The skeletal muscle pump or musculovenous pump is a collection of

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

s that aid the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

in the circulation of

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

. It is especially important in increasing

venous return Venous return is the rate of blood flow back to the heart. It normally limits cardiac output. Superposition of the cardiac function curve and venous return curve is used in one hemodynamic model. __TOC__ Physiology Venous return (VR) is the flow ...

to the heart, but may also play a role in

arterial blood Arterial blood is the oxygenated blood in the circulatory system found in the pulmonary vein, the left chambers of the heart, and in the artery, arteries. It is bright red in color, while venous blood is dark red in color (but looks purple through ...

flow.

General

The skeletal muscle pump is vital in negating orthostatic intolerance when

standing Standing, also referred to as orthostasis, is a position in which the body is held in an upright (orthostatic) position and supported only by the feet. Although seemingly static, the body rocks slightly back and forth from the ankle in the ...

. 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 p ...

moves to the peripheral parts of the body. To combat this, the

muscles Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

involved in standing contract and help to bring

venous blood Venous blood is deoxygenated blood which travels from the peripheral blood vessels, through the venous system into the right atrium of the heart. Deoxygenated blood is then pumped by the right ventricle to the lungs via the pulmonary artery whi ...

volume to the heart. The pump is important in affecting the central and local supply of blood output.

Venous return Venous return is the rate of blood flow back to the heart. It normally limits cardiac output. Superposition of the cardiac function curve and venous return curve is used in one hemodynamic model. __TOC__ Physiology Venous return (VR) is the flow ...

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: tha ...

, and

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

were all increased during

exercise Exercise or workout is physical activity that enhances or maintains fitness and overall health. It is performed for various reasons, including weight loss or maintenance, to aid growth and improve strength, develop muscles and the cardio ...

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. It is postulated that this change in

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

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 Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel wa ...

, 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

{{reflist

External links

Medical College of Georgia The Medical College of Georgia (often referred to as MCG) is the medical school of Augusta University, the state's only public medical school, and one of the top 10 largest medical schools in the United States. Established in 1828 as the Medical ...

article on th
Skeletal-muscle pump
Muscular system Veins

General

Arterial blood pumping

See also

References

External links