Sherwood 6th Ed.

Blood Vessels
Heart →Arteries → Arterioles → Capillaries → Venules → Veins
Arteries – relatively large, branching vessels that conduct blood away from
the heart. Major artery is aorta
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Arterioles – small branching vessels with high resistance
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Capillaries – site of exchange between blood and tissues
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Venules – small converging vessels - drain blood to veins
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Veins – relatively large converging vessels that conduct blood to the heart.
Major vein is vena cava (superior and inferior)
Closed system
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Vessel Composition
Vessel Composition
Berne & Levy 3rd Ed., fig 22.1
Circulatory Pressures
Boron & Boulpaep, fig 18.3
Circulatory Blood Volume
Sherwood 6th Ed., fig 10.27
Continuity of Blood Flow
Sherwood 6th Ed., fig’s 10.6 & 10.32
Arterial Pulse Wave
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Systolic P: on ventricular contraction
Diastolic P: on ventricular relaxation
Dicrotic notch: Rebound wave or “echo” of valve closure
Sherwood 6th Ed., fig 10.7
Continuity of Blood Flow
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Major Arteries (aorta)
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Pressure reservoirs
 Provides continuity of flow
Receives high pressure
Veins
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Enormous compliance, little elastic recoil
 Capacitance vessels to store blood
Relies on pressure gradient to maintain flow
Assisted in upright posture by:
 Valves
 Skeletal muscle pump
Arterioles
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Resistance vessels
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High degree of smooth muscle
Large sympathetic input
Extensive branching
Highly sensitive control over
RESISTANCE
Pre-Capillary Sphincters
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Local metabolic control
Can seal vessel completely
Provides effective resistance over
WHOLE CAPILLARY BED
Sherwood 6th Ed., fig 10.19
Capillaries
Sherwood 6th Ed., fig 10.18
Lymph Vessels
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Blind ending capillaries
Single layer endothelium
Large vessels empty into
subclavian vein
Valves prevent backflow
Regular lymph nodes
Major functions
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Tissue drainage
Return leaked plasma proteins
Absorption of digested fat
Defence
Sherwood 6th Ed., fig 10.24
Starling Forces
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PC
PIF
πp
πIF
– capillary hydrostatic pressure
– interstitial fluid hydrostatic pressure
– plasma colloid osmotic pressure (oncotic pressure)
– interstitial fluid colloid osmotic pressure (oncotic pressure)
Sherwood 6th Ed., fig 10.22
Oedema
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Build up of fluid in the interstium, via
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Reduced [plasma proteins]
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Increased capillary permeability
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Inflammation & allergic responses
Increased venous pressure
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Loss in urine (kidney disease)
Reduced synthesis (liver disease)
Dietary
Uterine venous compression during pregnancy
Aeroplane flight (via decompression & immobility i.e. ↓Muscle pump
activity
Lymph blockage
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Damage during surgery