3 - Pulmonary Blood Flow Flashcards
Alveolar capillaries receive blood from the _______ _______.
Right Ventricle
Alveolar capillary blood has (HIGH/LOW) O2 and (HIGH/LOW) CO2.
Low
High
There are millions of alveolar capillaries and they are involved in the exchange of O2 and CO2 between the ________ and the ________.
Blood
Air
Extra-Alveolar (bronchial) capillaries receive blood from the ________ ________.
Left Ventricle
Extra-alveolar capillary blood has (HIGH/LOW) O2 and (HIGH/LOW) CO2.
High
Low
What is the job of the extra-alveolar capillaries?
To deliver O2 and CO2 to the tissue of the lungs.
Extra-alveolar capillary blood returns to the heart in the ________ _______, creating venous admixture. This reduces the _______ of the arterial blood by a few mmHg and increases the _______ to a small degree.
Pulmonary veins
PaO2
PaCO2
What is the PaO2 levels in the artery leading to the alveolar and extra-alveolar capillaries?
Alveolar = Low Extra-alveolar = High
What is the PaCO2 levels in the artery leading to the alveolar and extra-alveolar capillaries?
Alveolar = High Extra-alveolar = Low
How do the alveolar and extra-alveolar capillaries return blood to the heart?
Pulmonary veins to the Left Ventricle
What is the blood gas levels in the vein from the alveolar and extra-alveolar capillaries?
Alveolar = High PaO2 and Low PaCO2 Extra-alveolar = Low PaO2 and High PaCO2
***This creates a venous admixture due to the extra-alveolar blood gas levels.
What is the equation for pulmonary BP?
PBP = CO x PVR
PBP = Pulmonary blood pressure (25/15 mmHg) CO = Cardiac Output (at rest 5 L/min) PVR = resistance to blood flow through lungs (very low)
PVR can depend on the number of capillaries open at a given time. During exercise, the PVR (INCREASES/DECREASES) as more pulmonary capillaries open up to accommodate the increased cardiac output.
Decreases
PVR also depends on the lung ________.
Volume
At low or very high lung volumes, the resistance (INCREASES/DECREASES) a little because the stretch of the tissue compresses the capillaries. Just like a rubber band gets a little thinner when stretched, the diameter of the capillaries decreases a little.
Increases
Why does a person pass out if they stand with their knees locked too long?
– Gravity was acting on their blood, pulling it into their legs while they stood there with their knees locked.
– They passed out because less blood was returning to their heart (and therefore the brain).
***Not locking their knees will allow them to use skeletal muscle activity to increase the blood flow from their legs back up into their thorax.
Gravity works on the blood in our bodies – when we stand, the blood pressure in our legs is increased compared to the level of the heart or in the brain. The same is true in the ________.
Lungs
At the apex of the lung, the blood pressure is _________ because it is slightly above the level of the heart. However, the alveoli are somewhat _________. The blood flow is ________.
Reduced
Expanded
Less
In the middle regions of the lung, the blood pressure is a little ________ because we are at the level of the heart. The alveoli are ________ size. The blood flow is ________.
Higher
Average
Normal
At the base of the lung, the blood pressure is ________ because we are below the level of the heart. The alveoli are ________. The blood flow is ________ than in other regions of the lung.
High
Smaller
Greater
This is made by the endothelium and causes smooth muscle relaxation and vasodilation. It plays a significant role in normal pulmonary blood flow.
Nitric Oxide
This is also made in the lungs and is a vasoconstrictor. It seems to be a player under pathologic conditions (not under normal conditions).
Endothelin 1
We treat this the same as Endothelin 1, and it can be found in the pulmonary vasculature under the right conditions.
Thromboxane A2
The job of the ________ is to allow oxygen to move from the air to the blood. The problem is that oxygen is not terribly water soluble. If we were to allow the capillaries to leak water into the _______, we would impair the ability of oxygen to cross to the blood.
Alveoli
Alveoli
So what determines whether the water moves from the capillaries to the alveoli?
The Starling Forces control how much fluid moves from the capillary to the lung.
The ________ pressure is the fluid pushing against the tissue or walls of the capillary.
Hydrostatic
The hydrostatic pressure is in which two places?
The capillary = Pc
***This is the blood pressure in the capillary. It is trying to push fluid into the alveoli.
The tissue = Pt
***This is in the rest of the body. It pushes fluid into the capillary.
It appears that the same forces that give rise to the negative intrapleural pressure (the lung always trying to collapse, the chest wall trying to spring away) creates a negative hydrostatic pressure in the tissue. That means Pt is now a force favoring _________ of fluid from the capillary into the alveolus.
Filtration
The ________ pressure is the osmotic pressure of the fluids involved.
Oncotic
The oncotic pressure is in which two places?
The plasma (capillary oncotic pressure) = πc ***This tries to pull water into the capillary.
The tissue (tissue oncotic pressure) = π tissue ***This tries to pull water into the alveolus.
What are the forces moving water from the capillary to the alveolus?
Pc - capillary hydrostatic pressure
π tissue - tissue oncotic pressure
Pt - tissue hydrostatic pressure
***These are filtration
What are the forces moving water from the alveolus to the capillary?
πc - capillary oncotic pressure
***This is reabsorption
To figure out which way fluid will move, we add the forces favoring water moving into the tissue together and subtract the forces favoring water moving into the capillary. What is this equation?
(Pc + π tissue + Pt) - (πc)
***Filtration - Absorption
In the lung, the Pc (hydrostatic pressure in the capillary) is the single (GREATEST/SMALLEST) force.
Greatest
The Starling forces favor net filtration (movement) of fluid into the alveoli. But, that fluid is bad for gas exchange. So what do we do?
Lymphatics!
***Remove fluid and prevent pulmonary edema
This is an enzyme that converts angiotensinogen (a protein added to the plasma by the liver) to angiotensin 1.
Renin
Angiotensin 1 is converted to the more active Angiotensin 2 by _______ in the lungs.
ACE (Angiotensin Converting Enzyme)
ACE also inactivates _________. About 10-15% of people who are placed on ACE inhibitors for blood pressure control develop a cough due to accumulation of this.
Bradykinin
The lungs also participate in the metabolism of the _________ ________ metabolites.
Arachidonic Acid
***Both leukotrienes and prostaglandins/Thromboxane A2 are produced by immune system activation in the lungs.
Enzymes in the lungs break down the leukotrienes and _______ and _______.
PGF-2a (Prostaglandin F2-alpha)
PG-E (Prostaglandin E2)
