Module 1 - Vascular System Flashcards
What is the basic equation for blood flow?
F = ΔP/R
F – flow rate of blood through a vessel
ΔP – pressure gradient
R – resistance of blood vessels
What is the pressure gradient in regards to blood flow?
Pressure Gradient (ΔP)
• Difference in pressure between beginning and end of a vessel
• Frictional resistance drops pressure as blood flows through a vessel
• The greater the difference, the greater the blood flow
What is resistance as it relates to blood flow?
- Measure of opposition to blood flow
* Caused by friction of blood against vessel walls
What has to happen in the resistance in a vessel increases in order to try to maintain adequate blood flow?
o Pressure gradient must increase
o Heart works harder to maintain circulation
What are the 3 main factors that affect resistance?
Blood viscosity (η)
Refers to friction as molecules sliding over each other
Primarily determined by RBCs, which is generally consistent
Increase in RBCs causes blood flow to be more sluggish than normal
Vessel length (L) Greater length results in greater resistance, but is constant
Vessel radius (r)
Arterioles most important factor to control resistance to blood flow
The greater the radius, the lesser the resistance
Resistance is inverse to the 4th power of the radius
Double radius results in only 1/16 the resistance and a 16-fold increase in flow
Half the radius results in only 1/16 the blood flow
What does Poiseuille’s Law tell us and what is the equation?
• Integrates factors that affect flow rate
F = πΔPr4
8ηL
F – flow rate of blood through a vessel
ΔP – pressure gradient
r - vessel radius
η - Blood viscosity
L - vessel lengthDescribe the distribution of blood flow at rest, and postulate how this might change during exercise
At rest, blood flow is widely distributed and includes the digestive system and the kidneys. During exercise, blood flow is diverted to organs such as skeletal muscle for increase oxygen delivery and the skin to help remove excess heat. Blood flow to the digestive system and kidneys will be reduced as they are not important at this time
Name the reconditioning organs
Digestive tract, kidneys, and skin
Give the equation showing the relationship among flow rate of blood through a vessel, the pressure gradient, and the resistant to flow, and give the equation for the relationship between resistance and vessel radius
F = ΔP/R
R ∝ 1/r^4
What is reconditioning?
Blood is constantly adjusted by reconditioning organs (digestive, kidneys, and skin) to ensure that its composition remains relatively stable, despite an ongoing drain of supplies and continual addition of wastes
What are the 3 layers of the blood vessels?
Tunica intima (interna) Tunica media Tunica adventitia (externa)
Describe the tunica intima
- Forms inner lining and is in contact with blood
- Made of several layers but still very thin
Endothelium
• Innermost layer only one cell thick
• Continuous with endocardial lining of heart
• Smooth surface reduces friction for blood
Basement Membrane • Deep to endothelium • Made of connective tissues • Provides physical support • Collagen fiber provides lots of tensile strength
Internal Elastic Lamina
• Thin sheet of elastic fibers
• Facilitates diffusion through window like openings that make it looks like Swiss cheese
What part of the blood vessels allows diffusion through window like openings?
Internal elastic lamina
What fibers make up the blood vessels?
- Collagen fibers provide tensile strength
* Elastin fibers allow for stretch
Describe the tunica media
- Smooth muscle and connective tissue in circular arrangements
- Thickest layer
- Greatest variation between vessel types
- Regulates diameter of vessel and blood pressure
External Elastic Lamina
• Forms outer part of tunica media
• Only located in some vessels
