Gas exchange in humans
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Where is the gas exchange system located?
In the thorax
What path does air take when we breathe it in
Breath in, air flows through the trachea, down the bronchi, further into the lungs through the bronchioles, into the alveoli where they diffuse into the blood
What is the trachea, what does it do
The trachea is another name for the windpipe. connects the larynx (or voice box) to the bronchi of the lungs. It is an integral part of the body’s airway and has the vital function of providing air flow to and from the lungs for respiration.
What is the thorax
The thorax is the upper part of the body
What are the bronchioles, what do they do
They are small branches leading to everywhere in the lungs. They transfer gases to and from the lungs
What are alveoli, what do they do
Microscopic air sacs which are optimised for gas exchange in lungs
What is the pleural membrane, what does it do
this forms a double layer between the lungs and the thorax walls. In between the membranes, there is a thin layer of pleural fluid. Together they form an airtight seal and prevent the lungs from sticking to the thorax wall as the inflate and deflate.
What are intercostal muscles, what do they do
Intercostal muscles between the ribs help to connect the bones and are important in moving air into and out of the lungs.
What is the diaphragm, what does it do
This domed sheet of muscle and fibrous tissue is also important in moving air into and out of the lungs
What is ventilation
Ventilation is the process of moving air into and out of the lungs (inhalation and exhalation). Moving air relies on differences in air pressure between the lungs and the atmosphere
What happens during inhalation
Diaphragm contracts, moving down and flattening. Intercostal muscles contract, moving rib cage up and out. This causes the volume of the thorax to increase and air pressure in the thorax to fall. Air pressure in the thorax is now less than atmospheric pressure, causing air to move into the lungs.
What happens during exhalation
Diaphragm relaxes, moving up and doming. Intercostal muscles relax, moving rib cage down and in. This causes the volume of the thorax to decrease and air pressure in the thorax to rise. Air pressure in the thorax is now more than atmospheric pressure, causing air to move out of the lungs.
Why are the alveoli suited for gas exchange
Large surface area (60m^2), surrounded by a network of capillaries which maintains a high CG, each alveolus is one cell thick
Where does gas exchange occur in the lungs
In the alveoli. Oxygen diffuses from alveoli into RBC, carbon dioxide diffuses another way round
How does exercise affect our breathing rate
During exercise our breathing rate increases, as well as the depth of each breath. This is in response to the increased concentration of carbon dioxide in the blood. Because of our breathing rate increases, we excrete carbon dioxide more rapidly. Oxygen can also diffuse into the blood at a faster rate (as there is a higher concentration gradient).
How do we measure breath rate
we simply count the number of breaths a person takes each minute.
How do we measure breath depth
use a device called a spirometer to measure the volume of air inhaled and exhaled.
How many chemicals do cigarettes have
4000 chemicals
What addictive drug is present in cigarettes/tobacco smoke
Nicotine. Many anti-smoking products contain nicotine, which gradually decreases to help a person get rid of their smoking habit
How many carcinogens are in a cigarette/tobacco smoke
There are at least 17 carcinogens. These carcinogens alter DNA and increase the risk of cancer
Name 5 carcinogens in tobacco smoke and what they do
Arsenic results in high levels of skin cancer, bladder cancer and lung cancer Formaldehyde irritates the eyes, nose and throat Acetaldehyde can increase chance of getting digestive tract cancers Lead can damage almost every organ system, damages nervous system Benzene causes irreversible damage to the bone marrow, may cause anaemia
What disease is closely linked with smoking
Lung cancer, but also bronchitis, emphysema, atherosclerosis, myocardial infection, larynx cancer, oesophagus cancer
What does carbon monoxide do to your body
This irreversibly (permanently) binds to the haemoglobin forming carboxyhaemoglobin, and so reducing the amount of oxygen transported by the blood. If a pregnant woman smokes, the baby will receive less oxygen and as a result is likely to weigh less at birth. This can cause other problems.
How are cilia affected by chemicals in tobacco
Chemicals in tobacco smoke destroy cilia, reducing their number. At the same time, mucus production will increase; this is in response to the smoke. The mucus cannot be moved out of the airways quickly. This causes smoker’s cough and increases the risk of infections.