The circulatory system

Need to know

What you need to know

• transports oxygenated blood at high pressures to tissues.
• pulmonary artery and aorta have semilunar valves in the beginning.
• tunica intima/interna – very smooth, single layer of flat cells.
• tunica media – smooth muscle, collagen fibres, elastic fibres.
• tunica externa – collagen fibres, elastic fibres Image: http://www.hcc.ac.uk.
• tunica media is the thickest in arteries.
• depending on the pressure, thickness of arteries’ walls differs.
• tunica media contains large amounts of elastic fibres to allow the artery wall to stretch as blood surges through at high pressure.

Explanation

The circulatory system

1. transports oxygenated blood at high pressures to tissues.
2. pulmonary artery and aorta have semilunar valves in the beginning.
3. tunica intima/interna – very smooth, single layer of flat cells.
4. tunica media – smooth muscle, collagen fibres, elastic fibres.