Intro to Respiratory System

Question 1

Outline the Respiratory system structures starting form top to bottom

Answer 1

1. Nasal cavity plexus
2. Paranasal sinuses
3. Nostril
4. Oral cavity
5. Pharynx
6. Larynx
7. Trachea
8. Carina of strachea
9. Left main (primary bronchus)
10. Right main bronchus
11. Bronchi
12. Alveoli
13. Lungs
14. Parietal Pleura
15. Ribs
16. Diaphragm

Question 2

Describe the upper airways roles

Answer 2

Upper airways are nasal passages

Question 3

What are the lower respiratory airways?

Answer 3

Tracheae & bronchi

Question 4

What is the role of the bronchi?

Answer 4

They reach into lung structures and into alveoli to transport oxygen

Question 5

What causes movement within the respiratory system?

Answer 5

Respiratory muscles and pleural membranes contribute to movement

Question 6

What is the significance of the respiratory system?

Answer 6

1. provide cells the energy required to function via O₂
2. Aerobic Respiration requires O₂ and produces CO₂
3. Atmosphere provides O₂ source and CO₂ can be
   expelled
4. Our bodies are too large to rely on simple diffusion of
   gases from atm -> tissues

Question 7

How does O₂ reach gas exchange structures?

Answer 7

To reach gas exchange structures, air must pass through a series of increasingly narrow and numerous airways

Question 8

What is the consequence of impaired airway function?

Answer 8

Insufficient ventilation occurs

Question 9

Why are alveoli good gas exchange structures?

Answer 9

Have intricate structures and multiple adaptations to maximise rate of gas exchange

Question 10

Describe the structural features of alveoli?

Answer 10

• Large SA (big SA:vol ratio)
• Alveolar walls are 1 cell thick
• Basement membrane is fused with blood vessels
• Richly innervated by capillaries providing an adequate
  blood supply

Question 11

What is the link between CVS and Resp. system?

Answer 11

Both work together to provide O₂ to cells

Question 12

What are the functions of the Respiratory system?

Answer 12

Provides and ventilates specialised gas exchange surfaces

Contributes to acid-base balance (blood pH)

Communication

Metabolism & production of specific mediators

Pulmonary circulation filters particulate matter and emboli, reducing systemic circulation exposure

Immunological defence

Question 13

Describe how O₂ transport occurs from the atmosphere to the cells

Answer 13

1. O₂ inhaled from atmosphere –> lungs
2. O₂ diffuses from alveoli –> blood within pulmonary
   circulation
3. O₂ transported in blood mainly bound to Hb
4. O₂ diffuses into cells / tissues for aerobic respiration
   use
5. CO₂ diffuses out of respiring tissues –> blood,
   exchanged at lungs

Question 14

What do lung volumes and capacities depend upon?

Answer 14

Age
sex
height
lung properties e.g. compliance, obstruction / damage due to disease

Question 15

How does age and sex affect lung capacity?

Answer 15

With age lung volume decreases

Men tend to have a larger lung capacity compared to women

Question 16

What is ventilation?

Answer 16

Volume of (fresh) air reaching respiratory surfaces over a given time 
- dependent on volume (depth) and rate of breathing

Question 17

Outline the equation for ventilation

Answer 17

V = VT x f

V = minute volume (ml)
- total volume of air inhaled in all breaths over 1 minute

VT = tidal volume (ml)
- volume of air inhaled in each breath

f = frequency (per minute)
- number of breaths a minute

Question 18

What factors need to be taken into consideration when using the ventilation formula?

Answer 18

V = VT x f calculates ventilation without taking into consideration:

• fresh atm air reaching gas exchange surfaces
• always some degree of air present in respiratory system

Question 19

What kind of air (fresh / stale) is present within lungs?

Answer 19

The lungs contain a mixture of ‘fresh’ and ‘stale’ air

Question 20

Where does gas exchange occur?

Answer 20

Gas exchange only takes place in alveoli, but air must pass through the airways

airways = anatomic dead space

Question 21

Why is the respiratory system described as a two-way system?

Answer 21

Air enters and leaves via the same path

Question 22

Why are the lungs never completely empty?

Answer 22

A residual volume of air remains in the airways and lungs at the end of each expiration

Question 23

What is dead space volume?

Answer 23

The final ~150 ml of each inspiration never reaches the alveoli / takes place in gas exchange as it’s always expired first

Question 24

What is alveolar ventilation?

Answer 24

Alveolar ventilation corrects for the volume of inspired air which doesn’t take part in gas exchange (due to dead space)

Question 25

Outline the formula used to calculate alveolar ventilation

Answer 25

VA = (VT - VD) x f VA = alveolar minute volume (ml) - total volume of fresh air entering alveoli across all breaths over a 1 minute period VT = tidal volume (ml) VD = Dead space volume (ml) - volume of air remaining in respiratory system at the end of each expiration f = frequency (per minute)

Question 26

Describe the movement of gases

Answer 26

Gases naturally move from (connected) areas of higher pressure to lower pressure, until an equilibrium is re-established.

Question 27

Assuming Person A has a dead space vol. of 150 ml, Calculate their total and alveolar ventilation if ``` VT (L): 0.5 Breathing Rate (min-1): 12 ```

Answer 27

(VT (ml) - VD) x f ((0.5 x 1000) - 150) x 12 = 4200 ml / min = 4.2 L/min

Question 28

Assuming Person B also has a dead space vol. of 150 ml, Calculate their total and alveolar ventilation when: ``` VT (L): 0.2 Breathing rate (min-1): 30 ```

Answer 28

(VT -VD) x f ((0.2 x 1000) - 150) x 30 = 1500 ml/min = 1.5 L/min

Question 29

What is the Ideal Gas Equation?

Answer 29

PV = nRT ``` P = pressure (pa) V = volume (m³) N = no. of moles R = gas constant (8.32) T = temperature (K) ```

Question 30

What is Boyle's Law?

Answer 30

P ∝ n/v Pressure = the no. of gas molecules within a given volume If n remains constant, increased volume = decreases pressure

Question 31

How does the number of molecules affect pressure?

Answer 31

A lower no. of molecules = less pressure

Question 32

How does connecting 2 spaces allow equilibrium to be reached?

Answer 32

Connecting spaces causes equilibrium as gases move from high to low pressures (down a pressure gradient) until a constant pressure is reached

Question 33

How does volume affect pressure?

Answer 33

Decreasing volume will increase pressure due to compression caused

Question 34

What is partial pressure of a gas?

Answer 34

The pressure of that constituent gas if it alone occupied that same volume at the same temperature e.g. Ptotal = PA + PB + PC

Question 35

How is partial pressure of a gas calculated?

Answer 35

Multiply total pressure by mole fraction

Question 36

What are the mole fractions of the gases present in air?

Answer 36

Nitrogen - 0.78 Oxygen - 0.21 Carbon dioxide - 0.03 Water - variable

Question 37

How can we calculate Ptotal when taking the water present in air, into consideration?

Answer 37

Ptotal = PH₂O + {Pconstituent gases

Question 38

How do you calculate the partial pressures of constituent gases if water is present in the air?

Answer 38

Pgas = (P barometric - P H₂O) x ngas P barometric - atm pressure P H₂O - water vapour (0 in dry air, 6kpa in humidified air)

Question 39

what is PO₂ of dry air at the summit of mount Everest (8844m) if Pᵦₐᵣₒₘₑₜᵣᵢ₍ = 34kPa?

Answer 39

34 kPa x 0.21 = 7.14 kPa

Question 40

What does the partial pressure of gas dissolved in liquid tell us?

Answer 40

It's equivalent to the amount of gas that would dissolve (at eqb.) if the liquid was placed in contact with a gas phase of equivalent partial pressure