Pressure and Flow in Arteries and Veins Flashcards
How can you measure mean arterial pressure
Auscultation of Korotkoff sounds using sphygmomanometer
What are the disadvantage and advantages of using sphygmomanometer
- Not accurate, discontinuous and needs care
2. Cheap and non-invasive
Tapping sound
Systolic
Muffled sound
Diastolic
Pressure flow in arteries
Elastic arteries act as a pressure reservoir and absorb some of the pressure
Pressure wave is affected by (4)
SV
Velocity of ejection
Elasticity of arteries
TPR
What is normal arterial pressure
120/80 mmHg
What pressure increases with age
Arterial
Reduction in elasticity does what to the systole and diastole pressure
Increases systole and decreases diastole
What is systemic filling pressure
Blood from the venules and veins filling the right atrium (deoxygenated)
Arteries and Arteriole pressure chnage
Small drop 95 to 90 mmHg
Arteriole and Capillaries pressure change
Large drop 90 to 40 mmHg
RESISTANCE VESSELS
Capillaries to veins
Small pressure change 40 to 20mmHg
Pulmonary circulation pressure is ___ of systemic
1/5th
What external influences affect flow in veins (5)
Gravity Skeletal muscle pump Respiratory pump Venomotor tone Systemic filling pressure
How does gravity affect the blood flow in veins
Standing upright adds more pressure Reduces EDV Reduces preload Reduces SV- reduces CO Reduces MAP
What is Orthostatic hypotension
When a person’s blood pressure falls when suddenly standing upright
What can the height of jugular collapse be used to estimate
CVP (measurement of pressure inside the vena cava)
What is jugular vein distention
Increased CVP
How does skeletal muscle pump effect the blood flow in the vein
Rhythmic skeletal muscle contractions force blood in the extremities toward the heart
What causes varicose veins
Valves of veins fall and allow backflow of blood
How does the respiratory pump affect blood flow in veins
When you inhale this creates negative pressure as the diaphragm lowers
Blood is directed to the heart:
Increases EDV, preload and SV
How does the venomotor tone effect the blood flow in veins
Increased contractile activity results in rise in tension referred ad venomotor tone
The smooth muscle in the wall of the veins contains what receptor
alpha adrenergic (sympathetic)
How does the systemic filling pressure affect the blood flow through the vein
Pressure created by ventricles and transmitted through vascular tree to veins
What is the anti-clotting mechanism of the endothelium (2)
- Formation of platelet plug
2. Formation of fibrin clot
What converts fibrinogen to fibrin
Thrombin
What is the purpose of the endothelium
Stops blood contacting collagen
What does the endothelium produce and what are the functions (2)
Prostacyclin and NO- inhibit platelet aggregation Tissue Factor Pathway Inhibitor thrombomodulin Heparin plasminogen activator (t-PA)
What is the function of Tissue Factor Pathway Inhibitor
Stops thrombin production
Function of thrombomodulin
Binds to thrombin and inactivates it
Purpose of Heparin
Inactivates thrombin
Purpose of plasminogen activator (t-PA)
Digests plasminogen to plasmin and digests clot
