Respiratory System Functions and Lung Capacities

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Questions and Answers

What is the primary difference between compliance and elastance in respiratory physiology?

Compliance and elastance are synonymous terms with no significant difference.

Elastance is only relevant in diseases affecting lung capacity.

Compliance refers to the ability to stretch but elastance refers to the ability to return to its original shape. (correct)

Compliance is the ability to recoil, while elastance is the ability to stretch.

How do surfactants influence surface tension in the alveoli?

Surfactants reduce surface tension to help stabilize the alveoli. (correct)

Surfactants increase surface tension, which is necessary for lung expansion.

Surfactants only affect surface tension in the bronchi.

Surfactants have no effect on surface tension.

Which factor is most significant in affecting airway resistance?

Viscosity of the air

Temperature of the air

Radius of the airway (correct)

Length of the airway

What is the effect of bronchoconstriction on airway resistance?

It increases resistance by partly closing the airways. Signup and view all the answers

What initiates bronchodilation in the respiratory system?

Binding of epinephrine to B2 receptors. Signup and view all the answers

What is the role of local control mechanisms in ventilation and blood flow?

They ensure perfusion is matched to alveolar ventilation for optimal gas exchange. Signup and view all the answers

What happens to blood flow when ventilation decreases in a group of alveoli?

Vasoconstriction occurs upstream to prioritize oxygenation. Signup and view all the answers

What is the typical dead space volume in the lungs?

150 ml Signup and view all the answers

How is total pulmonary ventilation calculated?

As the product of ventilation rate and tidal volume. Signup and view all the answers

What role does the diaphragm play during inspiration?

It contracts to increase thoracic volume. Signup and view all the answers

Which volume represents the air that remains in the lungs after maximal exhalation?

Residual volume Signup and view all the answers

What is the main function of the protective mechanism of the respiratory system?

To protect from inhaled pathogens. Signup and view all the answers

How does intrapleural pressure contribute to normal lung function?

It is normally sub-atmospheric to maintain lung inflation. Signup and view all the answers

What defines the total lung capacity?

The combination of all lung volumes. Signup and view all the answers

During expiration, what happens to alveolar pressure?

It increases as thoracic volume decreases. Signup and view all the answers

Which capacity is defined as the sum of expiratory reserve volume and residual volume?

Functional residual capacity Signup and view all the answers

When does alveolar pressure reach its highest point during a respiratory cycle?

Halfway through inspiration. Signup and view all the answers

Which statement correctly explains the tidal volume?

It is the volume of air moved during normal, restful breathing. Signup and view all the answers

What is the effect of decreasing thoracic volume during expiration?

It results in an increase in alveolar pressure. Signup and view all the answers

Study Notes

Respiratory System Functions

Four major functions:
- Gas exchange between atmosphere and blood
- Homeostatic regulation of body pH
- Protection from inhaled pathogens
- Vocalization

Lung Volumes and Capacities

Tidal volume (VT): Normal breathing volume at rest
Inspiratory reserve volume: Volume breathed beyond tidal volume during a deep breath
Expiratory reserve volume: Extra volume exhaled beyond tidal volume
Residual volume: Air remaining in lungs after maximal exhalation (cannot be exhaled)
Capacities: Combinations of two or more volumes
- Functional residual capacity (FRC): Air remaining in the lungs after a normal exhalation (Expiratory reserve volume + Residual volume)
- Total lung capacity (TLC): The sum of all lung volumes
- Vital capacity (VC): The maximum amount of air that can be exhaled after a maximum inhalation (Inspiratory reserve volume + Tidal volume + Expiratory reserve volume)

Spirometer Tracing

Visual representation of lung volumes and capacities
Shows the different phases of inhalation and exhalation
Illustrates the various volumes (tidal, inspiratory reserve, expiratory reserve, residual) and capacities (inspiratory capacity, vital capacity, total lung capacity, functional residual capacity)

Pressure and Lung Volumes During Breathing

Inspiration: Alveolar pressure decreases, thoracic volume increases (due to diaphragm contraction)
Expiration: Diaphragm relaxes, thoracic volume decreases, alveolar pressure increases

Intrapleural Pressure

Sub-atmospheric pressure
Keeps lungs inflated (-3 mm Hg)
Pleural cavity: sealed compartment

Alveolar and Intrapleural Pressure Changes

Alveolar pressure is always greater than intrapleural pressure to inflate lungs
Intrapleural pressure has greater oscillation
Lowest pressure point in alveoli: halfway through inspiration
Highest pressure point in alveoli: halfway through expiration

Lung Compliance and Elastance

Compliance: Ability to stretch
Elastance: Ability to return to normal (recoil)

Surface Tension and Surfactants

Surface tension: Due to water lining alveoli surface
Surfactants: Reduce surface tension, ensuring alveoli stability

Airway Resistance

Radius: Largest factor affecting airway resistance; affects bronchoconstriction/dilation
Bronchoconstriction: Increased resistance (caused by parasympathetic stimulation, binding to muscarinic receptors, closes airway)
Bronchodilation: Decreased resistance (caused by sympathetic stimulation, binding to B2 receptors, opens airway)

Ventilation and Alveolar Blood Flow Matching

Perfusion of blood matched to alveolar ventilation for efficient gas exchange
Decreased ventilation in a region leads to increased CO2, decreased O2, causing vasoconstriction to divert blood to better-ventilated areas

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Description

This quiz explores the key functions of the respiratory system, including gas exchange, pH regulation, and protection. It also covers essential lung volumes and capacities, such as tidal volume, inspiratory reserve, and vital capacity. Test your understanding of these crucial physiological concepts.