3.1 Exchange surfaces and breathing Flashcards
What is surface area to volume ratio?
The surface area of an organism divided by its volume, expressed as a ratio.
What are some examples of substances organisms need to survive?
- Oxygen
- Glucose
What are some examples of what animals need to get rid of to survive?
- Urea
- Lactic acid
What factors effect the need for an exchange system?
- size
- surface area to volume ratio
- level of activity
Why don’t some organisms need exchange systems?
In very small organisms, such as single-celled organisms, all the cytoplasm is very close to the environment in which they live. Diffusion will supply enough oxygen and nutrients to keep the cell alive and active.
Why do some organisms need exchange systems?
Multicellular organisms need exchange systems because they have multiple layers of cells so that oxygen or nutrients diffusing in from the outside have a longer diffusion pathway- diffusion is too slow to enable a sufficient supply to the innermost cells.
Is the surface area to volume ration large or small to small organisms?
They have a large surface area to volume ratio- meaning that there surface area is large enough to supply all their cells with sufficient oxygen.
Is the surface area to volume ration large or small to larger organisms?
Larger organisms have a small surface area to volume ratio.
This is because they have a larger surface area but also a large volume- as volume rises more quickly than surface area, when u divide surface area by volume, you get a small number.
How have some organisms adapted to have a larger surface area to volume ratio?
Some organisms have adapted by increasing their surface area by adopting a different shape. e.g. a flat worm has a very thin, flat body.
How does level or activity effect an organisms need for exchange systems?
Metabolic activity uses energy from food and requires oxygen to release the energy in aerobic respiration. The cells of an active organism need for good supplies of nutrients to supply the energy of movement. The need for energy is increased in those animals, such as mammals, that keep themselves warm.
What are the features of a good exchange system?
- Large surface area
- Thin barrier to reduce the diffusion distance
- Good blood supply
Why does having a large surface area make a good exchange system? How can it be achieved? Example of where this can be seen?
Provides more space for molecules to pass through. Often achieved by folding the walls and membranes involved. Root hair cells in plants is a good example of having a large surface area.
Why does having a thin barrier make a good exchange system? Example of where this can be seen?
Reduces the diffusion distance- and that barrier must be permeable to the substances being exchanged. This can be seen well in the alveoli of the lungs.
Why does having a good blood supply make a good exchange system? Example of where this can be seen?
This can bring fresh supplies of the molecule on one side, keeping the concentration gradient high, or it may remove molecules from the demand side to keep the concentration low. This is important to maintain a steep concentration gradient so that diffusion can occur rapidly. The gills on a fish is a good example.
Why does some exchange systems being moist make them work better?
Gases dissolve in the moisture helping them to pass across the gas exchange surface.
Define alveoli.
Tiny folds of the lung epithelium to increase the surface area.
Define bronchi and bronchioles.
Smaller airways leading into the lungs.
What is a diaphragm?
A layer of muscle beneath the lungs.
What are intercostal muscles?
Muscles between the ribs. Contraction of the external intercostal muscles raises the ribcage.
What is the trachea?
The main airway leading back from the mouth to the lungs.
Define ventilation.
The refreshing of air in the lungs, so that there is a higher oxygen concentration than in the blood, and a lower carbon dioxide concentration.
What does the gaseous exchange system in mammals consist of?
The lungs and associated airways that carry air into and out of the lungs.
- Lungs
- Trachea
- Bronchi
- Bronchioles
- Alveoli
What are the ribs held together by?
Intercostal muscles.
What produce breathing movements in the lungs?
The intercostal muscles and the diaphragm.
How does gaseous exchange occur in the lungs?
Gases pass by diffusion through the thin walls of the alveoli. Oxygen passes from the air in the alveoli to the blood in the capillaries. Carbon dioxide passes from the blood to the air in the alveoli. The lungs must maintain a steep concentration gradient in each direction in order to ensure that diffusion can continue.
how are the lungs adapted for gaseous exchange?
- Large surface area
- Barrier to exchange is permeable to oxygen and carbon dioxide
- Thin barrier
- Good blood supply
- Ventilation
How do the lungs have a large surface area?
Individual alveoli are very small however, they are so numerous that the total surface area is much larger than that of our skin.
Why are the alveoli lined by a thin layer of moisture?
They are lined by a thin layer of moisture, which evaporates and is lost when we breath out.
The lungs produce a surfactant that coats the internal surface of the alveoli to reduce the cohesive forces between water molecules, as these forces tend to make the alveoli collapse.
How do the lungs have an exchange barrier that is permeable to oxygen and carbon dioxide?
The barrier is composed of the wall of the blood capillary
The cells and their plasma membranes readily allow the diffusion of oxygen and carbon dioxide, as the molecules are small and nonpolar.
How do the lungs have a thin barrier to reduce the diffusion distance?
- Alveolus wall is one cell thick
- Capillary wall is one cell thick
- Both walls consist of squamous cells
- Capillaries are in close contact with the alveolus walls
- Capillaries are narrow so red blood cells are squeezed against capillary walls- making them closer to the air in the alveoli and reducing their rate of flow.
So total barrier to diffusion is only 2 flattened cells, and is less than 1um thick.
How do the lungs have a good blood supply?
Blood system transports carbon dioxide from the tissues to the lungs. This ensures that the concentration in the blood than in the air in the alveoli. Therefore, carbon dioxide diffuses into the alveoli.
Blood also transported oxygen away from the lungs. This ensures that the concentration of oxygen in the blood is lower than that in the alveoli- so that the 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 alveoli remains lower than that in the blood.
What words do we use for ‘breathing in’?
Inspiration/ Inhalation
What words do we use for ‘breathing out’?
Expiration/ Exhalation
What is happening during inspiration and expiration?
Ventilation.
What happens during inspiration?
- The diaphragm contacts to move down and become flatter- displacing digestive organs downwards.
- External intercostal muscles contract to raise the ribs.
- The volume of the chest cavity is increased.
- The pressure in the chest cavity drops below the atmospheric pressure.
- Air is moved into the lungs.
What happens during expiration?
- The diaphragm relaxes and is pushed up by the displaced organs below.
- The external intercostal muscles relax and ribs fall; the internal intercostal muscles can contact to help push air out more forcefully- this only happens during exercise, coughing or sneezing.
- The volume of chest cavity is decreased.
- The pressure in the lungs is increased and rises above the pressure in the surrounding atmosphere.
- Air is moved out of the lungs.
What is cartilage?
A form of connective tissue.
What is ciliated epithelium?
A layer of cells that have many hair like extensions called cilia.
What are elastic fibres?
Protein fibres that can deform and then recoil to their original shape.
What are goblet cells?
Cells that secrete mucus.
What is smooth muscle?
Involuntary muscle that contracts without the need for continuous thought.
Describe what lung tissue looks like under a light microscope and why does it look like this?
Under the microscope, you will mostly see alveoli.
Alveoli are made of squamous epithelium and are surrounded by blood capillaries, so that the distance for diffusion is very short. The alveoli walls are so then, it may not be possible to distinguish separate cells under a light microscope.
What path does air take from the mouth to the bloodstream?
Trachea, bronchi, bronchioles, alvioli.
To be effective, what do the lungs must be adapted to be?
- Must be large enough to allow sufficient air to flow without obstruction.
- Be supported to prevent collapse when the air pressure is low during inspiration.
- Be flexible in order to allow movement.
How do ciliates epithelium and goblet cells work together in the airways?
The airways are lines with ciliated epithelium, which contributes to keeping the lungs healthy. Goblet cells in the epithelium release mucus, which traps pathogens. Then the cilia then waft the mucus up to the top of the airway, where it is swallowed.
What is the difference between the structure of the trachea and the bronchi?
The bronchi is narrower than the trachea.
What is similar between the trachea and bronchi?
The trachea and bronchi are supported by rings of cartilage which prevent collapse during inhalation. The rings of cartilage in the trachea are C-shaped rather than a complete ring which allows flexibility ans space for food to pass down the oesophagus.