CVS Flashcards
What are the five components of the CVS?
- Pump: heart
- Distribution system: vessels and blood
- Exchange mechanism: capillaries
- Flow control: arterioles and pre-capillary sphincters
- Capacitance: veins
Why do we require a cardiovascular system?
- Carries O2 and nutrients to cells and waste products away
- Diffusion takes too long over large distances
How do lipophilic molecules diffuse from the capillaries to the tissues?
Directly through lipid bilayer
How do hydrophilic molecules diffuse from the capillaries to the tissues?
Through small pores in the endothelium
What three factors is the diffusion rate dependent on?
Area
Diffusion resistance
Concentration gradient
What is the capillary density and how does it vary?
Area available for exchange in a given tissue
Highest in metabolically active tissues
What three factors determine the level of diffusion resistance?
Nature of molecule (size, lipophilic, hydrophilic)
Nature of barrier (pore number and size)
Path length (diffusion distance, dependent on capillary density)
What is the concentration gradient dependent on?
Perfusion rate
What is the average cardiac output of a 70kg man at rest?
5.0L/min
Which vessels confer resistance to regulate blood flow?
Arterioles
What is capacitance?
Temporary storage of blood in veins to control flow rate, as their thin walls easily distend/collapse
