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Chapter 17. Mechanics of Breathing. About this Chapter. The respiratory system Gas laws Ventilation. Respiratory System. Functions External Respiration Exchange of gases between the atmosphere and the blood Homeostatic regulation of body pH

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chapter 17

Chapter 17

Mechanics of Breathing

about this chapter
About this Chapter
  • The respiratory system
  • Gas laws
  • Ventilation
respiratory system
Respiratory System

Functions

  • External Respiration
    • Exchange of gases between the atmosphere and the blood
  • Homeostatic regulation of body pH
  • Protection from inhaled pathogens and irritating substances
  • Vocalization
respiratory system1
Respiratory System

Principles of Bulk Flow

  • Flow from regions of higher to lower pressure
  • Muscular pump creates pressure gradients
  • Resistance to flow
    • Diameter of tubes
respiratory system2
CO2

O2

Exchange I:atmosphereto lung(ventilation)

Airways

Alveoliof lungs

O2

CO2

Exchange II:lung to blood

O2

CO2

Pulmonarycirculation

Transport ofgases inthe blood

Systemiccirculation

O2

CO2

CO2

Exchange III:blood to cells

O2

Cellularrespiration

Cells

Nutrients

ATP

Respiratory System
  • Overview of external and cellular respiration

Figure 17-1

respiratory system components
Respiratory System Components
  • Conducting system
  • Alveoli
  • Bones and muscle of thorax
respiratory system3
Respiratory System

ANATOMY SUMMARY

THE LUNGS AND THORACIC CAVITY

Pharynx

Nasal cavity

Vocal cords

Upperrespiratorysystem

Tongue

Esophagus

Larynx

Trachea

Lowerrespiratorysystem

Right lung

Left lung

Diaphragm

Left bronchus

Rightbronchus

(a) The respiratory system

Figure 17-2a

muscles used for ventilation
Muscles Used for Ventilation

Sternocleido-mastoids

Scalenes

Internalintercostals

Externalintercostals

Diaphragm

Abdominalmuscles

Muscles ofinspiration

Muscles ofexpiration

(b) Muscles used for ventilation

Figure 17-2b

the respiratory system
The Respiratory System

Air spaceof lung

Air-filledballoon

Pleuralfluid

Pleuralmembrane

Fluid-filled balloon

Figure 17-3

branching of airways
Branching of Airways

ANATOMY SUMMARY

THE LUNGS AND THORACIC CAVITY

Larynx

Trachea

Cartilagering

Left primarybronchus

Secondarybronchus

Bronchiole

Alveoli

(e) Branching of airways

Figure 17-2e

conditioning air
Conditioning Air
  • Warming air to body temperature
  • Adding water vapor
  • Filtering out foreign material
ciliated respiratory epithelium
Ciliated Respiratory Epithelium

Cilia move mucus to pharynx

Dust particle

Mucus layer trapsinhaled particles.

inhaled particles.

Watery saline layerallows cilia topush mucustoward pharynx.

Cilia

Goblet cellsecretes mucus.

Nucleus ofcolumnarepithelial cell

Basementmembrane

Ciliated epithelium of the trachea

Figure 17-5

pulmonary circulation
Pulmonary Circulation
  • Right ventricle  pulmonary trunk  lungs  pulmonary veins  left atrium
  • Note oxygenation
anatomy review
Anatomy Review

PLAY

Interactive Physiology® Animation: Respiratory System: Anatomy Review

gas laws
Gas Laws

Table 17-1

gas laws1
Gas Laws
  • Pgas = Patm % of gas in atmosphere

Table 17-2

boyle s law
Boyle’s Law
  • Gases move from areas of high pressure to areas of low pressure

Figure 17-6

spirometer
Spirometer

Bell

Inspiration

Expiration

Inspiration

Expiration

Air

0.5

Volume(L)

Water

0

Time

Figure 17-7

air flow
Air Flow
  • Flow  P/R
  • Alveolar pressure or intrapleural pressure can be measured
  • Single respiratory cycle consists of one inspiration followed by one expiration
pressure changes during quiet breathing
Pressure Changes During Quiet Breathing

Inspiration

Expiration

Inspiration

Expiration

+2

Alveolarpressure(mm Hg)

A4

Trachea

+1

A1

0

A3

A5

Bronchi

–1

A2

–2

Lung

Intrapleuralpressure(mm Hg)

B3

B1

–3

–4

–5

Diaphragm

–6

B2

Right pleuralcavity

Left pleuralcavity

750

Volumeof airmoved(mL)

500

C2

250

C3

C1

0

1

2

3

4

5

6

7

8

Time (sec)

Figure 17-11

subatmospheric pressure in the pleural cavity
Subatmospheric Pressure in the Pleural Cavity

P = –3 mm HgIntrapleural pressureis subatmospheric.

Ribs

Intrapleuralspace

Pleuralmembranes

Diaphragm

Elastic recoil of thechest wall tries to pullthe chest wall outward.

Elastic recoil of lungcreates an inward pull.

(a) Normal lung at rest

Figure 17-12a

subatmospheric pressure in the pleural cavity1
Subatmospheric Pressure in the Pleural Cavity
  • Pneumothorax results in collapsed lung that cannot function normally

P = Patm

Knife

Lung collapses tounstretched size

Air

Intrapleuralspace

Pleuralmembranes

The rib cageexpands slightly.

If the sealed pleural cavity is openedto the atmosphere, air flows in.

(b) Pneumothorax

Figure 17-12b

compliance and elastance
Compliance and Elastance
  • Compliance: ability to stretch
    • High compliance
      • Stretches easily
    • Low compliance
      • Requires more force
      • Restrictive lung diseases
        • Fibrotic lung diseases
        • Inadequate surfactant production
  • Elastance: returning to its resting volume when stretching force is released
law of laplace
Law of LaPlace
  • Surface tension is created by the thin fluid layer between alveolar cells and the air

Figure 17-13

surfactant
Surfactant
  • More concentrated in smaller alveoli
  • Mixture containing proteins and phospholipids
  • Newborn respiratory distress syndrome
    • Premature babies
    • Inadequate surfactant concentrations
air flow1
Air Flow

Table 17-3

pulmonary ventilation
Pulmonary Ventilation

PLAY

Interactive Physiology® Animation: Respiratory System: Pulmonary Ventilation

ventilation
Ventilation
  • Total pulmonary ventilation is greater than alveolar ventilation because of dead space
  • Total pulmonary ventilation = ventilation rate  tidal volume
ventilation1
P

=

O2

~

P

~

O2

Ventilation

Dead space filledwith fresh air

The first exhaledair comes out ofthe dead space.Only 350 mLleaves the alveoli.

150mL

1

End of inspiration

1

2700 mL

2

Exhale 500 mL(tidal volume)

Atmospheric

air

150

350

At the end of expiration, thedead space is filled with“stale” air from alveoli.

3

2

Dead space isfilled withfresh air.

150mL

150

RESPIRATORYCYCLE INADULT

4

Inhale 500 mLof fresh air (tidal volume).

Only 350 mLof fresh airreaches alveoli

350

2200 mL

150

2200 mL

The first 150 mLof air into thealveoli is staleair from thedead space.

4

Dead space filledwith stale air

KEY

150 mm Hg (fresh air)

150mL

100 mm Hg (stale air)

3

2200 mL

Figure 17-14

ventilation2
Ventilation
  • Alveolar ventilation = ventilation rate  (tidal volume – dead space volume)

Table 17-4

ventilation3
Ventilation

Table 17-5

ventilation4
Ventilation

Table 17-6

ventilation5
Ventilation
  • As alveolar ventilation increases, alveolar PO2 increases and PCO2 decreases

Figure 17-15

ventilation6
Ventilation

Table 17-7

ventilation7
Ventilation
  • Local control mechanisms attempt to match ventilation and perfusion

Figure 17-16a

ventilation8
Ventilation

Figure 17-16b

ventilation9
Ventilation

Figure 17-16c

ventilation10
Ventilation
  • Auscultation = diagnostic technique
  • Obstructive lung diseases
    • Asthma
    • Emphysema
    • Chronic bronchitis
summary
Summary
  • Respiratory system
    • Cellular respiration, external respiration, respiratory system, upper respiratory tract, pharynx, and larynx
    • Lower respiratory tract, trachea, bronchi, bronchioles, alveoli, Type I and Type II alveolar cells
    • Diaphragm, intercostal muscles, lung, pleural sac, and pleural fluid
  • Gas Laws: Dalton’s law and Boyle’s law
summary1
Summary
  • Ventilation
    • Tidal volume, vital capacity, residual volume, and respiratory cycle
    • Alveolar pressure, active expiration, intrapleural pressures, compliance, elastance, surfactant, bronchoconstriction, and bronchodilation
    • Total pulmonary ventilation, alveolar ventilation, hyperventilation, and hypoventilation
ad