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Section 12.1 Your Cardiovascular System

Objectives

Describe the main functions of the cardiovascular system.

Trace the pathway of blood through the heart.

Section 12.1 Your Cardiovascular System

Identify three types of blood vessels and the four components of blood.

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Section 12.1 Your Cardiovascular System

Myth Blood is blue in color when it is not carrying oxygen.

Fact Blood is bright red when it is carrying oxygen and dark red when it is not. Veins appear blue in some people because of the way light reflects from their skin.

What other knowledge about the cardiovascular system do you hope to gain from this chapter?

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Section 12.1 Your Cardiovascular System

• Your cardiovascular system, or the circulatory system, consists of your heart, blood vessels, and blood.

Functions of the Cardiovascular System

• The main functions of the cardiovascular system include

• delivering materials to cells• carrying wastes away

• In addition, blood contains cells that fight disease.

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Section 12.1 Your Cardiovascular System

• Your heart continually pumps the blood in your blood vessels throughout your body.

Delivering Materials

• Many substances that your body needs dissolve in the blood.

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Section 12.1 Your Cardiovascular System

• Your cardiovascular system transports wastes from your cells.

Removing Wastes

• Your blood picks up carbon dioxide and transports it to the lungs, where it is exhaled.

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Section 12.1 Your Cardiovascular System

• Your blood contains cells that attack microorganisms that cause disease.

Fighting Disease

• It also contains substances that seal cuts.

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Section 12.1 Your Cardiovascular System

• Think of your cardiovascular system as a network of blood vessels with two major loops.

The Heart

• The first loop leads from your heart to your lungs.

• Each time the heart beats, strong cardiac muscles push blood through the blood vessels.

• The second loop circles through to the rest of your body.

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Section 12.1 Your Cardiovascular System

• Each side of the heart has two chambers: an upper chamber called an atrium (plural, atria) and a lower chamber, or ventricle.

Structure of the Heart

• The atria receive blood entering the heart.

• Blood flows from the atria to the ventricles, which pump blood out of the heart.

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Section 12.1 Your Cardiovascular System

4) Right VentricleThe right ventricle pumps oxygen-poor blood to the lungs.

3) Right AtriumThe right atrium receives blood from the body that is low in oxygen and high in carbon dioxide.

The Heart

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1) Major vessel from upper body to heart

2) Vessels from lung to heart

5) The aorta carries blood from the left ventricle to the body.

6) Vessel from heart to lungs

7) Vessels from lung to heart

8) Left AtriumOxygen-rich blood is carried from the lungs to the left atrium.

9) Left VentricleThe left ventricle pumps oxygen-rich blood from the heart.

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Section 12.1 Your Cardiovascular System

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Section 12.1 Your Cardiovascular System

• The action of the heart has two main phases.

Your Heartbeat

• The rate at which your heart muscles contract is regulated by the pacemaker, a small group of cells in the wall of the right atrium.

• Average heart rate varies from one person to the next and from one situation to the next.

• In the first phase, the heart relaxes and the atria fill with blood.

• In the second phase, the heart contracts and pumps blood.

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Section 12.1 Your Cardiovascular System

Active Art: The Heart

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Section 12.1 Your Cardiovascular System

Blood Vessels• Your heart pumps blood through an extensive

network of blood vessels.

• The three main types of blood vessels in your body are

• arteries

• capillaries

• veins

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Section 12.1 Your Cardiovascular System

Blood Vessels

Artery

Artery Cross Section

Layer of cells

Connective tissueSmooth muscle

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Section 12.1 Your Cardiovascular System

• Blood vessels that carry blood away from the heart are called arteries.

Arteries

• Most arteries carry oxygen-rich blood.

• The largest artery in the body is the aorta (ay AWR tuh).

• Arteries have thick walls that are both strong and flexible.

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Section 12.1 Your Cardiovascular System

• Branching from the smallest arteries are capillaries, the smallest blood vessels in your body.

Capillaries

• As blood flows through the capillaries, oxygen and dissolved nutrients diffuse through the capillary walls and into your body’s cells.

• Capillaries are involved in temperature regulation.

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Section 12.1 Your Cardiovascular System

• From the capillaries, blood flows into small blood vessels that join together to form veins.

Veins

• Veins are large, thin-walled blood vessels that carry blood to the heart.

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Section 12.1 Your Cardiovascular System

Blood Vessels

Capillary

Capillary Cross Section

Single layer of cells

Vein

Layer of cells

Connective tissueSmooth muscle

Vein Cross Section

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Section 12.1 Your Cardiovascular System

• Blood pressure is the force with which blood pushes against the walls of your blood vessels.

Measuring Blood Pressure

• Normal Blood Pressure A blood pressure reading is considered normal if it falls within the range of 90/60 to 119/79.

• Low Blood Pressure Blood pressure lower than 90/60 is considered to be low blood pressure.

• High Blood Pressure A person whose blood pressure is consistently 140/90 or greater has high blood pressure, or hypertension.

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Section 12.1 Your Cardiovascular System

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Section 12.1 Your Cardiovascular System

• The average adult has about 4 to 6 quarts of blood circulating through his or her blood vessels.

Blood

• The four components of blood are

• plasma• red blood cells• white blood cells• platelets

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Section 12.1 Your Cardiovascular System

• The liquid component of the blood is called plasma.

Plasma

• This straw-colored liquid makes up about 55 percent of the blood.

• Plasma is mostly water, with substances such as nutrients, hormones, and salts dissolved in it.

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Section 12.1 Your Cardiovascular System

• The cells that carry oxygen from the lungs to all the parts of your body are red blood cells.

Red Blood Cells

• Red blood cells contain hemoglobin, which is an iron-containing substance to which oxygen binds.

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Section 12.1 Your Cardiovascular System

• White blood cells help protect you against diseases and foreign substances.

White Blood Cells

• Some white blood cells make chemicals that help your body resist diseases such as cancer.

• Others destroy invading microorganisms by surrounding and consuming them.

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Section 12.1 Your Cardiovascular System

• Platelets (PLAYT lits) are cell fragments that play an important role in the blood clotting process.

Platelets

• When you get a cut, platelets stick to the edges of the cut and release proteins called clotting factors.

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Section 12.1 Your Cardiovascular System

• A person’s blood type is determined by the proteins present on the surface of the red blood cells.

Blood Types

• Depending on which proteins are present, a person’s blood type can be type A, B, AB, or O.

• A second blood type is determined by the presence or absence of the Rh factor protein.

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Section 12.1 Your Cardiovascular System

• After an injury, surgery, or some illnesses, a person may require a blood transfusion.

Transfusions

• During a transfusion, blood from a donor is transferred to the patient’s bloodstream.

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Section 12.1 Your Cardiovascular System

Transfusions

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Section 12.1 Your Cardiovascular System

Vocabulary

atrium An upper chamber of the heart that receives blood from the rest of the body.

ventricle A lower chamber of the heart that pumps blood out of the heart.

pacemaker A small group of cells in the wall of the right atrium that controls the rate at which the heart muscles contract.

artery A thick-walled blood vessel that carries bloodaway from the heart.

capillary The smallest type of blood vessel in the body.

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Section 12.1 Your Cardiovascular System

Vocabulary

vein A large, thin-walled blood vessel that carries blood to the heart.

blood pressure The force with which blood pushes against the walls of blood vessels.

hypertension Blood pressure that is consistently 140/90 or greater.

plasma A liquid that makes up about 55 percent of the blood.

red blood cell A hemoglobin-containing cell that carries oxygen from the lungs to other parts of the body.

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Section 12.1 Your Cardiovascular System

Vocabulary

white blood cell A cell that helps protect the body from diseases and foreign substances.

platelet A cell fragment that plays an important role in the blood clotting process.

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Section 12.1 Your Cardiovascular System

QuickTake Quiz

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Section 12.1 Your Cardiovascular System

End of Section 12.1

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