Lecture 2 Flashcards
What is Tidal Volume?
The volume of air breathed in and out of the lungs at each breath at rest. Typically 500ml, approx at 1/2 total lung capacity.
What is Expiratory Reserve Volume (ERV)
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration. 1100ml av. men, 900ml av. women.
What is Inspiratory Reserve Volume (IRV)?
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration. Average 3L for men 1900ml for women.
Residual Volume (RV)
The volume of gas in the lungs at the end of a maximal expiration. 1200ml av. men, 1100ml av. women. Prevents alveoli collapse, which would take a lot more energy to open when collapsed. Also provides place for gas exchange to take place even between breaths.
What is Vital Capacity (VC)?
tidal volume + inspiratory reserve volume + expiratory reserve volume. Used to measure lung funtion. 4600ml av men, 3100ml women , max. amount of air voluntarily expire.
What is Total Lung Capacity (TLC)?
vital capacity + the residual volume
What is Inspiratory Capacity?
tidal volume + inspiratory reserve volume
What is Functional Residual Capacity (FRC)?
expiratory reserve volume + residual volume.
FEV1:FVC =
Fraction of forced vital capacity expired in 1 second.
What lobes are the lungs divvied into?
RIght Lung: Superior, Middle, Inferior
Left lung: Superior and Inferior
How many pleural sacs are there
2 - left and right
What is the differenc ebetween parietal and visceral pleura?
Parietal pleura is the outer layer lining inner surface of ribs/deep surface of chest wall
Visceral is the inner layer lining lungs
Think parietal brain is the upper outermost part therefore parietal pleura is outermost too
What fills pleural cavity?
intrapleural fluid
Are lungs effectivelystuck to rib cage through relationships of pleural membranes with ribs/lungs?
Yes
What causes unforced exhalation?
the elastic connective tissue in the lung leads to recoil of the chest wall
What is Boyles law?
Pressure exerted by a gas is inversely proportional to its volume (big volume low pressure, small volume high pressure)
BP - Boyle=Pressure
What law states that the total pressure of a gas mixture is the sum of the pressures of the individual gases?
Daltons Law (SID the sloth - Sum of Individ gasses = Daltons)
What law states that the volume occupied by a gas is directly related to the absolute temperature (v a T)
Charles law (Prince charles checking temparature)
Which law states that the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid?
Henry’s law - finding Henry (the underwater law)
What muscles does inspiration use?
External Intercostals and diaphragm, accessorary muscles inc : sternocleidomastoid and scalenes
What muscles does expiration use?
Passive at rest, but uses internal intercostals and abdominal muscles during severe load.
What shape is the diaphragm when it is relaxed?
Dome shaped.
What is Intra-thoracic (Alveolar) Pressure (PA):
pressure inside the thoracic cavity, (essentially pressure inside the lungs). May be negative or positive compared to atmospheric pressure
What is Intra-pleural Pressure (Pip)
pressure inside the pleural cavity, typically negative compared to atmospheric pressure (in healthy lungs at least!)
What is Transpulmonary pressure (PT):
difference between alveolar pressure and intra-pleural pressure. Almost always positive because Pip is negative (in health). PT = Palv – Pip
State the role of pulmonary surfactant
It stops water molecules being able to “see” each other (blocks intermolecular forces) therefore reduces surface tension urge (tendency) of alveoli to collapse. Water and other fluid is required as gasses can only move across in solution
What is the Law of Laplace?
P=2T/r P=Pressure T=surface Tension r=radius
Surface tension is the same across different alveoli because water droplets are attracted to each other with same attractive force across alveoli regardless of big or small alveoli.
T without surfactant =3??? T with surfactant = proportional to size (more cocentrated in smaller alveoli)! Therefore pressure should be the same in big and small alveoli with functioning surfactant.
Define the term compliance
change in volume relative to change in pressure
i.e. how much does volume change for any given change in pressure
It represents the stretchability (ability to get air in) of the lungs (not the elasticity - recoil!)
HIGH COMPLIANCE = large increase in lung volume for small decrease in ip pressure (not much effort to increase lung vol. (inspire))
LOW COMPLIANCE = small increase in lung volume for large decrease in ip pressure (hard to inspire!)
What factors affect compliance
Changes in disease states/age
Is determined, in part, by action of surfactant
What are the 2 cell types make the alveolar walls?
Thin walled “Type I” cells which permit gas exchange
Specialised “Type II” cells which secrete surfactant fluid
What is Pleurisy?
Inflammation of the Pleura, making any movements/breaths etc painful as the pleural membranes don’t slide over each other as much
How much pleural fluid is between the pleural membranes?
About 3mm
At the end of a normal expiration at rest what forces are in equilibrium?
Outward force of chest wall (through pleural membrane stuck to rib cage) and inward force of elastic fibres wanting to recoil further
What is Pneumothorax
When pleural membranes are pierced and so the elastic fibres in the lung recoil the lung and it shrivels up as it can no longer help and pushes out in the opposite direction by the chest wall which is now able to move freely as the plural membrane is no longer cohesive.
What is the Hilum of the lungs
The region where the bronchi, arteries, veins, and nerves enter and exit the lungs.
Which nerve innervates the diaphragm?
Phrenic nerve
During inspiration/expiration what happens to the airways?
Inspiration = increase diameter expiration = decrease diameter,
How does asthma affect the bronchiole smooth muscles?
Inappropriate constriction, aggravated on expiration. Restricts air flow even more. Asthma wheeze on expiration .
Why is surfactant more effective in smaller alveoli compared with larger alveoli?
Surfactant molecules come closer together and therefore more concentrated.
When does surfactant production start and when is it complete? What is it stimulated by? What do premature babies suffer from?
25 weeks gesation start - 36 weeks complete (40 weeks full term). Stimulated by thyroid hormones and cortisol which increase towards end of pregnancy. Premature babies suffer Infant Respiratory Distress Syndrome (IRDS) as they dont have adequate surfactant (before 36 weeks). These days is overcome with synthetic surfactant aerosol.
