Respiratory System Mechanisms and Gas Exchange

Parietal pleura

cover the thoracic wall, superior face of the diaphragm and lateral wall of mediastinum, the outer layer of pleura

Visceral pleura

directly cover the outer lung surface, the inner layer of the pleura

Pleural cavity

the thin space between the parietal and visceral pleura filled with pleural fluid

Atmospheric pressure (Patm)

the pressure exerted by the air on the body

Inspiration (inhalation)

air flows into the lungs

Expiration (exhalation)

air flows out of the lungs

Intrapulmonary pressure (Ppul)

the pressure inside the alveoli that oscillates with breathing but will always equal atmospheric pressure between breaths

Intrapleural pressure (Pip)

the pressure in the pleural cavity that oscillates when breathing but will always be negative to intrapulmonary pressure

Transpulmonary pressure

the difference between intrapulmonary pressure and intrapleural pressure; prevents the lungs from collapsing

Pneumothorax

air in the pleural cavity

Hemothorax

blood in the pleural cavity

Boyle’s Law

volume and pressure are inversely proportional

Quiet inspiration

the thoracic cavity volume increases and pressure decreases, lung volume increases and air moves into the lungs

Quiet expiration

thoracic cavity volume decreases and pressure increases, lung volume decreases and air moves out of the lungs

Forceful breathing

requires more muscles than quiet breathing

Forced inspiration

the diaphragm, external intercostals, sternocleidomastoid, scalenes, and serratus anterior muscles all contract to greatly increase thoracic volume

Forced expiration

internal intercostals and abdominal muscles contract to compress thoracic cavity while the diaphragm and external intercostals relax to decrease thoracic volume

Airway resistance

resistance that is mainly determined by airway diameter (bronchoconstriction/bronchodilation), mucus accumulation, infectious material and tumors

Bronchoconstriction

smooth muscle contracts in airway walls due to parasympathetic simulation

Bronchodilation

smooth muscle dilates in airway walls due to sympathetic stimulation

Alveolar surface tension

surfactant in the alveoli creates surface tension and resistance to stretch

Surfactant

reduces alveolar surface tension allowing for easier inflation

Infant respiratory distress syndrome (IRDS)

premature babies won't have sufficient surfactant made in their alveoli

Lung compliance

the ability of the lungs to stretch

Spirometry

a ay to measure ventilation, patient exhales/blows into a machine

Tidal volume

the amount of air that moves into/out of the lungs during quiet breathing

Inspiratory reserve volume

the amount of air that can be inspired forcefully beyond the tidal volume

Expiratory reserve volume

the amount of air that can be expelled from the lungs after a normal tidal volume expired

Residual volume

the amount of air that remains in the lungs even after the most strenuous expiration

Inspiratory capacity

tidal volume + inspiratory reserve volume

Functional residual capacity

expiratory reserve volume + residual volume

Vital capacity

TV + IRV + ERV

Total lung capacity

TV + IRV + ERV + RV

Obstructive pulmonary disease

increases airway resistance (specifically during exhalation) so its harder to push air out, caused by bronchitis, emphysema, asthma, CF

COPD

chronic obstructive pulmonary disease

Restrictive pulmonary disease

involves reduced total lung capacity, lungs cannot expand fully due to tuberculosis, pneumonia, fibrosis

Anatomical dead space

the volume of air in the conducting zone and never reaches the alveoli for gas exchange

Minute ventilation

total amount of air that flows into or out of the respiratory tract in one minute; MV \= breathing rate x TV

Alveolar ventilation

how much air reaches alveoli in one minute aka the amount of air available for gas exchange AV \= breathing rate x (TV minus dead space)

Boyle's Law

pressure of gas in a container is inversely related to the volume of the container

Dalton’s Law

the total pressure of gases is the sum of the pressures exerted by individual gases

Henry’s Law

when a gas is in contact with a liquid, the gas will dissolve in the liquid in proportion to its partial pressure

Atmospheric Air

not very humid, much less water vapor

Atmospheric Pressure

the total pressure of gases in the atmosphere

Partial Pressure

pressure exerted by a specific gas in a mixture of gases, it is proportional to the percentage of the gas in the mixture

Gas Solubility

the ability of a gas to diffuse into a liquid

Hypoxia

low oxygen in the blood

Hypercapnia

high carbon dioxide in the blood

Ventilation

air flow

Perfusion

blood flow

Ventilation

perfusion coupling

Oxyhemoglobin

hemoglobin with oxygen bound to it

Deoxyhemoglobin

hemoglobin that has released its oxygen

Oxygen to hemoglobin dissociation curve

X axis is PO2 in tissues, Y axis is the % of hemoglobin saturated with oxygen; it shows how local PO2 controls oxygen loading and unloading from hemoglobin

Hemoglobin saturation

the amount of oxygen bound to the hemoglobin, normal resting it 98%

Bohr effect

conditions that weaken the bond of oxygen and hemoglobin cause the release of more O2 into the tissues

Fetal hemoglobin

has a greater affinity for oxygen than adults and makes it possible for for it to pick up oxygen from the placenta

Carbaminohemoglobin

when carbon travels bound to a hemoglobin

Bicarbonate Ion

the end reactant when CO2 reacts with water, travels through the blood as a way for CO2 to travel

Carbonic anhydrase

a catalyst that promotes the reaction of CO2 and H2O into H2CO3

Haldane effect

dissociation of O2 allows more CO2 to bind with hemoglobin