Organisms Exchange Substances with their Environment: Mass Transport in Animals - Circulatory System - Structure of Blood Vessels Flashcards
List structural features of arteries
- Thick muscular walls
- Thick elastic tissue
- Folded endothelium
Why do arteries have thick muscular walls?
- Withstand high blood pressure
Why do arteries have thick elastic tissue?
- Vessel can stretch at stysole
- Vessel can recoil back at diastole
- Called elastic recoil
- Helps maintain high pressure
Why do arteries have folded endothelium?
- Allows artery to stretch
- Maintains high pressure
List structural features of arterioles
- Thinner and less muscular walls (than arteries)
- Thinner elastic layer
Why do arterioles have thinner and less muscular walls than arteries and what are their function?
- Arterioles carry blood at a lower pressure than arteries
- Contract to control flow of blood into capillaries that supply tissues with blood
Why do arterioles have thinner elastic tissues than arteries and what are their function?
- Blood pressure is lower
- Stretches and recoils to maintain blood pressure
List structural features of veins
- Thinner muscle layer (than arteries)
- Thinner elastic layer
- Wider lumen
- Valves
Why do veins have thin muscle tissue and what are their function?
- Veins carry blood at a low pressure
- Veins carry blood away from tissues so don’t control blood flow into tissues
- Blood flow through veins is helped by contraction of body muscles surrounding them
Why do veins have thin elastic layers?
- Lower blood pressure makes vessel unlikely to burst
Why do veins have wider lumen?
- Maximise blood flow into heart
Why do veins have valves?
- Prevent back-flow of blood
List structural features of capillaries
- Endothelium is one cell thick
- Large number of capillaries - highly branched
- Narrow lumen
Why do capillaries have endothelium that are one cell thick?
- Short diffusion pathway
Why do capillaries occur in large numbers?
- Large surface area
- No cell is far from capillary
