Respiratory System Physiology

Flashcards covering the structure and functional physiology of the respiratory system, including lung volumes, mechanics, and gas exchange laws.

What are the four main processes involved in the coordinated functioning of the respiratory system?

a. Pulmonary ventilation (mechanical exchange of $O_2$ and $CO_2$), b. Gas diffusion (across the alveolo-capillary membrane), c. Perfusion (transport of gases by blood), and d. Regulation of breathing (respiratory centers and reflexes).

What is the partial pressure of water vapor in the respiratory tract when the air is fully humidified?

$$47\,mmHg$$

According to Boyle's law, what is the relationship between temperature, volume, and pressure?

At a constant temperature, the product of pressure and volume is constant ($P \times V = \text{const.}$).

Which type of pneumocytes are structural-functional cells where gas diffusion takes place?

Pneumocytes Type I (representing $95\,\%$ of cells).

What is the primary function of Pneumocytes Type II?

They produce surfactants to reduce the surface tension of the alveoli and enable the regeneration of type I and II pneumocytes.

What is the formula for Laplace's law as applied to alveolar pressure?

$P = \frac{2 \times \gamma}{r}$, where $P$ is the pressure in the alveolus, $\gamma$ is the surface tension, and $r$ is the radius of the alveolus.

What defines the "Anatomical Dead Space"?

The part of the conducting pathway (~$150\,mL$) where only the flow of air occurs (convection) and no gas exchange takes place.

How do sympathetic and parasympathetic nervous systems affect the respiratory tract?

Sympathetic activation via $\beta_2$-adrenergic receptors causes relaxation (dilation), while parasympathetic activation via muscarinic receptors causes contraction (constriction).

Which nerve innervates the diaphragm, and from which spinal segments does it originate?

The nervus phrenicus, originating from segments $C3-C5$.

What is the typical value for intrapleural pressure ($P_{IP}$) at the end of a normal expiration?

$$-5\,cmH_2O$$

Define Transpulmonary Pressure ($P_{L}$).

The difference between alveolar pressure and intrapleural pressure ($P_{L} = P_{A} - P_{IP}$).

What is Lung Compliance ($C$) and how is it calculated?

Compliance describes the change in lung volume per unit change in pressure: $C = \frac{\Delta V}{\Delta P}$. The normal value is approximately $200\,mL/cmH_2O$.

How does Lung Compliance change in patients with emphysema?

Compliance is increased because the loss of elastic fibers makes the lungs more loose and prone to air trapping.

What is the typical Tidal Volume ($V_T$) in a healthy adult?

Approximately $500\,mL$.

How is Vital Capacity ($VC$) calculated?

$VC = V_T + IRV + ERV$, where $V_T$ is tidal volume, $IRV$ is inspiratory reserve volume, and $ERV$ is expiratory reserve volume.

What is the difference between restrictive and obstructive lung diseases regarding the Tiffeneau index ($FEV_1 / FVC$)?

In obstructive diseases, the Tiffeneau index is significantly decreased, while in restrictive diseases, it remains approximately normal despite reduced total volumes.

Which method is used to measure the Functional Residual Capacity (FRC) using an inert gas?

The Helium Dilution Method.

What is the Respiratory Quotient ($R$ or $RQ$)?

The ratio of the flow of produced $CO_2$ to the flow of consumed $O_2$: $R = \frac{\dot{V}_{CO2}}{\dot{V}_{O2}}$. For pure glucose oxidation, it is $1$, but it is lower ($~0.7$) for fatty acids.

What is the Alveolar Gas Equation for the partial pressure of carbon dioxide ($P_{ACO2}$)?

$P_{ACO2} = \frac{\dot{V}_{CO2} \times k}{\dot{V}_A}$, where $\dot{V}_{CO2}$ is $CO_2$ production and $\dot{V}_A$ is alveolar ventilation.

How do the systolic and diastolic pressures in the pulmonary artery compare to systemic circulation?

The pulmonary artery has significantly lower pressures: systolic is approximately $24\,mmHg$ and diastolic is approximately $9\,mmHg$, with a mean pressure of $14\,mmHg$.