6.4 Gas Exchange Flashcards
How can you monitor ventilation rate in experiments?
- The most simple way is by observation, count the number of times air is exhaled or inhaled per minute.
- Or by using an inflatable chest belt which is placed around the thorax and air is pumped in with a bladder. A pressure sensor is then used to measure pressure variations inside the belt due to chest expansions.
How can we measure tidal volume in experiments?
You have a delivery tube going into water and pushed up into a test tube, you breath in and it bubbles up into the test tube.
What are type 1 pneumocytes?
Type 1 pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange. Most of the epithelial cells in the alveolus are type 1 pneumocytes. They are flattened very thin cells. Because of how thin these cells are the air in the alveolus is extremely close to the blood in the capillaries.
What are type 2 pneumocytes?
These are rounded cells and they secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveoli adhering to each other by reducing surface tension. The moist surface also allows the gases to dissolve and provides an area which carbon dioxide can evaporate back out.
The fluid secreted by type 2 pneumocytes contains a pulmonary surfactant. Its molecules have a structure similar to that of phospholipids in cell membranes. They form a monolayer on the surface of the moisture lining the alveoli with the hydrophobic tails facing the air. This reduces the surface tension and prevents the water from causing the sides of the alveoli to adhere when air is exhaled from the lungs. This helps to prevent collapse of the lung.
What is the route air takes?
Air enters the ventilation system through the nose or mouth and then passes down the trachea. This has rings of cartilage in its wall to keep it open even when air pressure inside it is low or pressure in the surrounding tissues is high. The trachea divides to form two bronchi, also with walls of strengthened cartilage. One bronchus leads to each lung.
Inside the lungs the bronchi divide repeatedly to form a tree-like structure of narrower airways, called bronchioles. They have smooth muscle allowing their width to vary. Then at the end there are alveoli where gas exchange occurs.
How is the trachea adapted?
Has rings of cartilage in its walls to keep it open even when air pressure inside is low or pressure in surroundings is high.
How is the bronchioles adapted?
They have smooth muscle in them and so the width of them can vary.
How does breathing work?
Muscles only work in one direction, the other direction is passive and therefore, breathing requires two sets of muscles, when you need to breathe very quickly.
External Intercostal muscles pull the ribcage up and out and the diaphragm contracts and flattens. Pressure inside decreases so air comes in.
Then to breathe out very quickly the internal intercostal muscles will contract and so will the abdomen wall muscles and push the organs and diaphragm upwards.
What causes lung cancer?
- Smoking, the tobacco smoke contains many mutagenic chemicals
- Passive smoking
- Air pollution - nitrogen oxides
- Radon gas that leaks out of certain rocks
- Asbestos, silica and other solids can cause lung cancer if dust or other particles of them are inhaled.
What is Emphysema?
In a normal person each bronchiole leads to a group of small thin-walled alveoli, however in a patient with emphysema these are replaced by a smaller number of larger air sacs with much thicker walls. The surface area is significantly reduced and so gas exchange efficiency is much reduced. The lungs also become less elastic and so ventilation is more difficult.
CAUSED BY
Phagocytes inside alveoli normally prevent lung infections by engulfing bacteria and produce elastase, a protein digesting enzyme to kill them.
An enzyme inhibitor called A1AT usually prevents elastase and other proteases from breaking down lung tissue. However in smokers they have more phagocytes in their lungs and they produce more and more of the enzyme elastase.
In some smokers because of this the alveolus wall is digested, the walls are weakened and destroyed.
This means gas exchange is much less effective and that they may run out of breath very easily.
How does emphysema happen?
Phagocytes inside alveoli normally prevent lung infections by engulfing bacteria and produce elastase, a protein digesting enzyme to kill them.
An enzyme inhibitor called A1AT usually prevents elastase and other proteases from breaking down lung tissue. However in smokers they have more phagocytes in their lungs and they produce more and more of the enzyme elastase.
In some smokers because of this the alveolus wall is digested, the walls are weakened and destroyed.
This means gas exchange is much less effective and that they may run out of breath very easily.
