Peripheral circulation I

Total cross-section of the vessels

smallest in the arteries, it is the highest in the capillary system, and decreases in the venous system

rate of blood flow

inversely proportional to the total cross section

Blood pressure

high in the arteries and is synchronous with the heart cycle, blood pressure decreases continuously in the capillaries and veins, oscillations in the pressure cease in the arterioles.

flow in tubes with rigid wall

the intensity of the flow is directly proportional to the pressure gradient.

flow in Elastic tubes

at a critically low-pressure blood vessel collapses, the flow disappears (critical closure pressure)

Total peripheral resistance

vessel’s diameter and the viscosity of the blood

Redistribution of blood in resting conditions

25% coronary and cerebral vessels, 25% muscle and skin, 25% kidney, and 25% veins of the liver and the gastrointestinal tract.

Bayliss effect

stretching of the vascular smooth muscle cells leads to an action potential series and leads to contraction of the vessels.

Microcirculatory system

precapillary vessels (terminal arterioles), arteria sensuous (AV) capillaries, true capillaries, and postcapillary venules

Venous circulation

• Driving force of the circulation is the pressure gradient between the post capillary vessels and the atria.
• Venous valve, muscle pump (veins are compressed and decompressed during rhythmic contraction and relaxation), respiratory pump
• Capacity vessels (blood stores, venous depot)
• Vasoconstriction in veins leads to higher venous return and cardiac output
• Redistribution, physical activity

Mean arterial pressure

determined by the stroke volume and total peripheral resistance.

peripheral resistance

affected by the resistance of the vessels determined by the diameter of the vessels (basal tone, neurogenic, humoral effect).

Stroke volume

depends on venous return, sympathetic nervous system activity, basal tone.