Intro to Respiratory System Flashcards
Outline the Respiratory system structures starting form top to bottom
- Nasal cavity plexus
- Paranasal sinuses
- Nostril
- Oral cavity
- Pharynx
- Larynx
- Trachea
- Carina of strachea
- Left main (primary bronchus)
- Right main bronchus
- Bronchi
- Alveoli
- Lungs
- Parietal Pleura
- Ribs
- Diaphragm
Describe the upper airways roles
Upper airways are nasal passages
What are the lower respiratory airways?
Tracheae & bronchi
What is the role of the bronchi?
They reach into lung structures and into alveoli to transport oxygen
What causes movement within the respiratory system?
Respiratory muscles and pleural membranes contribute to movement
What is the significance of the respiratory system?
- provide cells the energy required to function via O₂
- Aerobic Respiration requires O₂ and produces CO₂
- Atmosphere provides O₂ source and CO₂ can be
expelled - Our bodies are too large to rely on simple diffusion of
gases from atm -> tissues
How does O₂ reach gas exchange structures?
To reach gas exchange structures, air must pass through a series of increasingly narrow and numerous airways
What is the consequence of impaired airway function?
Insufficient ventilation occurs
Why are alveoli good gas exchange structures?
Have intricate structures and multiple adaptations to maximise rate of gas exchange
Describe the structural features of alveoli?
- 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
What is the link between CVS and Resp. system?
Both work together to provide O₂ to cells
What are the functions of the Respiratory system?
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
Describe how O₂ transport occurs from the atmosphere to the cells
- O₂ inhaled from atmosphere –> lungs
- O₂ diffuses from alveoli –> blood within pulmonary
circulation - O₂ transported in blood mainly bound to Hb
- O₂ diffuses into cells / tissues for aerobic respiration
use - CO₂ diffuses out of respiring tissues –> blood,
exchanged at lungs
What do lung volumes and capacities depend upon?
Age
sex
height
lung properties e.g. compliance, obstruction / damage due to disease
How does age and sex affect lung capacity?
With age lung volume decreases
Men tend to have a larger lung capacity compared to women
What is ventilation?
Volume of (fresh) air reaching respiratory surfaces over a given time - dependent on volume (depth) and rate of breathing
Outline the equation for ventilation
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
What factors need to be taken into consideration when using the ventilation formula?
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
What kind of air (fresh / stale) is present within lungs?
The lungs contain a mixture of ‘fresh’ and ‘stale’ air
Where does gas exchange occur?
Gas exchange only takes place in alveoli, but air must pass through the airways
airways = anatomic dead space
Why is the respiratory system described as a two-way system?
Air enters and leaves via the same path
Why are the lungs never completely empty?
A residual volume of air remains in the airways and lungs at the end of each expiration
What is dead space volume?
The final ~150 ml of each inspiration never reaches the alveoli / takes place in gas exchange as it’s always expired first
What is alveolar ventilation?
Alveolar ventilation corrects for the volume of inspired air which doesn’t take part in gas exchange (due to dead space)
Outline the formula used to calculate alveolar ventilation
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)
Describe the movement of gases
Gases naturally move from (connected) areas of higher pressure to lower pressure, until an equilibrium is re-established.
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
(VT (ml) - VD) x f
((0.5 x 1000) - 150) x 12 = 4200 ml / min
= 4.2 L/min
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
(VT -VD) x f
((0.2 x 1000) - 150) x 30 = 1500 ml/min
= 1.5 L/min
What is the Ideal Gas Equation?
PV = nRT
P = pressure (pa) V = volume (m³) N = no. of moles R = gas constant (8.32) T = temperature (K)
What is Boyle’s Law?
P ∝ n/v
Pressure = the no. of gas molecules within a given volume
If n remains constant, increased volume = decreases pressure
How does the number of molecules affect pressure?
A lower no. of molecules = less pressure
How does connecting 2 spaces allow equilibrium to be reached?
Connecting spaces causes equilibrium as gases move from high to low pressures (down a pressure gradient) until a constant pressure is reached
How does volume affect pressure?
Decreasing volume will increase pressure due to compression caused
What is partial pressure of a gas?
The pressure of that constituent gas if it alone occupied that same volume at the same temperature
e.g.
Ptotal = PA + PB + PC
How is partial pressure of a gas calculated?
Multiply total pressure by mole fraction
What are the mole fractions of the gases present in air?
Nitrogen - 0.78
Oxygen - 0.21
Carbon dioxide - 0.03
Water - variable
How can we calculate Ptotal when taking the water present in air, into consideration?
Ptotal = PH₂O + {Pconstituent gases
How do you calculate the partial pressures of constituent gases if water is present in the air?
Pgas = (P barometric - P H₂O) x ngas
P barometric - atm pressure
P H₂O - water vapour (0 in dry air, 6kpa in humidified air)
what is PO₂ of dry air at the summit of mount Everest (8844m) if Pᵦₐᵣₒₘₑₜᵣᵢ₍ = 34kPa?
34 kPa x 0.21 = 7.14 kPa
What does the partial pressure of gas dissolved in liquid tell us?
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
