The Circulatory System -...

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Chapter 30 The Circulatory System

Animal Circulatory Systems

Section 30.1

Blood is the fluid of the circulatory system. It carries many substances, including dissolved respiratory gases, through the body.

Blood cells: ©Dr. Dennis Kunkel/Visuals Unlimited

Section 30.1

The heart pumps blood through vessels.

Blood vessels

Section 30.1

Blood vessels lead to respiratory surfaces, where blood exchanges gases with the environment. They also lead to body tissues, where blood exchanges gases and nutrients.

Figure 30.1

Blood vessels

Respiratory surface

Body tissues

Section 30.1

Blood travels through circulatory systems, which have multiple forms.

Section 30.1 Figure 30.1

An open circulatory system has short, open-ended vessels.

Section 30.2

In a closed circulatory system, blood remains in vessels.

Figure 30.1

Closed circulatory systems are distinguished based on the number of heart chambers.

Fishes and larval amphibians, for example, have a two-chambered heart. Blood is pumped across the gills and then to the rest of the body.

Birds and mammals have a four-chambered heart. Blood is pumped to the lungs, and then returns to the heart to be pumped to the rest of the body.

Adult amphibians and most nonavian reptiles have a three- chambered heart. Blood mixes in a single chamber before it is simultaneously pumped to the lungs and the body.

30.1 Mastering Concepts

Distinguish between open and closed circulatory systems.

Artificial blood: ©Philippe Plailly/Science Source

Re-cap of the Heart

How does the heart work?

Blood Has Diverse Functions

Section 30.2

Blood consists of cells suspended in a liquid extracellular matrixcalled plasma.

Figure 30.3Blood cells: © Dr. Dennis Kunkel/Visuals Unlimited

Section 30.2

Plasma is mostly water but also contains antibodies and many other dissolved substances.

Section 30.2

Plasma carries red blood cells, white blood cells, and platelets.

Section 30.2

Red blood cells carry oxygen to body tissues.

Section 30.2

Red blood cells contain hemoglobin, a protein that binds to oxygen at respiratory surfaces and “unloads” oxygen at body tissues.

Section 30.2

A person’s blood type depends on what carbohydrates are on the surface of red blood cells.

Section 30.2

The immune system reacts to blood cells with foreign carbohydrates. The foreign blood clumps together in a reaction called agglutination.

Figure 30.4Blood cells: © Dr. Dennis Kunkel/Visuals Unlimited; ABO: ©Jean Claude Revy - ISM/Phototake

Section 30.2

White blood cells are part of the immune system. They provoke inflammation and destroy microbes, among many other functions.

Figure 30.3Macrophage engulfing bacteria: © Dr. David M. Phillips/Visuals Unlimited

Section 30.2

Platelets are cell fragments that initiate blood clotting.

Section 30.2

Platelets adhere to each other at a break in a blood vessel. Plasma proteins called clotting factors reinforce the clot.

Figure 30.5Blood cells: © Dr. Dennis Kunkel/Visuals Unlimited; fibrin threads: © Dr. David Phillips/Visuals Unlimited

Section 30.1 Table 30.1

Here is a summary of blood’s functions.

Both photos of blood cells above: © Dr. Dennis Kunkel/Visuals Unlimited;

macrophage engulfing bacteria: © Dr. David M. Phillips/Visuals Unlimited

Clicker Question #1

Which of the following components occupies the greatest volume in a sample of blood?

A. antibody proteinsB. red blood cellsC. white blood cellsD. waterE. platelets

Flower: © Doug Sherman/Geofile/RF

Clicker Question #1

Which of the following components occupies the greatest volume in a sample of blood?

A. antibody proteinsB. red blood cellsC. white blood cellsD. waterE. platelets

Describe each of the components of blood.

The Cardiovascular System: An Overview

This diagram shows some of the major components of the human cardiovascular system.

The heart pumps blood through three main types of blood vessels.

Arteries carry blood away from the heart.

Arteries branch into smaller arterioles.

Capillaries are the tiniest blood vessels. Water and dissolved substances diffuse between each capillary and the interstitial fluid that bathes body cells.

Capillaries flow into slightly larger venules. Venules combine into veins, which carry blood back to the heart.

Clicker Question #2

Which of the following statements about the human circulatory system is true?

A. Diffusion occurs rapidly across artery walls into body cells.B. Veins always carry blood away from the heart.C. Our circulatory system is open because the lungs are open to the atmosphere.D. The heart pumps blood directly into arteries.

Clicker Question #2

Which of the following statements about the human circulatory system is true?

A. Diffusion occurs rapidly across artery walls into body cells.B. Veins always carry blood away from the heart.C. Our circulatory system is open because the lungs are open to the atmosphere.D. The heart pumps blood directly into arteries.

Describe the relationships among arteries, veins, and capillaries.

The Heart Is a Muscular Pump

The muscular heart pumps thousands of liters of blood through the body each day.

How does the heart work?

A thick layer of muscle called the myocardium makes up most of the wall of the heart.

The myocardium contains cardiac muscle.

Cardiac muscle

The heart is surrounded by a sac called the pericardium, which anchors the heart but also allows it to beat without being obstructed.

Blood passes through the four chambers of the human heart.

Atria receive blood from veins.

Ventricles pump blood into arteries.

The right half of the heart receives blood from the body and pumps it to the lungs.

The left half of the heart receives blood from the lungs and pumps it to the rest of the body.

The right atrium receives oxygen-depleted blood.

The right atrium pumps oxygen-depleted blood to the right ventricle, which then pumps it to the lungs.

Blood travels through pulmonary arteries to the lungs.

Blood picks up oxygen at the lung capillaries and returns to the heart through pulmonary veins.

Pulmonary veins dump blood into the left atrium of the heart.

The left atrium pumps oxygen-rich blood to the left ventricle, which then pumps it through the aorta, the largest artery, to the rest of the body.

How does the heart “know” when to contract its ventricles and atria to regulate blood flow through the circulatory system?

Pathway of Blood Through the Heart and Lungs

• Right atrium tricuspid valve right ventricle

• Right ventricle pulmonary semilunar valve pulmonary arteries lungs

• Lungs pulmonary veins left atrium

• Left atrium bicuspid valve left ventricle

• Left ventricle aortic semilunar valveaorta

• Aorta systemic circulation

Electrical signals coordinate the heartbeat. A single beat of the heart, including contraction of both atria and both ventricles, is called a

cardiac cycle.

The signal to contract begins at the pacemaker, also called the sinoatrial (SA) node.

Each signal from the pacemaker spreads along the sides of the heart. The two atria contract in unison.

After a brief delay—giving time for the ventricles to fill with blood—the signal reaches the atrioventricular (AV) node,

which sends the signal to contract through the ventricle walls.

The two ventricles contract in unison.

The ventricles then relax, completing the cardiac cycle.

Physicians track the heartbeat with an ECG, which measures the electrical signals that pass through the heart walls from the

pacemaker to the ventricles.

The letters PQRST indicate different parts of a cardiac cycle.

Two sets of valves prevent blood from flowing backward through the heart.

When the ventricles contract, valves between the ventricles and atria slam shut.

When the ventricles relax, valves between the arteries and the ventricles slam shut.

The familiar “lub-dup” sound of the heart comes from the two sets of heart valves closing.

The amount of blood pumped each minute, called cardiac output, is determined by the heart rate and the strength of the heart.

Strong heart muscles pump more blood with each stroke than weaker muscles.

Clicker Question #3

A red blood cell is in the heart’s right ventricle. When it next enters the heart, which heart chamber will it enter?

A. left atriumB. right atriumC. left ventricleD. right ventricle

Clicker Question #3

A red blood cell is in the heart’s right ventricle. When it next enters the heart, which heart chamber will it enter?

A. left atriumB. right atriumC. left ventricleD. right ventricle

Describe the path of blood through the heart’s chambers and valves, and through lungs and body tissues.

Blood Vessels Form the Circulation Pathway

Venule Arteriole

Capillary bed

ArteryVein

Venule Arteriole

Artery

Endothelium

Connective tissue

Smooth muscle

Connective tissue

Capillary bed

ArteryVein

Arteries carry blood away from the heart. They have a thick layer of smooth muscle that can withstand high blood pressure.

Venule Arteriole

Artery

Endothelium

Connective tissue

Smooth muscle

Connective tissue

Capillary bed

ArteryVein

Arteries lead to slightly smaller arterioles.

Arterioles lead to capillary beds, where vessels are only about as wide as a red blood cell.

Capillary walls are only one cell layer thick, allowing water and substances to easily diffuse to body tissues.

Venule Arteriole

Capillary bed

ArteryVein

Capillary beds lead to venules, which in turn lead to veins.

Venule Arteriole

Endothelium

Connective tissue

Smooth muscle

Connective tissue

Capillary bed

ArteryVein

Blood pressure in veins is low. They therefore have a thinner layer of smooth muscle than arteries.

Venule Arteriole

Endothelium

Connective tissue

Smooth muscle

Connective tissue

Capillary bed

ArteryVein

Without much smooth muscle, veins collapse when they are not filled with blood.

Section 30.5

Valves keep blood from flowing backward in veins.

Figure 30.12

Section 30.5

Skeletal muscle contraction propels blood through open valves toward the heart.

Figure 30.12

Anatomical Structures of Veins and Arteries

Arteries• Away from heart• Thicker tunica media• BP=120/80 mmHg• Spurt• Bright Red blood• No valves• Pulse

Veins• To the heart• Valves present• BP=2/12 mmHg• Ooze when cut• Dark Red blood• Smaller Tunica media• No pulse

Doctors measure blood pressure using a sphygmomanometer.

The higher reading (systole) reflects the pressure in arteries when the ventricles contract.

The lower reading (diastole) reflects the pressure in arteries when the ventricles relax.

Blood pressure decreases during its path through the circulatory system.

Blood velocity is lowest in the capillaries because the total cross sectional area is high.

A negative feedback system helps regulate blood pressure. Vasoconstriction is the narrowing of arterioles. Blood pressure increases as the arterioles narrow. The opposite process, vasodilation, causes blood pressure to drop.

Clicker Question #4

How many of the following phrases correctly complete this sentence?Caffeine causes arterioles to constrict. After drinking a large coffee, a man may have

higher blood pressure in his arterioles; lower blood velocity in his arterioles; lower cross-sectional area of his arterioles

A. oneB. twoC. three

Clicker Question #4

How many of the following phrases correctly complete this sentence?Caffeine causes arterioles to constrict. After drinking a large coffee, a man may have

higher blood pressure in his arterioles; lower blood velocity in his arterioles; lower cross-sectional area of his arterioles

A. oneB. twoC. three

Compare and contrast the structures of arteries, capillaries, and veins.

The Lymphatic System Transports Defense Cells

The lymphatic system collects fluid that leaks from blood vessels, removes bacteria, debris, and cancer cells, and returns the liquid to the blood.

Lymph is the colorless fluid of the lymphatic system. Lymph capillaries absorb interstitial fluid and deliver it to larger lymph vessels.

Lymph passes through lymph nodes, which remove foreign substances from lymph. Each lymph node contains millions of white blood cells called lymphocytes.

Lymphoid organs produce, accumulate, or aid in the circulation of lymphocytes.

When a person has a malfunctioning lymphatic system, excess fluid accumulates in body tissues. A parasite causes the condition shown here, called elephantiasis.

Section 30.6 Wuchereria bancrofti: © Sinclair Stammers/Science Source.; elephantiasis: © R. Umesh Chandran, TDR, WHO/Science Source

Where does lymph come from?

Investigating Life: In (Extremely) Cold Blood

Section 30.7

Not all animals use red blood cells to transport O2 and CO2.

Section 30.7

Icefishes lack red blood cells and hemoglobin. Respiratory gases are transported in blood plasma.

Figure 30.17

Section 30.7

In the cold waters, metabolic rates are so low that a lack of hemoglobin does not reduce reproductive success.

Figure 30.17

Section 30.7

Therefore, mutations that arose in icefish hemoglobin genes were not selected against, and hemoglobin eventually disappeared from the population.

Figure 30.18

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