Microcirculation, venous blood flow and venous return Flashcards
What does the intersitium consist of?
Collagen and proteoglycan filaments
What are crystalloids?
Low molecular water solutes
What are colliods?
Plasma proteins
What is the permeability of albumin through the capillary wall in comparison to water?
1/1000th
What is the oncotic pressure generated by plasma proteins?
~ 28 mmHg
What is the interstitial oncotic pressure?
~ 5 - 8 mmHg
What is the capillary hydrostatic pressure at the arterial end?
~ 30 - 40 mmHg
What is the capillary hydrostatic pressure at the venous end?
10 - 15 mmHg
How much water do capillaries lose?
2-3 L per day
What is the lymphatic system important for controlling?
- The concentration of proteins in interstitial fluid
- Volume of interstitial fluid
- Interstitial fluid pressure
- Immune response
What is the blood pressure in the venous system?
3 - 18 mmHg
What percentage of blood is contained in the venous system?
~ 60%
How is venous return increased?
- Sympathetic innervation
- Skeletal muscle pumps
- Inspiratory movements
- Blood volume
What is orthostatic (postural) hypotension?
- When moving from supine to upright
- Around 500 ml of blood drains from the upper body to the legs
- Decreased venous return and therefore decreased Cardiac Output and decreased blood pressure.
What are the most common types of capillaries in the body?
Continous
What capillaries contain pores which allow small lipophobic molecules to pass through?
Fenestrated capillaries
What capillaries are you more likely to find in skeletal muscle?
Fenestrated capillaries
What capillaries are more likely to be found in the liver?
Sinusoidal or discontinous capillaries
What are the features of sinusoidal or discontinous capillaries?
Large gaps between endothelial cells
What plasma proteins generate oncotic pressure?
Mostly albumin, to a lesser extent globulins
