Circulatory System - Blood Vessels Flashcards
(20 cards)
what are the 3 different types of blood vessels
- arteries
- capillaries
- veins
what do veins do
they carry blood to the heart
what do arteries do
they carry the blood away from the heart
what do capillaries do
they are involved in the exchange of materials at the tissue
what are the characteristics of the arteries
- elastic fibres
- strong walls
- thick walls compared to the lumen
- thick layers of muscle
what do arteries branch into
capillaries
what are the characteristics of the capillaries
- very tiny, too small to see
- very narrow
- permeable walls
- walls are only one cell thick
why are capillaries very narrow
- so they can squeeze into gaps between cells
- means that they can carry blood really close to every cell in the body and exchange substances with them
why do capillaries have permeable walls
so substances can easily diffuse in and out
what is the primary function of the capillaries
to supply food and oxygen and take away waste like CO2
why are the walls of capillaries only one cell thick
because it increases the rate of diffusion by decreasing the distance over which it travels
what do capillaries eventually join up to form
veins
what are the characteristics of the veins
- quite thin walls
- bigger lumen
- have valves in the lumen
why do veins only have quite thin walls
because the blood is at a lower pressure in the veins so they dont need to be as thick as artery walls
why do veins have a bigger lumen than arteries
to help the blood flow despite the low pressure
why do veins have vales
to keep the blood flowing in the right direction
why do arteries have elastic fibres
to allow them to stretch and spring back from the high blood pressure
why do arteries contain thick layers of muscle
to make them strong due to the high blood pressure
in what order does the heart pump blood through the vessels and what is the pressure in each part
- heart pumps blood out into arteries at high pressure
- blood passes through capillaries at medium pressure
- blood travels through veins at a low pressure back to heart
what is the lumen
the hole down the middle, where the blood actually flows through
