3.1 - Exchange surfaces and breathing Flashcards
why are exchange surfaces needed? (Molecules)
- To take in and remove molecules (Take in O2 or glucose and get rid of waste products like CO2)
If the surface area of an object is 12 and the volume is 4 what is the SA:Vol?
3:1
How is the SA:Vol affected by the size of the object?
- As the object gets larger (normally) the SA:Vol decreases
- Smaller organisms often have a large SA:Vol but larger objects have a smaller SA:Vol
How does the SA:Vol affect the need for an exchange surface in organisms?
Smaller organisms have a large SA:Vol meaning that diffusion is sufficient for gas exchange rather larger organisms have a smaller SA:Vol so they require exchange surfaces
What is an example of an organism that does not require a specialised exchange surface?
An amoeba is less than 1mm in size meaning it has a high SA:Vol meaning diffusion is sufficient by itself
or a flatworm is similar however a flatworm is larger but has a much larger SA still
How do levels of activity affect the need for an exchange surface?
Organisms that are more active have a higher metabolic rate meaning they are more in need of an exchange surface than organisms that are not as active and have a lower metabolic rate
What are the characteristics of a good exchange system?
- A large surface area = More space across in which diffusion can take place
- A short diffusion distance = Increases the speed of diffusion from one place to another
- A good blood supply = Maintains the concentration gradient
What are some examples of exchange surfaces?
- Intestines (Have microvilli)
- Lungs (Alveoli)
- Gills (Counter-current flow)
- The tracheal system in insects (Using tracheal fluid)
- Leaves (Have the stomata and spongy mesophyll)
- Root hair cells (Large SA)
How would the lungs be labelled from top down?
- Trachea
- Ribcage and intercostal muscles lying between the ribs, surround the:
- x2 Bronchus
- Many bronchioles
- Many alveoli
- Pleural space outside of lungs but within the ribcage
How is the trachea fit for function?
-Contains “C shaped” rings of cartilage to support it = keep the trachea open and stops the collapsing (the “C shape allows for flexibility when swallowing large quantities of food)
Where does gas exchange occur in humans?
In respiratory bronchioles and the alveoli
How are the bronchi fit for function?
- Contains goblet cells that secrete mucus
- Contains ciliated epithelial cells that wafts the mucus with particles up the trachea to be swallowed and neutralised by the stomach acid or expelled
- Contains smooth muscle that constricts the airways
- Contains connective tissue (with elastic fibres)
- Contains small blood vessels
- Contains “C shaped” cartilage
How are the bronchioles fit for function?
- Contains smooth muscle that constricts to narrow the airways to stop harmful air from entering the alveoli
- Contains connective tissue (With elastic fibres)
- Contains ciliated epithelial cells that wafts the mucus with particles up the trachea to be swallowed and neutralised by the stomach acid or expelled
How are the alveoli (air-sacs) fit for function?
- Have a dense network of capillaries that provides a good blood supply to maintain the concentration gradient
- Contains very large surface area due to lots of alveoli
- Contains squamous epithelial cells that are very thin meaning it provides a short diffusion distance
- Contains elastic fibres that work to re-inflate the airways in the alveoli
What are the two movements of the diaphragm used to inflate/deflate the lungs?
- The diaphragm moves up when it is relaxed, this increases the pressure in the thorax so that air is forced out
- The diaphragm moves down when it is contracted, this decreases the pressure in the thorax so that air is forced in