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port the blood back to the heart and are thus also known Physiology and pathophysiology of venous return
as deep or transport veins. The lower leg veins, the ante- The return transport of the blood to the right ventricle of
rior and posterior tibial veins, unite to form the popliteal the heart requires the presence of various physiological
vein, which continues on towards the heart as the driving forces and assistive mechanisms to overcome the
2
femoral vein. high total hydrostatic pressure which acts on the leg vein
system when the body is upright. The principle of com-
1
The interconnections within a venous system, e.g. only in municating tubes with postcapillary residual pressure,
the suprafascial system, are provided by the communicat- variations in respiratory pressure in the thoracic and
ing veins (venae communicantes). The interconnections abdominal space and the elastic aspiration of the heart
between the supra- and subfascial venous system, on the provides the necessary mechanisms. The most effective
3
other hand, are created by numerous perforating veins factor, however, is the functional unit of the calf muscle
(venae perforantes) which “perforate” the fascia for this pump.
purpose. Main groups are Cockett’s veins above the
ankle, Boyd’s veins below the knee joint and Dodd’s During movement of the legs, the deep veins are com-
Schematic diagram
veins in the thigh. pressed with every muscular contraction. This forces the
1) vein
12
blood out towards the heart and the venous valves pre-
2) open venous valve
3) closed venous valve
Almost all veins have more or less numerous venous vent the blood from pooling back into the veins. When
valves that serve as volume regulators. They make sure the muscles relax, the deep veins expand to create a neg-
that the blood flows only in one direction, namely ative pressure which results in blood being aspirated
towards the heart or from the superficial to the deeper through the perforating veins from the more distally
levels. located venous segments and the suprafascial venous
plexuses. The alternating compression-suction effect of
the muscle pump is complemented by similar mecha-
nisms in the joints and the firm resistance surface provid-
ed by the fascia which ensures that the pressure that
builds up during the contraction also acts in an inward
direction.
Schematic diagram of the calf
muscle pump during contraction
(1) and relaxation (Relaxation/2)
The interplay of these mechanisms results in the blood
of the muscles: Circles = cross-
Cross-section through an artery being raised towards the heart through several consecu-
sections through relaxed and con-
(left) and a vein (right) in a mus-
tive and coordinated levels on a kind of “paternoster”
tracted muscles with intramuscu-
cle tissue. The artery walls are
lar deep veins and transfascial
principle from the foot, through the ankle, through the
thick and consist of highly con-
veins on different levels, fascia =
tractile elastic fibres allowing
calf, the hollow of the knee, the thigh and the groin,
green
them to withstand sudden while simultaneously being withdrawn through the perfo-
increases in blood pressure. The
rating veins from the suprafascial plexus. The blood
veins have a less contractile
therefore flows from the more superficial to the deeper
structure, but a larger volume
suited to their drainage and
levels and from distal to proximal; the venous pressure
transport functions. falls.
Causes [8.9]
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