12. Overview of Circulation

Systemic Circulation (Peripheral Circulation)

Serves all tissues except for the lungs

Systemic Circulation contains ________ of blood volume

84%

Pulmonary Circulation

Serves the lungs

The lungs contain ________ of blood volume

9%

The heart contains ______ of blood volume

7%

Arteries

Transport blood under high pressures away from the heart to tissues
-Strong vascular walls
-High velocity

Arterioles

Last small branches of the arterial system
-Resistance vessels of circulation

Capillaries

Location where fluids, nutrients, electrolytes, hormones, and other substances diffuse and are transported between blood and interstitial fluid

Venules

Collect blood from capillaries and form progressively larger veins

Veins

Function as conduits for transport back to the heart
-Reservoir of blood

Aorta

Main vessel to distribute blood to the arterial system
-Dampens the pulsatile pressure that results from outflow from the left ventricle

Large arteries that branch from the aorta distribute...

Blood to specific organs

The large arteries serve virtually...

No role in the regulation of pressure and blood flow

When the blood from large arteries reaches organs...

Smaller arteries branch and distribute blood within the organ

Small arteries and arterioles are what represent the...

Primary vessels that are involved in the regulation of arterial blood pressure as well as blood flow within the organ

The primary vessels are highly innervated by...

Autonomic nerves

Capillaries are the primary...

Exchange vessels within the body

Systemic Arterial Pressures

Systolic = 120 mm Hg
Diastolic = 80 mm Hg
Mean = 100 mm Hg

Pulmonary Arterial Pressure

Systolic = 25 mm Hg
Diastolic = 8 mm Hg
Mean = 16 mm Hg

Atrial Pressures during Systole

Right atria ~ 2 - 6 mmHg
Left atria ~ 4 - 10 mmHg

The flow through a vessel can be calculated using...

Ohm's Law

Ohm's Law

Flow (Q) = Pressure Difference (Delta P)/Resistance (R)

Blood Flow

Quantity of blood that passes a given point in the circulation in a given period of time.

Unit of blood flow

Liters or mL per minute

Laminar Flow

Silent, smooth flow in streamlines with each layer of blood remaining the same

Turbulent Blood Flow:

-high velocities
-sharp turns in the circulation
-rapid narrowing of blood vessels
-movement in opposite directions
-Causes murmurs

Blood Pressure

Force exerted by the blood against any unit area of the vessel wall.

Units for Blood Pressure

mmHg or cm H2O

A decrease in Resistance would cause...

An increase in blood flow and vice versa

Small changes in the diameter of a vessel can cause...

Dramatic changes in blood flow through a tissue

What does Poiseuille's Law state?

-increasing the viscosity of a solution and increasing the length of the tube will decrease blood flow.
-increasing the pressure gradient and increasing the radius of the tube will increase flow.

When we talk about viscosity of blood, we mean the...

Hematocrit or PCV

An increase in hematocrit will...

Increase viscosity, which decreases blood flow

Total Peripheral Vascular Resistance

Sum of resistances of arteries, arterioles, capillaries, venules, and veins