Fluid Exchange in Capillaries Flashcards
What is the basic structure of capillaries?
Thin walls made of endothelium and a basement membrane, no smooth muscle, highly permeable.
What is the function of capillaries?
Exchange between blood and interstitial fluid.
What are the smallest blood vessels called?
Capillaries (5-10 μm).
What controls capillary blood flow?
Metarterioles, vasomotion in precapillary sphincters.
Name the three types of capillaries.
- Continuous/Somatic
- Discontinuous/Sinusoidal
- Fenestrated.
What is the permeability of continuous capillaries?
Low (<10nm).
Where are discontinuous/sinusoidal capillaries located?
Liver, spleen, bone marrow.
What is the permeability of discontinuous/sinusoidal capillaries?
Extremely high (<600-3000nm).
What are the three mechanisms for exchange across the capillary wall?
- Diffusion (most important)
- Vesicular transport
- Bulk flow (ultrafiltration & reabsorption).
What regulates fluid volume in capillaries?
Capillary exchange mechanisms.
What is the significance of Starling forces?
They regulate the balance between hydrostatic and osmotic pressures affecting bulk flow.
What is the capillary hydrostatic pressure at the arteriolar end?
37 mmHg.
What is the net exchange pressure formula?
Net exchange pressure = (PC + πIF) - (πP + PIF).
What conditions can lead to oedema?
- Increased venous pressure
- Decreased oncotic pressure
- Increased capillary permeability.
What is pitting oedema?
Skin stays hollow for a few seconds after being pressed.
What is the plasma oncotic pressure due to plasma proteins?
25 mmHg.
What can cause decreased oncotic pressure leading to oedema?
- Protein deficiency
- Tissue damage.
What is a common result of increased capillary pressure?
Net loss of fluid from plasma and expansion of interstitial fluid.
What is the interstitial fluid hydrostatic pressure typically around?
1 mmHg.
Fill in the blank: The capillary hydrostatic pressure at the venular end is ______.
17 mmHg.
True or False: Oedema can be caused by prolonged standing.
True.
What happens during inflammation that affects capillary permeability?
Increased capillary permeability.
What is a life-threatening consequence of oedema?
Limits exchanges of O2, CO2, nutrients, and end products of metabolism.
