Shorty answer questions

Question 1

Describe how the air is prepared in the nasal cavity

Answer 1

Air is filtered by the vibrissae, small hairs within the nares. Mucous secreted from goblet cells also filters pathogens from the air. Nasal epithelium-cilliated pseudo stratified columnar lines the nasal cavity which consists of three ridge like turbinate bones make up the conchae. This increases the surface area and creates turbulant air flow assisting in warming and humidifying the air, larger particles also get thrown into the mucous helping with filtering.

Question 2

Describe the 2 sources of mucus in the respiratory tract, and give the location of these sources.

Answer 2

Goblet cells and seromucus glands of the sub mucosa. There are two layers of mucus a serous, sol layer where the cilia beat and above it a viscoelastic gel layer which traps particulate matter. These mucus producing sources are in the conducting zones.

Question 3

Describe the function of the turbinate bones within the nasal cavity

Answer 3

To increase the surface area of the nasal cavity and to create turbulent airflow both assisting with warming, filtering and humidifying the air.

Question 4

Connective tissues of the respiratory tree: Describe the organisation of hyaline cartilage and elastic fibres within the repiratory tree and explain their respective functions

Answer 4

Hyaline cartilage found around airways up until terminal bronchioles, arranged in c shaped curves and then plates. Elastic fibres arranged longitudinally along conducting airways and in basket weave around alveoli. Cartilage helps to keep the airways open against negative pressure from IP. Elastic fibres allow for elastic recoil of the lungs.

Question 5

Describe 4 features that distinguish a bronchus from a bronchiole

Answer 5

Bronchus has pseudo stratified, ciliated epithelium, bronchiole have simple cuboidal ciliated epithelium. Bronchus have cartilage, bronchioles do not Bronchus have goblet cells and mucous glands, bronchioles have club cells. Bronchus are soley for conducting wheras some gas exchange can occur in respiratory bronchioles.

Question 6

Describe the cells types and their function that line a respiratory bronchiole

Answer 6

Simple cuboidal ciliated epithelium transitioning to squamous. Beginning to provide for a thin gas-blood barrier for better gas exchange, cilia transport small particles up muco-cilliary escalator. Type 1 pneumocytes in alveoli buds off bronchioles- thin gas exchange barrier Type 2 pneumocytes produce surfactant to reduce surface tension Alveolar macrophages- protection

Question 7

Name the 3 cell main cell types present in an alveolus. Provide their function and location

Answer 7

Type 1 pneumocytes- form the epithelium of alveoli. Type 2 pneumocytes- secrete surfactant that reduces surface tension within the alveoli Alveolar macrophages- in lumen of alveoli and interstitium phagocytose pathogens

Question 8

Describe 2 conditions that affect the lung parenchyma and how they affect the function of the blood air barrier.

Answer 8

Emphysema- reduction in elastic fibres increasing lung compliance resulting in diminished elastic recoil. Destruction of alveoli causes decrease in surface area and thus reduced area available for diffusion. Fibrosis- increase in collagen tissue in the parenchyma creating increased resistance, stiff lung. Thickens blood-air barrier decreasing diffusion.

Question 9

Describe how the cells and tissues of the respiratory zone are supplied with oxygen.

Answer 9

The supply of oxygen to the respiratory zone cells is from rich inspired air within the respiratory zone, the bronchopulmonary anastomoses can also play a role.

Question 10

Where are the pulmonary arteries located?

Answer 10

Arise from the pulmonary trunk and travel with the airways

Question 11

Describe the route of the pulmonary vein

Answer 11

Arise from pulmonary capillaries, travel in lung parenchyma to form two main pulmonary veins for each lung entering the left atrium.

Question 12

Describe the 2 locations (or levels) that the pulmonary and bronchial circulations anastamose

Answer 12

-Bronchial arteries to pulmonary arteries at the level of the respiratory bronchioles -Bronchial capillaries to pulmonary vein

Question 13

Sketch a spiromatic trace to indicate TLC, FRC, VT, VC, and RV.

Answer 13

Question 15

Describe physiologic and anatomic dead space, and explain how they relate to each other.

Answer 15

They represent the space in the conducting zones that do not undergo respiration. Anatomic dead space is all of the conducting airways, making up a volume of around 150mls. Physiological dead space is all the areas of the lungs that do no undergo respiration, in a healthy person it equates to the anatomic dead space

Question 16

Compare two methods for estimating the anatomical dead space. What are the advantages and disadvantages of each?

Answer 16

It can be estimated using the Bohr Equation which compares the fraction of dead-space volume to tidal volume using the difference between the arterial partial pressure of CO2 and expired PCO2

Another mothod is by measuring the percentage of expired CO2 using a rapid gas analyzer and when the percentage of CO2 of the exhaled air rapidly increases is when most of the ADS air has been exhaled and the volume noted.

Question 17

For a situation where the dead space has doubled (e.g. patient ventilated via a fase mask, or breathing through a snorkel), what needs to happen to the tidal volume to maintain the same level of alveolar and exhaled CO2? (explain using the Bohr equation given in the following question)

Answer 17

The tidal volume would also need to double to maintain the same VD/VT ratio.

Question 18

If alveolar and mixed expired PCO2 are 40 and 30 mmHg respectively, what is the physiologic dead space from the Bohr equation (VD/VT = (PaCO2 - PECO2)/PaCO2)

Answer 18

VD/VT = (40-30)/40

VD/VT = 0.25

VD = 0.25VT

It is ¼ of tidal volume

Assuming tidal volume is 500mL then 0.25 x 500 = 125mL

Question 19

How does a pneumothorax caused by a puncture to the chest wall change this balance of pressures?

Answer 19

Pneumothorax introduces air into the pleural space which means that the visceral lung surface is no longer adhered to the parietal pleural surface of the chest wall by surface tension and thus the outwards force of the elastic recoil of the chest wall can no longer act on the lung and thus the lung collapses under its own elastic recoil inwards.

Question 20

Consider a subject who is starting to have an asthma attack, in which the smooth muscle around the airways constricts and the airways coated in extra mucus.

(a) What will be the effect on airway resistance?
(b) What will this do to the driving pressure for ventilation?
(c) Describe and explain the distibution of airway resistance with generation in the conducting airway tree.
(d) If only the smallest conducting airways were to constrict (e.g. the ~32,000 terminal bronchioles), what would this do to the total airway tree resistance? Why?

Answer 20

a) airway resistance will increase with the decreased diameter
b) Pressure will have to be increased to compensate for the increased resistance in order to maintain the same volumes
c) AIrway resistance is greatest in the intermediate sized airways where the diameter is smaller than the main bronchi but surface area is not much greater. Airway resistance is smallest in the most distal airways where surface area is very large.
d) The total airway resistance would increase dramatically. This is because even though each terminal bronchiole only constricts a little, because there are so many of them, this leads to a massive decrease in cross sectional area and thus increase in total airway tree resistance.

Question 21

A 36 year old female patient, seated at the ‘metabolic cart’ in the Lung Function Laboratory, has a measured rate of oxygen consumption of 300 mL.min-1. Laboratory temperature is 22ºC and the barometer pressure is 99.4 kPa. The patient’s oral temperature is 37.8ºC. What is her rate of oxygen consumption corrected to Standard conditions (i.e. OºC, 101.3 kPa (760 mmHg), dry)?

Question 22

Explain the mechanisms that determine the general distribution of ventilation in the lung (gravitational and non-gravitational), for a healthy adult breathing from FRC.

Answer 22

Gravity means that there is increased b

Question 23

Explain the balance of pressures that dertermine FRC.

Answer 23

The inward recoil of the lungs and the outward recoil of the chest wall. When these forces are at equilibrium the individual is at FRC

Question 24

The chest wall in the newborn is very compliant. What effects does this have on the FRC volume of the lung?

Answer 24

It is decreased becuase the outword force of the chest wall is not as great and thus inward pressure from elastic recoil of the lungs is not countered to the same extent reducing FRC

Question 25

Emphysema is characterised by a loss of lung parenchyma. Explain the consequences for FRC

Answer 25

Emphysema results in a loss of elastic fibres in the lung resulting in reduced elastic recoil and thus increased lung compliance meaning that FRC is increased. Loss of parenchyma also results in loss of support for alveoli and they are more likely to collapse (atelectasis) this leads to gas trapping increasing the residual volume, one of the volumes that makes up FRC (the other being end expiratory volume)

Question 26

In pulmonary fibrosis, the stiffness of the lung is increased. Explain the consequential change of FRC

Answer 26

Increased lung stiffness means that the lungs are restricted from fully expanding meaning all volumes are decreased.

Question 27

Sketch a forced expiratory flow-volume curve for a healthy person who is exhaling with maximal effort. Label axes, TLC and RV.

Answer 27

Flow Y axis, Volume X axis. TLC on volume axis left side RV volume axis right side

Question 28

Considering that this person is young and healthy, what is one meachnism that limits the rate of exhaled aire flow in the effort independent region?

Answer 28

Negative transmural pressure (positive intrapleural pressure) leads to airway collapse during forced expiration which limits the flow of air in the effort independent region. No matter how much force is applied, air-flow cannot be increased because of the air being trapped downstream.

Question 29

What would happen to RV if the subject had a mild obstructive disease? A restrictive disease?

Answer 29

An obstructive disease like emphysema would result in an increased RV as the increased resistance in airflow means more gas trapping, increased RV.

A restrictive disease would result in a smaller residual volume as compliance is increased moving air from lungs and tissue cannot get as much air in.

Question 30

The ‘normal’ value for DL (diffusing capacity of the lung) (CO), measured at rest using the single-breath test, is about 25 mL.min-1.(mmHg)-1. A 22 year old male patient with a persistant cough presents. The Respiratory Lab reports his values of DL(CO) to be 20 and 30 mL.min-1.(mmHg)-1 during rest and moderate exercise respectively. Comment on the likely state of health of his alveolar-capillary membranes.

Answer 30

At rest his DL(CO) is decreased from the normal value. This means that there is not enough diffusion occuring across his alveolar-capillary membrane. Therefore the health of his alveolar-capillary membrane is somehow compromised. This could either be due to thickening (fibrosis) or a decreased surface area available for gas exchange.

During exercise it should increase around 2 or 3 fold whereas in his case it only increased by 0.5. Usually during exercise there is recruitment of much more pulmonary capillaries which thus increases surface area for diffusion. However, in this case ithis shows that even if perfusion to these recruited capillaries is occuring, they are not in good health because gas exchange is not occuring effectively across them in order to increase DL(CO) by 2 or 3 fold. This may be due to pulmonary oedema, V/Q mismatch or shunting