Basics of the venous system of the lower extremities

Woman with damaged leg veins at the doctor's appointment

The special structure of venous vessels and the composition of their walls determine their capacitive properties. Veins differ from arteries in that they are tubes with thin walls and lumens that are relatively large in diameter. In addition to the walls of the arteries, the composition of the walls of the veins includes smooth muscle elements, elastic and collagen fibers, of which there are many more.

In the vein wall, structures are divided into two categories:

  • Support structures comprising reticulin and collagen fibers;
  • elastic-contractile structures, which include elastic fibers and smooth muscle cells.

Collagen fibers maintain the normal configuration of the vessel under normal conditions, and when an extreme shock is applied to the vessel, these fibers maintain it. Collagen vessels are not involved in the formation of tone in the vessel and also do not influence the vasomotor reactions, since smooth muscle fibers are responsible for their regulation.

Veins consist of three layers:

  • Adventitia - outer layer;
  • medium - middle layer;
  • intima - the inner layer.

Between these layers there are elastic membranes:

  • internal, which is more pronounced;
  • externally, which is very slightly different.

The middle membrane of the veins consists mainly of smooth muscle cells that are located in a spiral along the circumference of the vessel. The development of the muscle layer depends on the width of the diameter of the venous vessel. The larger the diameter of the vein, the more the muscle layer develops. The number of smooth muscle elements increases from top to bottom. The muscle cells that make up the middle membrane are located in a network of collagen fibers that are strongly curled in both the longitudinal and transverse directions. These fibers are only straightened up when the vein wall is strongly stretched.

Superficial veins, located in the subcutaneous tissue, have a highly developed smooth muscle structure. This explains the fact that superficial veins, unlike deep veins, which are at the same height and diameter, perfectly withstand both hydrostatic and hydrodynamic pressure, since their walls have elastic resistance. The venous wall has a thickness that is inversely proportional to the size of the muscle layer surrounding the vessel.

The outer layer of the vein, or adventitia, is a dense network of collagen fibers that make up a type of skeleton, as well as a small number of muscle cells that are longitudinally arranged. This layer of muscle develops with age and is most clearly seen in the venous vessels of the lower extremities. The role of additional support is played by the more or less large venous trunks, which are surrounded by a dense fascia.

The structure of the vein wall is determined by its mechanical properties: in the radial direction, the vein wall is highly expandable, in the longitudinal direction it is small. The degree of vascular extensibility depends on two elements of the vein wall - smooth muscle and collagen fibers. The rigidity of the vein walls during their strong dilation depends on collagen fibers, which only prevent a strong expansion of the veins when there is a significant increase in pressure inside the vessel. If changes in intravascular pressure are physiological, then smooth muscle elements are responsible for the elasticity of the vein walls.

Venous valves

Leg vein valve

Venous vessels have one important feature - they have valves that allow centripetal blood flow in one direction. The number of valves and their location are used to provide blood flow to the heart. On the lower extremity, the greatest number of valves are located in the distal regions, namely slightly below the point where the mouth of a large tributary is located. In each of the superficial vein highways, the valves are located 8-10 cm from each other. With the exception of the valveless foot perforators, the communicating veins also have a valve apparatus. Often, perforators in multiple candelabra-like trunks can penetrate deep veins and prevent retrograde blood flow along with the valves.

The venous valves usually have a bicuspid structure and their distribution in a specific vascular segment depends on the degree of functional load on the spur of the inner elastic membrane. The cusp of the valve has two surfaces covered with endothelium: one on the sinus side and the other on the lumen side. Smooth muscle fibers, which are located at the base of the valves and are directed along the vein axis, when they change direction transversely, form a circular sphincter muscle, which, in the form of a kind of attachment, prolapses into the sinus of the valve edge. The stroma of the valve is made up of smooth muscle fibers that are bundled in a fan shape around the valve leaflets. With the help of an electron microscope, you can find elongated thickenings - nodules that are located on the free edge of the valve leaflets of large veins. According to scientists, these are a type of receptor that records the moment the valves close. The cusps of an intact valve are longer than the diameter of the vessel, therefore, when closed, longitudinal folds are observed on them. In particular, a valve leaflet that is too long is due to physiological prolapse.

The venous valve is a structure strong enough to withstand pressures up to 300 mmHg. Art. However, some of the blood is released into the sinuses of the valves of large veins through thin tributaries that do not flow into valves, causing the pressure above the valve leaflets to decrease. In addition, the retrograde blood wave is scattered at the edge of the attachment, which leads to a decrease in its kinetic energy.

With the help of fibrofleboscopy performed during one's lifetime, one can imagine how the venous valve works. After the retrograde wave of blood enters the sinuses of the valve, their cusps move and close. The nodules send a signal that they have touched the muscle sphincter. The sphincter begins to expand until it reaches the diameter at which the valve valves open again and reliably block the path of the retrograde blood wave. When the pressure in the sinus rises above the threshold, the opening of the mouth of the efferent veins occurs, which leads to a decrease in venous hypertension to a safe level.

Anatomical structure of the venous pelvis of the lower extremities

The veins of the lower extremities are not superficially and deeply divided.

The superficial veins include the cutaneous veins of the foot, which are located on the plantar and dorsal surfaces, large, small trunk veins, and their numerous tributaries.

The trunk veins in the area of the foot form two networks: the cutaneous plantar vein network and the cutaneous vein network of the dorsum of the foot. Common dorsal finger veins that enter the cutaneous network of veins on the dorsum of the foot because they anastomose with one another form the cutaneous dorsal arch of the foot. The ends of the arch continue in the proximal direction and form two longitudinal trunks - the medial marginal vein (v. Medial marginalis) and the lateral marginalis vein (v. Lateral marginalis). On the lower leg, these veins have a continuation in the form of a large or a small trunk vein. The subcutaneous venous arch of the foot protrudes on the sole of the foot, which anastomoses with the marginal veins and guides the intercapital veins into each of the interdigital spaces. The intercapital veins, in turn, anastomose with the veins that make up the arch of the spine.

The continuation of the medial marginal vein (v. Marginalis medialis) is the great saphenous vein of the lower extremity (v. Saphena magna), which runs along the front edge of the inside of the ankle to the lower leg and then goes along the medial edge of the tibia, bends aroundthe medial condyle and goes from the back of the knee joint to the inside of the thigh. In the area of the lower leg, the GSV is located near the saphenous nerve, which is used to innervate the skin on the foot and lower leg. This feature of the anatomical structure should be taken into account in phlebectomy, since damage to the saphenous nerve leads to long-term and sometimes lifelong disorders of the innervation of the skin in the lower leg area as well as to paresthesia and causalgia.

In the thigh area, the great saphenous vein can have one to three trunks. The mouth of the GSV (saphenofemoral anastomosis) is located in the area of the oval fossa (hiatus saphenus). At this point, its end section bends through the seropid process of the fascia of the thigh and opens into the femoral vein through perforation of the ethmoid plate (lamina cribrosa). The location of the saphenofemoral anastomosis can be 2-6 m below where the pupar ligament is located.

Many tributaries flow into the great saphenous vein along its entire length, carrying blood not only from the lower extremities, from the external genital organs, from the anterior abdominal wall, but also from the skin and subcutaneous tissue in the buttocks area. The great saphenous vein normally has a lumen width of 0. 3-0. 5 cm and has five to ten pairs of valves.

Permanent vein trunks that open into the terminal section of the great saphenous vein:

  • V. pudenda externa - external genital or pubic vein. The occurrence of reflux in this vein can lead to perineal varicose veins;
  • Superfacial epigastric vein - superficial epigastric vein. This vein is the most constant inflow. In a surgical procedure, this vessel serves as an important point of orientation, on the basis of which the immediate vicinity of the saphenofemoral anastomosis can be determined;
  • V. Circumflexa ilei superfacialis - superficial vein. This vein is around the iliac bone;
  • Medial accessory saphenous vein - posterior medial vein. This vein is also known as the medial accessory saphenous vein;
  • Lateral accessory saphenous vein - anterolateral vein. This vein is also known as the lateral accessory saphenous vein.
the location of the veins in the leg

The external marginal vein of the foot (v. Marginalis lateralis) continues with a small vena saphena (v. Saphena parva). It runs along the back of the lateral ankle and then goes up: first along the outer edge of the Achilles tendon, and then along its back surface, which is next to the midline of the back surface of the lower leg. From this point on, the great saphenous vein can have one trunk, sometimes two. Near the small saphenous vein is the medial medial sural cutaneous nerve of the calf, through which the skin of the posteromedial surface of the leg is innervated. This explains the fact that the use of traumatic phlebectomy in this area is fraught with neurological disorders.

The small saphenous vein, which passes through the junction of the middle and upper third of the leg, penetrates the deep fascia zone, which is located between its leaves. When reaching the hollow of the knee, the SSV crosses the deep sheet of the fascia and mostly connects to the popliteal vein. In some cases, however, the small saphenous vein runs over the hollow of the knee and connects either with the femoral vein or with tributaries of the deep femoral vein. In rare cases the SSV joins one of the tributaries of the great saphenous vein. Many anastomoses form in the upper third of the leg between the great saphenous vein and the great saphenous vein system.

The largest permanent inflow of the V. saphena parva near the mouth, which is located epifascial, is the V. femoralis poplitea (v. Femoropoplitea) or V. Giacomini. This vein connects the SSV with a large trunk vein in the thigh. If reflux occurs through the Giacomini vein from the GSV pool, varicose vein expansion of the small saphenous vein can begin. However, the reverse mechanism can also work. If valve insufficiency of the SSV occurs, varicose veins can be observed in the popliteal femoral vein. The great saphenous vein will also be involved in this process. This must be taken into account during surgical interventions, as the popliteal femoral vein can be the reason for the recurrence of varicose veins in the patient if preserved.

Deep venous system

Deep veins include veins on the dorsum and soles of the feet, on the lower leg, and in the knee and thigh area.

The deep venous system of the foot is formed by paired accompanying veins and arteries in their vicinity. The accompanying veins curve in two deep arches around the posterior and plantar area of the foot. The dorsal deep arch is responsible for the formation of the anterior tibial veins - vv. tibiales anteriores, the plantar deep arch is responsible for the formation of the posterior tibia (vv. tibiales posteriores) and the receiving peroneal veins (vv. peroneae). That is, the dorsal veins of the foot form the anterior tibial veins, and the posterior tibial veins are formed from the plantar medial and lateral veins of the foot.

On the lower leg, the venous system consists of three pairs of deep veins - the anterior and posterior tibial veins and the peroneal vein. The main load on the outflow of blood from the periphery is assigned to the posterior tibial veins, into which the peroneal veins are drained.

The merging of the deep veins in the legs creates a short trunk of the popliteal vein (v. Poplitea). The knee vein houses the small saphenous vein and the paired veins of the knee joint. After the knee vein enters this vessel through the lower opening of the femoral-popliteal canal, it is called the femoral vein.

The sural venous system consists of paired calf muscles (v. Gastrocnemius), which divert the sinus of the gastrocnemius muscle into the popliteal vein, and the unpaired soleus muscle (v. Soleus), which drains into the popliteal vein of the Msoleus is responsible for sinus.

At the level of the joint space, the medial and lateral gastrocnemius veins join the popliteal vein either through the common mouth or separately and leave the heads of the gastrocnemius muscle (gastrocnemius muscle).

The artery of the same name, which in turn is a branch of the popliteal artery (a. Poplitea), runs near the soleus muscle (v. Soleus). The flounder vein flows independently into the popliteal vein or is located proximal to the mouth of the calf veins or flows into it.

The vena femoralis (v. Femoralis) is divided into two parts by most specialists: The vena femoralis superficialis (v. Femoralis superfacialis) is located further away from the confluence of the deep femoral vein, the vena femoralis communis (v. Femoralis communis. ). ) is closer to where the deep vein of the thigh joins. This unit is both anatomically and functionally important.

The most distal major tributary of the femoral vein is the deep femoral vein (v. Femoralis profunda), which opens into the femoral vein about 6-8 cm below the point of the inguinal ligament. A little deeper is the point where tributaries with a small diameter flow into the femoral vein. These tributaries correspond to small branches of the femoral artery. If the lateral vein surrounding the thigh has not one trunk, but two or three, its lower branch of the lateral vein opens into the femoral vein at the same point. In addition to the vessels mentioned above, in the femoral vein, at the point where the mouth of the deep femoral vein is located, there is most often the confluence of two accompanying veins that form the para-arterial venous bed.

In addition to the great saphenous vein, the medial lateral veins that run around the thigh also flow into the common femoral vein. The medial vein is more proximal than the lateral. The place of its confluence can either be at the same level as the mouth of the great saphenous vein or slightly above it.

Perforation veins

Perforation veins of the leg

Venous vessels with thin walls and different diameters - from a few fractions of a millimeter up to 2 mm - are called perforating veins. These veins are often oblique and six inches long. Most perforating veins have valves that direct blood flow from superficial veins to deep veins. In addition to the perforating veins that have valves, there are valve-less or neutral ones. These veins are mostly not in the foot. The number of valveless perforators compared to the valve is 3-10%.

Direct and indirect perforation veins

Direct perforating veins are vessels through which the deep and superficial veins are connected. The safenopliteal junction is the most typical example of a straight perforating vein. There are not many direct perforation veins in the human body. They are larger and, in most cases, are located in the distal regions of the limbs. For example, the perforating veins of the cockett are located in the tendon part of the lower leg.

The main role of the perforating indirect vein is to connect the trunk vein to the muscular vein, which has a direct or indirect connection with the deep vein. The number of indirect perforating veins is quite large. These are usually very small veins that are mostly located where there are muscle masses.

Both direct and indirect perforating veins often do not communicate with the trunk of the saphenous vein itself, but only with one of its tributaries. For example, the perforating veins of the cockett, which run along the inner surface of the lower third of the leg, on which the development of varicose veins and post-thrombophlebic diseases is not infrequently observed, not the trunk of the great saphenous vein itself, the deep veins, but only its rear branch, the so-called Leonardo vein. Failure to take this feature into account can lead to a relapse of the disease, despite the fact that during the operation the trunk of the great saphenous vein was removed. In total there are more than 100 perforators in the human body. There are usually indirect perforation veins in the thigh area. Most of them are located in the lower and middle thirds of the thigh. These perforators are positioned transversely to connect the great saphenous vein with the femoral vein. The number of perforators is different - from two to four. Normally, the blood only flows through these perforating veins into the femoral vein. Large perforation veins are most commonly found near the entrance of the femoral vein (Dodd perforator) and the exit (Gunther's) from Gunter's canal. There are cases when the great saphenous vein is connected with the help of communicating veins not to the main trunk of the femoral vein, but to the deep femoral vein or to a vein that runs alongside the main trunk of the femoral vein.