Respiratory Physiology Flashcards
Respiratory pressures are described relative to
atmospheric pressures
Alveolar (intrapulmonary) pressure is
Pressure in the alveoli that rises/falls during respiration to eventually equalize with atmospheric pressure
Intrapleural pressure is
The pressure between the visceral and parietal pleura that is always less that alveolar to keep lungs inflated by creating a vacuum
Negative intrapleural pressure is due to the opposing forces of
- recoil force & surface tension of
alveolar fluid in lungs: pulls lungs
away from thorax - natural tendency of the chest wall to pull outwards: pulls thorax outward & enlarge lungs
Transpulmonary pressure is
The difference between the alveolar & intrapleural pressures
Greater transpulmonary pressure equals
larger lung volume
Boyle’s law:
at a constant temperature, the pressure of a gas varies inversely with its volume
Pulmonary ventilation is
The mechanical process of gas flow into & out of the lungs
Air flows to areas of
Low pressure
Quiet inspiration is
(At rest) The diaphragm & intercostal muscles contracting
- ↑ thoracic volume → alveolar pressure < Patm →
air flows into lungs
Forced inspiration is
(Deep breathing) The accessory muscles of neck & thorax contracting
- greater↑ thoracic volume than during quiet inspiration → greater air flow into the lungs
- further decreased pressure in lungs allows more air to move into them
Quiet expiration is
A passive process relying on the elastic recoil of lungs as thoracic muscles & diaphragm relax
- ↓ thoracic volume → alveolar pressure > Patm
→ air flows out of lungs
Forced expiration is
An active process relying on the contraction of abdominal muscles to↑ intra-abdominal pressure & depress rib cage
- contracting abdominal muscles makes volume smaller which increases the pressure and pushes more air out of the lungs.
Tidal volume is
The amount of air that moves in & out
of lungs with each breath during quiet breathing (~ 500 ml/breath)
Inspiratory reserve volume (IRV) is
The amount of air that can be inspired beyond the tidal volume
Expiratory reserve volume (ERV) is
The amount of air that can be evacuated
from the lungs after tidal expiration
Vital capacity (VC) is
The total amount of exchangeable air / max amount that you can move in and out of lungs
Residual volume
The amount of air remaining in lungs after maximal forced expiration
Total lung capacity is
The sum of all lung volumes
Anatomical dead space is
The volume of the conducting zone conduits that don’t contribute to gas exchange in lungs (~150 ml)
Amount of gas that will dissolve in a liquid depends on
The partial pressure of the gas in contact with the liquid, the solubility of the gas in liquid, and temperature of the liquid
Gas that diffuses rapidly from alveoli to blood
O2
Gas that diffuses from blood to alveoli along a partial pressure gradient that is less steep
CO2
Alveolar gas differ from atmospheric gas due to
- gas exchange occurring in the lungs
- humidification of air by conducting passages
- mixing of alveolar gas with each breath
Respiratory membrane provides
Efficient SA for gas exchange (very thin w/huge SA)
Ventilation and perfusion are
Balanced so that O2 & CO2 levels match physiological demands
Perfusion is controlled by
O2 pressure changing the arteriolar diameter
Ventilation is controlled by
CO2 pressure changing the bronchiolar diameter
Internal respiration is
Capillary gas exchange in body tissues (once blood has traveled to the tissues)
External respiration takes place between
The alveoli and blood
O2 is not very soluble in blood, 98.5% is carried by
Hemoglobin
Iron binds to
O2
1 hemoglobin can bind
4 O2 molecules
High affinity occurs at
High Ο2 levels
At low O2 levels
Hemoglobin wants to offload O2
The larger the difference between tissue O2 and blood O2
The more easily O2 detaches from hemoglobin to diffuse into the tissue
At high O2 pressure
The O2 saturation curve is flat; hemoglobin saturation of O2 is stable;
- O2 has to go down a lot to affect hemoglobin saturation
At low O2 pressure
hemoglobin easily releases O2
7-10% of CO2 is transported in the blood via
Dissolving in plasma
20% of CO2 is transported in the blood via
Being carried on globins of hemoglobin
70% of CO2 is transported in the blood
As bicarbonate ions
As blood CO2 increases
pH decreases (more acidic)
- slow shallow breathing
As blood CO2 decreases
pH increases (less acidic)
- rapid, deep breathing
