Blood Vessels Flashcards
What are the 3 types of blood vessels?
Arteries and arterioles
Veins and venules
Capillaries
What 3 layers are blood vessels comprised of?
Tunica Intima
Tunica Media
Tunica externa
Describe the Tunica externa?
Provides blood vessels with the strength needed to withstand the high pressure, particularly the arteries which operate in a very high pressure environment
Made from fibrous tissue
Protective outer layer
Describe the Tunica media?
Gives strength and contractivity to the blood vessels, much thicker and more powerful in arteries than it is in veins
Made from elastic fibres and muscles
Medial layer
Describe the Tunica Intima?
Smooth inner lining, only once cell thick
What is the Lumen?
The opening within a blood vessel
the bit that the blood flows through
What are arteries?
Thick walled, muscular vessels
The amount of muscular and elastic tissue varies in the arteries, depending on their size and function
Why do arteries have such thick walls?
They are operating in a high pressure system
they carry blood away from the heart
What are large arteries also known as?
Elastic arteries
How do large arteries differ?
The tunica media consists of more elastic tissue and less smooth muscle
This allows the vessel wall to stretch absorbing the pressure wave generated by the heart each time it beats
How do arteries differ according to size?
The arteries branch several times and become smaller and smaller until they get to the smallest artery which is the arteriole
The tunica media in arterioles consists almost entirely of smooth muscles
What effect does the tunica media of arterioles consisting almost entirely of smooth muscles have on its functions?
This enables the diameter to be precisely controlled, which regulates the pressure within them
This in turn regulates the systemic blood pressure (which is determined by the resistance of these tiny arteries)
What are veins?
Blood vessels that return blood flow at low pressure back to the heart
The walls of veins are thinner than those of arteries, but they still have the same three layers of tissue
Why are veins thinner than arteries?
They need less muscle and elastic tissue
The veins carry blood at a much lower pressure than the arteries
What would happen if you cut a vein compared to if you can an artery?
It would collapse because the walls are not that thick
If you severe an artery, particularly a large one, it will remain open
When you cut an artery the blood spurts out at a very high pressure
Whereas if you cut a vein, it has a much slower steadier flow of blood
What characteristic do veins have due to their lower pressure?
Veins posses valves
What is the purpose of veins having valves?
They prevent the back flow of blood, ensuring that blood moves forward towards the heart
They point towards the heart and keep blood flowing in one direction only
How are valves within veins formed?
From the tunica intima, they are strengthened by connective tissue
What shape are valves within veins?
Semi-lunar
Where are valves within your veins more abundant?
In your limbs, particularly lower limbs
Why are valves within your veins more abundant in your lower limbs?
This is because they have to fight gravity more to get the blood back up to the heart
What are valves within your veins assisted by?
The skeletal muscle that surrounds them
What are small veins also known as?
Venules
How many miles of blood vessels do we have in our bodies, mostly consisting of what?
About 25,000
This is mostly capillaries
