33. Functional characteristics of the blood vessels. Hemodynamic principles – characteristics of the vessels and the blood. Hemodynamic indices. Volume and linear velocity of the blood flow through the different parts of vascular system and determining factors

Hemodynamic – is the interrelationship of factors like flow, pressure, and resistance that affect the basic principles of blood circulation.

1.Arteries (elastic conducting) carries blood away from the heart >50um
2.Arterioles (muscular distributing) – carries blood from the arteries into the capillaries 20-50um 3.Metarteriole – links the arterioles and the capillaries 10-15um
5.Capillaries –where exchange materials between blood and tissue cells. Arterial end of capillary 5um, venous end of capillary 9um
6.Venules – smallest veins, receives blood from the capillaries 20um
7.Veins returns the blood to the heart

Arteries

• Have thick muscular walls- withstand high

pressure

• Made up of smooth muscle

• Walls are elasticated for flexibility

• Smooth muscle contacts and relaxes

following instructions from the sympathetic

nervous system.

• Transport blood away from the heart

• Transport oxygenated blood away from the

heart

2. Arterioles

• Small branches of the arteries that lead into

capillaries

• Under sympathetic control

• Constrict and dilate in order to regulate blood

flow and pressure

3. Capillaries

• Capillary cells are one cell thick, for

quick diffusion Allow for exchange of

nutrients and oxygen

• Can be fenestrated, continuous,

discontinuous

• Transport blood at low pressure,

connect arteries to veins

4. Venules

• blood from the capillaries → vein

• Many venules together form a vein

5. Veins

• Have a large lumen to hold a lot of blood

• Veins with valves- prevent backflow

• Transport blood to the heart

• Transport deoxygenated blood

• Only pulmonary vein supplies oxygenated

blood to the left atrium

hemodynamic indices

HEMODYNAMIC INDICES
àBlood flow velocity is the total volume flow divided by the cross-sectional area of the vascular bed and there it’s the same in different vascular regions = 5 l/min

HDI = BFV / TVF OVER CROSS SECTIONAL AREA OF

blood flow velocity
Blood flow= quantity of blood that passes a given point in the circulation in a given period of time (5l/m)
àLinear flow velocity (average) in: aorta 0.5 m/s, capillaries 0.5mm/s, venae cavae 0.2 m/s
àPulse wave velocity in: aorta 6-8 m/s, mid-size arteries 7-10 m/s, small arteries around 16m/s

veolity

Cross sectional area (cm2); cross sectional area in the capillaries is the highest

Velocity of the blood flow (cm/sec); velocity of the blood flow is the lowest in the capillaries

àAs you increase the cross-sectional area (cm2) = the velocity of the blood flow decreases (cm/sec)

blood flow:

Blood flow = change in perfusion pressure / resistance

1.Change in perfusion pressureàthe blood flows from higher pressure to lower pressure; the higher the change in perfusion pressure the higher the blood flow

2.Resistanceàthe higher the resistance the lower the blood flow

• Stroke Volume (SV) – the amount of blood ejected by one ventricle during systole.
  ✅ Normal SV ≈ 70 mL

• SV = EDV – ESV

  • EDV (End Diastolic Volume): volume of blood in the ventricle before contraction (≈ 130–140 mL)

  • ESV (End Systolic Volume): volume remaining after contraction (≈ 60–70 mL)
    🔢 Example: 140 mL – 70 mL = 70 mL

• Cardiac Output (CO) – the total volume of blood pumped by one ventricle per minute (mL/min or L/min)
  ✅ CO = SV × HR

• 🔢 Example:
  If SV = 70 mL and HR = 70 bpm
  Then: CO = 70 × 70 = 4900 mL/min = 4.9 L/min

LAMINAR FLOW:
-Concentric flow because the velocity of the blood flow is the highest in the center and lowest at the edges. This type of flow is silent; it has no effect on the resistance and therefore:
As you increase the perfusion pressure the volume of blood flow increases proportionally

TURBULENT FLOW:
-When there is some type of occlusion in the blood vessel the laminar flow will get disrupted. It decreases the volume of blood flow, and increase the perfusion pressure which means the resistance is also increased