Circulatory System Structure Flashcards
Why do multicellular organisms require a transport system?
Thy have a low SA:V and cannot rely on diffusion to supply all their cells and tissues with the substances they need to remove waste substances
What is the closed circulatory system?
Contains a pump, vessels and a medium to tranport substances around the body
What is the double closed circulatory system and why is it more efficient?
Where the heart has four chambers and blood passes through the heart twice for every circuit of the body
It increases pressure and speed of devilery of oxygenated blood to tissues
What are Arterioles?
Smaller arteries that control blood flow from arteries to capillaries
What does contracting Arterioles allow?
Allows blood to be directed to different areas according to demand
What are capillary beds?
Arterioles branch into capillaries which form networks in tissues
What is the smooth muscle layer?
Contracts o control the flow of blood in arteries, Arterioles and veins
What is the elastic layer?
Allows the vessel to stretch and recoil in arteries, Arterioles and veins
What happens to the deoxygenated blood after the exchange has occurred?
The blood flows from capillaries into venules, these then join to form veins and blood is transported back to the heart
What is the tough fibrous layer?
Resists pressure changes from both within and outside
What is the endothelium?
Thin inner lining which is smooth to reduce friction in all vessels
What are the adaptations of Arteries?
Narrow lumen to help maintain high pressure
Thick muscular walls and l elastic layer allows stretch and recoil with each ventricular contraction to maintain high blood pressure
Endothelium is folded to allow stretching to help maintain high pressure
What are the adaptations of Veins?
Wider lumen than arteries as blood is at low pressure
Thinner layers of muscle and elastic tissue
Valves to prevent backflow
When skeletal muscles contract, they compress veins, helping to increase pressure and push blood along
What are the adaptations of Capillaries?
Site of substance exchange with cells
very close to cells so short diffusion pathway
walls are only one cell thick for short diffusion pathway
Fenestrations between endothelial cells allow substances to diffuse out
large number of Capillaries to increase surface area for gas exchange
Why does blood lose pressure from the aorta?
Due to it branching into many vessels, the increasing of lumen size of the vessels and friction
