Resp. 1 - Structure and function of the lung Flashcards
Alveoli is where gas exchange occurs between the blood, in and out of the blood and into the lungs and into the atmosphere, movement of gas into aveoli by
BULK FLOW, due to changes in V and P. Move from high P to low P.
Ventilation
The exchange between atmosphere and alveoli
Ventilation occurs due to
Change in pressure between the atmosphere and alveoli that moves air in and out of lungs.
Air flows via ________ from a region of ______ to _______
Bulk flow
From higher pressure to lower pressure
Diffusion
How gas gets across the blood gas barrier, from blood vessel to aveoli.
Blood flow
How pulmonary circulation removes gas form lungs.
Ventilation - perfusion relationship
How matching of gas and blood determines gas exchange
Gas transport by blood
how gases are moved to the peripheral tissues
Control of Ventilation
- how gas exchange is regulated
The motor output to respiratory muscles are controlled by the
Control centres in medulla
Which bronchioles have the aveoli ?
Respiratory bronchioles
Which generations are alveolar ducts and alveolar sacs found?
Alveolar ducts in gen 20-22
Aveolar sacs in gen 23
What is generation 0-16 called and why
ANATOMIC deadspace or conducting airways cuz no alveoli = no gas exchange.
Where is cartilage found within the gear nation of the tracheobronchial tree?
0-16
In gen 0-16 there’s no cartilage, therefore pressure causes the bronchioles to
Collapse before all the alveoli collapse, this keeps normal amount of gas in alveoli = continuous gas exchange = lungs never actually empty.
Conducting zone contains the
Trachea, primary bronchioles, bronchioles and terminal bronchial
Around the aveolar sacs, there are thin
Capillary networks
How does air get into the alveoli
From terminal bronchioles, alveolar ducts, alveolar sacs = gas exchange
• Type l cells:
simple thin epithelial cells, facilitate gas diffusion between the blood and the alveoli,
Type ll epithelial cells
Produces surfactin to eliminate surface tension = more compliant
Surface tension
the thin layer of fluid inside of the alveoli, which tend to attract to one another, and if unregulated, would cause the alveoli to collapse due to the surface tension.
Alveolar macrophages:
protect against pathogens
Passage of blood through respiratory system (right to left shunt)
• Blood comes form right side of heart and top lungs via pulmonary arteries (deoxygenated blood = O2 removed, not void of it) going
up to lungs, then go into capillaries, which surround alveoli, gas exchange occurs (CO2 goes into alveoli to be expires, and O2 goes into blood) and goes back into the left side of heart via pulmonary veins, then distributed throughout the body, and picks up CO2,
Does the bronchiole artery participate in gas exchange
NO
What delivers deoxygenated blood from the right heart that goes into aveoli?
Pulmonary artery
What delivers almost all blood to the left heart
Pulmonary vein
Oxygenated blood form the left heart goes to the conducting airways via the
Bronchiole artery
• A right-to-left shunt is a cardiac shunt which allows blood to
flow from the right heart to the left heart (going from deoxygenated to oxygenated)
The bronchial artery brings oxygenated blood in, perfuses the
respiratory, or the conducting airways that dont have alveoli, and this will bring the oxygen to these cells, pick up CO2, the shunt into the pulmonary vein ( mixing its CO2 filled blood with highly oxygenated blood of pulmonary vein.
Why is the amount of oxygen in the pulmonary veins or left side of the heart always slightly less then what is its theoretical maximum?
Cuz of the CO2 filled blood form the pulmonary bronchiole mixing into it through the shunt.
The deoxygenated blood form the right heart goes into the aveoli,
gets oxygenated, then mixes in with the oxygenated blood of the pulmonary vein
The blood in the shunt is the portion of blood that
Doesn’t get oxygenated, and it’s the available for gas exchange.
Inspiration at Rest and During Forced Respiration:
Quiet inspiration (rest): diaphragm (contracts, pushing the abdominal content down and expanding the thorax as air comes in) and the external intercostals and parasternal intercostals
Expiration at Rest and During Forced Expiration:
- Quiet expiration (rest): at resting level, the abdominal and intercostal muscles are not active
- During forced expiration: abdominal muscles contract intensely. This causes the abdominal content to be pushed upward so that the diaphragm is moved even higher than its resting level and more air is expelled o Internal intercostal muscles contract and push the rib cage down
Going from normal inspiration to forces expiration, the pressure does what? And what happened to the diaphragm?
Pressure INC = Volume DEC
Diaphragm moves UP
Going from normal expiration to forced inspiration, the pressure does what? And what happened to the diaphragm?
Pressure DEC = Volume INC
Diaphragm moves DOWN
What are the static phases of lungs
- During end of inspiration and expiration
- no gas exchange or airflow
- elastic recoil of the lungs (inwards) and chest wall (outwards) = balance preventing collapse of lungs.
The intraplural pressure is how much, and what does it mean
-5 mmH2O, meaning we have -5 cm of water holding our lungs open, helping them to stay open so they dont collapse.
Where is pressure greatest in the lungs
Bottom due to gravity
Intrapleural pressure is the pressure
Immediately outside the lungs. At the end of normal expiration, static condition, having -5mmH2O in the lungs, holding them open.
Airflow (V) is proportional to the difference between
Alveolar (P A) and atmospheric pressure (P B), but inversely proportional to Airway Resistance (R)
When do we switch Pa and Pb in order to get negative airflow
Inspiration
Boyles law
PV = nRT
P = nRT/V
The way boyles law applies to inspiration:
The system has to increase the volume of the alveoli in order to decrease the pressure of the alveoli during static condition where there is no airflow. Decreasing alveolar pressure to 0, being = to barometric pressure, so that there is no airflow. Therefore 0-0 = 0 airflow.
Inspiration:
CNS sends an excitatory drive to the muscles of inspiration (diaphragm) → muscles contract = increase in
the thoracic volume → intrapleural pressure = more negative → transpulmonary pressure (which is dependent on the intrapleural pressure) increases → increase in lung volume → decrease the alveoli pressure → alveoli pressure will be smaller than the atmospheric pressure → a difference in pressure generates movement of gas → gas will move from a region of high pressure to a region of low pressure → alveolar pressure is smaller so air will move from the atmosphere into the lungs
Expiration:
Relaxation of the inspiratory muscles → chest wall recoils (goes back to its resting state) → intrapleural pressure moves back to a pre-inspiratory value→ as transpulmonary pressure is equal to the alveolar pressure minus the intrapleural pressure, the transpulmanory pressure will also will be reduced as the intrapleural pressure returns to pre-inspiratory values → as transpulmonary pressure is also linked to lung volume, lungs recoil and a reduce volume, generating compression of the gas molecules inside the alveoli → increase in alveolar pressure so it is greater than the atmospheric pressure → air will move from a region of high pressure to a region of low pressure, flowing out of the lungs to the environment
• transpulmanory pressure is what’s determines if our lungs
stay opened or closed. If they are opened or collopased ( if Ptp = 0).
• we always have have a transpulmanory pressure that can be measured, because its a
pressure across the lungs.
• Transpulmanory pressure is a very good and accurate marker of
volume. It’s the only pressure that is a constant accurate determination of lung volume
• all hollow organs and vessels and hearts have
transpulmanory pressure, in the case of the lungs its
alveolar pressure (PA) - immediate outside pressure (Pip) / plural pressure / intraplural pressure.
During inspiration and expiration air moves in and out of the lungs due to variations of the:
- Intrapleural pressure (PIP)- pressure that is inside the pleura
- Alveolar pressure (PALV)
- Transpulmonary pressure (PTP) - derived from the difference of the alveolar pressure minus the intrapleural pressure
Intrapleural Pressure (PIP):
PIP → pressure in the pleural cavity
- Acts as a relative vacuum
- Because the intrapleural space acts as a relative vacuum, the intrapleural pressure is always negative (ALWAYS negative due to the opposing directions of the elastic recoil of lungs and thoracic cage)
- If the Plp equals Palv lungs would collapse
Because the intrapleural space acts as a relative vacuum, the intrapleural pressure is always
negative
Alveolar Pressure (PALV):
- Pressure of air inside alveoli.
- when glottis open = no airflow = (Palv=Patm)
Formula of airflow
Airflow = diff in P / R
Diff in P = Palv - Patm
Transpulmonary Pressure (PTP):
- the force keeping alveoli open, expressed as pressure gradient across alveolar wall.
Does Ptp contribute to airflow
PTP is a static parameter which does not cause airflow, but determines lung volume.
Transpulmonary pressure is a static parameter that
doesn’t cause airflow, determines lung volume
airflow determined by alveolar pressure
Alveolar pressure is a dynamic component that
determines airflow
Tranpulmonary pressure should always be
Greater then itrapleural pressure (so transpulmanory > 0) in order to maintain the lungs expanded in the thorax.
(Palv-Patm) governs
gas exchanges between lungs and atmosphere
F = DELTA P / R
