L16 - Respiration 3 Flashcards
What are alveoli surrounded by?
elastic fibres and capillaries
What are Type I alveolar cells?
very thin cells used for gas exchange
What are Type II alveolar cells?
surfactant releasing cells used to break down surface tension
How thick is the exchange surface of alveoli?
0.1 - 1.5µm
What is pulmonary oedema?
when there is a build up of fluid in the exchange surface of alveoli, a greater diffusion distance and therefore, a decreased rate of gas exchange
What is the order of pulmonary circulation?
right ventricle (low O2 blood) -> pulmonary trunk (divides into 2 pulmonary arteries) -> lungs -> pulmonary veins (oxygenated blood) -> left atrium
Does the systemic or pulmonary system have higher resistance?
the systemic system
What is the blood pressure of the pulmonary system in comparison to the systemic system?
blood pressure is lower in the pulmonary system
What are three properties of pulmonary circulation?
- 10% of blood volume (0.5 litres) at any given time
- pulmonary blood pressure low (25/8 mmHg)
- resistance of pulmonary circulation low
What is normal ventilation-perfusion (V/Q) matching?
when an alveolus is constricted and is not able to carry out gas exchange, bronchioles to this alveolus will constrict and blood will be rerouted to nearby alveoli which are able to carry out gas exchange
When oxygen content of pulmonary interstitial fluid decreases, pulmonary arterioles do what?
constrict
Why is it called ventilation-perfusion matching?
because the amount of gas exchange able to occur in the alveolus is matched with the amount of blood flow provided to the alveolus
What happens when partial pressure of CO2 increases?
bronchioles dilate, pulmonary arterioles constrict weakly and systemic arterioles dilate
What happens when partial pressure of CO2 decreases?
bronchioles constrict, pulmonary arterioles dilate weakly and systemic arterioles constrict
What happens when partial pressure of O2 increases?
bronchioles constrict weakly, pulmonary arterioles dilate weakly and systemic arterioles constrict
What happens when partial pressure of O2 decreases?
bronchioles dilate weakly, pulmonary arterioles constrict and systemic arterioles dilate
What is the partial pressure of oxygen at sea level?
160 mm Hg
Is the oxygen concentration in lungs lower or higher than oxygen concentration in the atmosphere?
lower in lungs
Which factors affect diffusion?
constants such as surface area, membrane thickness and diffusion distance + the most important factor which is concentration / pressure gradient
Why does oxygen flow into venous blood and peripheral tissue?
because venous blood and peripheral tissue usually have lower partial pressures of oxygen resulting in oxygen moving down the pressure gradient
Is oxygen or carbon dioxide more soluble in water?
carbon dioxide
How much oxygen is carried in plasma and how much oxygen is carried by hemoglobin?
3 mL O2/L blood (plasma)
197 mL O2/L blood (Hb)
What is the partial pressure of oxygen in the alveoli compared to a resting cell? Why is this important for oxygen-hemoglobin dissociation?
100 mm Hg in alveoli and 40 mm Hg in a resting cell
this is important because a drop in partial pressure is required for oxygen to dissociate from hemoglobin in resting cells
What is the partial pressure of oxygen in exercising cells? Why is this important for oxygen-hemoglobin dissociation?
25 mm Hg
this is important because large amounts of oxygen will dissociate from Hb
