Physiology
The blood vessels have the ability to increase or decrease the lumen of the vessel and thus modify the blood flow. To do this, they require the muscle layer of the tunica media, which tenses or relaxes the muscles through nerves supplied by vegetative nerves. This results in either one: since the arteries have a much thicker muscular layer, this phenomenon applies mainly to these and less to veins.
By means of this simple mechanism, the body can control the available blood volume, contribute to temperature regulation or improve the oxygen supply in the tissue. In the blood vessels there is a physiological blood pressure that is between 80 and 120 mm Hg in the arterial vascular system and does not exceed 10 mm Hg in the venous system.
- Vasodilation (vasodilatation) or a
- Vasoconstriction (vasoconstriction).
Clinic
There are many diseases that affect the vascular system. These include, for example:
- Arteriosclerosis,
- Closure diseases,
- Inflammatory vascular diseases (vasculitis),
- Functional circulatory disorders (agrocyanosis, Raynaud’s syndrome, erythromegaly),
- Varicose veins,
- Thromboses;
Neovascularization
All forms of new formation of blood vessels in the adult organism are called so. These include: In angiogenesis, new blood vessels are formed by budding or splitting already formed blood vessels. It plays a decisive role in wound healing.
Vasculogenesis is important in the embryonic period. Here vascular structures develop through circulating stem cells, so-called angioblasts, which further mature into endothelial cells. Arteriogenesis is the formation of arteries and small arterioles.
By recruiting smooth muscle cells, a complete vessel wall is formed. In veins, the new formation proceeds in a similar way.
- The angiogenesis,
- Vasculogenesis and
- The arteriogenesis.
Lymphatic vessels
Lymph vessels are very similar to blood vessels. However, they do not transport blood, but lymph, which is a fluid located in the tissue and contains small amounts of protein. Filter stations, so-called lymph nodes, are inserted into the lymphatic system.
A distinction is made between four types of vessels: lymph vessels of the same level, for example superficial collectors in subcutaneous fatty tissue, are connected to each other by so-called anastomoses. Such vessels, which are located at different levels, such as superficial and deep collectors, are connected to each other by so-called perforating vessels. These create a fluid exchange from the deep to the superficial lymph vessels.
In lymphatic drainage by means of massages, this property is utilized. Anastomoses are especially important for the prevention of lymphedema. They serve as a detour if there is a congestion in a system or the lymph transport is completely interrupted.
- The lymph capillaries represent the smallest unit in the lymph vessel system. They have their beginning in the interstitial space (interstitium). They consist of endothelial cells that overlap like roof tiles.
Thus they form a lumen of about 50 μm. Anchor filaments fix the lymph capillaries in the surrounding tissue and additionally keep the lumen of the vessels open. Lymph formation takes place in the lymph capillaries.
It is formed by absorbing the tissue fluid in the space between the cells.
- The precollectors are the next largest lymphatic vessels, which are formed by the union of several lymph capillaries. The precollectors transport the lymph to the collectors by means of isolated muscle cells. They are also involved in lymph formation, since they also absorb tissue fluid.
- Several pre-collectors combine to form one collector.
The collectors are exclusively responsible for the transport of lymph from the existing lymph vessels. In anatomy they are very similar to veins with a three-layer wall structure and valves. The valves prevent the lymph from flowing back and thus ensure a centrally directed lymph flow.
The area between two valves is called the lymphangion (“lymph heart“). This contracts at rest every 10-12x/minute, pushing the lymph into the next section. Furthermore, the collectors are divided into superficial and deep collectors.
The superficial collectors are located in the subcutaneous fatty tissue. They absorb the lymph from the skin and subcutaneous tissue. The deep collectors are located within the fasciae in the extremities and trunk wall.
They transport the lymph from muscles, ligaments, joints and bones. Intestinal collectors, as the name suggests, collect the lymph from the intestines.
- The lymphatic collecting trunks are the largest lymphatic vessels in the body. They are divided into lymphatic trunks of the upper and lower half of the body.
The lymphatic trunks include the trunkus trachealis and the ductus thoracicus. They absorb lymph from the collectors. Their final destination is the venous angle near the heart, where they enter the venous bloodstream.
The lymphatic vessel system is responsible for collecting the protein molecules and the liquid remaining in the surrounding tissue and transporting them to the venous conduction system.
It is also necessary for the digestion of fat.In this process, a large proportion of the fats taken in from food are packed by cells of the small intestine into so-called chylomicrons and then transported into the blood via the lymph vessels. If there is a backlog in the lymph vessel systems, for example due to right heart failure, this can lead to lymphedema, especially in the legs. As already mentioned, the lymph is important for protein transport.
If the protein were to remain in the tissue, the colloid osmotic pressure in the surrounding tissue (the interstitium) would change and blood cells could thus also enter the interstitium. This would result in a lack of volume (hypovolaemia), which in the worst case could trigger a life-threatening shock.
