Exchange Surfaces And Breathing Flashcards
Why do single celled organisms NOT need specialised exchange surfaces?
Their s.a : volume ratio is large which means that their surface area is greater than the amount of substances needed so the outer surface is enough to provide the organism
What are the features of an efficient exchange surface?
They have large surface area to provide more space for diffusion of molecules
They have a thin barrier to reduce the diffusion distance
Fresh supply of molecules on one side to keep the concentration high/low
Removal of required molecules on the other side to keep the concentration low
What are the features of alveoli that make it a specialised exchange surface?
There are many alveoli which increases the surface area in the lungs
The capillary wall is one cell thick, reducing the diffusion distance
Both walls consists of squamous cells
The capillaries are in close contact with the alveolus walls
The red blood cells are squeezed against the wall of the capillaries making it easier for the oxygen and co2 to diffuse from and to the air in the alveoli
The total barrier to diffuse is only 1 micro metre thick
How are the lungs adapted for exchange?
LARGE SURFACE AREA:
Provides more space for molecules to pass through
Numerous alveoli that the total surface area of the lungs is much more than skin
THIN BARRIER TO REDUCE DIFFUSION DISTANCE
The alveoli wall is extremely thin
The capillary wall is extremely
Diffusion distance between the two is less than 1 micro metre thick
PERMEABLE BARRIER
The plasma membrane than surrounds the very thin squamous cells allow oxygen and carbon dioxide to diffuse through
MAINTAINING DIFFUSION DISTANCE:
Inspiration and expiration keeps the concentration of oxygen in the alveoli low
The heart beating keeps the blood flowing keeping the concentration of oxygen in the blood low
Describe the layers of the trachea and bronchi
The outer layer has a thick wall of cartilage. This is for structure and stability of the trachea. The incomplete rings of cartilage also allow flexibility.
The middle layer consists of smooth muscle that allows contraction and can constrict the airways
The elastic fibres allow the airways to recoil back into shape after smooth muscle relaxes
Glandular tissue is under the epithelium and it secretes mucus to trap tiny particles
The inner layer is the epithelium.
Ciliates epithelium moves in a synchronised way to waft mucus to back of the throat
Squamous epithelium provides. Very short diffusion distance
How are the bronchioles different from the trachea and bronchi?
Bronchioles don’t have cartilage wall.
They are much narrower than the bronchi.
The wall is mostly made of smooth muscle and elastic fibres
He snakes bronchioles have clusters of alveoli at their ends
Why do multicellular organisms need specialised exchange systems?
Their Surface are:volume ratio is small, so their outer surface is not enough to absorb nutrients and remove waste products.
They need a more complex system to keep up with the amount of materials they need in order to survive.
