1. Introduction / Epidemiology

Question 1

Outline the structure and function of alveoli

Answer 1

In the lungs, air is diverted into smaller and smaller microscopic branches called respiratory bronchioles, which connect to the alveolar ducts

At the end of each duct are approximately 100 alveolar sacs, each containing 20 to 30 alveoli that are 200 to 300 µm in diameter

Each alveolar membrane is one cell thick and is in direct contact with capillaries that are also one cell thick

The function of the alveoli is to get oxygen into the blood stream for transport to the tissues, and to remove carbon dioxide from the blood stream

Question 2

Approximately how many alveoli are there in the lungs and what is their approximate total surface area?

Answer 2

There are about 600 million alveoli in the lungs, with a total surface area of about
75 m^2

Question 3

Define COPD

Answer 3

Chronic Obstructive Pulmonary Disease (COPD) is an umbrella term used to describe progressive lung diseases including emphysema, chronic bronchitis, refractory (non-reversible) asthma, and some forms of bronchiectasis

This disease is characterized by increasing breathlessness

Question 4

What percentage of atmospheric air is O2 and CO2 respectively?

Answer 4

O2 - 20.9%

CO2 - 0.04%

Question 5

What percentage of partial pressure in alveolar air is O2 and CO2 respectively?

Answer 5

O2 - 13.3kPa (100mmHg)

CO2 - 5.3kPa (40mmHg)

These pressures are the same for arterial blood

Question 6

What percentage of partial pressure in mixed venous blood is O2 and CO2 respectively?

Answer 6

O2 - 5.3kPa (40mmHg)

CO2 - 6.1kPa (46mmHg)

Question 7

What is the most common lung disease in the UK?

Answer 7

Asthma, followed by COPD in 2nd place

Question 8

What percentage of UK deaths can be attributed to lung disease and what makes up the highest proportion of these deaths?

Answer 8

~20%

Lung cancer makes up the most of this, with 6.2% of all UK deaths

Question 9

Which type of cancer is the biggest killer in the UK?

Answer 9

Lung cancer (in both men and women)

Question 10

What percentage of UK adults smoke?

Answer 10

~19%

Question 11

How much oxygen does the average resting adult need?

Answer 11

~250ml/minute

This is much more than can be acquired through simple diffusion

Question 12

Define ‘dyspnoea’

Answer 12

Difficult or laboured breathing

Question 13

Define ‘orthopnoea’

Answer 13

Dyspnoea that occurs when lying flat

Question 14

Define ‘apnoea’

Answer 14

Temporary cessation of breathing, especially during sleep

Question 15

Briefly outline spirometry

Answer 15

Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs)

It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled

Spirometry is helpful in assessing breathing patterns that identify conditions such as asthma, pulmonary fibrosis, cystic fibrosis, and COPD; it is also helpful as part of a system of health surveillance, in which breathing patterns are measured over time

Question 16

What does spirometry generate?

Answer 16

Pneumotachographs, which are charts that plot the volume and flow of air coming into and out of the lungs from one inhalation and one exhalation

Question 17

State some functions of the respiratory tract

Answer 17

Gas exchange

Host defence

Metabolism of endogenous and exogenous molecules

Repair

Vocalisation

Question 18

What is the most important function of the respiratory tract?

Answer 18

Oxygenation of the blood and removal of excess carbon dioxide

Aside from the placenta (which is produced by the foetus), it is the only organ which can carry out this crucial function

Question 19

State some anatomical and physiological requirements of the respiratory tract

Answer 19

It must open to the atmosphere

It requires a mechanism to warm and humidify atmospheric gases

It needs an effective system for gas delivery to the alveoli (respiratory pump)

It must have a large gas-permeable surface

It needs a large de-oxygenated blood supply in close apposition to the gas-permeable surface

Question 20

Outline how the respiratory tract acts in host defence

Answer 20

Particle trapping and removal systems in the upper airways

Resident cells able to produce mediators able to attack invading organisms

Migratory cells – macrophages, lymphocytes, neutrophils from the marginated pool ‘on standby’ in the pulmonary vasculature

Question 21

State some important endogenous substances that are present in the respiratory tract

Answer 21

Local hormones (Angiotensins)

Inflammatory mediators (Bradykinin and prostaglandin degradation)

Neurotransmitters (Noradrenaline, serotonin)

Question 22

What is the most common reason to visit a GP?

Answer 22

Respiratory conditions (~1/3 of all GP visits)

Question 23

Define ‘pleural empyema’

Answer 23

Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria

Often it happens in the context of a pneumonia, injury, or chest surgery

It is one of various kinds of pleural effusion

Question 24

Define ‘pleural effusion’

Answer 24

Pleural effusion, sometimes referred to as ‘water on the lungs’, is the build-up of excess fluid between the layers of the pleura outside the lungs

The pleura are thin membranes that line the lungs and the inside of the chest cavity and act to lubricate and facilitate breathing

Question 25

How can respiratory cilia be damaged and what are the implications of this?

Answer 25

Damage to the cilia can occur due to the
activity of enzymes such as neutrophil elastase – released from neutrophils which are attracted into the airways by cigarette smoke, bacterial products etc.

Cell walls of epithelial cells are broken down, damaging and destroying the cilia so that patients may have a reduced number of cilia as well as cilia that are not working effectively

Damaged cilia are less effective at removing mucus from the airways

Question 26

State 3 diagnostic techniques for examining the respiratory system

Answer 26

Chest X-rays

MRI scans

Spirometry