Intro into the respiratory system

Question 1

Why do humans need a respiratory system?

Answer 1

Our bodies are too large to rely on simple diffusion of gases from the atmosphere to the tissues in order for cells to receive an adequate amount of oxygen for aerobic respiration.
Evolution of a respiratory system overcomes this problem.

Also, ensures balance between 02 and C02 produced by cells during aerobic respiration

Question 2

Describe the passage of air through the respiratory system

Answer 2

Air is breathed in through your nose/mouth into the pharynx an then the larynx.
From the larynx air travels through the trachea and down into the intersection that forms the right/left primary bronchi.
From the main bronchi air travels down secondary and tertiary bronchi which get increasing narrow and numerous.
From tertiary bronchi the air enters the bronchioles and then finally into the alveoli.

Question 3

Describe some of the characteristics of the alveoli

Answer 3

Large surface area - contribute to large surface area to volume ratio of lungs
Wall is one cell layer thick
Basement membrane fused with blood vessel - decreases distance gases have to diffuse
Richly innervated by capillaries

Question 4

What are the main functions of the respiratory system within the body?

Answer 4

Provides (and ventilates) a specialised surface where gas exchange can take place between the atmosphere and blood.

Contributes to acid-base balance (e.g. maintaining pH of the blood).

Communication

Metabolism and production of specific mediators

The pulmonary circulation filters particulate matter and emboli reducing systemic circulation exposure

Immunological defence

Question 5

What are the main lung volumes and capacities used during different breathing manoeuvres?
Define these different lung volumes/capacities

Answer 5

Total Lung Capacity - Maximum amount of air that can fill the lungs

Vital Capacity - Maximum amount of air a person can expel from the lungs after a maximum inhalation.

Functional Residual Capacity - Volume of air present in the lungs at the end of normal expiration.

Inspiratory Reserve Volume - The maximal volume of additional air that can inhaled by determined effort after normal inspiration

Tidal Volume - Normal volume of air moved into or out of lungs during normal inspiration and expiration.

Expiratory Reserve Volume - The maximal volume of additional air that can exhaled by determined effort after normal expiration

Residual Volume - Volume of air remaining in the lungs after a maximal exhalation

Question 6

What are some of the factors that affect these lung volumes/capacities?

Answer 6

Age
Sex
Height
Lung properties (compliance, obstruction/damage due to disease)

Question 7

Define ventilation (breathing)

Answer 7

The exchange of air between the lungs and the atmosphere to facilitate gas exchange

Question 8

What is the equation for ventilation rate?

Answer 8

𝑉= 𝑉𝑇 ×𝑓

Question 9

What do each the variables in the equation for ventilation represent?

Answer 9

𝑉 = minute volume (mL), total volume of air inhaled in all breaths over one minute.

𝑉𝑇 = tidal volume (mL), the volume of air inhaled in each breath.

𝑓 = frequency (min-1), the number of breaths per minute

Question 10

Why doesn’t all the “fresh” air that you breath in during inspiration reach the gas exchange surfaces?

Answer 10

Lungs don’t completely empty during expiration so already some air within respiratory system before each inspiration.

Respiratory system is two-way system; air enters and leaves via the same path.

This means that the final 150mL of each inspiration never reaches the alveoli or takes place in gas exchange.

Question 11

Why are the airways known as “anatomic dead space?”

Answer 11

Gas exchange doesn’t take place in the airways so volume of air that fills the airways is just wasted volume.

Question 12

What happens to the volume of air within the “dead space” during expiration?

Answer 12

It gets pushed out of the respiratory system back to the atmosphere and so never reaches the lungs

Question 13

Define alveolar ventilation

Answer 13

The exchange of air between the alveoli and the atmosphere to facilitate gas exchange

Question 14

What is the equation for alveolar ventilation rate?

Answer 14

𝑉𝐴 = (𝑉𝑇 − 𝑉𝐷 ) ×𝑓

Question 15

What do each of the variables in the equation for ventilation represent?

Answer 15

𝑉𝐴 = alveolar minute volume (mL), the total volume of fresh air entering the alveoli across all breaths over one minute

𝑉𝑇 = Tidal volume (mL)

𝑉𝐷 = Dead space volume (mL), the volume of air remaining in the respiratory system at the end of expiration

𝑓 = frequency (min-1)

Question 16

What causes a gas to move from one area to another? What is it that causes this movement to stop?

Answer 16

A pressure gradient between two areas. Gases naturally move from (connected) areas of higher pressure to lower pressure, until an equilibrium is re-established which causes this movement to stop.

Question 17

What is the ideal gas law?

Answer 17

An equation used to approximate the behaviour of ideal gases under many different conditions

Question 18

What is the equation for the ideal gas law?

Answer 18

PV = nRT

Question 19

What do each of the variables in the equation for the ideal gas law represent?

Answer 19

P = Pressure 
V = Volume 
n = Number of moles 
R = Gas constant 
T = Temperature

Question 20

What does Boyle’s law state about the the pressure of a gas?

Answer 20

States that the pressure of a given mass of an ideal gas is proportional to the number of moles/ volume at a constant temperature.
Essentially, pressure is proportional to the density of a gas at a constant temperature.

Question 21

What is the equation for Boyle’s law?

Answer 21

P ∝ n/V 
Where: 
P = Pressure 
n = Number of moles within a given volume 
V = Volume

Question 22

If you had 2 containers with one container have a higher pressure than the other, what would happen if you then connected the 2 containers?

Answer 22

The appropriate number of gas molecules will move down the pressure gradient to re-establish an equal pressure within both containers, equilibrium.

Question 23

What would occur if you had 2 connected containers of gas at the same pressure but then decreased the volume of one of the containers.

Answer 23

You momentarily increase the pressure in the container with less volume causing the movement of gas molecules down the newly established pressure gradient, until an equilibrium is re-established.

Question 24

What would occur if you had 2 connected containers of gas at the same pressure but then increased the volume of one of the containers.

Answer 24

You momentarily decrease the pressure in the container with more volume causing the movement of gas molecules down the newly established pressure gradient, until an equilibrium is re-established.

Question 25

What is the partial pressure of a gas within a gas phase mixture?

Answer 25

The pressure of each individual that is found within a mixture of gases if that one gas alone occupied the same volume that the mixture of gases does.

Question 26

What is the equation used to calculate the partial pressure of a gas within a mixture of gases?

Answer 26

𝑃 𝑔𝑎𝑠 = (𝑃 𝑏𝑎𝑟𝑜𝑚𝑒𝑡𝑟𝑖𝑐 −𝑃 𝐻2𝑂) × 𝑛 𝑔𝑎𝑠

Question 27

What do each of the variables in the equation used to calculate the partial pressure of a gas represent?

Answer 27

𝑃 𝑔𝑎𝑠 = Partial pressure of individual constituent gas
𝑃 𝑏𝑎𝑟𝑜𝑚𝑒𝑡𝑟𝑖𝑐 = Atmospheric pressure
𝑃 𝐻2𝑂 = Water vapour pressure
𝑛 𝑔𝑎𝑠 = Mole fraction: the % of total moles represented by the individual gas

Question 28

What is the equation used to calculate the total pressure of a gas phase mixture?

Answer 28

𝑃 𝑇𝑜𝑡𝑎𝑙 =𝑃 𝐻2𝑂 + ∑𝑃 𝐶𝑜𝑛𝑠𝑡𝑖𝑡𝑢𝑒𝑛𝑡 𝑔𝑎𝑠𝑒𝑠

Question 29

Explain the concept of a partial pressure of a gas dissolved in a liquid?

Answer 29

The partial pressure of gas dissolved in a liquid reflects the amount of gas that would dissolve (at equilibrium) if the liquid was placed in contact with a gas phase of equivalent partial pressure.