Capillaries II Flashcards
List the importance of fluid exchange
- Important for normal physiological function - need H2O for chemical reactions
- Fluid re-absorption from tissues to blood can maintian circulation during haemorrhage
- Abnormalities in fluid exchange can lead to oedema/tissue swelling
How does fluid movement occur at the capillary wall
HYDRAULIC PRESSURE - fluid moves across membrane into interstitial space due to blood flow
Create a osmotic pressure - because large molecules can’t pass through the membrane
ONCOTIC PRESSURE - fluid movement across capillary wall depends on balance between hydraulic and oncotic pressures across the capillary wall
Hydrostatic pressure > oncotic pressure
πp
Plasma proteins
πi
Interstitial proteins
Pi
Interstitial fluid pressure
Pc
Capillary blood pressure
Lymphatic circulation function
Return excess tissue fluid/solutes back to the cardio-vascular system
Structure of lymph vessel and what contributes to lymph flow
Have valves and smooth muscle
Spontaneous contraction of smooth muscle contributes to lymph flow
Surrounding skeletal muscle contractions/relaxation also contribute to lymph flow
Overall control of extracellular fluid balance depends on
Capillary filtration
Capillary reabsorption
Lymphatic system
Starling’s factors determine changes in fluid balance
Circulation
Interstitial fluid
Lymphatic system
Oedema
Excess fluid within interstitial space
Imbalance between filtration, reabsorption, lymph function
Causes of Oedema
Increased capillary pressure
Decreased plasma protein - oncotic pressure
Inflammatory response
Lymphatic problems
Clinical scenarios of increased capillary pressure
Dependent (gravitational) oedema
Deep venous thrombosis
Cardiac failure
Clinical scenarios of decreased plasma osmotic pressure
Low protein oedema:
Malnutrition/malabsorption
Nephrotic syndrome: urinary protein loss - replaced by liver production
Liver disease: not enough endogenous albumin produced
Inflammatory oedema
Large increase in capillary permeability
