UNIFYING CONCEPTS OF ANIMAL CIRCULATION

• Every organism must exchange materials with its

environment, relying upon

– diffusion, the spontaneous movement of molecules from an area of higher concentration to an area of lower concentration, and

– a circulatory system, which facilitates the exchange of materials for all but the simplest animals.

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6 Open and Closed Circulatory Systems

• Circulatory systems typically consist of a

– central pump,

– vascular system, and

– circulating fluid.

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7

• In an open circulatory system,

– the heart pumps blood into large open-ended vessels and

– fluid circulates freely among cells.

• Open circulatory systems are found in many

invertebrates, including

– arthropods and

– most molluscs.

Open and Closed Circulatory Systems

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8

• In a closed circulatory system, blood

– stays within a set of tubes and

– is distinct from the interstitial fluid, the fluid that fills the spaces around cells.

• Closed circulatory systems are found in

– many invertebrates, including earthworms and octopuses, and

– vertebrates.

Open and Closed Circulatory Systems

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Figure 23.1

(a) Open circulatory system (b) Closed circulatory system

Tubularheart

Circulating fluid

Interstitial fluidHeart

Heart

Vessels

VesselsCapillaries

Artery(O2-richblood)

Artery(O2-poor blood)

Vessels

CapillariesArteriole

Venule

Vein

HeartVentricle

Atrium

10 Figure 23.1a

(a) Open circulatory system

Tubularheart

Circulating fluid

Heart

Vessels

11

Figure 23.1b

(b) Closed circulatory system

Interstitial fluid

Heart

VesselsCapillaries

Artery(O2-richblood)

Artery(O2-poor blood)

Vessels

CapillariesArteriole

Venule

Vein

HeartVentricleAtrium

12

• The cardiovascular system of vertebrates

consists of the

– heart and

– blood vessels.

• In the heart,

– the atrium receives blood and

– the ventricle pumps blood away from the heart.

Open and Closed Circulatory Systems

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• Blood is confined to three main types of blood

vessels:

1. Arteries carry blood away from the heart into smaller arterioles as they approach the organs.

2. Capillaries are the site of exchange between blood and interstitial fluid.

3. Venules collect blood from the capillaries and converge to form veins, which return blood back to the heart.

Open and Closed Circulatory Systems

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14 UNIFYING CONCEPTS OF ANIMAL RESPIRATION

• Cellular respiration

– uses oxygen and glucose and

– produces water, carbon dioxide, and energy in the form of ATP.

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98

UNIFYING CONCEPTS OF ANIMAL RESPIRATION

• Cells using cellular respiration

– need a steady supply of oxygen and

– must continuously dispose of CO2.

• The respiratory system promotes this gas

exchange.

99 Figure 23.UN01

Environment

Cell

Glucose Oxygen Water EnergyCellular

respiration Carbon

dioxide

C6H12O66 O2 6 CO2 6 H2O ATP

CO2O2

100

The Structure and Function of Respiratory Surfaces

• Animals can get oxygen from

– the atmosphere, which contains about 21% oxygen, and

– bodies of water, which contain about 3–5% oxygen.

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101 The Structure and Function of Respiratory Surfaces

• Gas exchange occurs at the respiratory surface, which must be

– large enough to take up oxygen for every cell in the body and

– adapted to the lifestyle of the organism.

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102

• Moist skin is used as a respiratory surface in

earthworms.

• In aquatic environments, the main respiratory

surfaces are

– skin and

– extensions of the body surface called gills.

The Structure and Function of Respiratory Surfaces

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103 Figure 23.15

Cross section ofrespiratory surface (the skin covering the body)

Respiratorysurface (gill)

Body surface

CapillariesCapillariesCO2

CO2

O2O2

(a) Skin (b) Gills

104

Figure 23.15a

Cross section ofrespiratory surface (the skin covering the body)

CapillariesCO2

O2

(a) Skin

105 Figure 23.15b

Respiratorysurface (gill)

Body surface

Capillaries

CO2

O2

(b) Gills

106

• In most land-dwelling animals, the respiratory

surfaces are

– folded into the body and

– open to the air only through narrow tubes.

The Structure and Function of Respiratory Surfaces

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107

• Insects breathe using a tracheal system, an

extensive network of internal tubes called

tracheae that

– branch throughout the body and

– extend to nearly every cell.

The Structure and Function of Respiratory Surfaces

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108

Figure 23.16

Respiratory

surface

(tracheae)

Body cells(no capillaries)

Respiratory

surface

(within lung)

Body

surface

Body

surface

Capillary

(a) Tracheae (b) Lungs

CO2

CO2

CO2

O2

O2

O2

109 Figure 23.16a

Respiratory

surface

(tracheae)

Body cells(no capillaries)

Body

surface

(a) Tracheae

CO2

O2

110

Figure 23.16b

Respiratory

surface

(within lung)

Body

surface

Capillary

CO2

CO2

O2

O2

(b) Lungs

111

• Lungs

– are located in only one part of the body and

– are the most common respiratory surface of snails, some spiders, and terrestrial vertebrates.

• The circulatory system transports gases between

the respiratory surface and the rest of the body.

The Structure and Function of Respiratory Surfaces

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112

Figure 23.17

Skin(entire body

surface)

Gills(extensions of the

body surface)

Tracheae(branching

internal tubes)

Lungs(localized

internal organs)

RESPIRATORY ORGANS

Moist skin of a leech Gills of a sea slugTracheae of a silkmoth caterpillar

Model of a pair ofhuman lungs

Tracheae(internaltubes)

Gills

113 Figure 23.17a

Skin(entire body surface)

Moist skin of a leech

114

Figure 23.17b

Gills(extensions of the

body surface)

Gills of a sea slug

Gills

115 Figure 23.17c

Tracheae(branching

internal tubes)

Tracheae of a silk moth

caterpillar

Tracheae(internaltubes)

116

Figure 23.17d

Lungs(localized

internal organs)

Model of a pair of human lungs

117 THE HUMAN RESPIRATORY SYSTEM

• The human respiratory system has three phases

of gas exchange:

1. breathing, the ventilation of the lungs by alternate inhalation and exhalation,

2. transport of oxygen from the lungs to the rest of the body via the circulatory system, and

3. diffusion of oxygen from the blood and release of CO2 into the blood by cells of the body.

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118

Figure 23.18-1

Circulatory system

Breathing

Lung

CO2

O2 1

119 Figure 23.18-2

Circulatory system

Breathing

Lung

CO2

O2

Transport of gases bythe circulatory system

2

1

120

Figure 23.18-3

Circulatory system

Breathing

Lung

CO2

O2

Transport of gases bythe circulatory system

Exchange of gaseswith body cells

Mitochondria

Capillary

Cell

CO2

O2

2

1

3

121