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
