Microcirculation

Question 1

capillary exchange

Answer 1

• Capillary exchange – wash out tissues, clean out waste, deliver oxygen
• Local control of blood flow
• The further you go away from the heart, the less of a difference between pressure at systole and diastole
• When the tissue or organ demands it, the capillary dilates and invites more blood into that system
• So far removed from the arteries, there’s not really a pulse, it’s just flow and not flow
• Precapillary sphincters dictate flow into the capillary and the extent to which the capillary bed is perfused at any given time

Question 2

number of capillaries and SA

Answer 2

10B caps with 500-700m2 surface area

Question 3

vasomotion

Answer 3

o Vasomotion = the capillary sphincters and the metarteriole are the only things left controlling flow into the vessel
o Elements of the tissue and its metabolic need results in dilation of vessels and opening of sphincters and increased blood flow
o Vasomotion yields intermittent flow
o Vasomotion regulation – tissue oxygenation
o Diffusion through capillaries product of thermal motion

Question 4

interstitial fluid

Answer 4

o Solid components of interstitium
o Looks like plasma absent proteins and RBCs
o Fluid like plasma with no proteins
 Proteins are big and negatively charged so they are repelled by basement membrane of the capillary
o Only 1% free fluid
o Proteins and plasma and ICF determine volume
o Collagen fibers, hyaluronic acid, glycosaminoglycans, etc. in the interstitium – these are the solid things in the interstitium
o What we call the interstitial fluid is actually a sort of semisolid fluid

Question 5

donnan equilibrium effect

Answer 5

 “Donnan equilibrium effect” – most proteins are negatively charged – they attract a halo of calcium ions
• You don’t see as much movement of calcium as you would expect from calcium alone and this is because they are attracted to the proteins

Question 6

why is the interstitial hydrostatic pressure so low

Answer 6

lymphatics drain the fluid back into the circulatory system

Question 7

lymph pathway

Answer 7

• Accessory flow route – these are one-way vessels with valves – they use the muscular forces to move fluid continuously back to the heart
• Lymphatic pump – compression with muscles against organs that allows us to pump things back to the heart
• We put nodes where orifices where pathogens can enter – this helps prevent pathogens from becoming disseminated into the circulatory system