6. Fluid Exchange in Capillaries Flashcards
Describe the basic structure of capillaries
Smallest blood vessels Thin walls Endothelium and basement membrane No smooth muscle Highly permeable Numerous- Large surface area
Describe the basic function of capillaries
Exchange between blood & interstitial fluid
What are the different types of capillary?
Continuous
Fenestrated
Discontinuous
What controls capillary blood flow?
Vasomotion in Precapillary sphincters & and metarterioles
Where are continuous capillaries located?
Muscle, skin, lung. CNS
Where are Fenestrated capillaries located?
Exocrine and endocrine gland, enal glomeruli, inestinal mucosa
Where is the discontinuous capillaries located?
Liver, spleen, bone marrow
What is the order of permeability of capillaries starting with most permeable?
Discontinuous
Fenestrad
Continuous
What are the three ways that substances can enter and leave capillaries?
Diffusion
Vesicular transport - these two to regulate fluid composition
Bulk Flow- regulates fluid volume
Why are capillaries suited to enhanced diffusion?
One cell thick
Intercellular pores to increase permeability
Huge number of capillaries to increase surface area
Velocity id slowest in capillaries
Close proximity to all cells
What is the force that describes the balance between hydrostatic and osmotic pressure?
Starlings forces
What is the significance of blood flow in normal conditions
Loss from plasma almost equals gain from plasma
What is the significance of bulk flow when there is increased capillary pressure?
Net loss of fluid from plasma & expansion of intersitial fluid in tissue
What is an odema?
Excessive fluid accumulation in interstitium due to alteration in balance of starling forces
What is the result of increased venous pressure or decreased oncotic pressure?
Oedema
