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Unformatted text preview: • The muscular pump arises from contractions of skeletal muscles surrounding the veins. The contractions squeeze the veins, forcing the blood to move forward, the only direction it can move when valves in the veins close to prevent backflow. • The respiratory pump is created by the expansion and contraction of the lungs during breathing. During inspiration (inhaling), pressure in the abdominal region increases while pressure in the thoracic cavity decreases. These pressures act upon the veins passing through these regions. As a result, blood flows toward the heart as it moves from regions of higher pressure (the abdomen) to those of lower pressure (the chest and right atrium). When the pressures are reversed during expiration (exhaling), backflow in the veins is prevented by valves....
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This note was uploaded on 11/10/2011 for the course PT 101 taught by Professor Staff during the Spring '10 term at Texas State.
- Spring '10