Mammals have a transport mechanism called circulatory system. The circulatory system is composed of the heart and the associated blood vessels
Arteries
- Carry blood away from the heart.
- Blood that flows through arteries is pulsing and at a high pressure.
- Contain elastic fibres and collagen fibres
- Arteries have narrow lumen maintaining high pressure facilitate faster movement of blood
- Have thick, elastic walls which can expand and recoil as the blood pulses through.
- The artery wall contains variable amounts of smooth muscle.
- It carries oxygenated blood except in pulmonary artery
Relate the structure of the artery to its function
- Arteries transport swiftly and at high pressure to the tissues
- made up of an inner endothelium
- this layer is very smooth, minimizing friction with the moving blood.
- also made up of tunica media
- Contain smooth muscle and elastic fibres
- Tunica extern
- Contain elastic fibres and collagen fibres.
- Arteries have narrow lumen maintaining high pressure facilitate faster movement of blood.
- Elastic walls to allow for expansion when pressure increases
- semilunar valves to prevent backflow of blood
Veins
- Carry low-pressure blood back to the heart
- the lumen is larger than in arteries, reducing friction which would otherwise slow down blood movement
- Have thin muscular wall with little elastic tissue
- Contain valves, to prevent the backflow of blood
- No pulses and blood flows slowly.
- Deoxygenated blood except pulmonary vein
Capillaries
- Tiny vessels with just enough space for red blood cells to squeeze through
- Have no muscles or elastic tissue.
- Blood flows slowly and no pulses.
- Large lumen relative to diameter
- single cell walled and they are permeable and unable to constrict.
- there are often gaps in the walls through which plasma (the liquid component of blood) can leak out
- deliver nutrients, hormones and other requirements to body cells, and take away their waste products
- Small size and thin walls minimize diffusion distance
- this enables the exchange to take place rapidly between the blood and the body cells.
How the structure of arteries and capillaries is related to their function.
- artery
- thick elastic layer in artery
- even outflow/associated with recoil
- thick muscular layer to allow pausatile flow of blood;
- endothelium layer for smooth flow of blood;
- thick collagen layer to allow blood flow under pressure
- small lumen allow rapid flow of blood
- capillary
- capillary wall is thin/only endothelium
- gaps for the exchange of materials like white blood cells
- capillary form a branched network to increase surface area for exchange of materials
- narrow diameter to minimize diffusion distance
- narrow lumen -more diffusion efficient