Blood Vessels Flashcards
What direction do arteries always pump blood in?
Away from the heart
What direction do veins always pump blood in?
Towards the heart
List the properties of arteries
- Thick walls of muscle
- Folded endothelium
- Narrow lumen
- No valves
- Elastic fibre tissue
Why do arteries have thicker muscle walls? 2
- Withstand high pressure
- Can widen/contract [vasodilation, vasoconstriction] to change blood flow
Why do arteries have a narrow lumen?
Extra support from lumen not needed as already has thick walls and high blood pressure
Why do arteries have no valves?
High pressure and gravity prevents backflow
Why do arteries have elastic tissue?
Arteries can recoil behind the blood to push it forward - maintains smooth pressure
Why do arteries have a folded endothelium?
Allows artery to expand and cope with high pressure
List the properties of a vein
- Thinner walls of muscle
- Wide lumen
- Valves
- Less elastic tissue
Why do veins have thinner walls of muscle? 4
- Lower pressure
- To accommodate wide lumen
- They don’t undergo vasoconstriction/dilation
- Veins close to skeletal muscles, when muscles contract they compress vein walls, pumping blood forwards
Why do veins have a wide lumen?
Ensures pressure stays low
Why do veins have less elastic tissue?
Lower pressure
Why do veins have valves?
Lower pressure risks backflow of blood
How do valves work?
- Higher pressure behind valve: its forced open
- Higher pressure in front of valve: forced shut
What is the purpose of valves?
To ensure blood flows in one direction, preventing backflow
What are the 3 types of blood vessel?
- Artery
- Vein
- Capillary
Where are capillaries?
They surround all cells and exchange substances e.g glucose
List the properties of the capillaries
- Very thin walls
- Forms capillary beds [network of capillaries]
- Narrow lumen
How thin are capillary walls?
1 single layer of endothelial cells
Why do capillaries? have very thin walls
Short diffusion distance
Why do capillaries form capillary beds/networks?
Increased surface area for diffusion
Why do capillaries have a narrow lumen?
- Forces blood to slow down due to friction against wall
- More time for diffusion
What are all blood vessels made of?
Collagen
What is collagen?
Tough fibrous protein
What does collagen do for blood vessels?
Makes them strong and durable
What do all blood vessels have?
Smooth endothelium
What does a smooth endothelium do in blood vessels?
Reduce friction
