2.1 Structure and Function of the Ventilatory System Flashcards
Principal structures of the ventilatory system
- Nose
- Mouth
- Pharynx
- Larynx
- Bronchi
- Bronchioles
- Lungs
- Alveoli
Passage of Air
- Air enters the nostrils/mouth
- Passes through larynx
- Into the trachea
- Into the right and left lungs - starting at bronchi, which branches into
- Bronchioles, each of which terminates in a cluster of
- Alveoli
Functions of the conducting airways
- Low resistance pathway for air flow
- Defence against chemicals and other substances that are inhaled
- hair in nose
- mucus
- Warming and moistening the air
- nose
Pulmonary Ventilation
Inflow and outflow of air between the atmosphere and lungs (breathing)
Total Lung Capacity
Volume of air in the lungs after a maximum inhalation
Vital Capacity
Maximum volume of air that can be exhaled after a maximum inhalation
Tidal Volume
Volume of air breathed in and out in any one breathe
Expiratory Reserve Volume
Volume of air in excess of tidal volume that can be exhaled forcibly
Inspiratory Reserve Volume
Additional inspired air over and above tidal volume
Residual Volume
Volume of air still contained in the lungs after a maximal exhalation
Mechanics of ventilation in the human lungs.
Air flows because of the pressure difference between atmosphere and gases in the lungs
During inhalation
- Intercostal muscles and diaphragm contract to expand the chest cavity
- diaphragm - moves downwards
- intercostal muscles - move rib cage upwards and out
- this increases space for the lungs
- Increases in size decreases the internal air pressure
- so air from outside (now higher pressure) rushes into the lungs to equalise the pressures
During exhalation
- Intercostal muscles and diaphragm relax to their resting positions
- Reduces the size of the thoracic cavity and increases pressure forcing air out of the lungs
Accessory muscles
Accessory muscles are also important during strenuous exercise
Includes diaphragm and intercostal muscles
Nervous and chemical control of ventilation during exercise
- Ventilation increases as a direct result of increases in blood acidity levels (low pH levels)
- Acidity due to increased CO2 content of the blood detected by the respiratory centre
- Results in increase in rate and depth of ventilation
- Neural control of ventilation includes lung stretch receptors, muscle proprioreceptors and chemoreceptors
Lung stretch receptors
When lung expands, receptors initiate the reflex in which reduces the respiratory rate
Muscle proprioreceptors
A nerve ending that functions as a sensory receptor - relay information about motion or position and make us aware of our own body position and movement in space
