3.1 Flashcards
Features of a good exchange surface
- large surface area to provide more space for molecules to pass through
- a thin, permeable barrier to reduce the diffusion distance
- a good blood supply which helps maintain the steep concentration gradient
Factors affecting the need for an exchange system
Size
Surface area to volume ratio
Level of activity
Why does side affect an organism
Smaller organisms have their cytoplasm closer to the environment in which they live maiming diffusion alone supplies enough oxygen and nutrients to keep the cells active and alive.
In larger organisms diffusion would take too long to enable a sufficient supply of oxygen
Why do warm blooded animals need a lot of oxygen
They are warm blooded so they generate heat to keep them warm. Therefore, they require more oxygen for metabolism as it produces energy which helps them maintain their body temperature
Why is the nose good
It warms air up so it has increased energy so diffusion can happen quicker
Adaptations to reduce the distance the gases have to diffuse:
- alveolus wall is one cell thick
- the cells are squamous (flattened/thinned)
- capillaries are in close contact with the alveolus walls
- capillaries are so narrow (1 cell) that the red blood cells are squeezed against the capillary wall - making them closer to the air in the alveoli and reducing their rate of flow
Carbon dioxide and the blood
The blood transports carbon dioxide from the tissues to the lungs. This insures that the concentration of carbon dioxide in the blood is higher than that in the air of the alveoli therefore carbon dioxide defuses into the alveoli
Oxygen and the blood
The blood transports oxygen away from the lungs this insures that the concentration of oxygen in the blood is kept lower than that in the alveoli – so that oxygen diffuses into the blood
What does ventilation ensure?
The concentration of oxygen in the air of the alveolus remains higher than that in the blood
The concentration of carbon dioxide in the alveolus remains lower than that in the blood
Inspiration steps
- The diaphragm contracts to move down and become flatter
- External intercostal muscles contract to raise the ribs
- The volume of the chest cavity is increased
- The pressure in the chest cavity drops below atmospheric pressure
- There is a pressure gradient to air is moved into the lungs
Expiration steps
- The diaphragm relaxes and is pushed up by the displaced organs underneath
- The external intercostal muscles relax and the ribs fall (the intercostal muscles can contract to help push air out more forcefully - this usually only happens during exercise/coughing/sneezing)
- The volume of the chest cavity decreases
- The pressure in the lungs increases and rises above the pressure in the surrounding atmosphere
- Air is moved out of the lungs
How are the airways effective?
- large enough to allow sufficient air flow without obstruction
- be supported to prevent collapse when the air pressure inside is low during inspiration
- be flexible in order to allow movement
Function of goblet cells
Release mucus - traps pathogens
Function of the cilia
Move the mucus to the top of the airway where is it swallowed
What is the ciliated epithelium
A layer of cells that have many hair like extensions called cilia
What do the trachea and bronchi have in common
Both have cartilage
Function of cartilage in trachea and bronchi
Prevent collapse during inspiration.
Rings in cartilage are C shaped rather than a complete ring which allows flexibility and space for food to pass down the oesophagus
Structure of bronchioles
Narrower than bronchi
Larger bronchioles may have some cartilage, narrower ones don’t
Wall mainly consists of smooth muscle and elastic fibres
Smallest bronchioles end in clusters of alveoli
Smooth muscle function
Contracts, constricts the airway making the lumen of the airway narrower which restricts air flow to and from the alveoli
This could prevent harmful substances entering your body
Is elongated by elastic fibres
When it contracts the elastic fibres deform. As the muscle relaxes the fibres recoil to their original shape
This dilates the airway
What is a spirometer
A device that measures the movement of air in and out of the lungs
What happens in a spirometer during inspiration
Air is drawn from the chamber so that the lid moves down
What happens to the spirometer during expiration
Air resigns to the chamber raising the lid
Feature of a spirometer to prevent carbon dioxide being misinterpreted for oxygen
The carbon dioxide is passed through soda lime, which absorbed the co2
Precautions to be taken when using a spirometer
- person should be healthy (free from asthma)
- soda lime should be fresh and functioning
- no air leaks in the apparatus
- sterilised mouthpiece
- water chamber shouldn’t be overfilled to prevent air from entering the tubes
What is vital capacity
Maximum volume of air that can be moved by the lungs in one breath
Factors affecting vital capacity
-size of a person
- age
- gender
- level of regular exercise
What is the residual volume?
The volume of air that remains in the lungs after forced expiration
Where does the air left in the lungs (residual volume) stay?
In the airways and alveoli
What is the tidal volume?
The volume of air moved in and out with each breath at rest
How/why can you measure o2 uptake from a spirometer trace?
When you breathe in, the chamber decreases, so you can measure the amount it has decreased by and this is the amount of oxygen that you have inhaled
How to measure oxygen uptake from a spirometer trace
Mark a starting point at the start
Mark an end point at the end
Measure the difference in volume
Measure the time taken
Divide them so you get dm3/second
How to calculate breathing rate using a spirometer
Measure the number of peaks per minute
Increased oxygen uptake will result from
- increased breathing rate
- deeper breaths
Why so some organisms need transport systems
- have demands therefore need o2
- diffusion distance too far
- sa:vol too low
- maintain concentration gradient
