Respiratory Flashcards
(46 cards)
Ficks Law
The shorted the distance through which diffusion takes places and the greater the surface area of which this can occur will affect diffusion rate.
Basic functions
- Homeostasis of CO2, O2 and blood pH
- Speech generation
- Warm, humidify and clean insiparted air
- Nose is olfactory organ
- Activates hormones (angiotensin 2), inactivates hormones (prostaglandins)
Key points about anatomy
Type 1 alveolar cells - form the walls
Type 2 alveolar cells - produce the watery lining, which will decrease surface tension and O2 needs to dissolve in water before lung
Note the very close proximity of the capillaries to the alveolar walls (decrease diffusion distance)
Inner lung surface is about 50 times larger than surface of the skin, this means it is easier for diffusion and this is able to happen via the great amounts of branching that the bronchi’s perform
Pulmonary surfactant
Pulmonary surface reduces the lungs tendency to recoil and increases pulmonary compliance. Does this more in smaller alveoli because the surfactant molecules are closer.
It improves ling stability to prevent small alveoli to collapse into the larger ones
Law of LaPlace
Magnitude of inward directed pressure in a bubble = 2xsurface tension/radius of bubble
Therefore, with the same surface tension their will be smaller pressure in larger balloon. Meaning smaller alveoli would collapse into the larger ones.
Inspiration of molecules blocked by cells
Blocks inspiration of molecules over certain lengths
Nasal cavity capable of cleaning particles larger than 10 nano-meters
Large airways 5-10
Respiratory bronchioles stop particles between 1 and 5
Suspended in air >0.5
Dynamic airway closure
Frictional losses causes the pressure in the air ways to drop. If this falls below the surrounding elevated intrapleural pressure the small compliant airways are compressed closed, blocking further expiration and trapping air in alveoli. The amount of air left in the alveoli after this is called residual volume.
Tidal Volume
Tidal volume = difference between end expiratory and end inspiratory (quite breathing)
Vital capacity
Vital capacity= total amount of air moved in and out of the lung (- res volume)
Functional residual capacity
Functional residual capacity = amount of air in lungs after quite expiration (COPD indicator)
Residual volume
Residual volume = amount of air left in lungs after force expiration (minimal lung volume)
Expiratory reserve volume
Expiratory reserve volume = amount of air exhaled after normal breathing
Why does tidal volume increases first during exercise
Tidal volume increases first. Any increases in tidal volume will increase alveolar ventilation by the same amount. Increase in respiratory rate will increase alveolar ventilation by a smaller amount due to the anatomical dead space (air left from preceding respiration).
Difference between physiological dead space and anatomical dead space
Physiological is when there is more perfusion than there is ventilation. Anatomical shut is when there is more ventilation than perfusion (some old air left)
How does Asthma cause small airway closure
There is increased small airway resistance (from inflammation) which causes a loss of pressure in the small airways. This causes early small airway closure meaning there is an increase in RV and decrease in FVC
How does Emphysema cause small airway closure
The breakdown of alveoli walls causes a decrease in lung recoil, increases intrapleural pressure. Meaning that early small airway closer occurs with decreases FVC and increased RV
What is henrys law
At a given temperature the amount of a gas is proportional to the partial pressure of that gas.
Factors that effect the rate of gas transfer
Diffusion coefficient (higher in Co2 than O2 = pp can be lower)
Partial pressure gradient
Surface area
Thickness of membrane
Diffusion Coefficient (D) and how does this relate to O2 and CO2 exchange
Rate of gas transfer directly proportional to this.
It is a constant value related to solubility of a gas and its molecular weight
D for Co2 is 20 times that of O2 because it is much more soluble and also heavier due to the extra Carbon. However this difference is offset by the differences in pp for O2 and CO2 meaning equal amounts of O2 and CO2 are exchanged.
Transport of CO2 and O2 in the blood
Only 1.5% of O2 is dissolved in blood, the rest is carried in RBC by haemoglobin
CO2 transported as bicarbonate
What is the Bohr effect
The influence of CO2 and acid on the release of O2 from haemoglobin.
Increased offloading of O2 with increased CO2 and H+
Carrying capacity of O2 in haemoglobin
1 g Hb can hold 1.34 ml O2
Other respiratory pigments
Myoglobin - monomer with one heme. Stores O2 in aerobic muscle and offloading occurs at lower pp.
Neuroglobin - found in neurons
CO2 Transport
- Co2 produced in tissues
- Diffuses into plasma and some will then move into RBC
- Some can sty in ICF but some will bind to haemoglobin by binding onto the globin chains (not the heme molecule)
- Majority of Co2 in RBC with water and under presence of carbonic anhydrase forms carbonic acid, this dissociates into Hydrogen ion and bicarbonate ion.
- Hydrogen ion can also now bind onto globin chains and therefore don’t change pH of RBC
- And the bicarbonate is transported into plasma via chloride shift.
- After reaching alveoli the Co2 in plasma and ICF will diffusion out, some of the Co2 on the globin chains will detach and diffuse. Some H+ will leave globin chains and with bicarbonate will form Co2 and water via carbonic anhydrase
Net result is that majority of the produce CO2 in the tissues is transported as bicarbonate ions within the plasma
