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

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

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

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

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