Pressure and flow in arteries and veins Flashcards
Systolic pressure
- Normal
Pressure of blood in arteries when the heart pumps
- 120 mmHg
Diastolic pressure
- Normal
Pressure of blood in arteries when the heart is at rest
- 80 mmHg
Pulse pressure
- Normal
Difference between systolic and diastolic pressure
- 30-50 mmHg
- Strong indicator of heart problems
Korotkoff sounds
Sounds heard with a stethoscope as a BP cuff is gradually deflated.
- Silence
- Tapping and thumping
- Muffled = diastolic
- Silence
Arterial pulse tracing
- Anacrotic limb: ascending
- Catacrotic limb: descending
- Dicrotic notch (secondary upstroke in descending portion): aortic valve closure
Pressure in arteries
95-90 mmHg
Pressure in arterioles
90-40 mmHg
Pressure in veins
20-5 mmHg
Pulmonary circulation pressure
1/5th of systemic
Blood velocity
Inversely proportional to the cross-sectional area of the blood vessels
- Fastest in aorta and vena cava
- Slowest in capillaries
Factors affecting pressure and flow in veins (5)
- Gravity
- Skeletal muscle pump
- Respiratory pump
- Venomotor pump
- Systemic filling pressure
Gravity (pressure and flow in veins)
Lying down
- 10mmHg on head and legs
- no effect on driving pressure
- venous distension in legs (decreased EDV)
Standing up
- -30 mmHg on head and +90 mmHg in legs
- blood in chest flows down to feet and accumulates
Skeletal muscle pump
- collection of skeletal muscles that aid circulation by increasing VR
- rhythmic vs static
Respiratory muscle pump
Inhalation: -ve chest pressure and +ve subdiaphragmatic pressure pulls blood back to heart
- increased RR during exercise
Venomotor pump
State of contraction of smooth muscle surrounding venules and veins mobilises capacitance
Systemic filling pressure
Pressure created by ventricles that is transmitted through vascular tree
