Blood Vessels Flashcards
What do artificial do
They carry blood away from the heart to the organs
What is blood in the arteries under
High pressure
What happens when the heart beats and what is it called
A surge of even higher pressure blood is pushed down the arteries and this is called the pulse
What is a feature of the blood in arteries
It is always moving forward even between heart beats.
What is the average diameter of an artery
4-10mm
What is a feature of the artery wall and why
The artery wall is very thick allowing the artery to withstand the high pressure of the blood.
What does the artery wall consist of
several layers of
What is the outer layer made up of and why
It has a collagen rich outer layer. And the collagen plays a structural role, strengthening the artery wall against the pressure of the blood.
What is the 2nd layer of the artery made out of and what does it do
Smooth muscle , and when the smooth muscle contracts the diameter of the artery narrows allowing the body to control how much blood flows through different organs.
What do smaller arteries have compared to larger arteries and why
They tend t have a greater proportion of smooth muscle compared to larger arteries because they have a greater role in controlling blood flow.
What is the 3rd layer of arteries made out of
It is a layer rich in elastic fibres and the elastic fibres. Contain the protein called elastin which can stretch.
What occurs to the elastic fibres when the heart beats.
When the heart contracts a surge of high pressure blood passes through the artery as the surge moves through the elastic fibres stretch. They then recoil once the surge has passed. The elastic recoil helps to keep the blood moving smoothly forward in between contractions of the heart.
What is the central cavity of the artery called and what does it do
It is called the lumen and it is where the blood flows through
What is the lumen lined with
A thin layer of endothelial cells, presenting a very smooth surface to reduce friction as the blood flows through.
What do arteries branch into
Smaller blood vessels called arterioles.
What is the job of the arterioles
Is to deliver blood to capillaries.
What is similar about the walls of arterioles and arteries and what is different
The walls of the arterioles contain the same layers as arteries. However, they differ in their relative thickness, having a diameter of around 50uM.
What is the difference in pressure in arteries and arterioles
In arterioles the blood pressure is lower than in arteries and the elastic layer is relatively thin compared to arteries.
What is the smooth muscle layer in arteries compared to arterioles
It is relatively thicker in arterioles compared to arteries
As they are involved in controlling the amount of blood that passes through capillaries.
What happens when the smooth muscle in arterioles contracts and relaxes
When the smooth muscle in the arterioles contracts, blood flow through capillaries is reduced, called vasoconstriction.
When the smooth muscle is arterioles relaxes, blood flow through capillaries increases, called vasodilation.
When does vasodilation occur
Takes place when an organ requires an increased amount of oxygen.
