Lecture 10: Fluid Distribution, Homeostasis Flashcards
True or False: Apoptosis is typically associated with inflammation
- True
- False
True or False: Apoptosis is typically associated with inflammation
- True
- False
When does edema happen?
- Decreased plasma oncotic pressure
- Increased hydrostatic pressure on far side of the capillary
- Lymphatic obstruction
- Increased vascular permeability (“inflammation edema”)
In the event of decreased oncotic pressure, how does edema form?
If the animal is in a hypoproteinemic state (Generalized process, the entire body is subject to this)
The same amount of fluid exits on the arteriole side, but it is not taken back up on the venule side of the capillary. Because there’s not as much oncotic pressure there. Decrease in albumin, and the oncotic pressure is lost.
Some of that fluid will be taken up by lymphatics, but there’s only so much fluid that the lymphatics can handle. The rest will remain in the interstitium as edema.
In the event of increased hydrostatic pressure, how does edema form?
Increase in hydrostatic pressure, esp if there’s an increase in pressure on the venous side due to heart failure. If the right heart isn’t adequately doing its job, that will put back pressure on every vein and venule systemically, leading to edema.
Or maybe there’s a local obstruction. Maybe local trauma, crushing injury. Again, fluid won’t be taken up as readily. Will result in edema
In the event of lymphatic obstruction, how does edema form?
Local lymphatic obstruction? Maybe a tumor that’s compressing the exterior of the lymphatic vessel, or you may have an embolus within the lymphatic itself.
If that’s the cause, that extra fluid has nowhere to go. Can’t go into the lymphatics. There’s only so much that will be taken up by the post capillary venule, and the rest will end up as edema.
Lymph vessels are weak, thin, doesn’t take much to compress them. So if lymphatics are obstructed, fluids won’t dissipate the way they should.
In the event of increased vascular permeability, how does edema form?
In the case of Inflammation, you have multiple factors working to get fluid out, and not many working to bring fluid back in.
What’s the advantage of having all this fluid come out in the presences of inflammation? Dilution. Trying to flood the area, trying to get whatever toxin, whatever foreign material… First line of defense is to dilute the material so it doesn’t have as strong of an effect. That works for a number of things, but doesn’t work forever
Endo cells may be contracting to allow more fluid to exit the vascular space. Also losing protein in this process. Many inflammatory mediators and acute phase proteins that will exit the vascular space to do their function in the interstitium. That’s going to cause a local reduction in oncotic pressure on the post-capillary venule. Will pull less fluid back in. Which is, for the most part, on purpose. That’s the desired thing at that time and in that moment.
So while some fluid will be taken up by lymphatics, you’re leaving fluid in that area initially for a good purpose. If that goes on for too long, that in itself can become dangerous
What is edema, and what are some characteristics of it?
Edema is an accumulation of fluid in extravascular space.
Edema is a transudate, low in protein and cell concentration
Edema is watery, typically clear, and has a low specific gravity of <1.012
What is the pathogenesis of the edema in this guinea pig?
Glomerular amyloidosis results in a loss of protein in the urine, or proteinuria. This leads to a systemic results of hypoproteinemia, which leads to a decrease in oncotic pressure. There’s a decreased pull of fluid back into the venule side of the capillary, creating a net increase of interstitial fluid. That fluid then behaves on the rate of diffusion, it’s not under any pressure anymore. The fluid will equalize over spaces, and over membranes. The end result is edema, ascites, and hydropericardium.
In this process, there’s no bacteria. Not an inflammatory process at all, simply the dysregulation of fluid reentering the vascular spaces, because of hypoproteinemia. If this was due to an inflammatory process, the fluid wouldn’t be clear.
How do you recognize edema?
Grossly: Swollen, pitted, spongy, pale, cool to the touch, with or without pain.
Microscopically: Expansion of intercellular spaces, pale eosinophilic fluid
What does edema look like in solid tissue?
This is an equine colon. Note the very severe thickening of gut layer.
What are we looking at here?
What’s the red circle? What’s the arrow pointing to?
Another example of edema, this is pulmonary edema in a rat.
Air should move in and out of alveolar spaces easily. In severe pulmonary edema, air can’t move in and out well. Air will move through, but nowhere near at the rate that it should. The red circle is an alveolar space.
This is potentially fatal. If it’s rapid enough, the animal may not be able to survive. Fires, toxic gases can have an immediate effect of pulmonary edema.
If all surfaces are layered with fluid, then gas exchange will not take place and the animal will not survive.
What’s the significance of edema?
Edema can be fatal: Too much fluid in the lungs or brain? Bad news.
Edema can be an indication of underlying disease:
- Could be pointing out protein loss, maybe from the kidney or gi tract
- Could also indicate a lack of production by the liver (hepatic failure, hepatic insufficiency)
Edema may be reversible if the primary cause is eliminated.
Hypoproteinemia promotes edema due to:
- Decreased oncotic pressure
- Increased ontotic pressure
- Decreased hydrostatic pressure
- Increased hydrostatic pressure
Hypoproteinemia promotes edema due to:
- Decreased oncotic pressure
- Increased ontotic pressure
- Decreased hydrostatic pressure
- Increased hydrostatic pressure
Increased oncotic pressure is more of a dehydration situation
Increased hydrostatic pressure is the increased pressure probably coming from right heart failure
Glomerular amyloid is to proteinuria as hypoproteinemia is to:
- Hyaline
- Hypertension
- Edema
- albumin
Glomerular amyloid is to proteinuria as hypoproteinemia is to:
- Hyaline
- Hypertension
- Edema
- albumin
What’s dehydration?
What are the consequences of dehydration?
At what point could dehydration be fatal?
Dehydration is the inadequate amount of body water.
Consequences:
- Decreased cardiac output
- Decreased blood volume
- Decreased tissue perfusion
- Decreased renal function
10-12% dehydration can be fatal
Hyperemia vs active hyperemia vs passive hyperemia?
Hyperemia: increased amount of blood in tissues within vessels.
Active hyperemia: increased arterial blood in capillary beds
Passive hyperemia: decreased venous blood flow out of capillary bed
