Transport in Animals Flashcards
Why do multicellular animals need transport systems?
High metabolic rate - multicellular animals need lots of oxygen + food and produce lots of waste so diffusion over long distances is not enough to supply the quantities needed.
Small SA:V ratio - larger diffusion distances and small SA to absorb/remove substances.
What is a closed circulatory system?
Blood enclosed in blood vessels and doesnt have direct contact with all cells.
Heart pumps blood under pressure, blood returns to the heart.
substances enter/leave blood through blood vessel walls.
Blood flow of tissues adjusted by widening/constricting blood vessels.
effective transport system for multicellular mammals - allows blood to travel rapidly under high pressure to wherever it’s needed.
What is a single closed circulatory system?
Blood passes through 2 sets of capillaries beforing returning to heart.
1st set of capillaries - O2 and CO2 exchanged.
2nd set of capillaries - substances exchanged between blood and cells in different organ systems.
Narrow capillaries so blood pressure drops before slowly returning to the heart. This limits efficiency of exchange processes so metabolic activity is relatively low.
Most animals with a closed ciruclatory system have a low metabolic activity. Why are fish the exception?
Fish have counter-current exchange system.
Water with high concentration of O2 flow past blood with low concentration of O2 at high pressure, in opposite directions.
This ensures that there is always a concentration gradient maintained.
Efficient exchange process so metabolic activity is high.
What is a double closed circulatory system?
Blood completes two circuits.
Blood pumped from heart to lungs, to pick up O2 and unload CO2 and then returns to heart.
Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again.
Describe open circulatory system in insect
Blood fills body cavity (haemocel) at a low pressure.
Blood doesnt transport O2/CO2 but transports food and nitrogenous waste products and immunological cells.
O2/CO2 transported via spiracels and trachae.
Haemolymph (insect blood bathes organs directly and moves slowly through the tissue, returning to heart via collecting ducts.
What is the function of blood?
. Transports materials to and from cells
. Transports nutrients, carries O2, waste products, hormones to their target cells, regulates body temperature, protects against bacteria and viruses
. Transports platelets to damages areas
Function of arteries
Carries oxygenated blood away from heart except the pulmonary artery which carries deoxygenated blood away from the heart.
Carry blood from heart to rest of body at high pressure to meet cell’s metabolic demands.
Thick muscle layer to maintain high pressure.
Thick elastic tissue layer to help stretch and recoil as the heart beats to maintain high pressure. This evens out the surges pumped from the heart to give a continous flow.
Endothelium is folded to allow the artery ot expand which helps maintain high pressure.
Describe arterioles
Branched off from artery, carries oxygenated blood.
smaller than arteries.
Has a layer of smoth muscle but less elastic tissue than arteries.
Smooth muscle allows them to expand/contract, controlling blood flow to tissues.
What are capillaries?
Branched off from arterioles - smallest blood vessel.
Describe venules
Brached off from capillaries
carries deoxygenated blood from capillaries to veins.
thin walls.
contains some muscle cells.
Function of veins
Takes deoxygenated blood back to heart under low pressure except in pulmonary veins where they carry oxygenated blood.
Very little elastic and muscle tissue.
Wide lumen relative to artery.
contains valves to stop blood backflow.
