BIOM1001 MOD4 LEC5 - Gas Exchange

What are the Factos affecting alveoli gas exchange

• Ventilation

Air way resistance, lung compliance and elasticity, rate & depth of breathing

• Amount of oxygen in air

• Amount of water in air

• Solubility of oxygen in water

How does airway resistance affect gas exchange.

Flow (proportionate to) Pressure difference (inversely proportional) Resistance

• reduce radius of airways → increased resistance

• Can occur through mucus in upper airways and bronchoconstriction

What i lung compliance, and what are factors reducing it.

Compliance:

• the stretchability of lungs during inspiration

• High compliance = easily stretched

• low compliance = hard to stretch

Factors reducing compliance:

• high surface tension (reduced surfactant)

• Scarring of lung tissue (fibrosis)

What is elastic recoil, what are factors that reduce it

Elastic recoil:

• ability of lungs to rebound after stretching

• Creates some expiratory force during expiration

Factors reducing:

• Broken down elastic fibres around alveoli.

• Emphysema (obstructive lung disease)

What is Atmospheric pressure & partial pressure

Atmospheric Pressure:

• pressure exerted by weight of air on objects on earth’s surface.

Partial Pressure:

• pressure one gas contributes to total pressure.

Daltons Law:

• total pressure = sum of all partial pressure

how to calculate partial pressure with amount of water in air

• water vapour ‘dilutes’ air

• To calculate partial pressure of a gas in humid air, subtract water Vapor pressure.

What is the solubility o oxygen in water

Henrys Law:

• at a given temperature, amount of gas in solution is proportional to partial pressure of that gas.

Gases must dissolve in fluid before undergoing gas exchange.

What is in the Alveoli

Alveolar Sacs contain clusters of alveoli:

• tiny thin-walled structures surrounded by high number of capillaries

• High blood flow through capillaries: perfusion (Q)

What is Fick’s Law of Diffusion

• Shorter diffusion distance → faster rate of diffusion

• Greater surface area of diffusion → faster rate of diffusion

How does Gas exchange work?

• The movement of gases across respiratory membrane is driven by differences in partial pressures.

• O2 diffuses from alveoli into blood, CO2 diffuses from blood to alveoli

Gases diffuse down pressure gradients