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
