Lung Mechanics and Gas Laws

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Questions and Answers

What role do the external intercostals play during normal quiet breathing?

They help lift the rib cage. (correct)

They contract the diaphragm.

They activate abdominal muscles.

They pull the rib cage downward.

Which of the following best describes Dalton's Law?

The total pressure of a mixture of gases equals the sum of the partial pressures. (correct)

The total pressure is independent of the individual gas pressures.

The partial pressures of gases become equal in mixtures.

The partial pressure of a gas is always higher than the total pressure.

What is the significance of the fluid attachment in the lungs?

It significantly hinders lung expansion.

It prevents the rib cage from lifting.

It assists in gas exchange.

It helps keep the lungs partially inflated. (correct)

According to the composition of Earth's atmosphere, what is the percentage of oxygen in the mixture?

21% Signup and view all the answers

During expiration, which muscle is primarily responsible for pulling the rib cage down and in?

Internal intercostals Signup and view all the answers

What is the primary role of surfactant lipoproteins in the alveoli?

To reduce the work required to stretch the alveoli during inhalation Signup and view all the answers

What condition is primarily caused by inadequate surfactant lipoprotein production in newborns?

Newborn Respiratory Distress Syndrome (NRDS) Signup and view all the answers

How does the production of surfactant lipoproteins change over the course of pregnancy?

It reaches adequate levels around the 7th month of pregnancy Signup and view all the answers

What is the effect of decreased compliance in the lungs of premature infants?

Greater work effort required for inhalation Signup and view all the answers

What type of resistance primarily affects airflow in the trachea and bronchi?

Fixed resistance due to the fixed radius of airways Signup and view all the answers

Which formula represents the relationship between resistance to airflow and airway radius?

R α 1/r^4 Signup and view all the answers

What is required to help treat infants with Newborn Respiratory Distress Syndrome?

Forced ventilation to keep alveoli inflated Signup and view all the answers

What effect does insufficient surfactant have on alveoli during exhalation?

Causes them to collapse Signup and view all the answers

What role does the diaphragm play during inspiration?

It contracts and pulls downward. Signup and view all the answers

According to Boyle's law, what happens to the pressure inside the lungs as their volume increases?

The pressure decreases. Signup and view all the answers

What happens during normal expiration?

It is a passive process. Signup and view all the answers

Which muscles assist in expanding the thoracic cavity during heavy breathing?

Sternocleidomastoid and scalene muscles. Signup and view all the answers

Why does air move into the lungs during inspiration?

Because atmospheric pressure is higher than lung pressure. Signup and view all the answers

What occurs to the lung pressure during expiration?

It rises above atmospheric pressure. Signup and view all the answers

What is the role of pleura fluid in breathing?

To create a connection between lungs and thoracic cavity walls. Signup and view all the answers

What is a key characteristic of lung tissue that aids in expiration?

Increased elasticity. Signup and view all the answers

What occurs when the smooth muscle in the bronchioles contracts?

Decreased bronchiole radius Signup and view all the answers

Which factor is the most important in influencing bronchiole smooth muscle tone under normal conditions?

Level of CO2 in exhaled air Signup and view all the answers

What effect does increased CO2 levels in the exhaled air have on bronchioles?

Bronchodilation Signup and view all the answers

Which of the following can cause bronchoconstriction in bronchioles?

Inhalation of allergens Signup and view all the answers

What is the consequence of bronchoconstriction on airflow?

Decreased airflow and difficulty breathing Signup and view all the answers

What role do histamine blockers play in managing bronchoconstriction?

Reduce the binding of histamine to its receptors Signup and view all the answers

What is the primary effect of administered epinephrine on the bronchioles?

Causes bronchodilation Signup and view all the answers

During an allergic reaction, what is a primary physiological response related to bronchioles?

Bronchoconstriction due to histamine release Signup and view all the answers

How is Total Pulmonary Ventilation (TPV) calculated?

TPV = Ventilation Rate x Tidal Volume Signup and view all the answers

How does decreased CO2 levels in exhaled air affect the bronchioles?

Causes bronchoconstriction Signup and view all the answers

What is the normal adult tidal volume (VT) during quiet breathing?

500 ml Signup and view all the answers

If the ventilation rate is 15 breaths per minute, what is the Total Pulmonary Ventilation (TPV)?

4500 ml/min Signup and view all the answers

What is considered 'Dead Air' in the context of tidal volume?

150 ml that does not reach the alveoli Signup and view all the answers

Which of the following best describes Alveolar Ventilation (AV)?

The volume of air reaching the alveoli per minute Signup and view all the answers

What is the impact of a ventilation rate below the normal range on Total Pulmonary Ventilation?

It decreases TPV Signup and view all the answers

Why is only a portion of tidal volume used during gas exchange?

Some air is used to fill the trachea and bronchi Signup and view all the answers

Study Notes

Lung Mechanics

The continuous presence of fluid between the pleura and the lungs causes partial inflation.
The diaphragm contracts when inhaling causing a downward pull.
The external intercostals contract when inhaling causing the rib cage to expand upwards and outwards.
The muscles of expiration are not active during normal respiration.

Universal Gas Laws

Dalton's Law states that the total pressure of a mixture of gases is equal to the sum of the individual pressures of the gases in the mixture.
The partial pressure of a gas is the individual pressure of that gas.
78% of the atmosphere is nitrogen, 21% is oxygen, 0.03% is carbon dioxide, and 0.9% are other gases.

Lung Ventilation Inspiration

An increase in the thoracic cavity's volume causes a reduced pressure within the lungs.
According to Boyle's Law, the pressure of gas is inversely proportional to the volume it occupies.
When the pressure inside the lungs drops below atmospheric pressure, a pressure gradient is created that causes air to move from the atmosphere into the lungs.

Lung Ventilation Expiration

Normal, quiet breathing is a passive process that does not require muscle contraction.
When the inspiratory muscles relax, the volume of the thoracic cavity decreases.
This causes an increase in the pressure within the lungs, as the volume decreases.
This pressure gradient causes air to move from the lungs to the atmosphere.

Lung Ventilation During Heavy Breathing

During heavy breathing, the scalene and sternocleidomastoid muscles increase their contraction to further expand the volume of the thoracic cavity and lungs.

Surfactant

Surfactant is secreted by type II alveolar cells and is a mixture of lipoproteins.
Surfactant reduces the surface tension in the alveoli, making it easier to stretch them during inspiration.
Insufficient surfactant production results in:
- Increased surface tension in the alveoli.
- Greater work effort required to inhale.
- Increased chance of alveolar collapse.
Newborn Respiratory Distress Syndrome (NRDS) is caused by insufficient surfactant production in premature babies.
The lungs of babies born before the 7th month of fetal development typically do not have enough surfactant to overcome the surface tension in their alveoli.
Premature babies need treatment to increase surfactant levels to prevent alveolar collapse and death.

Resistance to Airflow

The radius of the airway is a key factor in determining the resistance to airflow, just as in blood flow.
Resistance to airflow is inversely proportional to the radius of the airways to the fourth power.
The majority of airflow resistance is found in the trachea and bronchi, which have a fixed radius.
The bronchioles have a variable radius due to the presence of smooth muscle in their walls.

Bronchoconstriction and Bronchodilation

Bronchoconstriction occurs when the smooth muscle of the bronchioles contracts, decreasing their radius and increasing resistance to airflow.
Bronchodilation occurs when the smooth muscle of the bronchioles relaxes, increasing their radius and decreasing resistance to airflow.
Changes in CO2 level, histamine release, and autonomic nervous system (ANS) innervation influence smooth muscle contraction in the bronchioles.

CO2 Levels and Airflow

Increased CO2 levels in the exhaled air cause bronchodilation, increasing airflow.
Decreased CO2 levels in the exhaled air cause bronchoconstriction, decreasing airflow.
CO2 levels are crucial in maintaining a normal blood pH.

Histamine and Airflow

Histamine is released from mast cells in the lungs in response to tissue irritation.
Histamine can be released upon inhalation of allergens, leading to bronchoconstriction.
Histamine blockers are used to block histamine receptors and reduce bronchoconstriction during allergic reactions.

Ventilation Efficiency - Total Pulmonary Ventilation

Ventilation efficiency is a measurement of how effectively the respiratory system moves air into and out of the lungs.
Total Pulmonary Ventilation (TPV) represents the total amount of air moved in or out of the lungs per unit time.
TPV is calculated by multiplying the ventilation rate (VR) by the tidal volume (VT).

Tidal Volume

The tidal volume (VT) is the amount of air moved into or out of the lungs during a single breath during quiet breathing.
Normal tidal volume for adults is approximately 500ml.

Ventilation Efficiency - Dead Air

Dead air is the portion of inhaled air that does not participate in gas exchange with the blood.
Dead air fills the airways and is typically about 150ml of the 500ml tidal volume.

Ventilation Efficiency - Alveolar Ventilation

Alveolar ventilation (AV) is a more accurate measurement of lung ventilation efficiency, representing the volume of air that actually reaches the alveoli per minute.
AV is calculated by subtracting the dead space (Vd) from the tidal volume (VT) and multiplying by the ventilation rate (VR).
AV = (VT - Vd ) x VR

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Description

This quiz covers key concepts in lung mechanics, including diaphragm function and gas laws such as Dalton's and Boyle's. Understand how these principles apply to respiration and ventilation. It's perfect for students studying human physiology or respiratory systems.