Blood II Flashcards
There are […] major forms of fluid transport across the capillary wall: […]
2, filtration and osmotic flow
What is bulk flow?
Bulk flow is the flow of molecules subjected to a pressure difference. It is directly proportional to hydrostatic pressure difference.
How does bulk flow relate to filtration in the capillaries?
Filtration is bulk flow across a porous membrane (the capillary wall), where large particles will be withheld.
Filtration tends to […] fluid in the capillaries because […], while osmotic flow tends to […] fluid in the capillaries because […]
Push out, hydrostatic pressure difference, pull in, of the osmotic pressure exerted by plasma proteins
The two […] forces in the capillaries, […] and […], come together to form the […]
Opposing, filtration and osmotic flow, starling forces
Explain how blood pressure changes as it travels through the circulatory system.
When the heart contracts, it generates a pressure of around 120 mm Hg. When it relaxes, the pressures comes down to 80 mm Hg. When the blood reaches the capillaries at the arterial end, the pressure drops to 35 mm Hg because the surface area is greater and there is energy loss. When the blood leaves the capillaries at the venous end, the pressure has dropped further to 15 mm Hg.
Exchanges between the plasma and the ISF take place in the […]
Capillary bed
Why do exchanges between the plasma and the ISF only take place where they do?
They only take place in the capillary bed because the capillaries have thin enough walls for exchanges. Everywhere else, the walls are too thick.
The blood pressure in the capillaries at the arterial side is […], while at the venous side it is […]
35 mm Hg, 15 mm Hg
The COP is equal to […]
25 m Hg
Describe the major forces involved in transcapillary dynamics and where net absorption and net filtration are observed in the capillary bed.
At the arterial end, filtration exerts a pressure 35 mm Hg and COP exerts an opposing pressure of 25 mm Hg, creating a net filtration of 10 mm Hg. At the venous end, filtration exerts a pressure fo 15 mm Hg and COP exerts an opposing pressure of 25 mm Hg, creating a net absorption of 10 mm Hg.
Name the 4 substances that exchange through the capillary wall (aside from fluid) and the mode of transport.
Nutrients, O2, CO2, and waste are exchanged via simple diffusion.
Starling’s capillary dynamics determine the […] of the […] volume
Distribution, ECF
Filtration/absorption takes place […]
Along the whole length of the capillary
Describe how filtration/absorption varies across the length of the capillary.
Arterial end: high rate of fluid moving out of the cell, as we move towards the center net filtration decreases, at the middle it’s bidirectional, moving towards the venous end the net absorption increases, at venous end there’s a lot more absorption.
[…]% of the fluid that leaves the capillary is reabsorbed. The other [..]% goes into the […]
90%, 10%. lymphatic system
The walls of the lymphatic vessels are made up of […] and are permeable to […]
A single layer of endothelial cells, all ISF constituents including proteins that may have leaked from the plasma
Explain how the flow of blood remains in balance (include numbers) - draw a diagram to illustrate
Of the 6000 L of blood flow per day, 20 L get filtered through the capillary wall into the interstitial fluid. 17 L get reabsorbed into the capillary and 3 get picked up by the lymphatic system and are returned to the capillary by lymph drainage. [See slide for diagram]
Each protein fraction exerts an osmotic pressure, which depends on […]
Its concentration (higher concentration = higher COP), its molecular weight (smaller MW = higher COP)
Explain the relationship between plasma protein COP and molecular weight.
It is an inverse relationship. Albumin is the lightest protein but is high in concentration, and is responsible for 20 mm Hg out of 25 total in the plasma. Fibrinogen is the heaviest protein but is low in concentration, and is responsible for <1 mm Hg out of 25. Globulins fall in the middle and exert 5 mm Hg out of 25.
Albumin exerts […] mm Hg COP in the plasma out of […]
20 out of 25
Globulins exert […] mm Hg COP in the plasma out of […]
5 out of 25
Fibrinogens exert […] mm Hg COP in the plasma out of […]
<1 out of 25
The main protein that causes the COP to rise is […]
Albumin
The key function of albumin is to […]
Control fluid shifts across the capillary wall
Name the 4 major factors involved in determining transcapillary dynamics
Hydrostatic pressure, COP, capillary permeability (can vary under certain conditions), and lymphatic drainage
What is edema?
The accumulation of excess fluid in interstitial spaces
When someone has edema, the proportion of […] increases, while the proportion of […] decreases
ISF, plasma
Name the four possible conditions that can lead to edema.
- Increased hydrostatic pressure
- Decrease in plasma proteins (decreased COP_
- Increased capillary permeability
- Obstruction of lymphatic drainage
Explain how hydrostatic pressure affects edema.
If hydrostatic pressure increases enough, it may overwhelm the COP and prevent any net absorption from occurring, even at the venous end - instead you could get no net absorption or just net filtration.
Explain how plasma proteins affect edema.
If the prevalent of plasma proteins decreases such that COP decreases, it may overwhelm the hydrostatic pressure and prevent any net absorption
Name two possible causes of decreased COP.
Failure to synthesize plasma proteins (e.g. due to liver disease) or severe protein malnutrition (lack of amino acids)
Explain how capillary permeability affects edema.
If the capillary wall becomes more permeable, some of the plasma proteins escape into the ISF where they exert an oncotic effect. So this works against the COP and encourages outflow of fluid from the capillaries into the ISF.
Explain how lymphatic drainage affects edema.
If the 10% of ISF cannot be absorbed and brought back into the capillaries, the remaining fluid just remains in the interstitial space.
Obstructed lymphatic drainage can lead to a condition known as […]
Elephantiasis
The cause of elephantiasis is [..]
A parasite (Filaria nematode) that blocks lymphatic drainage.
Name the 3 roles of plasma proteins.
- Controlling transcapillary dynamics
- Contribution to the viscosity of plasma, maintaining blood pressure
- Contribution to the buffering power of plasma to maintain it at its normal pH of 7.4
Name the specific function(s) of fibrinogen
Clotting
Name the specific function(s) of globulins
Clotting, Y globulins provide resistance to infection, some act as carriers for lipids, minerals, and hormones
Name the specific function(s) of albumin
Act as carriers for lipids, minerals, and hormones
The production of platelets is called […]
Thrombopoiesis
The production of white blood cells is called […]
Leukopoiesis
