Circulation and Respiration

Chapter 21

21.1 Impacts/IssuesUp in Smoke

Smoking, a habit that usually begins in the teens, impairs the health of smokers and the people around them

Video: Up in smoke

21.2 Moving Substances Through a Body

All animals must supply their cells with nutrients and oxygen, and remove wastes

In some small invertebrates, materials simply diffuse through interstitial fluid

Interstitial fluid • Fluid between cells of a multicelled body

Circulatory Systems

Complex animals distribute materials through a circulatory system, in which a heart pumps blood through blood vessels

Heart • Muscular organ that pumps fluid through a body

Two Types of Circulatory Systems

Open circulatory system • Circulatory system in which blood leaves vessels

and flows among tissues

Closed circulatory system • Circulatory system in which blood stays inside a

continuous network of vessels• Flow is faster than in open systems• Found in all vertebrates and some invertebrates

Closed Circulatory System

In a closed circulatory system, materials are transferred between blood and cells of other tissues by diffusion through capillaries

Capillaries • Smallest-diameter blood vessels; site of

exchanges of gases and other materials with tissues; a capillary bed supplies an organ

Open and Closed Circulatory Systems

Fig. 21-1a, p. 419

Fig. 21-1a, p. 419

aorta heart

Fig. 21-1b, p. 419

Fig. 21-1b, p. 419

pump

spaces or cavities in body tissues

Fig. 21-1c, p. 419

Fig. 21-1c, p. 419

dorsal blood vessel

two of five hearts

ventral blood vessels

gut cavity

Fig. 21-1d, p. 419

Fig. 21-1d, p. 419

pump

large-diameter blood vessels (rapid flow)

large-diameter blood vessels (rapid flow)

capillary bed (many small vessels that serve as a diffusion zone)

Animation: Types of circulatory systems

Evolution of Vertebrate Cardiovascular Systems

Fishes have a two-chambered heart (atrium and ventricle), and blood flows in one circuit

Atrium • Heart chamber that receives blood from a vein

and pumps it into a ventricle

Ventricle • Heart chamber that pumps blood out of the heart

and into an artery

Evolution of Vertebrate Cardiovascular Systems

In most vertebrates, blood flows in two circuits

Amphibians and most reptiles have a three-chambered heart with two atria and one ventricle

Crocodilians, birds, and mammals have a four-chambered heart that separates oxygen-rich blood from oxygen-poor blood

Two Cardiovascular Circuits

Pulmonary circuit • Circuit through which blood flows from the heart

to the lungs and back

Systemic circuit • Circuit through which blood flows from the heart

to the body tissues and back

Vertebrate Circulatory Systems

Fig. 21-2a, p. 420

Fig. 21-2a, p. 420

capillary beds of gills

ventricleheart

rest of body

atrium

Fig. 21-2b, p. 420

Fig. 21-2b, p. 420

lungs

right atrium

left atrium

ventricle

rest of body

Fig. 21-2c, p. 420

Fig. 21-2c, p. 420

lungs

right atrium

left atrium

right ventricle left ventricle

rest of body

Animation: Circulatory systems

21.3 Human Cardiovascular System

The human heart has four chambers, and pumps blood through two separate circuits: pulmonary and systemic

Each circuit has a network of blood vessels that carry blood between the heart and capillary beds

Types of Blood Vessels

Artery • Large-diameter blood vessel that carries blood

from the heart to an organ

Arteriole • Blood vessel that carries blood from an artery to a

capillary bed

Types of Blood Vessels

Venule • Small-diameter blood vessel that carries blood

from capillaries to a vein

Vein • Large-diameter vessel that returns blood to the

heart

The Pulmonary Circuit

Oxygen-poor blood collected by the right atrium is pumped from the right ventricle, through pulmonary arteries, to the lungs

In the lungs, blood gives off CO2 and picks up O2

Oxygen-rich blood returns through pulmonary veins to the left atrium

The Systemic Circuit

Oxygen-rich blood collected by the left atrium is pumped from the left ventricle, through the aorta, to capillary beds of the body

Aorta • Large artery that receives blood pumped out of

the left ventricle

The Systemic Circuit

At capillary beds in the body, blood gives up O2 and picks up CO2

• Most blood flows through only one capillary bed, but blood from gut capillaries also passes through liver capillaries before retuning to the heart

Oxygen-poor blood returns to the right atrium

The Human Cardiovascular System

Fig. 21-3a, p. 421

Fig. 21-3a, p. 421

Heart

atrium ventricle

veins arteries

venules arterioles

capillaries

Fig. 21-3b, p. 421

Fig. 21-3b, p. 421

right pulmonary artery left pulmonary artery

capillary bed of right lung

capillary bed of left lung

pulmonary trunk

to systemic circuit

from systemic circuit

pulmonary veins

heart

Fig. 21-3c, p. 421

Fig. 21-3c, p. 421

capillary beds of head, upper extremities

to pulmonary circuit

aorta

from pulmonary circuit

heart

capillary beds of other organs in thoracic cavity

capillary bed of liver

capillary beds of intestines

capillary beds of other abdominal organs and lower extremities

Animation: Human blood circulation

21.4 The Human Heart

Structures of the human heart• Pericardium protects the heart• Each half of the heart has two chambers: an

upper atrium and a lower ventricle • Superior and inferior vena cava deliver blood to

the right atrium• Pulmonary veins deliver blood to the left atrium• Atrioventricular (AV), aortic, and pulmonary

valves prevent blood from moving backwards

The Human Heart

Fig. 21-4, p. 422

aorta (to body)superior vena cava (flow from head, arms) trunk of pulmonary

arteries (to lungs)pulmonary valve (closed) aortic valve (closed)right pulmonary veins (from lungs) left pulmonary veins

(from lungs)

Right Atrium Left Atrium

right AV valve (open)

left AV valve (open)

Right Ventricle Left Ventricle

inferior vena cava (from trunk, legs)

cardiac muscle

septum

Fig. 21-4, p. 422

trunk of pulmonary arteries (to lungs)

pulmonary valve (closed)

aorta (to body)

aortic valve (closed)

left AV valve (open)

right AV valve (open)

superior vena cava (flow from head, arms)

Right Atrium Left Atrium

Right Ventricle Left Ventricle

inferior vena cava (from trunk, legs)

cardiac muscle

septum

right pulmonary veins (from lungs) left pulmonary veins

(from lungs)

Stepped Art

Animation: The human heart

The Cardiac Cycle

Cardiac cycle • Sequence of contraction and relaxation of heart

chambers that occurs with each heartbeat

Signals from the cardiac pacemaker trigger contraction of the atria, then the ventricles • Atria fill ventricles; ventricular contraction drives

blood flow away from the heart • Closing heart valves cause heartbeat sounds

The Cardiac Cycle

Fig. 21-5, p. 423

1 Relaxed atria fill. Fluid pressure opens AV valves and blood flows into the relaxed ventricles.

2 Atrial contraction squeezes more blood into the still-relaxed ventricles.

3 Ventricles start to contract and the rising pressure pushes the AV valves shut. A further rise in pressure causes the aortic and pulmonary valves to open.

4 As blood flows into the arteries, pressure in the ventricles declines and the aortic and pulmonary valves close.

Fig. 21-5, p. 423

4 As blood flows into the arteries, pressure in the ventricles declines and the aortic and pulmonary valves close.

Stepped Art

1 Relaxed atria fill. Fluid pressure opens AV valves and blood flows into the relaxed ventricles.

2 Atrial contraction squeezes more blood into the still-relaxed ventricles.

3 Ventricles start to contract and the rising pressure pushes the AV valves shut. A further rise in pressure causes the aortic and pulmonary valves to open.

Animation: Cardiac cycle

Setting the Pace of Contractions

Spontaneous signals from the cardiac pacemaker cause cardiac muscle fibers of the heart wall to contract in a coordinated rhythm• Gap junctions connect cardiac muscle cells

Cardiac pacemaker • Group of heart cells (SA node) that emits

rhythmic signals calling for atrial contraction• Signals AV node to begin ventricular contraction

The Heart’s Signaling System

Fig. 21-6, p. 423

SA node (cardiac pacemaker)

AV node

fibers that relay signals

Animation: Cardiac conduction

Animation: Bony fish respiration

SA Node Malfunctions: Cardiac Arrest

CPR increases chances of survival

Cardiopulmonary resuscitation (CPR) • Life-saving technique that keeps oxygen flowing

to tissues when the heart stops beating; involves mouth-to-mouth respiration, chest compressions

Defibrillator • Device that administers an electric shock to the

chest wall to reset the SA node, restart the heart

Video: ABC News: Second-chance heart

21.5 Blood and Blood Vessels

An average adult has about 4.5 liters of blood, consisting of plasma, red blood cells, white blood cells, and platelets

Plasma • Fluid portion of blood, composed of water with

dissolved ions and molecules • Transports gases, nutrients, wastes, signaling

molecules, plasma proteins

Blood Cells and Platelets

Blood cells and platelets arise from stem cells in bone marrow

Red blood cells • Hemoglobin-filled blood cells that transport

oxygen and, to a lesser extent, carbon dioxide• Lack nucleus and organelles, live about 4 months

Blood Cells and Platelets

White blood cells (leukocytes) • Various kinds function in housekeeping (digest

debris) and defend against viruses, bacteria, and other pathogens

Platelet • Cell fragment that patches tears in blood vessels

and initiates blood clotting

Components of Blood

Fig. 21-7, p. 424

plasma

blood cells

red blood cell

white blood cell platelet

Animation: Vertebrate lungs

Animation: Bird respiration

Rapid Transport in Arteries

Blood is pumped from ventricles into arteries under high pressure• Muscular, elastic walls propel blood forward when

ventricles are relaxed

Pulse • Brief stretching of artery walls that occurs when

ventricles contract

Blood Pressure

Blood pressure is higher in the systemic circuit than in the pulmonary circuit• Left ventricle is stronger than the right

Blood pressure • Pressure exerted by blood against the walls of

blood vessels• Highest in arteries, lowest in veins

Measuring Blood Pressure

Normal blood pressure is about 120/80 mm Hg (systolic/diastolic)

Systolic pressure • Blood pressure when ventricles are contracting

Diastolic pressure • Blood pressure when ventricles are relaxed

Adjusting Resistance at Arterioles

Depending on need, the body alters the distribution of blood flow through the body by adjusting the diameter of arterioles• Example: more blood sent to gut when eating

Smooth muscles in arteriole walls widen or narrow vessel diameter in response to nervous and endocrine signals• Vasodilation, vasoconstriction

Exchanges at Capillaries

Capillary beds exchange materials between blood and interstitial fluid around cells• Gases diffuse across the plasma membrane• Blood pressure at arterial ends of capillary beds

causes plasma to leak out, carrying oxygen, ions, and nutrients

• Osmosis at venous ends of capillary beds causes water from interstitial fluid to enter blood, carrying wastes (excess fluid becomes lymph)

Blood Vessel Structure

Fig. 21-8a, p. 424

Fig. 21-8a, p. 424

outer coat

smooth muscle

basement membrane

elastic tissue elastic tissue

A Artery

endothelium

Fig. 21-8b, p. 424

Fig. 21-8b, p. 424

outer coat

smooth muscle rings over elastic tissue

basement membrane endothelium

B Arteriole

Fig. 21-8c, p. 424

Fig. 21-8c, p. 424

basement membrane endothelium

C Capillary

Fluid Movement at a Capillary Bed

Fig. 21-9, p. 425

capillaryblood to

venule

high pressure causes outward flow

inward-directed osmotic movement

cells of tissue

B

blood from arteriole

A

Back to the Heart

Venules converge into veins, which return blood to the heart

Veins are a blood volume reservoir (hold up to 70% of blood)

Skeletal muscles help blood move; valves in veins keep blood from moving backward

Skeletal Muscle’s Effect on a Vein

Fig. 21-10, p. 426

blood flow to heart

valve open

contracting skeletal muscle

valve closed

vein

Animation: Major human blood vessels

Animation: Vessel anatomy

Animation: Hemostasis

21.6 Animal Respiration

The respiratory system, working with the circulatory system, uses the process of respiration to exchange gases across a respiratory surface

Respiration • Physiological process by which animals obtain

oxygen and get rid of waste CO2

The Respiratory Surface

Gases enter and leave an animal body across a respiratory surface; the area of a respiratory surface affects the rate of exchange

Respiratory surface • Moist surface across which gases are exchanged

between animal cells and the air

Invertebrate Respiration

In some aquatic animals, the respiratory surface may be the body surface or external gills

Integumentary exchange • Gas exchange across the outer body surface

Gills • Folds or body extensions that increase the

surface area for respiration

Invertebrate Respiration

Insects, the most successful air-breathing land invertebrates, have a hard surface and a tracheal respiratory system

Tracheal system • Branching tubes that deliver air from the body

surface to tissues of insects and some other land arthropods with hard exoskeletons

Gills and Fish Respiration

Most fishes have internal gills that extend from the back of the mouth to the body surface• Water flows into the mouth and over gill filaments

containing blood vessels• Water and blood flow in opposite directions,

maximizing the amount of oxygen that diffuses into the blood

Gills and Fish Respiration

Fig. 21-11a, p. 426

Fig. 21-11a, p. 426

FISH GILLWater flows in through mouth.Water flows

over gills, then out.

Fig. 21-11b, p. 426

Fig. 21-11b, p. 426

gill arch

gill filament

Fig. 21-11c, p. 426

Fig. 21-11c, p. 426

respiratory surface

direction of water flow

direction of blood flow

oxygenated blood back toward body

oxygen-poor blood from deep in body

Evolution of Paired Lungs

All mammals and birds, most amphibians, and some fishes have lungs, which provide a large surface area for gas exchange

Lungs • Internal saclike organs; serve as the respiratory

surface in most land vertebrates and some fish

Examples of Vertebrate Lungs

Amphibians exchange gases across their skin and force air into and out of small lungs

Reptiles, birds, and mammals use skeletal muscles to draw air into lungs• Birds have a unique adaptation for flight: air sacs

that constantly move fresh air through the lungs• Mammals inhale fresh air that mixes in lungs with

residual, oxygen-depleted air

Examples of Vertebrate Lungs

Fig. 21-12, p. 427

Fig. 21-12a, p. 427

Fig. 21-12a, p. 427

lung

Fig. 21-12b, p. 427

Fig. 21-12b, p. 427

anterior air sacs

lung

posterior air sacs

Animation: Examples of respiratory surfaces

Animation: Frog respiration

Animation: Diffusion, osmosis, and countercurrent systems

21.7 Human Respiratory Function

When you take a breath, air flows in through nasal cavities, the pharynx, the larynx, the trachea, bronchi, and bronchioles, which end at alveolar sacs deep inside the lungs

Lungs

Two cone-shaped lungs are located in the thoracic cavity, one on each side of the heart, enclosed and protected by the rib cage

Two layers of pleural membrane cover the lung’s outer surface and line the thoracic cavity

Structures of the Human Respiratory System

Pharynx • Throat; opens to airways and digestive tract

Larynx • Short airway containing vocal cords (voice box);

contraction of vocal cords changes the size of the glottis

Glottis • Opening formed when the vocal cords relax

The Glottis and Vocal Cords

Fig. 21-14, p. 428

glottis open

glottis closed

vocal cords

glottis (closed)

epiglottis

tongue’s base

Fig. 21-14d, p. 428

Fig. 21-14d, p. 428

vocal cords

glottis (closed)

epiglottis

tongue’s base

Animation: Vocal chords

Structures of the Human Respiratory System

Epiglottis • Tissue flap at the entrance to the larynx• Folds down to prevent food from entering the

trachea when you swallow

Trachea • Major airway leading to the lungs; windpipe• Branches into two bronchi, each leading to a lung

Structures of the Human Respiratory System

Bronchus (bronchi) • Airway connecting the trachea to a lung

Bronchiole • Small airway leading from bronchus to alveoli

Alveoli (alveolus) • Tiny, thin-walled air sacs• Site of gas exchange in the lung

Structures of the Human Respiratory System

Fig. 21-13a, p. 428

Fig. 21-13a, p. 428

nasal cavity

pharynx (throat)

epiglottis

larynx (voice box)

trachea (windpipe)

left lung

bronchus

bronchiole

diaphragm

intercostal muscle

Fig. 21-13b, p. 428

Fig. 21-13b, p. 428

alveolar sac (sectioned)

alveoli

bronchiole

Animation: Human respiratory system

How You Breathe

Actions of the diaphragm and intercostal muscles allow you to breathe

Diaphragm • Dome-shaped muscle at base of thoracic cavity

that alters thoracic cavity size during breathing

Intercostal muscles • Muscles between the ribs; help alter the size of

the thoracic cavity during breathing

The Respiratory Cycle

Breathing in (inhalation) and breathing out (exhalation) is one respiratory cycle

Respiratory cycle • One inhalation and one exhalation• Inhalation is always active (requires energy)• Exhalation is usually passive

Muscle Actions During a Respiratory Cycle

In inhalation, muscle contractions expand the chest cavity; lung pressure decreases below atmospheric pressure, and air flows in

In exhalation, muscles of respiration relax; the volume of thoracic cavity and lungs decrease, pushing air out of lungs

Muscle Actions During a Respiratory Cycle

Fig. 21-15, p. 429

air flows in air flows out

rib cage expands

rib cage gets smaller

diaphragm contracts and flattens downward

diaphragm relaxes, moves upward

A Inhalation B Exhalation

Animation: Respiratory cycle

Control of Breathing

A respiratory center in the brain stem controls depth and rate of normal breathing• Signals diaphragm and intercostal muscles to

begin inhalation, 10 to 14 times per minute

When activity increases CO2 production, receptors in arteries and the brain signal for an increase in rate and depth of breathing

Exchanges at the Respiratory Membrane

Blood carries gases between lungs and body tissues

Fused basement membranes of alveolar and pulmonary capillary cells form the respiratory membrane

Oxygen and carbon dioxide diffuse across the respiratory membrane, each following its own concentration gradient

Alveoli and the Respiratory Membrane

Fig. 21-16, p. 430

cells of alveolar wall

cells of capillary wallO2

CO2 fused basement membranes of both epithelial cell layers

Oxygen Transport

Oxygen follows its concentration gradient from alveolar air spaces into pulmonary capillaries, then into red blood cells, where it binds reversibly with hemoglobin

In capillary beds, hemoglobin releases oxygen, which diffuses across interstitial fluid into cells

Carbon Dioxide Transport

CO2 diffuses from cells into interstitial fluid, then into blood

Enzymes in red blood cells converts most CO2 into bicarbonate, which dissolves in plasma• Converted back to CO2 in pulmonary capillaries

CO2 diffuses from pulmonary capillaries into air in alveoli, then is expelled

Animation: Structure of an alveolus

Animation: Pressure-gradient changes during respiration

Animation: Changes in lung volume and pressure

Animation: Structures that function in human respiration

Animation: Partial pressure gradients

21.8 Cardiovascular and Respiratory Disorders

Problem: too few or too many blood cells

Anemia • Red blood cells are impaired or fewer than normal• Decreases oxygen delivery to cells• Caused by sickle cell anemia, malaria, lack of iron

Leukemia • Cancer that increases white blood cell numbers• Impairs normal blood functions

Good Clot, Bad Clot

Hemophilia impairs normal blood clotting

Other disorders cause dangerous clotting• Thrombus: a clot that forms in a vessel and

remains there• Embolus: a clot that forms in a blood vessel,

then breaks loose

Atherosclerosis and Hypertension

Atherosclerosis and hypertension may cause heart attack or stroke

Atherosclerosis • Artery interior narrows because of lipid deposition

and inflammation• LDLs deposit cholesterol; HDLs remove it

Hypertension (a silent killer)• Chronically high blood pressure (above 140/90)

Atherosclerosis and Hypertension

Heart attack • Heart cells die because of impaired blood flow

through coronary arteries

Stroke • Brain cells die because a clot or vessel rupture

disrupts blood flow within the brain

Atherosclerosis

Normal artery; artery with atherosclerotic plaque

Two Treatments for Blocked Coronary Arteries

Fig. 21-18, p. 431

vein from leg used to bypass blockage

blocked coronary artery

plaque flattened by balloon angioplasty

stent (metal mesh) placed to keep artery open

Fig. 21-18a, p. 431

Staying Healthy

Maintaining a moderate weight, eating a healthy diet, and getting regular exercise can reduce the risk of many cardiovascular disorders

Respiratory Disorders

Ciliated and mucus-secreting epithelial cells lining bronchioles help protect us from respiratory infections such as bronchitis

Cigarette smoke damages the epithelial lining• Smoking is the main cause of emphysema, an

irreversible loss of lung function

Emphysema: The Effect of Smoking

Smoking’s Impact

“Tobacco remains the only legal consumer product that kills half its regular users”• Smoking kills 4 million people each year• May rise to 10 million by 2030

Direct medical costs of treating tobacco induced disorders in the US alone: $22 billion each year

Major Risks of Smoking and Benefits of Quitting

21.9 Impacts/Issues Revisited

Despite advertisers’ claims, nicotine in tobacco products causes premature aging and interferes with sexual function• Causes wrinkles by disrupting blood flow to skin• Directs blood flow away from sex organs,

contributing to male erectile dysfunction and inhibition of female sexual response

Digging Into Data:Risks of Radon