EPHE 160 - Respiration: Pressure + Respiratory Anatomy

goals of the respiration system

supply body with O2 and remove CO2

main steps of respiration

1. ventilation

2. pulmonary gas exchange

3. transport of gases through blood

4. systemic gas exchange

Key anatomic components of ventilatory pump

1. respiratory muscles

2. ribcage and abdomen

3. cortical + brainstem that control ventilation

4. neural connections

Involuntary vs Voluntary Breathing

Pons vs medulla

Alveoli

single layer epithelium(like capillaries)

2 types of cells

• type I alveolar cells → main site of gas exchange

• type II → secrete surfactant

Capillaries on Alveoli

covers outer surface of alveoli

rapid diffusion/gas exchange

Surfactant

amphiphillic compound that reduces surface tension between a liquid and a gas

Surface Tension of Aveolar Fluid

created by the thin film of fluid lining inside the alveoli

reduced by surfactant

Law of LaPlace

P= 2T/R

law that demonstrates that the presence of surfactant inside alveoli reduces the alveolar surface tension in larger alveolis in order to equate pressures and prevent alveolar collapse

Compliance of the Lung

how much effort is required to stretch the lungs and chest wall

High Compliance of the Lung

lungs expand easily

Low Compliance of the Lung

difficult for the lungs to expand

Ventilation

defined as breathing

movement of air in and out of the lungs

exchange of air from atmosphere into alveoli

What factors is ventilation dependent on?

atmospheric pressure

alveolar pressure

intrapleural pressure

What is the typical rule for gas exchange and ventilation?

gas goes to areas where the pressure is lower

Intrapleural pressure

pressure between pleural sac and chest walls in order to “pull” lungs to expand and contract with the chest wall

What would a lung puncture cause and why?

lung puncture would expose the pleura to atmospheric pressure which is always higher causing air to rush into the chest cavity and collapsing/crumpling the lung

Boyles Law

the volume of a gas varies inversely with its pressure

Volume x Pressure Relationship

inversely proportionate relationship

high pressure=low volume

low pressure=high volume

Inspiration

respiratory muscles contract

increase in thoracic volume

decrease in alveolar pressure

air flows into lungs

Expiration

respiratory muscles relax

ribcage decreases volume

alveolar pressure increases

air flows out

Functional Residual Capacity(FRC)

static lung volumes/capacites

Lung Volumes

measured to assess lung function

Lung Capacities

Combinations of Lung Voluems

Ventilation equation

V*=vT x RR

Tidal Volume

amount of air you take in and blowing out at a resting rate

Inspiratory Reserve Volume(IRV)

amount of air you can take in after normal respiration

Expiratory Reserve Volume(ERV)

amount of air you can expire after a normal tidal volume exhalation

Residual Volume

amount of air remaining in lungs after a forced exhalation

Exchange of O2 and CO2

Driven by differences in partial pressures of each gas

Daltons Law

gas molecules do not interact therefore each gas exerts it own pressure independently

→ we only need to know the pressures of each individual gas to understand how they move rather than the interactions of all the other mixed gases

Henry’s Law

quantity of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility