Factors Affecting Blood Flow
Blood Flow : the volume of blood that flows through any tissue in a given period of time (mL/min). Total blood flow is cardiac output (Q) which is the volume of blood that circulates through systemic or pulmonary blood vessels each minute. However, how cardiac output becomes distributed into circulatory routes that serve various body tissues depends on 2 factors :
1) The pressure difference that drives the blood flow through a tissue
2) The resistance to blood flow in specific vessels.
Blood flows from a region of high pressure to regions of low pressure; the greater the pressure difference, the greater the blood flow. But the higher the resistance, the smaller the blood flow.
Blood Pressure
Contraction of the ventricles generates blood pressure (BP) which is the hydrostatic pressure exerted by blood on the walls of a blood vessel. BP is determined by cardiac output, blood volume and vascular resistance. Horse BP rises to about 120mmHg during systole and drops to about 70mmHg during diastole. However, this varies greatly. Blood pressure is difficult and rarely measured in horses.
Vascular Resistance
This is the opposition to blood flow due to friction between blood and the walls of blood vessels. This depends of 3 factors:
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