3.1.2 Transport in animals Flashcards
why do large multicellular organisms need transport systems
3.1.2(a)
small SA:V ratio, large diffusions distance, high metabolic rate
-they have a high metabolic rate so demand for oxygen and glucose is high to supply aerobic respiration
What happens in a double circulatory system
3.1.2(b)
the blood passes through the heart twice and travels through two separate circuits
what is pulmonary circulation
3.1.2(b)
blood flows from the heart to the lungs and back
what is systemic circulation
3.1.2(b)
where blood flows from the heart to the body and back
what happens in a single circulatory system
3.1.2(b)
the blood flows through the heart once for each circuit of the body
what is an advantage of a double circulatory system for organisms with a high metabolic rate
3.1.2(b)
higher blood pressure can be achieved in the systemic circuit (where blood flows from the heart to the body and back) meaning the rate of oxygen and glucose delivery and carbon dioxide removal from respiring tissues is high.
what is an open circulatory system and how can fluid be moved
3.1.2(b)
the blood or fluid is not enclosed within the vessels it can be moved around by contraction of body muscles
what is a disadvantage of an open circulatory system
3.1.2(b)
as the fluid is not contained withing vesicles pressure is lowered
describe the circulatory system in fish
3.1.2(b)
single and closed
heart has 2 chambers
blood is pumped from heart to the gills to the rest of the body and back to the heart
heart->gills->body->back to heart
describe the circulatory system in insects
3.1.2(b)
they have a tube shaped heart that pushes haemolymph around the body cavity called haemocoel
what happens at the haemolymph
3.1.2(b)
exchange of substances like ions and glucose takes place between haemolymph and cells of the organ
What is a closed circulatory system and where is this present
3.1.2(b)
in larger animals blood is contained within vesicles
tissue fluid bathes the tissues and cells
what is an advantage of a closed circulatory system
3.1.2(b)
higher blood pressure can be maintained
so rate of delivery of oxygen and glucose is higher
describe the circulatory system in insects, fish and mammals
3.1.2(b)
insects-open single
fish-closed single
mammals-closed double
function of the arteries
3.1.2(c)
carry high pressure blood away from the heart
structure of the arteries
3.1.2(c)
-thin layer of collagen to provide structural support
-layer of smooth muscle provides strength to withstand high pressure
-elastic fibres allow stretch and recoil. This is so the arteries can stretch when ventricles contract and recoil when ventricles relax. This maintains the high pressure
-small lumen maintains high pressure
function of the arterioles
3.1.2(c)
distribute blood from arteries to capillary beds
structure of the arterioles
3.1.2(c)
-Arteriole walls contain a higher proportion of smooth muscle than artery walls do.
This smooth muscle can contract or relax to decrease or increase the blood flow to a particular area. For example, during the fight or flight response, arterioles supplying the digestive system contract to reduce blood flow to the digestive organs, instead prioritising blood flow to the muscle
function of the capillaries
3.1.2(c)
allow the exchange of materials between the blood and the tissue fluid
structure of the capillaries
3.1.2(c)
· Capillary walls are made only of a single layer of endothelial cells, reducing the diffusion distance
· The walls do not contain any other substances that would increase the diffusion distance e.g. collagen, smooth muscle, elastin
· The lumen is only wide enough to allow one red blood cell through at a time, giving more time for oxygen to diffuse out of red blood cells and into the tissue fluid
function of the venule
3.1.2(c)
carry blood under low pressure from capillary beds to veins
structure of the venule
3.1.2(c)
venules have a thin wall and collagen for structural support
function of the vein
3.1.2(c)
carry low pressure blood back to the heart
structure of the vein
3.1.2(c)
· Lumen is relatively large to reduce friction against the slow flow of low-pressure blood
· Very thin layers of elastic fibres and smooth muscle
· More collagen than arteries to provide structural support
· Valves prevent backflow of low-pressure blood due to gravity
Explain why tissue fluid forms at the arteriole end of a capillary bed
3.1.2(d)
Hydrostatic pressure > oncotic pressure
why is hydrostatic pressure high at the arteriole end
3.1.2(d)
as it closest to the heart and the powerful contraction of the left ventricle
Explain why tissue fluid returns to the capillaries at the venule end of a capillary bed
3.1.2(d)
Hydrostatic pressure < oncotic pressure
What causes oncotic pressure in capillaries?
3.1.2(d)
Large negatively charged plasma proteins that are too big to leave the capillary
how do large negatively charged plasma proteins affect the water potential
3.1.2(d)
makes the bloods water potential slightly negative
What happens to excess tissue fluid that doesn’t get drawn back into capillaries?
3.1.2(d)
drains into lymph vessels
what molecules can enter tissue fluid
3.1.2(d)
Only very small molecules are able to be squeezed out of the capillaries and enter the tissue fluid.
For example, blood plasma contains the large negatively charged plasma proteins these cannot enter the tissue fluid.
For small molecules like oxygen and ions, the composition of blood plasma and tissue fluid is similar. Most cells are unable to enter tissue fluid, but some white blood cells with immune functions (lymphocytes) can, including neutrophils.
Describe the composition of tissue fluid vs blood plasma
3.1.2(d)
Tissue fluid does not contain any large plasma proteins