B2.2.2 Circulatory System Flashcards
Function of cardiovascular system
Provides cells with nutrients
Transports oxygen around the body through blood
Remove waste products such as carbon dioxide and lactic acid
Three main blood vessels
Arteries
Veins
Capillaries
Describe artery
Thick outer wall
Thick layer of muscle and elastic fibres
Small lumen
Smooth lining
Describe vein
Fairly thin outer wall
Thin layer of muscle and elastic fibres
Large lumen
Smooth lining
Have valves to prevent back flow of blood
Describe capillary
Very small lumen
Wall made of a single layer of cells
Arteries carry blood
Away from the heart under high pressure
Veins
Return blood to the heart
How is a capillary adapted to its function
Form a network so that every cell is close to a capillary
Semipermeable walls are only one cell thick so substances can easily move through them
Why is the artery wall thick and muscular
The strong contractions of the heart cause the blood to leave at very high pressure
To withstand the high pressure waves created when the heart beats
Wall expands with the force of each contraction then snaps back to push blood forward (recoil)
Why is the human circulation system referred to as a double circulatory system?
Blood passes twice through the heart in one complete circulation
Explain why very small organisms don’t need transport systems like heart and blood vessels to survive
Very small organisms have a larger surface area to volume ratio so their diffusion distance is smaller.
This means they don’t require transport systems to dispose of their waste products
