(3.1) Exchange Surfaces Flashcards
What is the need for exchange systems?
- Take in oxygen
- Get rid of waste
Where are the exchange systems in the human body?
Lungs and Intestines
What are the factors affecting the need for an exchange system?
- SA:V ratio
- Size and shape - e.g. flatworms are very thin and very long so have a very high surface are to volume ratio
- rate of metabolic activity
What makes a good exchange system?
- Large surface area
- Short diffusion distances
- Good blood supply
Where does gas exchange occur in the lungs?
At the respiratory bronchioles and alveoli
What is the benefit in an exchange system of a large surface area?
More space for diffusion
What is the benefit in an exchange system of short diffusion distances?
Diffusion happens quickly so more diffusion can take place
What is the benefit in an exchange system of a good blood supply?
A good blood supply means constant replacement of oxygen and carbon dioxide meaning a high concentration gradient is maintained
What is the structure of the trachea?
Rings of cartilage in C shapes to make sure the trachea is supported and stays open
Why are the rings of cartilage in the trachea C shaped?
To allow flexibility for chunks of food going down the oesophagus
What is the name of the muscles in the rib cage?
Intercostal
Describe the pathway of air in the lungs
Trachea —> bronchus —> bronchioles —> respiratory bronchioles —> alveoli
What are the respiratory bronchioles?
The ends of the bronchioles where there is no cartilage and where gaseous exchange takes place
What is the space between the diaphragm and the lungs called?
Plural space
Describe what a Bronchus cell looks like
- goblet cells and epithelium cells on the outside to secrete and waft mucus up the airway
- smooth muscle
- connective tissues
- small blood vessels
- cartilagge
What is the role of smooth muscle?
To constrict the airways
What is connective tissue made of?
Elastic tissues and fibres
Describe what a bronchioles cell looks like
- alveolus wall on edge
- smooth muscle rings
- loose tissue
- ciliated epithelium
- cartilage (apart from at the respiratory bronchioles)
What is happening when the smooth muscle constricts the airway?
The lumen is narrowing
Describe what an alveoli looks like
Alveoli/air sacs have a network of capillaries over them. The outside cell is a squamous epithelium cell which is very thin so there are short diffusion distances
Describe the process of inhalation/inflation of lungs
- The diaphragm moves down due to the contraction of intercostal muscles
- The contraction of the intercostal muscles cause the rib cage to move up
- The movement of the diaphragm was causes and increase in volume
- The increase in volume causes a decrease in pressure which drags air into the lungs
Describe the process of exhalation/deflation of the lungs
- The diaphragm moves up towards the lungs due to the relaxation of the intercostal muscles
- The relaxation of the intercostal muscles causes the rib cage to move down
- The movement of the diaphragm up decreases the volume
- The decrease in volume causes an increase in pressure which causes air to be pushed out of the lungs
Describe what is needed when using a spirometre
- A healthy person
- Sterile disposable mouthpiece
- water chamber (not overfilled)
- In the chamber of water, medical grade oxygen (to prevent hypoxia)
- fresh soda lime (helps to absorb CO2 and prevent the air from becoming toxic - also shows oxygen intake by amount of CO2 absorbed)
What is the process of how a spirometer works?
- as the person breathes in air from the chamber decreasing pressure so the hinged lid moves down
- as the person breathes back out the pressure increases again moving the hinged lid up
- due to the pen on the hinged lid, a trace is drawn on a piece of paper creating a spirometer trace which is then turned upside down
What is tidal volume?
Normal breath, usually at a rest
What is residual volume?
The amount of air left in the lungs after forced exhalation
What is vital capacity?
The range between maximum inhale and maximum exhale
Why is total lung capacity hard to measure?
Due to the residual volume
What can you calculate from a spirometer trace?
Oxygen uptake
What things affect total lung capacity?
- fitness and exercise
- age, size, gender, height
How do you calculate oxygen uptake?
- Pick points that are easily recognisable
- Calculate change in volume
- Calculate change in time
How do fish ventilate?
- Through movement e.g. great whites are obligate ram ventilators - have to keep swimming
- Open and closing of mouth
What is special about a fish’s ventilation system?
It has a countercurrent flow
Describe the flow of water through a fish’s exchange system?
Into the mouth/buccal cavity then over the gill arch and out of the perculum
Describe the structure of the gill arches
- 2 blood vessels one carrying oxygenated blood one carrying deoxygenated blood
- Blood flows one way and water the other
Why is countercurrent flow beneficial?
It maintains a concentration gradient the whole way along the gill arch, stopping equilibrium from being reached
What type of circulatory system does an insect have?
Open circulatory system with no blood
Describe the pathway of air within an insect
Spiracle —> Trachea —> Tracheoles —> Site of gas exchange
What happens when an insect stops moving?
The tracheal fluid fills the trachea however when there is a high demand the tracheal fluid is withdrawn
Do insects ventilate?
- some extremely active insects can
- some expand and contract body segments e.g. pump abdomen
- sometimes flight muscles will ventilate
What is special about a Locusts ventilation?
Can open and close spiracles
