pulmonary blood flow, gas exchange, and transport Flashcards
what are the two circulations that supply blood to the lungs?
bronchial circulation and pulmonary circulation
what is the bronchial circulation supplied by?
bronchial arteries
what circulation does bronchial arteries arise from?
systemic
which circulation supplies oxygenated blood to the airway smooth muscle, nerves and lung tissue?
bronchial circulation
what does the pulmonary circulation supply the blood to?
Supplies the dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein
what does the pulmonary circulation consist of?
consists of L & R pulmonary arteries originating from the right ventricle.
is the rate of diffusion most rapid over shorter distances or longer?
short distances
is rate of diffusion proportional to the partial pressure gradient?
yes
is rate of diffusion proportional to gas solubility?
yes
is rate of diffusion proportional to the available surface area?
yes
is rate of diffusion proportional to the thickness of the membrane?
no
what does partial pressure in alveoli correspond to?
partial pressure in systemic arterial blood
what does partial pressure in pulmonary arterial blood correspond to?
partial pressure at tissue
where is PO2 highest?
alveoli
where is PCO2 highest?
pulmonary arterial blood
what is the characteristics of the membrane in fibrotic lung disease? And what happens to the compliance
thick, slows gas exchange
loss of lung compliance may decrease alveolar ventilation
PO2 normal or low
what is the characteristics of the membrane in emphysema?
destruction of alveoli reduces surface area for gas exchange
what are the characteristics of pulmonary edema?
fluid in interstitial space increases diffusion distance. Arterial Pco2 may be normal due to higher CO2 solubility in water
what are the characteristics of asthma?
increased airway resistance decreases airway ventilation
PO2 low
Bronchioles constricted
what is perfusion?
local blood flow
what is ventilation?
air getting to alveoli
is ventialtion and perfusion matched?
yes
does blood flow and ventilation increase or decrease with height across the lung?
decrease
what happens to blood flow and ventilation at the base of the lungs?
blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure. This compresses the alveoli
what happens to blood flow and ventilation at the apex of the lungs?
blood flow is low because arterial pressure is less than alveolar pressure. This compresses the arterioles.
where does the majority of the mismatch in the lungs take place?
apex
what happens when ventilation decreases in a group of alveoli?
Pco2 increases and po2 decreases, blood passing those alveoli does not get oxygenated.
how is bronchodilation caused?
increased PCO2
what is a shunt?
term used to describe the passage of blood through areas of lung that are poorly ventilated
what is the opposite of dead space
shunt
true or false:
alveolar dead space refers to alveoli that are ventilated but not perfused
true
what does the anatomical dead space refer to?
refers to air that cant take part in gas exchange as walls are too thick
whats the physiological dead space?
alveolar dead space and anatomical dead space
is pulmonary arterial pressure low?
yes
what are the advantages of having pulmonary low pressure?
more suspectible to effects of gravity and this gives rise to a great degree of variability in blood flow within the lung
what transports oxygen from lungs to tissue?
blood
is Arterial partial pressure of O2 (PaO2 ) the same as arterial O2 concentration/content?
no
what is arterial pressure of o2 determined by?
by O2 solubility and the partial pressure of O2 in the gaseous phase that is driving O2 into solution.
how much oxygen does each litre of systemic arterial blood contain?
200ml
if the oxygen is not bound to haemoglobin what happens to it?
dissolved in the plasma
how much oxygen is bound to each gram of haemoglobin?
1.34ml
what determines the degree to which haemoglobin is saturated with oxygen?
partial pressure of oxygen in arterial blood
what two molecules have a higher affinity for oxygen than haemoglobin?
myoglobin and foetal haemoglobin
what use is myglobin and HbF?
necessary for extracting o2 from maternal/arterial blood
what is anaemia?
any condition where the oxygen carrying capacity of the blood is compromised
what factors effect the haem-ox disssociation curve?
decreased by a decrease in pH, or and increase in PCO2, or temperature.
does carbon monoxide have a higher affinity for haemoglobin than oxygen?
yes 250 times greater
what are symptoms of carbon monoxide poisoning
hypoxia and anaemia, nausea and headaches
what are the fates of carbon dioxide in transport?
7% remains dissolved in plasma and erythrocytes
23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds
70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions. Most of the bicarbonate then moves out of the erythrocytes into the plasma in exchange for Cl- ions (chloride shift) & the excess H+ ions bind to deoxyhemoglobin
why is pH normally stable?
all CO2 that is produced is eliminated in expired air.
when will pH not be stable?
hypo/hyperventilation will alter plasma PCO2 and plasma H will vary
will hypoventilation lead to increased or decreased H+
increased
which type of ventilation causes acidosis?
hypoventilation
which type of ventilation causes respiratory alkalosis
hyperventilation
will hyperventilation lead to increased or decreased H+
decreased
whats the normal systolic pressure
25mmHg
in pulmonary circulation is the pressure low or high and is the flow low or high
high flow, low pressure
learn slide 7/27 chart shell test in lecture 1
snake
how much oxygen dissolves per litre of plasma?
3ml
which molecule carries oxygen round the blood?
haemoglobin
whats the solubility of oxygen in water?
0.03
do gases travel in the gaseous phase in plasma?
no they travel in solution, if it was gas it there would be bubbles and this is fatal i.e., divers.
what is the oxygen demand of resting tissues?
250ml
what percentage of arterial oxygen is extracted by peripheral tissues at rest?
25%
how many polypeptide chains does haemoglobin consist of/?
4
what are the two types of chains in the haemoglobin polypeptides
2 alpha and 2 beta
how many oxygen does haemoglobin bind?
4
what are the different types of combination a haemoglobin can have?
92% haemoglobin in RBC is in the form HbA (below). Remaining 8% is made up of HbA2 (δ chains replace β), HbF (γ chains replace β), and glycosylated Hb (HbA1a, HbA1b, HbA1c)
why can you lose 40 units of partial pressure of oxygen and only lose a very little amount of saturation?
60 mm Hg is enough for haemoglobin to have a high affinity for oxygen
whats the saturation like belwo 60 mm Hg PO2?
steep decline
where is deoxyhaemoglobin found?
venous blood
where is haemoglobin found?
arterial blood
what would happen to PaO2 in anaemia?
remain the same as its the amount of oxygen in plasma, doesnt have anything to do with rbc
what happens to the affinity for oxygen if there is a decrease in pH?
decrease
what happens to the affinity for oxygen if there is there is a decrease in PCO2?
increase
what happens to the affinity for oxygen if there is a decrease in temperature?
increase
what happens to the affinity for oxygen if 2,3-DPG is added?
decreases
what are the four factors that affect % saturation of Hb?
pH
temp
2,3-DPG
Pco2
why is carbon monoxide so dangerous?
binds to haem making deoxyhaemoglobin and then you cant get anymore oxygen
how much carbon monoxide is needed to cause progressive carboxyhaemoglobin formation?
0.4 mmHg
when you have carbon monoxide poisining, why do you still have normal respiration rate?
becuase you still have a normal arterial PCO2
what is hypoxaemic hypoxia?
Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology.
what is Anaemic Hypoxia
Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).
what is Stagnant Hypoxia
Heart disease results in inefficient pumping of blood to lungs/around the body
what is Histotoxic Hypoxia
poisoning prevents cells utilising oxygen delivered to them e.g. carbon monoxide/cyanide
what is Metabolic Hypoxia
oxygen delivery to the tissues does not meet increased oxygen demand by cells.
