Dla: Microcirculation After Lecture 11 Flashcards
Differentiate the following terms:
osmotic pressure
oncotic pressure
hydrostatic pressure
as they pertain to movement across the endothelium of the capillaries.
Osmotic pressure:
-more permeable e.g. inflammation, ischemia,
burns
Oncotic pressure:
-Capillary oncotic pressures keep fluid in capillaries and drive reabsorption
Hydrostatic pressure:
-Capillary pressures drive fluid out of capillaries into interstitial space
Based on the Starling hypothesis, explain how permeability, hydrostatic pressure and oncotic pressure influence transcapillary exchange of fluid
Starlings hypothesis:
Amount of fluid filtering outward from the arterial ends of the capillaries = fluid returned to the circulation by absorption
1) Permeability
2) Hydrostatic pressure
- Makes more fluid leave capillaries
3) Oncotic pressure
- makes more fluid come back into capillaries
Define the Starling equation and discuss how each component influences fluid movement across the capillary wall
- Calculates Net filtration pressure (NFP) and flux
- positive value = filtration
- Negative value = absorption
Calculation:
1) Net Filtration Pressure (NFP)
= ΔHydrostatic pressure –Δoncotic pressure
2) NFP = (Pc-PIF) - sigma(pic-piIF)
3) 𝐽𝑉 = 𝐾 [(𝑃𝑐 − 𝑃𝐼𝐹) − 𝜎(𝜋𝑐 − 𝜋𝐼𝐹)]
JV= (K)(NFP)
Key: Pc= capillary pressure PIF= interstitial fluid pressure PIC= oncotic pressure Sigma= reflection coeff. plasma protein Jv= Flux/net volume of fluid K= hydraulic conductivity and area
Describe the lymphatics, and explain how the structural characteristics allow the reabsorption of large compounds, such as proteins
- Arterial end = filters fluid
- Venous end= reabsorbs fluid
- Lymph= fluid not reabsorbed by capillaries
Path:
Lymphatic capillaries + thoracic duct. –> left subclavian vein
Contrast the structure of lymphatic capillaries and systemic capillaries,
including the significance of the smooth muscle in the walls of the lymphatic vessels
Lymph capillaries:
- Pressure lymph low (Lymph terminal)
- Pressure lymph higher (after valves)
- Terminal lymphatic end
- walls are thinner
- more valves (Prevents backflow of lymph)
Systemic capillaries:
- Arterial end
- Midsection
- Venous end
Identify critical functions of the lymphatic system in fat absorption, interstitial fluid reabsorption, and clearing large proteins from the interstitial spaces
1) fat absorption
- Takes place in GI
2) interstitial fluid reabsorption
3) large proteins from the interstitial spaces
- Uses active pumping activity/high pressures in lymph vessels, increases when interstitial pressures increase
What’s the relationship between interstitial pressure and lymph flow.
Explain why edema does not normally develop as interstitial pressure increases
-Pumping action of open terminal ends of lymphatics draw fluid into lymphatics (Lymph P >Pif). Pumping increases when more fluid in Pif
- Edema wouldn’t develop because increase interstitial pressure acts by
1) Increasing lymph flow
2) reducing the vascular transmural pressure gradient and physically compresses capillaries, thereby reducing nutritive tissue perfusion
Explain how edema develops in response to:
a) venous obstruction
b) lymphatic obstruction
c) increased capillary permeability
d) heart failure
e) tissue injury or allergic reaction
f) malnutrition
a) venous obstruction
- heart failure or increase BP
b) lymphatic obstruction
- Local edema before block nodes
c) increased capillary
- more permeability = ischemia, inflammation, burns
d) heart failure
- Pressure in atria backing up
- -> Increase pressure in veins/capillaries –> increase hydrostatic pressure –> increase filtration and edema
- Right heart –> tissue edema
- Left heart –> lung issues
e) tissue injury or allergic reaction
- They didn’t cover
f) malnutrition
- They didn’t cover
Describe Edema and its locations
- Problem w filtration/reabsorption/lymph
- fluid accumulation
- Increase hydrostatic pressure
- Decrease oncotic pressure
Locations:
1) Subcutaneous tissue: → peripheral edema
2) Lungs: → pulmonary edema
3) Abdominal cavity: → ascites
Hypoalbuminemia
Edema: when interstitial fluid volume accumulation > lymph clearance
Cause:
•Decreased albumin production: cirrhosis (chronic alcoholism increases risk), hepatitis
•Increased albumin clearance: kidneys. Albumin in urine- marker for kidney disease.
•Pregnancy
Effects:
•Reduced oncotic pressure in capillaries
•Less fluid reabsorbed into capillaries
•More fluid in interstitial fluid (Edema)
How does hydrostatic and oncotic pressure cause edema?
1) Hydrostatic pressure:
- Capillary pressures drive fluid out of capillaries into interstitial space
- pulmonary edema: slight increases in hydrostatic pressures in lung
capillaries.
-peripheral edema: Inc in systemic capillary pressures result in inc
filtration in lower extremities and intestine.
2) Oncotic pressure: Capillary oncotic pressures keep fluid in
capillaries and drive reabsorption.
-Edema →reduction of plasma proteins: (protein lost in urine,
pregnancy, malnutrition, or reduced albumin production by liver).
Describe how changes in capillary surface area affect the capacity for fluid exchange.
An objective that they didn’t cover
Predict how altering pressure or resistance in pre- and post-capillary regions alters capillary pressure and the consequence of this change on transmural fluid movement
An objective that they didn’t cover
Define filtration and reabsorption
Filtration:
-Going out of blood vessels
Reabsorption: Going into blood vessels
What does right ventricle failure and left ventricular failure cause?
-Edema
right ventricle failure = ankle swelling
left ventricle failure = fluid in the lungs
