Heart Physiology 2 Flashcards
What are the functions of the circulatory system? 1) 2) 3) 4) 5)
1) Distribution of dissolved gasses
2) Waste removal
3) Chemical signalling
4) Mediate inflammatory, immune responses
5) Conserve or release heat from skin surface
What is a portal system?
Two capillary beds in series
EG: In kidneys, stomach, liver
Which blood vessels have elastic tissue?
Arteries, veins
Which blood vessels have smooth muscle?
Arteries, arterioles, veins
Where is the highest and lowest mean systemic blood pressure?
Aorta (highest) Vena cavae (lowest)
Where is blood flow slowest?
Capillaries
What is the Windkessel effect?
Reduction in arterial pressure changes during systole and diastole (heartbeat)
Caused by elastin in walls of arteries, walls distend in systole, recoil in diastole
Where is the Windkessel effect relevant?
In arteries
How to proteins move across the membranes of capillaries?
Transcytosis
Which tissues make up the walls of arteries?
Endothelium
Elastic tissue
Smooth muscle
Fibrous tissue
Which tissues make up the walls of veins?
Endothelium
Elastic tissue
Smooth muscle
Fibrous tissue
Which tissues make up the walls of arterioles?
Endothelium
Smooth muscle
Which tissues make up the walls of capillaries?
Endothelium
Which tissues make up the walls of venules?
Endothelium
Fibrous tissue
Mean arterial diameter
4mm
Mean venous diameter
5mm
Mean arterial wall thickness
1mm
Mean venous wall thickness
0.5mm
Proportion of blood stored in systemic veins
64%
Proportion of blood stored in arteries
13%
How far are most cells from a capillary?
0.1mm
What is bulk flow?
Overall movement of fluid between blood and tissues
Difference between hydrostatic pressure and colloid osmotic pressure
What is absorption?
Movement of fluid from interstitium into capillaries
What is filtration?
Fluid movement out of capillaries into interstitium
What is oedema?
Interstitial fluid accumulation
Difference in solute concentrations between blood and interstitial fluid
Electrolyte balance the same
Proteins in blood, too large to get into interstitial fluid
What are the pressures influencing bulk flow?
Osmotic pressure (pi) - Movement into capillary
Hydrostatic pressure (P) - Movement out of capillary
What is colloid (or oncotic) osmotic pressure?
Osmotic pressure caused by proteins in the blood that can’t penetrate the endothelium of capillaries
What is the plasma oncotic pressure vs the interstitial fluid oncotic pressure?
25mmHg (plasma)
0mmHg (interstitial)
What is hydrostatic pressure?
The pressure exerted by the blood on the blood vessel walls.
Decreases with length
What is hydrostatic pressure in capillaries at the arteriolar end?
32mmHg
What is the hydrostatic pressure in capillaries at the venous end?
15mmHg
What is the hydrostatic pressure in the interstitial fluid?
0mmHg
What is the bulk flow at the arterial end of a capillary?
~7mmHg
What is the bulk flow at the venous end of a capillary?
~-10mmHg
Which pressure favours filtration?
Hydrostatic pressure
Which pressure favours absorption?
Colloid osmotic pressure
Is colloid osmotic pressure constant, or does it change with capillary length?
Constant
Is hydrostatic pressure constant, or does it change with capillary length?
Decreases with capillary length
What is the net fluid movement of fluid per day?
3L out of capillaries per day
Where does the excess fluid filtrated into the interstitial fluid go?
Into the lymphatic system
Where do the largest lymph vessels empty?
Into the venous system
Where the left/right subclavian veins join internal jugular veins
What plays a large role in pumping lymph?
Skeletal muscle pump
Roles of lymphatic system
1)
2)
3)
1) Return fluid and proteins filtered back into circulation
2) Pick up fat absorbed in small intestine, transfer to circulatory system
3) Immune system
What factors pump lymph?
1)
2)
3)
1) Smooth muscle contractions in larger lymph nodes
2) Skeletal muscle contraction
3) One-way valves
