Arteries/ Arterioles / Veins Flashcards
Function of arteries ?
Carry blood from heart to rest of body.
Pulmonary artery carries blood to lungs .
Structure of arteries
Walls are thick / muscular/ elastic to stretch and recoil - helps maintain high pressure.
Endothelium is folded allowing to stretch - helps maintain high pressure.
What type of blood do arteries carry?
All arteries carry oxygenated blood expect pulmonary arteries which take deoxygenated blood into lungs
Why does an artery stretch?
To cope with high pressure.
It then recoils under low pressure.
Describe structure of arteries
Outer elastic wall
Thick muscle layer
Folded endothelium
Lumen
What are the arteriole s?
Artistries divide into smaller vessels called arteriole
Network throughout the body
Blood is directed to different areas of demand in the body by muscles inside the arterioles which contract to restrict blood flow and relax to allow blood flow
Function of veins
To take blood back to heart under low pressure.
Blood flow through veins is helped by contraction of body muscles surrounding them.
Structure of veins
Wider links then arteries
Little elastic / muscle
Contain valves to stop blood flowing backwards
What type of blood to veins carry ?
Deoxygenated blood as oxygen (because oxygen has been used up by the body cells)
Pulmonary veins however carry oxygenated blood to heart from body
What are capillaries ?
Arteriole branch into capillaries - smaller blood vessels.
Substances (glucose/o2) are exchanged between cells and capillaries - efficient diffusion.
Where are capillaries located ?
Near cells in exchange tissue.
They attach arterioles and venule together at capillary beds.
Eg alveoli in lungs
Enables short diffusion pathway
Walls only 1 cell thick
Highly permeable.
Large number of capillaries to increase surface areas for exchange
What are networks of capillaries in tissue called ?
Capillary beds.
What are venules?
Small blood vessels that connect to veins
Why are the vein walls thinner / less muscular ?
Because blood travels through at low pressure.
Meaning lumen in middle is much larger
Why do capillaries have thin walls?
Allow for exchange of gases/ nutrients
