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Physical Properties of Blood Vessels
Properties of Blood Vessels that Vary at Different Levels of Branching are:
Number of vessels
Radius & Wall thickness
Aggregate cross-section area of all the parallel vessels at a particular level
Volume
Pressure
Flow
Velocity of the blood
Circulation time
Structure of the wall
Elastic property
Number of Vessels
Aorta: 1
Small arteries: 8000
Arterioles: 20 million
Capillaries: 40 billion
Towards veins: the numbers decrease as vessels merge
Vena cava: 2
Radius / Wall Thickness
The radius decreases as we go from aorta to capillaries. And increase from capillaries to vena cava.
Aorta: 12 mm / 2 mm
Medium-size artery: 2 mm / 1 mm
Arteriole: 15 ฮผm / 20 ฮผm
Capillary: 3 ฮผm / 1 ฮผm
Venule: 10 ฮผm / 2 ฮผm
Vein: 2.5 mm / 0.5 mm
Vena cava: 15 mm / 1.5 mm
Cross Section Area
Of Individual vessel
The radius decreases as we go from aorta to capillaries. And increase from capillaries to vena cava
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Crosss section area of individual blood vessel decreases as we go from aorta to capillaries. And increase from capillaries to vena cava.
Aggregate Cross-Section Area All the Parallel Vessels at a Particular Level
Aggregate cross-section area = number of vessels at that level ร cross-section area of unit vessel
In general, with branching, combined cross-section area of daughter vessels exceeds cross-section area of the parent vessel
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As arteries branch into subsequent levels
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Aggregate cross-section area increases i.e.
Aorta: 4 square cm
Small arteries: 60 square cm
Arterioles: 140 square cm
Capillaries: 2800 square cm
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Postcapillari venules: Have maximum aggregate cross-section area in spite of their fewer number than capillaries. This is because their significantly wider diameter than capillaries overcompensates for their slightly fewer numbers.
Volume
Systemic arteries: 700 ml
Systemic capillaries: 300 ml
Systemic veins: 3200 ml
Pulmonary circulation: 450 ml
Heart: 350 ml
Total: 5000 ml
Other parameters are more like physiological parameters and are explained in other videos.