Respiratory System
INTRODUCTION
Functions
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Provide for gas exchange
Intake of O2
Removal of CO2
Regulate blood pH
Sense of smell
Produces sounds
Filters, warms, moistens air
Water, heat balance
3 Major Steps
Pulmonary Ventilation
• Moving air in and out of lungs
External Respiration
• Gas exchange between alveoli and blood
Internal Respiration
• Gas exchange between blood and body cells
STRUCTURES AND
FUNCTIONS
Upper Respiratory
Nose (nares)
• Warm, humidify, filter dust
• Olfactory stimuli
• Modify vocal sounds
Pharynx
• 3 regions
• Tonsils, adenoids here
• Eustachian tubes
Lower Respiratory
Larynx
• “Voice box”
• Thyroid cartilage
• Epiglottis
• Cricoid cartilage
Lower Respiratory
Trachea
• Windpipe
• Lined with ciliated mucous membrane; traps
dust and moves it upward
• C-shaped rings of cartilage keep airway open
Lower Respiratory
Bronchi, Bronchioles
• Bronchi contain cartilage rings
• Primary (1° ) bronchi enter lungs
• Secondary bronchi branch from 1°, one for
each lobe (3R, 2L)
• Tertiary bronchi →→ terminal bronchi
• Smaller airways have less cartilage, more
smooth muscle
Lower Respiratory
Lungs
• Right lung has 3 lobes, left has 2
• Surrounded by pleural membrane
• Tertiary bronchioles divide into terminal
bronchioles
• These lead to respiratory bronchioles, which
lead to the alveoli
Lower Respiratory
Alveoli
• This is where gas exchange takes place
• Surfactant cells secretes a substance that
keeps the alveoli from collapsing
• Macrophages help fight infection
Pulmonary Ventilation
Volume and pressure are inversely related
Inhalation:
• Contraction of diaphragm lowers the muscle
and lung volume ↑
• Alveolar pressure ↓
• Air enters lungs to equalize pressure
Pulmonary Ventilation
Exhalation:
• Relaxation of the diaphragm raises the muscle
and lung volume ↓
• Alveolar pressure ↑
• Air rushes out
Air Flow
Frequency (f): Breaths/min; normal = 12
Tidal Volume (TV): volume moved in one normal
breath
• Normal = approx. 500ml
• About 70% reaches alveoli
• 30% remains in airway
Minute Ventilation (MV): f x TV = 6000 ml/min
Air Flow
Inspiratory Reserve Volume (IRV): volume of air
that can be inhaled beyond TV
Expiratory Reserve Volume (ERV): volume of air
that can be exhaled beyond TV
Residual Volume (RV): air remaining in lungs
after ERV
Nature of Air
Mixture of gases – N2, O2, CO2, H2O, etc.
Each gas exerts a partial pressure
Sum of partial pressures = atmospheric pressure
Each gas diffuses down its pressure gradient
• Example: O2
• In air, P = 105 mm Hg
• In blood, P = 40 mm Hg
Breathing Control
Brain Centers:
• Medullary rhythmicity area
• 2 areas in the pons
Factors:
• Voluntary adjustment (cortical)
• Chemoreceptors
• Limbic system; emotion, anticipation
• Body temperature
• Pain, airway irritation (cough, sneeze)