Blood vessels Flashcards
what are blood vessels
-tubes that transport blood to and from the heart, lungs and body
what are the three types of blood vessels?
Arteries: Carry blood Away from the heart
Capillaries: Tiny vessels that carry blood between cells
Veins: Carry blood towards the heart
what are capillaries
Microscopic blood vessels that form a network, carrying blood close to nearly every cell in the body.
structure and function of capillaries
Enables cells to get requirements from blood and to pass waste into blood
Capillary walls have only one layer of cells allows substances to pass easily between blood and surrounding cells
Size is small but there are many Increases surface area
what are arteries?
Carry blood away from heart
structure of arteries
Walls contain smooth muscle & elastic fibres
Walls of arteries can stretch to accommodate extra blood from ventricles
Elastic recoil keeps blood moving and maintains pressure
what do arteries form?
Form arterioles (smaller arteries that form capillaries)
vasoconstriction of arteries
muscle of walls contracts to reduce diameter of vessel and therefore reduce blood flow through artery
vasodilation of arteries
muscle of wall relaxes to increase diameter of vessel and therefore increase blood flow
what are veins/what do they do?
Carry blood towards the heart
why do veins have valves
Have valves to prevent backflow of blood (blood can only travel one way – to the heart)
blood pressure in veins
Blood pressure in veins is relatively low because blood loses most of its pressure as it flows from arteries through capillaries
Pressure is constant, so walls do not have a thick layer of elastic connective tissue as it’s not needed
structure of veins and how are they formed?
Capillary bed leads to venules (small veins) which join to form veins
Walls of veins much thinner than arteries due to less smooth muscle and less connective tissue.
Veins are not able to change their diameter
