Please enable JavaScript.
Coggle requires JavaScript to display documents.
Alveolar and systemic gas exchange (Gas Laws (Henry's Law (Solubility…
Alveolar and systemic gas exchange
Definitions
Ventilation: movement air into + out lungs
Pulmonary ventilation: Voln air taken in one breath * No breaths per min (around 6l)
Alveolar ventilation: (tidal voln - dead space) * breaths/min
Dead space
Voln gas in conducting airways + alveoli does not participate gas exchange
Physiological
Alveoli ventilated but don't take part in gas exchanage:
Blood as interference damaged
Pulmonary blood flow is occluded
Anatomical
Conducting airway trachea, bronchi, bronchioles: don't take part in gas exchange
Alveolar histology
Type 2 pneumocytes
Equal number, more compact, less space
Cells contain lamellar inclusion bodies: produce pulmonary surfactant
Capable rapid division + conversion into type 1
Type 1 pneumocytes
Thin, flat cells: 90% of alveoli SA
For gas exchange
Alveolar macrophages found near pneumocytes
Laplace's law + surface tension
P = 2T/R
Pressure within sealed bubble increases when its radius is reduced
Surface tension: tendency of fluid surface to occupy smallest surface area possible due to attractive forces of its surface molecules drawing inwards
Pulmonary surfactant
Stabilizes alveolar size reducing surface tension + prevents alveolar collapse
Increase lung compliance
Keeps lung dry
Hydrophobic protein + phospholipids: reduces surface tension by reducing number of H bonds between water moelcules
Gas Laws
Henry's Law
Solubility of gas in liquid dependent on its solubility coefficient and its partial pressure in air
Fick's Law
Volume of gas that diffuses through resistant barrier directly proportional to SA area of barrier + partial pressure difference each side. Inversely proportional thickness of barrier
Dalton's Law
Total pressure exerted from gas is sum of all partial pressures of each gas composing it
Graham's Law
Rate diffusion gas across barrier directly proportional to its solubility coefficient but inversely proportional to square root of its molecular weight
Gas exchange
Both move down gradients of partial pressure between alveoli and pulm capillaries + capillaries and interstital fluid
Both O2 and CO2 very soluble + rapidly equilibrate across blood gas interface during inspiration
Transport oxygen
Hb composed two aplha globin chains, two beta globin chains.
Each globin linked to heme group, consists of Fe2+ ion held in poryphorin ring
Each Hb capable carrying 4 O2 molecules
Once blood arrives at respiring tissue, Hb must release bound oxygen
Steep pressure gradient between blood and mitochindria in cells facilitates rapid trasnfer
Each time Hb loses O2, its affinity for remaining O2 molecule
Rightward shift of curve depends 4 factors
Temp
CO2
Protonation
2,3 - Diphosphoglycerate
Transport CO2
CO2 enters RBC, high levels of CA-1 convert CO2 to H2CO3 then dissociates
HCO3- leaves RBC and enters plasma by Cl- exchange
H+ binds to Hb enhancing O2 offload-Bohr effect
Protonated Hb favours carboamino compounds: Haldane effect
Blood arrives lungs, partial pressures gradient of O2 and CO2 reverse to that of tissues
High O2 content in alveolar lumen causes Hb to lose affinity for H+
HCO3- re-enters RBC by exchanging with chloride + combines with H+ form H2CO3: durther dissaciates to CO2 and H2O
CO2 diffuses out of RBC along partial pressure grad, into alveolar lumen, expelled during expiration
Transport CO2
in vascalature in 3 main forms
Bicarbonate
70% carried as HCO3-, formed through dissociation of carbonic acid via action of CA
Carboamino compounds
23% transported as CO2 binds to amine groups proteins, mainly Hb
Dissolved
7% dissolved plasma + intracellular fluid of RBCs
CO2 binds to globin whereas O2 binds to haeme
IMPORTANT LAWS
Haldane effect
Oxygenation of blood displaces CO2 from Hb, promoting its unloading. CO2 greater affinity for protonated HB (Hb-H)
CO2 binds better to HbH than HbO2
Chloride/hamburger shift
HCO3- exchanged for Cl-, maintains electrical balance of both ions in RBC and plasma
Bohr effect
H+ ions facilitate Hb losing affinity to O2 + promotes unloading. Hb-O2 curve shifts right with protonation as H+ stablizes deoxy-Hb
H+ cause HbO2 to give up O2