Week 9 - respiratory system, lung volumes

Question 1

Why do we need a respiratory system

Answer 1

It creates an interface between the environment and the tissues (via the blood), which are not very compatible.

Question 2

Why is dehydration a problem for the respiratory system

Answer 2

For effective diffusion between air and liquid (atmosphere and blood), the surface of the respiratory system must not only be thin, but also must be moist.

Question 3

Functions of the respiratory system

Answer 3

Gas exchange between environment and blood
Control of the acidity of the body
Filtering of the air that is inhaled
Vocalisation - producing sound

Question 4

What is special about the lungs

Answer 4

They are large, spongy elastic bags that fill up with air every breath, meaning they can expand and recoil with every breath

Question 5

The lobes of the lungs

Answer 5

Each lung is divided into compartments called lobes. The right (as you look the left) lung has three lobes but the left lung has only 2.
The left lung has a part missing - where the heart sits

Question 6

The pleural sac

Answer 6

The pleural sac is a double-walled enclosure of the lungs filled with fluid, the pleural fluid.
Prevents the lungs from collapsing

Question 7

Layers of the pleural sac

Answer 7

Outer layer is the parietal pleura and the inner layer is the visceral pleura - attaches to lungs

Question 8

The thoracic cavity turns into a

Answer 8

pump due to the muscles of respiration expanding and contracting the volume of the ribcage

Question 9

Role of the pleural sac

Answer 9

Reduces friction from movement on the surface of the lungs
Allows lungs to fix on the thoracic wall without having to touch themselves

Question 10

Bones and muscles in the thoracic cavity

Answer 10

The bones (rib cage and spine) offer rigid protection to sensitive organs (heart and lungs)
The muscles (diaphragm, intercostals abdominals) support the rib cage and turn the chest into a pump that drives air flow

Question 11

Role of the internal and external intercostals

Answer 11

External intercostals are lifting the ribs and the internal intercostals pull the ribs down

Question 12

Upper respiratory tract

Answer 12

Nasal cavity
Entry point of the respiratory system

Question 13

Lower respiratory tract

Answer 13

Trachea - contains the conductive zone or dead space
Bronchial tree
Alveoli - gas exchange

Question 14

Bronchial tree divisions

Answer 14

The bronchial tree undergoes a number of divisions (23 generations). At the end of the tree the surface area is enormous (100 m2)

Question 15

Functions of the airways

Answer 15

Warming up of inspired air
Humidification of dry inspired air
Filtration of inhaled foreign materials

Question 16

Components of the nasal cavity

Answer 16

Turbinates or conchae - bony dividers that increase the surface area of the nasal cavity. The surface of the nasal cavity has a very high blood supply, which helps warm up and humidify the inspired air as it flows over it.
Vestibule - entrance to cavity - first line of airway defence. Small hairs and mucus help trap inhaled particles so they can be blown back out
Cilia blocks unwanted objects from entering - has a stroke and relaxation phase

Question 17

What cells line the alveoli that allow gaseous exchange to take place

Answer 17

Capillary endothelial cells and a single layer of alveolar epithelial cells

Question 18

Boyles law

Answer 18

P1 X V1 = P2 X V2
The product of pressure and volume is always the same

Question 19

Relationship between resistance, airflow and pressure difference

Answer 19

Airflow is inversely proportional to pressure diff / resistance

Airflow is inversely proportional to resistance
Airflow is directly proportional to pressure difference

Question 20

Relationship between viscosity, length, radius and resistance

Answer 20

Resistance is proportional to length x viscosity / radius^4

Question 21

Viscosity and airway radius

Answer 21

Viscosity plays a small role in the resistance of the airways to airflow. Viscosity is affected by humidity and the concentration of air (high altitude)

Airway radius is the main factor affecting resistance.

Question 22

Inspiration

Answer 22

During inspiration, the diaphragm contracts and flattens out, increasing the volume of the thoracic cavity

External intercostal muscles pull ribs up and out

Question 23

Expiration

Answer 23

Normal expiration doesn’t require the contraction of any muscles
Heavy breathing requires the contribution of the expiratory muscles (internal intercostal and abs) in order to compress the thoracic cavity faster and further than restful breathing

Question 24

Pneumothorax

Answer 24

A collapsed lung
Happens when intrapleural pressure is equal to atmospheric pressure

Question 25

Inspiration and expiration occurs when

Answer 25

Inspiration occurs when pressure inside the lungs is below atmospheric pressure

Expiration occurs when pressure inside the lungs is above atmospheric pressure

Question 26

Law of LaPlace

Answer 26

Pressure = 2 x surface tension / radius
If two bubbles have the same surface tension, the smaller bubble will have the higher pressure

Question 27

What happens if there would be no surfactant in lungs

Answer 27

In the alveoli, with them being different sizes, contents from the smaller balloon would empty into the larger balloon (same surface tension –> smaller balloon would have greater pressure) therefore some alveoli may collapse, eventually creating one bubble

Question 28

What does a surfactant do

Answer 28

Surfactant contains proteins that result in a reduction in the surface tension of the alveolar walls
Big alveolus = lower conc of surfacant
Small alveolus = higher conc of surfactant due to greater pressure

Question 29

Give all of the lung volumes

Answer 29

Tidal volume
IRV
ERV
Residual volume
Functional residual capacity
Vital capacity
Inspiratory capacity
Total lung capacity

Question 30

Functional residual capacity

Answer 30

The amount of air left in the lungs at the end of a normal expiration

Question 31

What is different about residual volume and functional residual capacity

Answer 31

They cannot be measured using a spirometer as they stay inside the lungs

Question 32

Anatomical dead space

Answer 32

Part of the airways where gas exchange does not take place and is a fixed volume (150ml)

Question 33

Alveolar dead space

Answer 33

Areas of the lungs where gas exchange can take place but that are not properly perfused with blood

Question 34

Minute ventilation

Answer 34

Amount of air that is moved by the lungs in one minute
Tidal volume x breathing frequency

Question 35

Average minute ventilation

Answer 35

0.5 L x 12 br/min = 6 L/min

Question 36

Hyperpnoea

Answer 36

Minute ventilation increases in proportion to metabolic rate

Question 37

Hyperventilation

Answer 37

Minute ventilation increases more than metabolic rate does

Question 38

How can volumes of air be measured

Answer 38

Under ambient conditions (ATPS), corrected for body variables (BTPS) or corrected for standard variables (STPD)