Respiratory System

INTRODUCTION

Functions

• 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 lungsExternal Respiration• Gas exchange between alveoli and bloodInternal Respiration• Gas exchange between blood and body cells

STRUCTURES AND FUNCTIONS

Upper Respiratory

Nose (nares)• Warm, humidify, filter dust• Olfactory stimuli• Modify vocal soundsPharynx• 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 relatedInhalation:• 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 = 12Tidal Volume (TV): volume moved in one normal

breath• Normal = approx. 500ml• About 70% reaches alveoli• 30% remains in airwayMinute 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 pressureSum of partial pressures = atmospheric pressureEach gas diffuses down its pressure gradient• Example: O2 • In air, P = 105 mm Hg• In blood, P = 40 mm Hg

Breathing ControlBrain Centers:• Medullary rhythmicity area• 2 areas in the ponsFactors:• Voluntary adjustment (cortical)• Chemoreceptors• Limbic system; emotion, anticipation• Body temperature• Pain, airway irritation (cough, sneeze)