AWABS - Capillary Dynamics and Interstitial Fluid Flashcards
Role of arteries
Transport oxygenated blood
Role of arterioles
Adjust diameter to regulate blood flow
Highly muscular
Thickness variations of arteries / arterioles vs capillaries vs venous system
Types of capillary
Continuous (most common)
Fenestrated
Sinusoid
Fenestrated capillaries
Have small gaps to allow exchange
Found in endocrine glands and intestines
Sinusoid capillaries
Large gaps
Found in Bone marrow, liver and spleen
Forces acting at capillary
Hydrostatic capillary pressure
Colloid osmotic pressure
(Balanced against interstitial fluid pressure and interstitial fluid colloid osmotic pressure)
Pressures at arterial end of capillary
Capillary pressure 35 (out)
Interstitial fluid pressure -2
Plasma colloid osmotic pressure 27 (in)
Interstitial fluid colloid osmotic pressure 7
Net pressures act to draw out of capillaries
Pressures at venous end of capillary
Capillary pressure 15 (out)
Interstitial fluid pressure -2
Plasma colloid osmotic pressure 27 (in)
Interstitial fluid colloid osmotic pressure 7
Net pressures act to draw into capillaries
Lymphatic ducts
Lymphatic drainage system movement of fluid
Poorly understood
Possible muscle contraction, possible mild peristalsis action
Definition of a mole
Amount of a substance that contains number of molecules equal to Avogadro’s number (6.022 x10^23)
How much does one mole weigh
Molecular weights added together
Eg NaCL = molecular weight of Sodium ion + Molecular weight of Chloride ion
Osmole definition
Number of moles of osmotically acting particles in a solution
Osmolality (mmol/L)
Number of particles (osmoles / mmol) contained in 1 litre of water / solvent
Tonicity definition
The effective osmolality
Equal to the sum of concentrations of solutes which have the capacity to exert an osmotic force across a membrane
Tonicity vs Osmolality
Tonicity puts osmolality in context of a relevant membrane
Examples of isotonic fluids
Normal saline
Hartmann’s
Example of hypotonic fluid
0.45% NaCl
Types of transport across cell membrane
Passive transport
Active transport
Active transport
Requires energy
Converts ATP to ADP
Works against concentration gradients
Passive transport
Diffusion - Includes facilitated diffusion through aqueous channel or carrier protein
Works along concentration gradient
Bulk transport
Endocytosis vs phagocytosis
Endocytosis is receptor mediated using receptors on cell membrane
Approximate CSF volume
~150ml
Approximate volume of CSF production per day
~450ml per day
Site of CSF production
4 choroid plexuses in lateral, 3rd and 4th ventricles
Normal CSF opening pressures
10-15 cmH2O lying down
20-30 cmH2O sitting up
Flow of CSF
Pleural fluid, pericardial fluid and peritoneal fluid constituents
Ultrafiltrate of plasma
Pleural fluid volume
1-10 ml
Pericardial fluid volume
10-50 ml
Peritoneal fluid volume
Usually <100 ml
Pleural fluid charactersitics
Straw coloured
pH ~7.6
