Lung and Health Studies Flashcards
What are the essential features of the alveolar epithelium?
The surface is one cell thick, providing a short diffusion distance.
There is a high concentration of o2 and low concentration of blood.
There is a constant o2 supply due to ventilation.
There is a constant blood supply due to the circulatory system.
There are lots of alveoli at the end of each bronchiole to provide a large surface area.
They are moist due to liquid surfactant.
Membranes are permeable.
What is Fick’s Law?
Rate of diffusion = Surface Area X Difference in Conc
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Diffusion Distance
What is ventilation?
The flow of air in and out of the alveoli
Consists of inspiration and expiration
Involves the intercostal muscles and diaphragm
Describe the process of inspiration
External intercostal muscles contract
Internal muscles relax
This causes the ribs to raise upwards
The diaphragm contracts and flattens
The intercostal muscles and diaphragm cause the volume inside the thorax to increase, lowering the pressure
The difference between the pressure inside the lungs and atmospheric pressure creates a gradient, causing air to be forced into the lungs.
Describe the process of expiration
Internal intercostal muscles contract, external muscles relax
This lowers the rib cage
The diaphragm relaxes and raises upwards
This decreases the volume inside the thorax
Therefore increasing the pressure, forcing air out of the lungs
Fibrosis
Formation of scar tissue due to exposure to substances such as asbestos
Scar tissue is thicker and less elastic than normal lung tissue - less likely to expand
This decreases tidal volume and forced vital capacity
Rate of diffusion decreases due to a thicker membrane
Tuberculosis
Caused by bacteria
Immune system builds a wall around the bacteria in the lungs, forming hard lumps known as tubercles
Infected tissue within the tubercles die and so the gaseous exchange surface is now damaged
This reduces tidal volume, causing patients to breathe faster
What is a risk factor
Something which increases your chance of developing a disease
Emphysema
Caused by smoking/air pollution
Attracts phagocytes to the area which produce an enzyme which breaks down elastin
Loss of elastin reduces alveoli ability to recoil and also destroys the alveoli wall - gas exchange rate decreases
Correlation and cause
A correlation is when an increase or decrease in one variable leads to an increase or decrease in another variable
For example number of cigarettes smoked and incidents of lung cancer
In this case, this can be referred to as a causal link, or a causation, as there is scientific research to support the link
What is tidal volume
The volume of air in each breath, usually between 0.4dm^3 and 0.5dm^3 for adults
What is ventilation rate
The number of breaths per minute - normally around 15
What is forced expiratory volume
The maximum volume of air that can be breathed out in one sec
What is forced vital capacity
The maximum volume of air it is possible to breathe forcefully out of the lungs after a deep breath
What is pulmonary ventilation
Volume of air breathed in 1 min
Can be found using this equation:
Ventilation rate x Tidal volume
