Test 4 Study Guide Part 2 Flashcards
What is the predominant force which moves water out of the capillaries?
Which part of the capillary is where this occurs?
Blood pressure (hydrostatic pressure) Closer to the arteries, before blood pressure falls later (from fluid loss)
What is the predominant force driving the return of blood into the capillaries?
Where?
Osmotic pressure
At the venous end of the capillaries
Why does osmotic pressure eventually overcome hydrostatic pressure?
Osmotic pressure stays constant, but hydrostatic pressure drops as water flows outward (and as the lower resistance of the venous system is reached)
What level is hydrostatic pressure in the beginning of the capillary? The end?
Osmotic pressure?
37 mmHg -> 17 mmHg (fall in hydrostatic pressure) 25 mmHg (osmotic pressure is constant)
Net filtration pressure:
- Define terms in the equation
- Equation:
- Define terms in the equation Capillary hydrostatic pressure (CHP): blood pressure in capillary Interstitial fluid hydrostatic pressure (IFHP): blood pressure in interstitial fluid (normally much lower than CHP - Equation: Note: Positive = fluid out capillary Negative = fluid into of capillary BHP - IFHP
What keeps interstitial fluid pressure low?
- Hydrostatic:
- Osmotic:
- Hydrostatic:
Drained by lymphatic - Osmotic:
Low protein levels in interstitial fluid
Colloid:
- ability to stay in solution:
- ability to stay in solution:
Colloids do not settle out of a solution
Colloidal osmotic pressure define:
Osmotic Pressure resulting from molecules which never settle out of solution, and which cannot cross the capillaries (most proteins cannot cross readily)
What is the predominant contributor to colloidal osmotic pressure?
Albumin
Oncotic pressure:
Colloid osmotic pressure of the plasma (blood Colloid osmotic pressure) - interstitial fluid colloid osmotic pressure.
What size of molecules freely exit the capillaries?
Molecules around the size of glucose and ions (Na+)
What causes the lower interstitial conc. of proteins in capillaries?
Restricted filtration of proteins through capillaries
Starling forces:
- Define:
- List them:
- Define: Forces which dictate flow of water and molecules into or out of the capillaries - List them: Oncotic pressure Net Filtration Pressure
How could the capillaries be adapted to increase flow of fluid OUT of the capillaries?
If the precapillary sphincters are open blood flow to the capillaries will be great, and net filtration force will far exceed oncotic pressure
How could the capillaries be adapted to increase flow of fluid INTO of the capillaries?
If the precapillary sphincters are partially closed (they are ‘never’ completely closed) blood flow to the capillaries will be small, and oncotic pressure will far exceed net filtration pressure
Of the fluid that leaves the capillaries, how much returns?
What happens to the remaining fluid?
85% returns.
the other 15% flows through the lymphatic system into the subclavian veins
What is the single most reliable indicator of kidney disease?
Why?
Protein in the urine
Because the kidney is normally impermeable to plasma proteins, so protein in urine indicates damage
Edema:
- Causes:
High arterial blood pressure Venous obstruction Leakage of plasma protein into interstitial fluid Decreased plasma protein concentration Obstruction of lymphatic drainage
Why does high arterial blood pressure cause edema?
Increases net filtration pressure
Why does venous blockage cause edema?
- Example:
Increases net filtration pressure
- Example:
Compression of veins in pregnancy