CHAPTER 24 RESPIRATION. TYPES OF RESPIRATORY SYSTEMS Respiration is the uptake of oxygen and the...

CHAPTER 24

RESPIRATION

TYPES OF RESPIRATORY SYSTEMS

• Respiration is the uptake of oxygen and the simultaneous release of carbon dioxide.• Most primitive animal phyla obtain oxygen

directly from their environments through diffusion.• More advanced phyla have specific respiratory

organs:• Gills, tracheae, and lungs

GAS EXCHANGE IN ANIMALS

Flatworm

CO2 O2

Body wall

CO2

Tracheoles

Spiracles

Trachea

O2

O2

CO2

SpiracleTerrestrial arthropod

Gill filament

Blood vesselsFish

Gill

CO2

O2

O2

TracheaMammalian lung Blood vessels

Alveoli

Mammal

CO2

RESPIRATION IN AQUATIC VERTEBRATES

• Water always moves past a fish’s gills in one direction.

Gill raker Gill archGill raker Gill arch

Water

Gill filamentsLamellae withcapillary networks

Water

Direction of water flowDirection of blood flow

Vein

Water

Artery

Water

Water

Gill filaments

Blood (85%O2 saturation)

Countercurrent exchange Concurrent exchange

Water (50%O2 saturation)Water (100%

O2saturation)Blood (50%O2 saturation)

No furthernet diffusion

50%

60%

70%

80%

90%

(b)


Water(15%O2 saturation)


10%

20%

30%

40%

50%

60%

70%

80%

85% 100%

90%

80%

70%

50%

40%

30%

20%

10%15%

30%

40%

50%

60%

(a)

Water(100%O2saturation)

RESPIRATION IN AQUATIC VERTEBRATES

• Moving the water past the gills in the same direction permits countercurrent flow.• This process is an

extremely efficient way of extracting oxygen.

• Blood flows through a gill filament in an opposite direction to the movement of water.

• The blood in the blood vessels always encounters water with a higher oxygen concentration, resulting in the diffusion of oxygen into the blood vessels.

RESPIRATION IN TERRESTRIAL VERTEBRATES

• Lungs are less efficient than gills because new air that is inhaled mixes with old air already in the lung.• But there is so much more oxygen in air than in

water.


• The lungs of mammals possess on their inner surface many small chambers called alveoli, which greatly increases surface area for the diffusion of oxygen.

(a) Amphibian (b )Reptile (c) Mammal

Alveoli

Alveoli

Bronchiole

Bronchiole


• Flying creates a respiratory demand for oxygen that exceeds the capacity of the saclike lungs of even the most active mammal.• Birds have evolved the most efficient lung.• An avian lung is connected to a series of air sacs

outside of the lung.LungTrachea

Anteriorair sacs

(a)

Posteriorair sacs

(b)

Trachea Inspiration

Posteriorair sacs

Parabronchi of lungAnteriorair sacs

Inspiration Expiration

ExpirationCycle 1

Cycle 2http://youtu.be/kWMmyVu1ueY

Avian lungs

Mammalian lungs

Uniform pool

Cross current

Counter current

Fish gills

Blood(c)


• This creates a unidirectional flow of air through the lungs.• Blood flow and airflow are not opposite but

flow at perpendicular angles in crosscurrent flow.

THE MAMMALIAN RESPIRATORY SYSTEM

• In the mammalian respiratory system, air passes in and out of the lungs, which are housed in the thoracic cavity.• Air is warmed and

filtered as it flows through the nasal cavity.

• It passes next through the pharynx, then the larynx (or voice box), then to the trachea, or windpipe.

Nasal cavity

Nostril

Glottis

Larynx

Trachea

Right lung

Pharynx

Epiglottis

Left lung

Leftbronchus


• From there, air passes through several branchings of bronchi in the lungs and then to the bronchioles.• The tissue of the

lungs is divided into tiny air sacs called alveoli; through these thin-walled cells, gas exchange with the blood occurs.

Blood flow

Smooth muscle

Bronchiole

Pulmonary arteriole

Pulmonary venule

Alveolarsac

Alveoli

Capillary networkon surfaceof alveolus


• The mammal respiratory apparatus is simple in structure and functions as a one-cycle pump.• A diaphragm muscle separates the thoracic

cavity from the abdominal cavity.• Each lung is covered by a thin, smooth

membrane called the pleural membrane.• This membrane adheres to another pleural

membrane lining the walls of the thoracic cavity, basically coupling the lungs to the thoracic cavity.


• Air is drawn into the lungs by the creation of negative pressure.• The active pumping of air in and out is

called breathing.• During inhalation, muscular contraction

causes the chest cavity to expand.• During exhalation, the ribs and diaphragm

return to their original position.

KEY BIOLOGICAL PROCESS: BREATHING

14

<Plung > Pair

Before inhalation, the air pressure in thelungs (Plung) is equal to the atmosphericpressure (Pair).

During inhalation, the diaphragmcontracts, and the chest cavity expandsdownward and outward. This increasesthe volume of the chest cavity and lungs,which reduces the air pressure inside thelungs, and the air from outside the bodyflows into the lungs.

During exhalation, the diaphragm relaxes,decreasing the volume of the chestcavity. The pressure increases in thelungs, forcing air out of the lungs.

321

Diaphragmrelaxed

Plung

Pair Pair

Inhalation

Chestcavityexpands

Diaphragmrelaxed

Plung

Exhalation

Pair

Diaphragmcontracts

Plung Pair

Plung

Plung = Pair

HOW RESPIRATION WORKS: GAS EXCHANGE

• Oxygen moves through the circulatory system carried by the protein hemoglobin.• Hemoglobin molecules contain iron, which binds

oxygen in a reversible way.Heme group Beta (β) chains

Oxygen (O2)

Iron (Fe++)

Alpha () chains


• Hemoglobin molecules act like little sponges for oxygen.• At the high O2 levels that occur in the blood

supply at the lung, most hemoglobin molecules carry a full load of O2.

• In the tissues, the O2 levels are much lower, so hemoglobin gives up its bound oxygen.

• In the presence of CO2, the hemoglobin assumes a different shape that gives up its oxygen more readily.


• CO2 must also be transported by the blood.• About 8% simply dissolves in the plasma.• 20% is bound to hemoglobin but at a different

site than where O2 binds.• The remaining 72% diffuses into the red blood

cells.

• In order to maintain the gradient for CO2 to leave the tissues and enter the plasma, the CO2 levels in the plasma must be kept low.


• The enzyme carbonic anhydrase combines CO2 with water to form carbonic acid (H2CO3).• This acid dissociates into bicarbonate (HCO3

–) and H+.• Bicarbonate also acts as buffer in the blood

plasma.• In the lungs, the reverse reaction takes place,

and CO2 is released.

THE NATURE OF LUNG CANCER

• Lung cancer is one of the leading causes of death among adults.• Mutations to two tumor-suppressing genes are

implicated in the development of cancer.• Rb codes for Rb protein, which acts as a

brake on cell division.• p53 codes for p53 protein, which detects

damaged or foreign DNA and prevents its replication.

THE NATURE OF LUNG CANCER

• Smoking causes lung cancer.• The annual incidence of

lung cancer is much higher for smokers than for nonsmokers.• Changes in the

incidence of lung cancer have mirrored changes in smoking habits.

• Many types of mutagens are found in cigarette smoke that can damage genes.• The p53 gene is damaged in 70% of lung

cancers.• Smoking also leads to nicotine addiction.

INCIDENCE OF LUNG CANCER IN MEN AND WOMEN

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2000

1500

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10

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50

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10Males

Cigaretteconsumption

30years Lungcancerdeaths

Time

Females3000

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40

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201020001910 1920 1930 1940 1950 1960 1970 1980 1990

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30yearsLungcancerdeaths

1900 1910 1920 1930 1940 1950 960 1970 1980 1990 2000 2010

Time

CHAPTER 24 RESPIRATION. TYPES OF RESPIRATORY SYSTEMS Respiration is the uptake of oxygen and the...

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