Respiratory - Johnson Flashcards
Don't Suck!
What do we mean by Respiration?
The transport of oxygen from the ambient air to the tissue cells and the transport of CO2 in the opposite direction
Surface to volume ratio!
The bigger you get, the bigger the problem of getting oxygen in and CO2 out!
The 4 phases of respiration
- Ventilation: ambient air <> airway <> alveolus
• Stage 1 Ventilation from the ambient air into the lung (pulmonary) alveoli - Diffusion: alveolar-capillary membrane (pulmonary capillaries)
• Stage 2 Pulmonary gas exchange from the alveoli into the pulmonary capillaries - Transport: Perfusion <> circulation
• Stage 3 Gas transport from the pulmonary capillaries to the peripheral (tissue) capillaries - Diffusion: peripheral capillaries <> interstitial fluid <> cell mitochondria
• Stage 4 Peripheral gas exchange from the tissue capillaries into the cells (mitochondria)
• Stage 5 …and CO2 back again, though this is not usually considered to be one of the stages…
Physiological respiration involves ________
GAS FLOW
Conducting Zone
Trachea = 0 generations
Bronchi (segmental bronchi 1-8) = 1-3 generations
Bronchioles (segmental bronchi 1-8) = 4-5 generations
Terminal bronchioles (segmental bronchi 1-8) = 6-16 generations
*see slides 13 & 14
Notes from handout: Conducting Zone takes no part in gas exchange, and constitute the anatomic Dead Space, with a volume of about 150 ml in each breath
Transitional and Respiratory Zones
Respiratory bronchioles (17-24) = 17-19 generations Alveolar ducts (25-26) = 20-22 generations Alveolar sacs = 23 generations *see slides 13 & 14
Notes from handout: The respiratory zone, is comprised of the respiratory bronchioles (which have occasional alveoli budding from their walls) and alveolar ducts are completely lined with alveoli. The respiratory zone makes up most of the lung volume, about 2.5 to 3 liters during rest.
1cm H2O =
0.736mm Hg
Although airway diameter goes down Cross-sectional area goes ___ __!
way up
?
What jobs does the lung do?
- Conduction of air
- Diffusion of gas
- Transport
- Metabolism
- Defense
Flow =
Volume/Time
or
deltaP/Resistance
*Flow moves down a pressure gradient (deltaP)
Pressure =
Force/Area
Flow is ____ in the conducting zone (trachea and bronchi).
As cross-sectional area increases in the respiratory zone deltaP _______ and so does Velocity of flow which facilitates gas exchange!
fast
decreases
*Cross sectional area increase so pressure gradient decreases so flow velocity decreases!
The velocity of airflow in the respiratory system:
A. Is highest in the peripheral airways
B. Is low in the central airways because the pressure gradient is lower
C. Increases with every generation of the airway
D. Is lowest in the alveoli
E. Is highest where deltaP is lowest
D. Is lowest in the alveoli
Diffusion of gas
The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration
Fick’s Law
The rate of diffusion of a gas across a permeable membrane depends on:
- The nature of the membrane
- The surface area of the membrane (A)
- The thickness of the membrane (T)
- the partial pressure gradient of the gas across the membrane (deltaP)
- The diffusion coefficient of the gas (D)
Vgas ≈
(A / T) * D * (P1-P2)
A= Surface Area T= Thickness of membrane D= Diffusion Coefficient P1 and P2 = Pressures on either side of membrane D ≈ Sol / MW = diffusion constant
Diffusion in the lung:
In the normal lung:
• 300 million alveoli
• Barrier between blood and air is less than 1mm
• Capillaries are very small so almost all RBC in contact
• CO2 diffuses about 20X faster than O2
Gas exchange occurs predominantly during _______.
expiration
*notes from handout
The alveolocapillary membrane:
- thin structure dividing air from blood
- 0.3-0.5µM thick (thicken in various disease states which can reduce oxygen diffusion)
- alveolar epithelium on the ‘air’ side
- endothelium on the ‘capillary’ side
- interstitium which lies between the two membranes
*notes from handout
The alveolar epithelium has 2 types of cells:
Type 1 cells (sunny side up, or pavement cells)
Type 2 pneumocytes which secrete a surface active material (or surfactant) into the alveoli (slide 22).
The application of Frick’s Law suggests that:
A. The Product of Pressure and Volume are constant
B. Diffusion of a gas across a membrane is inversely related to membrane area
C. Diffusion of gas is usually faster for a light gas
D. Diffusion does not occur when the membrane is thin because of equilibration
E. Diffusion is independent of pressure
C. Diffusion of gas is usually faster for a light gas
Vgas ≈ (A / T) * D * (P1-P2)
A= Surface Area T= Thickness of membrane D= Diffusion Coefficient P1 and P2 = Pressures on either side of membrane D ≈ Sol / MW = diffusion constant
Pulmonary capillaries are of very _____ caliber (_µM), squeezing the Red Blood Cells (RBCs) close to the vessel wall, and ________ the distance for diffusion.
small, 7
decreasing
Pulmonary Circulation
• The lung is a reservoir for ______
• Receives almost all __
• ___ resistance circuit
blood
CO
Low
Pressure =
since _________ is low, the pressure gradient can also be low to get good flow
Flow x resistance
resistance
F=deltaP/R
The pulmonary circulation is a ___ RESISTANCE circuit, as the walls of the pulmonary artery and its branches contain relatively little smooth muscle and are extremely thin.
LOW
As pulmonary vascular resistance is so low, a mean pulmonary arterial pressure of only __ cm water (__ mmHg) is needed for a flow of _L/min, which is the __, and also the RV output into the lung, as the 2 systems are in series. (Fig. 5.)
20, 15, 6, CO
As pulmonary vascular resistance is so low, a mean pulmonary arterial pressure of only __ cm water (__ mmHg) is needed for a flow of _L/min, which is the __, and also the RV output into the lung, as the 2 systems are in series. (slide 25)
20, 15, 6, CO
Although each red blood cell spends only _ second in the capillary network, and probably traverses only 2 or 3 alveoli, this brief time suffices for near complete equilibration of __ in the alveolus, and return of ___ to the alveolus.
¾, O2, CO2
*handout
Function of Extra alveolar vessels
As the lung expands, larger vessels are pulled open by the traction of expanding lung parenchyma.
Slide 26-28
Alveolar vessels are exposed to the alveolar pressures and so they are ___________ at higher lung volumes. Alveolar vessel resistance thus __________ at high lung volumes.
compressed
increases
F=deltaP/R
- handout
- *Slide 26-28
At low lung volumes, the extra alveolar vessel resistance _________ significantly.
increases
Slide 26-28
If a lung is completely collapsed, pulmonary artery pressure has to be raised to several cms. above downstream pressure before any flow will occur; this is called the _____ ______ ________.
critical opening pressure
Pulmonary vascular resistance may be reduced by increased blood flow, a phenomenon referred to as __________, and occurs due to capillary distention, and opening of capillaries which are normally ‘closed’: no blood flows through them at rest. This happens during exercise, when cardiac output, and thus, pulmonary blood flow is increased.
recruitment
F=deltaP/R
- handout
- **Slide 29
Pulmonary vascular resistance _________ with alveolar hypoxia, due to constriction of small pulmonary arteries
increases
*handout
Pulmonary vascular resistance can be _________ with _____ _____, which is a powerful selective pulmonary vasodilator, and is used to treat pulmonary hypertension. Useful in neonatal pulmonary hypertension due to prematurity.
decreased, Nitric Oxide
- handout
- **and see slide 36!!!
At low lung volumes
• Extra alveolar vessel resistance ________
• Alveolar (capillary) vessel resistance ________ (not squashed)
At high lung volumes
• Extra-alveolar resistance ________ (traction of surrounding expanding lung pulls vessels apart)
• Alveolar (capillary) vessel resistance ________ (squashed)
Clinical: Important to maintain OPTIMAL lung volume so that overall resistance is ___ and pulmonary blood flow is maximized
increases, decreases
decreases, increases
low
Factors that Affect Pulmonary Circulation
• Pressures around the vessels: Extra alveolar vessels vs ______ _______
• Increased blood flow - _________ which occurs during exercise: decreases resistance
• Vasoconstrictor – ________
• Vasodilator: _____ _____
• Acid base status: Alkalemia is a pulmonary vaso______
alveolar vessels recruitment Hypoxemia Nitric oxide dilator
Why don’t alveoli collapse at low lung volume?
Surfactant
Surface tension:
The elastic tendency of a fluid surface which makes it acquire the least surface area possible.
_______ _______ exerts a force that would tend to collapse the alveoli at low lung volume
Surface tension
Respiratory Distress Syndrome (RDS)
• Babies born before about __ weeks do not make enough surfactant resulting in RDS
• Surfactant _______ surface tension in the alveoli
• As the healthy lung Expands, surface tension _________
• As lung volume decreases, surface tension _________
• Surfactant most effective at ____ lung volume
32 reduces INCREASES DECREASES low
Pulmonary Circulation:
A. Is uniform all over the lung
B. Can be considered to be a high resistance circuit
C. Extra alveolar resistance decreases as the lung expands
D. Alveolar vessel resistance is uniformly low regardless of lung expansion
E. Hypoxemia decreases pulmonary vascular resistance
C. Extra alveolar resistance decreases as the lung expands
Metabolism of
Vasoactive substances: Produces Angiotensin Converting Enzyme (ACE), which generates vasoconstrictor Angiotensin II (SLIDE 39!)
Bronchoactive substances such as leukotrienes (which cause bronchospasm)
Xenobiotics (plays a role)
Is an important reservoir of several
cytochrome P450 enzymes (CYPs)
Contains mast cells which produce the anticoagulant ______
heparin
Defense:
• The mucociliary escalator protects the lung from ______ ______
• Can be _________ (as in black lung)
• Production of ___ (Important first line of defense)
• APUD cells in the lung secrete ________
inhaled particles
overcome
IgA
serotonin
Acts as a filter:
Filters small clots before they can reach the brain or other vital organs.
Applied Aspect: In right to left shunts, such as cyanotic heart disease with Tetralogy of Fallot, septic and other emboli are released into the circulation, as the blood bypasses the lungs, and flows directly from right to left: this leads to cerebrovascular occlusion, causing strokes, or infections causing cerebral abscesses.
*handout
- The nose has cilia which filter larger particles and generate a sneeze. Particles over 25 mm are filtered out in the nose and nasopharynx.
- The cough and gag reflexes prevent us from inhaling or aspirating nasopharyngeal secretions or food particles.
- The ciliated columnar epithelium of the bronchial tree has mucous glands and goblet cells, which secrete mucous. The cilia beat to propel this mucous towards the ____ _____, like an escalator, which carries debris from ___ _____ ______ to the trachea, to be coughed up, or swallowed. Particles greater than __ mm are cleared in this way.
- Particles reaching alveoli are removed by ____________ and end up in the regional lymph nodes.
- Cellular immune responses unique to the lung exist. When over-activated, these cause _______.
oral cavity
the lower airways
25
macrophages
asthma
*handout
Dalton’s law of Partial Pressures states that
The partial pressure of each gas is thus a fraction of ___ mm Hg, depending on its concentration in the mixture of gases.
in a mixture of gases, each gas exerts a partial pressure proportional to its concentration in the mixture.
760 (Barometric pressure of the atmosphere at sea level)
Pressure in Different Compartments of the Respiratory Tract (mm Hg):
GAS Room Trachea Alveolar Arterial blood PCO2 0 0 40 40 PO2 159 150 100 95 PH2O 0 47 47 - PN2 601 563 573 578 TOTAL 760 760 760 713
NOTE that the total pressure in arterial blood is only 713 mm Hg. That’s because the gas is saturated with water vapor as soon as it comes into contact with the moist respiratory mucosa of the trachea. PH2O is 47 mm Hg. Water vapor does not enter the blood, and hence partial pressure in the artery is 760-47 = 713 mm Hg.
*handout
Henry’s Law states that
the solubility of a gas in a liquid solution is proportional to the partial pressure of the gas and the solubility constant (a) of Bunsen.
This constant is different for each gas; eg: carbon dioxide is 20 times more soluble than oxygen, a fact which has great physiological implications
*handout
Lecture 2!
10/7/19
Boyle’s Law states that
the product of pressure and volume of a gas is constant at constant temperature
• Pressure (P) x Volume (V) = Constant (K)
• P1xV1 = P2xV2…..TEMP = CONSTANT!
so, V is inversely proportional to P, as V increases, P decreases.
Inspiration is _____:
• _ in the chest increases
• _ decreases
active
V
P
• The diaphragm moves down, the ribs move forward, upward and outward
• Air flows into the lung down a pressure gradient
Expiration is generally _______:
• _ in the chest decreases so _ increases
Expiration can be _______:
• Wind instrument
• Asthma
passive
V,P
• Due to elastic recoil of the chest wall
• Air flows out passively down the pressure gradient
active
• Uses the muscles of the abdomen and internal intercostal muscles
Types of flow:
Bulk Flow depends on pressure gradient, size and resistance of the conduit and the nature of the fluid
• Laminar: __________________
• Turbulent: Branch points, ________ airway resistance
– asthma
– velocity is reduced and more pressure is required to drive flow
• Transitional: ______ _____
Most flow most of the time is __________
Laminar: Smooth, high velocity, streamlined
Turbulent: Branch points, increased airway resistance
Transitional: Branch points
Most flow most of the time is transitional
POISEUILLE’S LAW FOR LAMINAR FLOW
Volume Flow Rate, Q = ΔPπr4 / 8ηL
ΔP = Driving Pressure (Pressure gradient or ΔP) r = Radius η = Viscosity L = Length
Ohm’s Law
Resistance =
Resistance = Driving Pressure / Flow
or
Pressure difference between the mouth and alveolus (ΔP) / Flow rate
R = η8L / πr4
Flow = ΔP / Resistance
Thus radius of a tube has a significant impact on resistance.
For example, if radius is halved, resistance increases 16 fold!
