Blood vessels

Question 1

Structure of a veins / arteries

Answer 1

Tunica intima -
- single layer of endothelium
- smooth lining to reduce friction
- minimal resistance to flow
Tunica media -
- elastic fibres and smooth muscle
- fibres stretch when blood flow changes and recoils to push blood through the artery.
- contracting muscle regulates flow and maintains pressure
Tunica externa -
- contains collagen fibres which resists overstretching

Question 2

Arteries

Answer 2

• carry blood away from the heart
• thick walls withstand high blood pressure
• branch into arterioles which subdivide into capillaries

Question 3

Capillaries

Answer 3

• form a vast network that penetrates into all tissue and organs
• walls of one layer of endothelium on a basement membrane
• pores within the capillary walls makes it permeable to water and solutes

Question 4

Veins

Answer 4

• have a larger lumen
• thinner walls with less muscle
• blood pressure and flow rate are lower
• in veins above heart blood travel by gravity
• semi lunar valves to prevent back flow