The skeletal muscle pump or musculovenous pump is a collection of

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood

flow Flow may refer to: Science and technology * Fluid flow, the motion of a gas or liquid * Flow (geomorphology), a type of mass wasting or slope movement in geomorphology * Flow (mathematics), a group action of the real numbers on a set * Flow (psych ...

General

The skeletal muscle pump is vital in negating orthostatic intolerance when standing. When moving upright, the

blood volume Blood volume (volemia) is the volume of blood (blood cells and plasma) in the circulatory system of any individual. Humans A typical adult has a blood volume of approximately 5 liters, with females and males having approximately the same blood per ...

moves to the peripheral parts of the body. To combat this, the muscles involved in standing contract and help to bring venous blood volume to the heart. The pump is important in affecting the central and local supply of blood output. Venous return,

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: t ...

, and

stroke volume In cardiovascular physiology, stroke volume (SV) is the volume of blood pumped from the left ventricle per beat. Stroke volume is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood i ...

were all increased during

exercise Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...

experiments, as well as affecting the local muscle being used, blood volume.

Arterial blood pumping

Between muscle relaxations, intramuscular pressure transiently returns to a level below the venous blood pressure. This allows blood from the capillary system to refill the veins until the next

contraction Contraction may refer to: Linguistics * Contraction (grammar), a shortened word * Poetic contraction, omission of letters for poetic reasons * Elision, omission of sounds ** Syncope (phonology), omission of sounds in a word * Synalepha, merged ...

. It is postulated that this change in pressure may be great enough to draw blood from the arterial side to the venous side. It is hypothesized that this pressure drop during rhythmic contraction actually increases blood flow through the muscle, and may be responsible for a portion of the increase in muscle blood flow immediately at the onset of activity. This explanation is attractive, because it would explain the readily observable tight coupling between muscle contraction and a rapid increase in muscle blood flow. However, recent evidence has emerged that cast doubts on this theory. Experiments have shown that a strong muscle contraction can occur without a corresponding increase in skeletal muscle blood flow. Given the proposed manner of action of the muscle pump to increase arterial blood flow, it would seem impossible for a muscle contraction and skeletal muscle hyperemia to be uncoupled. Another experiment recently was only able to find evidence that vasodilation, not the skeletal muscle pump, was responsible for maintaining proper pressure and blood return. This might have to do with the lack of rigorous physiological tests thus far used to be able to prove the pump. Experiments have shown the use of passive leg exercises, where only vasodilation was used, was responsible for increased blood return.

References

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External links

* Medical College of Georgia article on th
Skeletal-muscle pump
Muscular system Veins

General

Arterial blood pumping

See also

References

External links