Gas Exchange Flashcards
(36 cards)
What are alveoli
Air filled pockets in the lungs where all gas exchange takes place
What are the types of cell of the alveoli
Pneumocytes type 1
Pneumocytes type 2
Macrophages
What are types one Pneumocytes and what do they do
Simple squamous
Thin cells, wall of alveoli
Short gas exchange distance
What are type two Pneumocytes and what do they do
More specialised
Produce surfactant
Larger cells
What is a macrophage and what does it do
Digest things that shouldn’t be there
Remove dust and foreign objects
What is the role of surfactant
Reduce surface tension to stop the alveoli from collapse h
Explain elasticity of the alveoli
Has a dense network of capillaries, is surrounded by elastic fibres
Fibres recoil during exhalation, reduce size of alveoli to push air out
Why is gas exchange efficient at alveoli
Walls less that one micro meter thick
Sa 35 x surface of the body
(Put together)
Explain alveolar epithelium
Simple squamous
Consists of thin delicate type 1 Pneumocytes
Patrolled by macrophages (dust cells)
Contain type 2 pneumocytes that produce surfactant
What is Henry’s law
When gas under pressure comes into contact with liquid, gas dissolves until liquid equilibrium is reached
At a given temperature:
Amount of gas in a solution is proportional to Pp of that gas
E.g the pp of oxygen at sea level is 20%
What are the factors that lead to efficient gas exchange
- Substantial differences in pp of O2 across the respiratory membrane
- Distances involved in gas exchange are short
- O2 and Co2 are lipid soluble
- SA is large
- Blood flow and air flow are coordinated
What does diffusion happen over
Concentration gradient, determined by pp
What is the pulmonary circuit
Heart and lungs,
Carries deoxygenated blood from the heart to the lungs to be oxygenated
What is the systemic circuit
Carries oxygenated blood from the left ventricle
How is gas transported
Plasma
Red blood cells - hb
- transport gas from peripheral tissues
- remove gas from plasma, allowing them to diffuse into the blood
How does oxygen bind to haemoglobin
Hemes - binding sites
Oxyhaemoglobin - saturated with oxygen
Deoxyhaemoglobin - without oxygen bound to it
Carbominohaemoglobin - carrying co2
Why is carbon monoxide dangerous
Haemoglobin has a higher affinity for it, stop oxygen binding
What factors effect o2 release
- ppo2
- blood ph
-temperature - bpg levels, increase with increase
Why is the oxyhaemoglobin saturation curve a curve not a line
Shape of hb molecule changes slightly every time it binds to an oxygen molecule
Each o2 binding makes more binding easier
Explain dissociation at equilibrium
Oxygen molecules bind at the same rate other oxygen molecules are released
What is normal saturation at rest
96%
How does temp effect affinity
Temp increase = hb releases more O2, less affinity
Decrease, release less, more affinity
What is the bohr effect
Result of ph on saturation curve
Caused by co2 production
= carbonic acid
Lower ph = lower affinity, more released- shift Right
Higher ph = higher affinity, less released, shift Left
How is co2 transported in the blood
Generated by aerobic metabolism
- dissolve in plasma 7%
- red blood cells 93%,
- 23 % of this bind to hb = cmhb
- converted to carbonic acid 70%
