1. PHED 1 Applied Physiology Blood Vessels and the Vascular Shunt
AS PE
PHED 1
Applied Physiology
Blood Vessels and the Vascular Shunt

2. Control of Blood Supply
BLOOD VESSELS
ARTERIES ARTERIOLES CAPILLARIES VENULES VEINS 3 layers 3 layers 1 layer 3 layers 3 layers middle layer smaller than thin muscular thinner middle thick elastic arteries, middle layer layer, thicker more smooth outer layer muscle, pre-capillary sphincters no valves no valves no valves no valves pocket valves high pressure high pressure pressure low pressure low pressure changes carries blood controls blood gaseous carries blood carries blood away from flow and exchange towards heart towards heart heart pressure

3. BLOOD VESSELS SMOOTH MUSCLE PHYSIOLOGY involuntary / myogenic
Control of Blood Supply
BLOOD VESSELS
SMOOTH MUSCLE
STRUCTURE
no striations (smooth)
spindle shaped
one nucleus per cell, positioned towards centre of cell
SMOOTH MUSCLE
PHYSIOLOGY
involuntary / myogenic
found in major systems and organs
arterioles contain smooth muscle which can vasodilate or vasoconstrict under vasomotor control
thereby changing diameter of blood vessels
and hence change blood pressure
venules contain smooth muscle which can venoconstrict under venomotor control
this increases blood velocity to the heart

4. BLOOD FLOW VENOUS RETURN is affected by : MUSCLE PUMP
Control of Blood Supply
BLOOD FLOW
VENOUS RETURN is affected by :
MUSCLE PUMP
contraction of skeletal muscle exerts pressure on veins forcing blood to flow towards the heart
backflow is prevented by pocket valves
RESPIRATORY PUMP
during inspiration, pressure in thoracic cavity decreases
pressure in abdominal cavity increases
blood moves up from compressed high pressure (in abdomen) to low pressure (in thorax)
during expiration, pocket valves prevent backflow of blood into abdomen

5. EFFECTS OF EXERCISE VASOMOTOR CONTROL VASODILATION
Control of Blood Supply
EFFECTS OF EXERCISE
BLOOD DISTRIBUTION
VASCULAR SHUNT
blood is redistributed towards active skeletal muscle during exercise
and away from inactive organs
VASOMOTOR CONTROL
VASODILATION
dilation of arterioles and opening of precapillary sphincters increases blood flow to active muscle
VASOCONSTRICTION
constriction of arterioles and closure of precapillary sphincters reduces blood flow to inactive organs
PULMONARY CIRCULATION
exercise causes a small increase in pulmonary blood pressure
this distorts red blood corpuscles within the alveolar capillary system
this enables 10 times as much oxygen to be picked up