Exchange Surfaces Flashcards
Why are specialised exchange surfaces needed
If there is low surface area to volume ratio organisms can’t rely on diffusion alone.
Larger multicellular organism have higher metabolic activity meaning they require more o2 and CO2 which diffusion alone can’t provide efficiently
Features of an efficient exchange surface
Increased surface area - root hair cells
Thin layer - alveoli
Good blood supply/ventilation to maintain gradient
Steps of inhalation
- Diaphragm contracts and flattens
- External Intercostal muscles contract which lifts the rib cage
- This leads to an increase volume and lowers pressure, as air pressure is lower than the out side air rushes in across a pressure gradient.
Steps for exhalation
- As diaphragm relaxes, it lifts
- External intercostal muscles relax losing the rib cage
- This decreases volume and increases pressure to air is pushed out as pressure inside is greater than pressure outside
Features in a Trachea
-c shaped cartilage reduces resistance in air flow but also prevents it from collapsing. It also allows flexibility and stops it from bursting.
-ciliated epithelium cells with goblet cells
Goblet cells secrete mucus and ciliates epithelial cells waft the muscles with trapped dirt up so it can be swallowed
-has smooth muscle, elastic fibres as well.
Features of bronchi
The trachea divides into bronchi leading to the left lung and right lung.
They have c shaped cartilage like the trachea but are smaller.
Has smooth muscle, elastic fibres and goblet cells as well.
Features of bronchioles
They have no c shaped cartilage but the walls contain smooth muscle.
When smooth muscle contracts the bronchioles constrict. When it relaxes bronchioles dilate and open up. This controls the diameter and the volume of air reaching the lungs.
Has elastic fibres
Features of the alveoli
Are tiny air sacks where gases are exchanged.
They contain elastic fibres which inflate and stretch breathing in and when breathing out the fibres recoil to help push air out.
They have a large surface area to volume ratio, good blood supply for steep gradient and thin layers.
What is tidal volume
Volume of air in each breath
Vital capacity
Maximum volume of air that can be breathed in or out
Breathing rate
How many breaths are taken per unit time
Oxygen uptake
The rate at which a person uses up oxygen
Residual volume
Is volume of air left in your lung when you have exhaled
What is total lung capacity
Is vital capacity + residual air
What does soda lime do
It absorbs carbon dioxide from expelled air
Ventilation in insects
- there are spiracles along the thorax and abdomen, these are opened and closed by sphincters.
- leading away from the spiracle are trachea which are lined with spirals of chitin. Chitin is relatively impermeable to gas.
- trachea branch off into tracheoles, they have no chitin lining and gas is exchanged
- at the end of tracheols there is tracheal fluid which prevents diffusion. When there is a build up of lactic acid tracheal fluid moves out leaving a greater surface area for gas exchange. Lactic acid creates a steep gradient as well.
How do insects ventilate
Insects use movement to change volume in the abdomen and thorax to change pressure. When pressure is Low air rushes in across a pressure gradient.
How do fish ventilate
Fish constantly open and close it operculum to act as a pump lowering the bucal cavity increasing and decreasing pressure.
How does counter current exchange work
- high oxygen blood meets high oxygen water
- low oxygen blood meets low oxygen water
- this maintains a constant concentration gradient so diffusion occurs across the entire length
Adaptation to gills
Each gill consist of rows called gill filament and each gill filament have second lamellae. This increases surface area.
Adaptations for effective gaseous exchange in fish
Counter current
Tips of adjacent gills overlap which increase resistance to the flow of water. This gives more time for gaseous exchange.
