Lung Structure & Function

Question 1

Describe the major physiological functions of the respiratory system regarding the transport of oxygen and carbon dioxide

Answer 1

Transport of O2 & CO2 occurs @ the alveoli via passive diffusion. The alveolar air sacs are covered by capillaries that give a large surface area for transport.

Question 2

Describe the major structures and functions within the respiratory system, including: the ventilatory apparatus

Answer 2

The ventilatory apparatus (lungs & chest wall) is used for pulmonary ventilation & consists of the conductive & respiratory zones.

Question 3

Describe the major structures and functions within the respiratory system, including: the branching system of airways

Answer 3

The branches increase the surface area of the lung to facilitate breathing.

The cross sectional area also increases as we go down the lung & since Q, flow is constant, the increase in A decreases v, the velocity, which increases the time for gas exchange via diffusion. Equilibrium is achieved when the partial pressure of oxygen is the same in alveolar gas and in pulmonary capillary blood; the same is true for carbon dioxide.

Question 4

Describe the major structures and functions within the respiratory system, including: the conductive zone

Answer 4

In the conductive zone, which consists of the first 16 branches of the lung, there is no gas exchange between the lung & blood. It conducts air to deeper part of lung where the gas exchange can occur. Includes the trachea, bronchi, bronchioles, & terminal bronchioles. Also called anatomic dead space. The epithelium of the conducting zone airways has a ciliated surface that continuously propels mucous (secreted by goblet cells) carrying ingested particles toward the mouth.

Question 5

Describe Henry’s law of gas solubility and their applicability to basic and clinical pulmonary physiology

Answer 5

Henry’s law states that the concentration of a dissolved gas at equilibrium is proportional to the partial pressure of the gas above the solution (gases dissolve in liquids). Alveolar compartment vs blood.

Dissolved gasses (partial pressures) do not contribute to blood volume or pressure.

Question 6

Describe the physiological model of an overview of the distribution of oxygen and carbon dioxide transport utilizing concepts including partial pressures and fractions of gases in air and in blood; begin to appreciate how this model enables you to understand how blood gases change in various lung and blood compartments in health and in disease

Answer 6

The partial pressure of a gas in a mixture of gases is the fractional contribution of that gas to the total pressure (so if larger fraction, it contributes more). Use this concept for ideal gas equation, can sum ideal gas law fraction for each gas & add them for total.

For a dry gas:
Partial pressure of A = (mole fraction of A) x Total pressure

For a wet gas:
Partial pressure of A = (mole fraction of A) x (Total pressure - Pressure H2O)

Question 7

Ventilation equation

Answer 7

Ventilation = the rate flow of air into & out of the lungs

V = f x TV

V = ventilation (L/min)
f = frequency (breaths/ min)
TV = tidal volume (L/breath)

f & TV in V both increase during exercise like HR & SV do for CO

Question 8

Blood gases in the diagnosis of blood disease

Answer 8

Remember that essentially we inspire 100% O2 & expire 100% CO2.

If the lung is diseased & cannot expire CO2 & the rate at which it is produced, CO2 mixes with water & blood pH decreases which sucks for the pH optimum metabolic rxns in the body

Question 9

Effects of smoking on the lungs

Answer 9

Smoking stimulates mucous secretions, that is why they always are coughing. The mucous can sink to the bottom of the lung & cause lung infection.

Question 10

Spirometers measure

Answer 10

ventilation (L/min)

See pg. 5 for graph & note that TV is the amplitude

Question 11

Ideal gas law equation

Answer 11

PV=nRT

P = pressure
V = volume
n = # moles
R = gas constant
T = absolute temperature in kelvin

Question 12

The water vapor pressure at a body temperature of 37C is

Answer 12

47 mm Hg

Question 13

Describe the major structures and functions within the respiratory system, including: the respiratory zones

Answer 13

In the respiratory zone, which constists of the last 7 branches of the lung, O2 & CO2 exchange with the blood occurs. Includes the respiratory bronchioles, alveolar (alveoli) ducts, & alveolar sacs.

Each alveolus is covered with pulmonary capillaries.

The epithelium of the respiratory zone contains Type I alveolar cells which line the alveoli and Type II alveolar cells which secrete a lipoprotein surfactant.

Question 14

What type of alveolar cells make surfactant? Discuss the importance of surfactant.

Answer 14

Type II alveolar cells secrete lipoprotein surfactant.

Pulmonary surfactant coats the inner alveolar surface which reduces alveolar surface tension, and contributes to the mechanical stability of the lung & facilitates breathing (especially inspiration). The major component of pulmonary surfactant is dipalmitoylphosphatidylcholine.

Question 15

Composition of air

Answer 15

N2 = 78%

O2 = 21%

CO2 = .03% (negligible)

Argon = 1% (inert so no exchange)

Question 16

When doing gas problems what must I do when I calculate the partial pressure of a gas?

Answer 16

You must use the dry gas pressure when calculating partial pressures so I must subtract the water pressure from the total pressure. 760 - PH2O.

Standard PH2O = 47 mm Hg

Question 17

Does the fraction of air decrease with altitude?

Answer 17

No

The fraction of oxygen in air is 21% at sea level as well as at high altitude. The total pressure decreases with increasing altitude but the fraction is independent of altitude.

Question 18

Standard temperature & pressure

Answer 18

0 C, 760 mmHg, & 0 mmHg water vapor presure

Remember 0 C = 273.15 Kelvin

Question 19

When converting the tidal volume for the partial pressure of a gas under different conditions to STP

Answer 19

I must theorize how changing the temperature & pressure (PV=nRT) would change the volume to make the conversions for each fraction less than 1 or greater than 1.

Question 20

Rank the gradient of oxygen partial pressures from: alveoli, arterial blood, venous blood

Answer 20

PO2 Alveoli > PO2 arteries > PvCO2

Question 21

Water vapor pressure is a function of ______ & is constant @ a given _______. Water vapor pressure _______ with increasing ________. The vapor pressure @ 37C is _______. @ 0C water vapor pressure is almost ___ mmHg.

Answer 21

Water vapor pressure is a function of temperature & is constant @ a given temperature. Water vapor pressure increases with increasing temperature. The vapor pressure @ 37C is 47 mmHg. @ 0C water vapor pressure is almost 0 mmHg.

See pg. 9

For nearly all problems, subtract water vapor pressure assuming it is 47mmHg when they say what is PO2 inside the body–alveoli or trachea are @ 37C. Do this especially when they say @ sea level or when they give a value for water vapor pressure. For changes in temperature, they must give water vapor pressure.