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📚 > Physiology > Cardiovascular System > Arteries and Veins_>

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 μm / 20 μm

  • Capillary: 3 μm / 1 μm

  • Venule: 10 μm / 2 μm

  • 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

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 × 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

As arteries branch into subsequent levels

Aggregate cross-section area increases i.e.

Aorta: 4 square cm

Small arteries: 60 square cm

Arterioles: 140 square cm

Capillaries: 2800 square cm

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.

 

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▶️ Blood Pressure Along the Vascular Circuit
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