Gas Exchange Flashcards
What are some features that gas exchange surfaces have?
Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster
Describe the ribs
Bone structure that protects internal organs such as the lungs
Describe the intercostal muscle
Muscles between the ribs which control their movement causing inhalation and exhalation
Describe the diaphragm
Sheet of connective tissue and muscle at the bottom of the thorax that separates the chest cavity from the abdomen and helps change the volume of the thorax to allow inhalation and exhalation.
The pressure in the thorax/chest/lung decreases;
Air moves/is drawn into the thorax
Describe the trachea
Windpipe that connects the mouth and nose to the lungs
Describe the larynx
Also known as the voice box, when air passes across here we are able to make sounds
Describe the bronchi
Large tubes branching off the trachea with one bronchus for each lung
Describe the bronchioles
Bronchi split to form smaller tubes called bronchioles in the lungs connected to alveoli
Describe the Alveoli
Tiny air sacs where gas exchange takes place
Describe the pleural cavity
The fluid filled space between the pleural membranes which reduces friction and allows the lungs to move freely
What are the passages down to the lungs are lined with?
The passages down to the lungs are lined with ciliated epithelial cells.
Describe the structure of cilia cells and their function
Cilia cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed
Why do cilia cells have tiny hairs on the end of them?
To beat and push mucus up the passages towards the nose and throat where it can be removed
What is mucus made out of?
The mucus is made by special mucus-producing cells called goblet cells because they are shaped like a goblet, or cup
What does the mucus do?
The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents them from getting into the lungs and damaging the cells there
Fill in the blanks - Muscles are only able to - on bones, not - on them
Muscles are only able to pull on bones, not push on them
How many sets of intercostal muscles are there and why?
There must be two sets of intercostal muscles to work antagonistically to facilitate breathing
What are the two types of intercostal muscles and what do they do?
External intercostal muscles, pull the rib cage up
Internal intercostal muscles pull the ribcage down
Explain what happens during inhalation.
During inhalation
The diaphragm contracts and flattens
The external set of intercostal muscles contract to pull the ribs up and out:
This increases the volume of the chest cavity (thorax)
Leading to a decrease in air pressure inside the lungs relative to outside the body
Air is drawn in
Explain what happens during exhalation.
During exhalation
The diaphragm relaxes it moves upwards back into its domed shape
The external set of intercostal muscles relax so the ribs drop down and in
This decreases the volume of the chest cavity (thorax)
Leading to an increase in air pressure inside the lungs relative to outside the body
Air is forced out
What do the external and internal muscles work as what and what does this mean?
The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)
Explain what happens during forced exhalation
When we need to increase the rate of gas exchange (for example during strenuous activity) the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly – this is called forced exhalation There is a greater need to rid the body of increased levels of carbon dioxide produced during strenuous activity
This allows a greater volume of gases to be exchanged
Percentage of inspired air (Oxygen) - inspired means inhaled
21%
Percentage of expired air (Oxygen) - expired means exhaled
16%
Percentage of inspired air (Carbon dioxide) - inspired means inhaled
0.04%
Percentage of expired air (Carbon Dioxide) - expired means exhaled
4%
Percentage of inspired air (Nitrogen) - inspired means inhaled
78%
Percentage of expired air (Oxygen) - expired means exhaled
78%
How are the alveoli specialised for gas exchange?
There are many rounded alveolar sacs which give a very large surface area to volume ratio
Alveoli (and the capillaries around them) have thin, single layers of cells to minimise diffusion distance
Ventilation maintains high levels of oxygen and low levels of carbon dioxide in the alveolar air space
A good blood supply ensures constant supply of blood high in carbon dioxide and low in oxygen
A layer of moisture on the surface of the alveoli helps diffusion as gases dissolve
What health conditions can smoking cause?
Smoking causes chronic obstructive lung disease (COPD), coronary heart disease and increased risks of several different types of cancer, including lung cancer.
What are the chemicals in cigarettes and describe them?
Tar - a carcinogen (a substance that causes cancer)
Nicotine - an addictive substance which also narrows blood vessels
Carbon monoxide - reduces the oxygen-carrying capacity of the blood
What is tar?
Tar - a carcinogen found in cigarettes and is linked to increased chances of cancerous cells developing in the lungs
Describe nicotine and its effects
Nicotine - an addictive substance found in cigarettes which narrows blood vessels leading to an increased blood pressure
It also increases heart rate
Both of these effects can cause blood clots to form in the arteries leading to heart attack or stroke
Describe what carbon monoxide do to the circulatory system and its risk
Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen
This puts more strain on the breathing system as breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood
It also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes
What health conditions does tar lead to?
It also contributes to COPD, which occurs when chronic bronchitis and emphysema (two different diseases which are frequently linked to smoking) occur together
Describe Chronic bronchitis
Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
It destroys cilia and mucus (containing dirt, bacteria and viruses) builds up blocking the smallest bronchioles and leading to infections
A smoker’s cough is the attempt to move the mucus
Describe Emphysema
Emphysema develops as a result of frequent infection, phagocytes that enter the lungs release elastase, an enzyme that breaks down the elastic fibres in the alveoli
This means the alveoli become less elastic and cannot stretch so many burst
The breakdown of alveoli reduces the surface area for gas exchange
As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive
Where is the content of the blood is highest?
Blood exiting the lungs is the most oxygenated
