which increase levels of bad cholesterol, but eat healthy fats to increase good cholesterol levels. The fats found in nuts, avocados, certain fish, olive oils and flax seed oils can have many positive effects on the body, including the skin, immune response and even cholesterol maintenance. Good fats increase a person’s HDL cholesterol and are very important for overall health.

Exercise is very important for keeping the cardiovascular system healthy. Set your goal at 30 minutes of moderate to vigorous physical activity each day. Here are some ways to exercise and keep your heart healthy:

l Help with yard work—gardening or mowing the lawn.

l Take a brisk walk before or after dinner.

l Volunteer to walk your dog. If you don’t have a pet, volunteer to help your neighbors walk their dogs.

l Walk or bike whenever possible.

l Take the stairs instead of the elevator.

l Get off the bus at an earlier stop and walk the rest of the way home.

When it comes to exercise, each person has his or her own strengths and weaknesses. Just because you’re not training to run a marathon doesn’t mean you can’t enhance your endurance and fitness levels with practice and time.

Start out by slowly increasing your daily physical activity—you may be surprised to see how well your body adjusts over time. Just remember that any type of aerobic activity is helpful to your cardiovascular health, both now and in the future.

Quick Notes

Exercise 30 minutes every day

to keep your heart healthy.

Start out slowly to build

up stamina and strength.


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Fact: if you avoid smoking, you’ll live a longer and healthier life.

The decision to live smoke-free is one of the most health-friendly choices you will ever make. Smoking and secondhand smoke damage every organ, tissue and cell in the body. The lungs, brain, heart, liver, pancreas, esophagus, kidneys, reproductive organs, digestive organs, skin, eyes, mouth, throat and nose are at higher risk of developing cancer every time you light up.

Smokers subject their lungs to constant irritation and the need to filter out smoke, tar and multiple carcinogenic chemicals. Smokers put themselves at a high risk for developing lung cancer, but also for other debilitating lung diseases such as chronic obstructive pulmonary disease (COPD). COPD is an incurable condition that gets worse over time. It causes death by destroying all respiratory function. Smokers are ten times more likely to die from COPD than non-smokers. Experts estimate that more than 11 million men and women in the United States are currently disabled by COPD.

The American Heart Association estimates that people who smoke or who are exposed to significant amounts of secondhand smoke are two to three times more likely to die of coronary artery disease. Coronary artery disease causes heart attacks and stroke.

Each year, more than 400,000 people die of tobacco-related deaths in the United States. Each cigarette steals seven minutes of life from a smoker. If you use tobacco, make the effort to quit now! Although quitting tobacco is not easy, it will make a big difference in your health today and in the future.



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NO SMOKING!11 of 12

Secondhand SmokeEven if you do not smoke, you still may be at risk from secondhand smoke. Spending time around people who smoke is dangerous in itself. Secondhand smoke is a proven health threat to the young and old—whether the exposure occurs at home, at work, at school, in restaurants, theaters or even on the sidewalk. Each year, more than 50,000 non-smokers die because of their exposure to secondhand smoke. The smoke that comes from the lit end of the cigarette has a higher concentration of carcinogens than the smoke inhaled from the filter end.

Be proactive about avoiding secondhand smoke. If someone in your home smokes and can’t quit, ask him or her to smoke outside. If someone is smoking in your workspace, speak to your boss about the problem. You have the right to live and work in a smoke-free environment.

1. Blood carries oxygen, important nutrients and hormones though a network

of vessels supported by our heart and cardiovascular system.

2. The cardiovascular system is a closed circulatory system comprised of the

heart and blood vessels—arteries, veins and capillaries.

3. Arteries carry blood away from the heart to the rest of our body, while veins

carry blood from the body back to the heart.

4. There are three important types of blood cells—red blood cells, white blood cells and platelets—all suspended in plasma, the fluid part of blood.

5. Coronary artery disease is a condition caused by atherosclerosis, the

narrowing of blood vessels due to an accumulation of plaque or fat deposits,

that build up in the blood.

6. A myocardial infarction, or a heart attack, is a result of the heart muscle

not receiving enough oxygen, usually due to plaque buildup in the

coronary arteries.

7. Stroke is a very serious condition caused by a lack of oxygen to the brain.

8. Choosing foods low in saturated and trans fat is very important in keeping

the heart strong and the blood vessels plaque-free.

9. Exercise helps to keep the heart strong. It is suggested that young adults

get at least 30 minutes of aerobic exercise 5 times a week.

10. People who smoke or are exposed to a lot of secondhand smoke are

2 to 3 times more likely to die of coronary artery disease. Stay away

from cigarette smoke!

End of Lesson 8.5

Note to self... STUDY this!


STUDY POINTS 12 of 12



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NOTES

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