Blood Vessels
Physical Education: AQA GCSE, topic 1.2.2
Arteries
Arteries are a type of blood vessel.
Thick walls
- Arteries are the largest in external (outer) diameter and have the thickest walls of all blood vessels.
- Because they have such thick walls, they have a slightly smaller lumen (internal diameter).
Can vasoconstrict and vasodilate
- During exercise, the body can vasoconstrict (make the lumen smaller) or vasodilate (make the lumen larger) to distribute blood efficiently.
- E.g. the arteries leading to the stomach will vasoconstrict to reduce blood flow to ‘non-essential’ organs. At the same time, the arteries leading to the working muscles will vasodilate to increase blood flow to where the blood is needed most at that time.
Elasticated walls
- Arteries are elasticated and thick. This lets them cope with the high pressures at which blood is pumped away from the thick, muscular ventricles of the heart. This is why you can feel a pulse in them.
- Think of the walls of arteries like elastic bands. They can stretch to cope with the high pressures from the heart but then return to their original shape and size. This prevents them from bursting.
Veins
Veins are another type of blood vessel.
Structure
- Veins have a large internal diameter (lumen) but thin walls as the pressure inside them is low.
- Veins have valves to prevent the backflow of blood, which is a possibility due to the lower pressures. This means that they do not have a pulse.
Function
- Veins carry blood towards the heart (mostly deoxygenated blood).
Test yourself on Blood Vessels
Characteristics of arteries
Characteristics of veins
Veins and arteries are types of...
Characteristics of veins