1. Introduction / Epidemiology Flashcards
Outline the structure and function of alveoli
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
Approximately how many alveoli are there in the lungs and what is their approximate total surface area?
There are about 600 million alveoli in the lungs, with a total surface area of about
75 m^2
Define COPD
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
What percentage of atmospheric air is O2 and CO2 respectively?
O2 - 20.9%
CO2 - 0.04%
What percentage of partial pressure in alveolar air is O2 and CO2 respectively?
O2 - 13.3kPa (100mmHg)
CO2 - 5.3kPa (40mmHg)
These pressures are the same for arterial blood
What percentage of partial pressure in mixed venous blood is O2 and CO2 respectively?
O2 - 5.3kPa (40mmHg)
CO2 - 6.1kPa (46mmHg)
What is the most common lung disease in the UK?
Asthma, followed by COPD in 2nd place
What percentage of UK deaths can be attributed to lung disease and what makes up the highest proportion of these deaths?
~20%
Lung cancer makes up the most of this, with 6.2% of all UK deaths
Which type of cancer is the biggest killer in the UK?
Lung cancer (in both men and women)
What percentage of UK adults smoke?
~19%
How much oxygen does the average resting adult need?
~250ml/minute
This is much more than can be acquired through simple diffusion
Define ‘dyspnoea’
Difficult or laboured breathing
Define ‘orthopnoea’
Dyspnoea that occurs when lying flat
Define ‘apnoea’
Temporary cessation of breathing, especially during sleep
Briefly outline spirometry
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
What does spirometry generate?
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
State some functions of the respiratory tract
Gas exchange
Host defence
Metabolism of endogenous and exogenous molecules
Repair
Vocalisation
What is the most important function of the respiratory tract?
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
State some anatomical and physiological requirements of the respiratory tract
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
Outline how the respiratory tract acts in host defence
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
State some important endogenous substances that are present in the respiratory tract
Local hormones (Angiotensins)
Inflammatory mediators (Bradykinin and prostaglandin degradation)
Neurotransmitters (Noradrenaline, serotonin)
What is the most common reason to visit a GP?
Respiratory conditions (~1/3 of all GP visits)
Define ‘pleural empyema’
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
Define ‘pleural effusion’
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
How can respiratory cilia be damaged and what are the implications of this?
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
State 3 diagnostic techniques for examining the respiratory system
Chest X-rays
MRI scans
Spirometry
