Gas Exchange And SA: Volume Flashcards
Why do organisms need exchange surfaces?
Size- in organisms where cells are too far from oxygen availability and hence have developed own specialised exchange systems
Activity- more active organisms require more oxygen and will have a greater need for an exchange surface
Surface are to volume ratio SA:VOL
(Larger the organisms the smaller the SA:V ratio
What is the equation to calculate diffusion rate?
Diffusion = SA X difference in concentration / thickness of exchange surface
Why are the lungs located inside the body?
Air is not dense enough to support and protect the delicate structures
The body would otherwise lose water and dry out
What is the structure of the lunges?
The lung s are a pair of lobed structure which have a central trachea
Trachea- surrounded by rings of cartilage and lined with goblet cells
Bronchi- divisions of the trachea leading into bronchioles
Bronchioles- series of branching subdivisions of the bronchi. Control the amount of air flowing in and out of the alveoli
Alveoli- minute air sacs which are the sites for gas exchange in the lungs
Why is the trachea surrounded by rings of cartilage?
To provide support and prevent the trachea from collapsing on itself causing it to close (keeps airways open)
What protects the lungs from damage?
Rib cage
How is the alveoli adapted for its function?
Alveoli are the site for gases exchange between O2 and CO2 and hence are adapted for quick diffusion.
Made of epithelial cells (1 cell thick) and so have a short diffusion pathway
Squamous epithelial cells and so have a large surface area for diffusion to take place on
Rich blood supply providing a steep and maintained concentration gradient
Contain surfactant which keeps alveolus moist and therefore has better efficiency in diffusion
Cell membranes are permeable to O2 and CO2
What are the main tissues in the mammalian gas exchange system?
Alveoli:
Squamous epithelium
Elective fibres ( stretch and recoil to force air out)
Capillaries:
Squamous endothelium
Trachea/bronchi/bronchioles: Large Supported (rings of cartilage) Flexible (elastic fibres for dilation) Ciliates epithelium with goblet cells (secrete mucous) Smooth muscle (involuntary contractions)
What happens to the volume of lumen when smooth muscle contacts?
Lumen constricts and therefore the volume decreases.
Contraction DOES NOT = constriction
What is the structure of the gills?
Gills are made up of full filaments which are each connected to fill lamellae.
Water flows in through the mouth and is passed over the gills and back out of the body of the fish
How is the gill structure adapted for their functions?
The gill lamellae increases the surface area in the gills for diffusion of gases to take place upon making diffusion more efficient.
Have a counter current flow system between blood and water to increase the diffusion efficiency.
Explain how the counter current flow system in a fish works to increase the efficiency of gas exchange?
The direction of blood flow is opposite to the direction of water flowing past the gills. This ensures that there is a constant and maintained concentration gradient allowing oxygen to diffuse out from the water and into the blood.
Using the counter current system ~80% of oxygen in the water can be absorbed however without it only about 50% would be taken in.
How does gas exchange take place in an insect?
Air flows in through spiracles and enters The tracheae. This then splits into smaller tracheoles which extend throughout all the body tissues of the insect. The oxygen in the air then diffuses from the tracheoles and into the respiring cells of the insect
How does air diffuse from the tracheoles and into the respiring cells in an insect?
When cells respire oxygen is used up and hence this forms a concentration gradient which causes gaseous oxygen to diffuse back into the cells from the trecheoles.
Contraction of muscles in an inset can squeeze the tracheoles enabling mass movements of air in and out.
The ends of the tracheoles are filled with water. This increases the volume in tracheoles and decreases the pressure which draws air further in enabling them to diffuse into other body cells.
Why are spiracles important?
Enable air to enter the insect however when open they also allow water to evaporate out from the insect and hence may cause the insect to lose water.
They are often closed to reduce water loss
