7.6 Blood vessels and their functions Flashcards
What are the 4 different types of blood vessels and what do they do
Arteries: Carry blood away from the heart, and into arterioles
Arterioles: Smaller arteries that control blood flow from arteries into capillaries
Capillaries: Tiny vessels that link arterioles to veins
Veins: Carry blood from capillaries to the heart
Arteries, arterioles, capillaries and veins all have the same 5 layers
Describe these
. Outer layer
.Muscle layer
. Elastic layer
. Inner lining
. Lumen
. Tough fibrous outer layer: Resists pressure changes from within and outside
. Muscle layer: It can contract and relax and so control the flow of blood
. Elastic layer: Helps to maintain blood pressure by stretching then springing back (recoiling)
. Thin inner lining (endothelium): that is smooth to reduce friction and thin to allow diffusion
. Lumen: A central cavity of the blood vessel in which blood flows
How is the structure of an artery related to its function
Thick outer muscle layer
Arteries have to transport blood rapidly under high pressure from the heart to tissues
. They have a really thick muscle layer compared to veins
. This means smaller arteries can be constricted and dilated to control the volume of blood passing through them
How is the structure of an artery related to its function
Thick elastic layer compared to veins
Arteries have to transport blood rapidly under high pressure from the heart to tissues
. Blood pressure in arteries needs to be kept high in order for blood to reach all body parts
. The elastic wall is stretched at each beat of the heart (systole), and then it springs back when the heart relaxes (diastole)
. This stretching and recoil action helps to maintain high pressure and smooth pressure surges created by the heart
How is the structure of an artery related to its function
Thick wall
No valves
Arteries have to transport blood rapidly under high pressure from the heart to tissues
The thick wall is very thick which can help the vessel resist bursting under pressure
There are no valves (except in arteries leaving heart eg aorta and pulmonary artery) because blood is kept under constant high pressure due to the heart pumping blood into the arteries.
Therefore it tends to not flow backwards so there is no need for valves
compare the structure of arterioles and arteries
. Arterioles carry blood under lower pressure than arteries , from arteries to capillaries, and they control the flow of blood between the two
- They have a thicker muscle layer than in arteries because it allows for the constriction of the lumen of the arteriole.
This constricts the flow of blood so can control the movement of it into capillaries - The elastic layer of them is thinner than in arteries because blood pressure is lower as they are further from the heart
Describe the difference in muscle layer between veins and arteries
. Muscle layer is relatively thin in veins compared to arteries
. This is because veins carry blood away from tissues, towards the heart so if they constrict and dilate, it won’t control the flow of blood to the tissues
Describe difference in elastic layer between veins and arteries
. It is thinner in veins compared to arteries
. This is because the blood pressure is low in veins so they won’t burst, and they won’t recoil
Describe difference in thickness of the wall for veins compared to arteries
. The wall is much thinner in veins than in arteries
. Because the pressure in veins is much lower so there is no need for a thick wall to prevent bursting
. It also allows them to be flattened easily which helps blood flow in them
Describe valves in veins
What happens to veins when body muscles contract
. Ensure that blood flows in the right direction and not backwards, which it might do because the pressure is so low
. When body muscles contract, veins are compressed which pressurises the blood within them
. Valves ensure that this pressure directs blood in one direction, towards the heart
What is the function of capillaries
. To exchange metabolic materials eg oxygen, carbon dioxide, and glucose between the blood and cells of the body
. The flow of blood in the capillaries is slow which allows more time for exchanging materials
They form the link between arteries and veins, which are on each end of it
Describe the walls of the capillaries and why this is important
. Thin walls of lining, only one cell thick
. This means the diffusion distance is much shorter (short diffusion pathway) which allows for more rapid diffusion between blood and cells
Why are capillaries numerous and highly branches
. To provide a large surface area for exchanging substances
Why do capillaries have a narrow diameter
. They can permeate tissues, so no cell is far from a capillary so there is a
short diffusion pathway
Why is the lumen of capillaries so narrow
. So red blood cells are squeezed flat against the walls of the capillary
. This brings them even closer to the cells that they supply oxygen to
. So makes a short diffusion pathway