System of the superior vena cava

The superior vena cava (v. Cava superior) is a short valveless vessel with a diameter of 21-25 mm and a length of 5-8 cm, which is formed by the fusion of the right and left brachiocephal veins behind the junction of cartilage I of the right rib with the sternum. This vein follows the sheer downward and at the level of the junction of the third right cartilage with the sternum falls into the right atrium. Ahead of the vein is the thymus and the pleura-covered mediastinal part of the right lung. On the right side of the vein is the mediastinal (mediastinal) pleura, on the left - the ascending part of the aorta. The posterior wall of the upper vena cava contacts the anterior surface of the root of the right lung. In the upper vena cava, the unpaired vein flows to the right, and to the left - small mediastinal and pericardial veins. The upper vena cava collects blood from three groups of veins: the veins of the thoracic and partly ventral cavity, the veins of the head and neck and the veins of both upper extremities, i.e. From those areas that are blood supplying the branches of the arch and the thoracic part of the aorta.

The unpaired vein (v. Azygos) is a continuation in the thoracic cavity of the right ascending lumbar vein (v. Lumbalis ascendens dextra) that passes between the muscular tufts of the right leg of the lumbar part of the diaphragm to the posterior mediastinum and on its way anastomoses with the right lumbar veins flowing into the lower a hollow vein. Behind and to the left of the unpaired vein are the vertebral column, the thoracic part of the aorta and the thoracic duct, and the right posterior intercostal arteries. In front of the vein lies the esophagus. At the level IV-V of the thoracic vertebrae, the unpaired vein wraps around the back and top of the right lung, then it goes forward and downwards and empties into the upper vena cava. At the mouth of the unpaired vein, there are two valves. In the unpaired vein, on its way to the superior vena cava, the semi- unpaired vein and veins of the posterior wall of the thoracic cavity: the right upper intercostal vein; posterior intercostal veins, as well as veins of the thoracic cavity organs: esophageal, bronchial, pericardial and mediastinapic veins.

The semi- unpaired vein (v.hemiazygos), sometimes called the left, or small unpaired, vein, is thinner than the unpaired vein, since only 4-5 lower left posterior intercostal veins enter it. The semi- unpaired vein is a continuation of the left ascending lumbar vein (v.lumbalis ascend ens sinistra), passes between the muscle bundles of the left foot of the diaphragm to the posterior mediastinum, adjacent to the left surface of the thoracic vertebrae. To the right of the semi-uneven vein are the thoracic part of the aorta, behind - the left posterior intercostal arteries. At the level VII-X of the thoracic vertebrae, the semi-unpaired vein turns steeply to the right, crosses the spine in front, is located behind the aorta, esophagus and thoracic duct) and flows into the unpaired vein. In the semi-unpaired vein, an additional semi-unpaired vein (v. Hemiazygos accessoria), taking 6-7 upper intercostal veins (I-VII), as well as esophageal and mediastinal veins, flows into the semi-unpaired vein . The most significant inflows of unpaired and semi-unpaired veins are the posterior intercostal veins, each of which, with its anterior end connected to the anterior intercostal vein, the inflow of the internal thoracic vein. The presence of such venous connections creates the possibility of an outflow of venous blood from the walls of the thoracic cavity back into the unpaired and semi-unpaired veins and forward into the internal thoracic veins.

The posterior intercostal veins (vv. Intercostales posteriores) are located in the intercostal spaces adjacent to the same arteries (in the groove of the corresponding rib). These veins collect blood from the tissues of the walls of the chest cavity and partly the anterior abdominal wall (lower posterior intercostal veins). Each of the posterior intercostal veins receives a dorsal vein (v. Dorsalis), which forms in the skin and back muscles, and the intervertebral vein (v. Intervertebralis), formed from the veins of the outer and inner vertebral plexuses. In each intervertebral vein spinal branch (spinalis) flows, which along with other veins (vertebral, lumbar and sacral) participates in the outflow of venous blood from the spinal cord.

Internal (front and back) vertebral venous plexuses (plexus venosi vertebrales interni, anterior and posterior) are located inside the vertebral canal (between the hard shell of the spinal cord and the periosteum) and are represented repeatedly by the anastomosing veins. The plexus extends from the large occipital orifice to the tip of the sacrum. In the internal vertebral plexuses spinal veins and veins of the spongy substance of the vertebrae flow . From these plexuses, the blood through the intervertebral veins passing through the intervertebral openings (next to the spinal nerves) flows into the unpaired, semi-unpaired and additional semi-unpaired veins. Blood from the inner plexuses also flows into the external (front and back) venous vertebral plexuses (plexus venosi vertebrales externi, anterior and posterior), which are located on the anterior surface of the vertebrae, as well as their arches and processes. From the external vertebral plexuses, the blood flows into the posterior intercostal, lumbar and sacral veins (vv. Intercostales posteriores, lumbales et sacrales), and directly into the unpaired, semi- and additional semi-unpaired veins. At the level of the upper spinal column, the plexus veins enter the vertebral and occipital veins (vv. Vertebrates et occipitales).

The brachiocephalic veins (right and left) (vv. Brachiocephalicae, dextra et sinistra) are valveless, are the roots of the superior vena cava. They collect blood from the organs of the head and neck and upper limbs. Each brachycephalic vein is formed from two veins - subclavian and internal jugular.

The left brachiocephalic vein is formed behind the left sternoclavicular joint. The vein has a length of 5-6 cm, follows from the place of its formation obliquely down and to the right behind the handle of the sternum and thymus. Behind this vein are the brachiocephalic trunk, the left common carotid and subclavian arteries. At the level of the cartilage of the right rib I, the left brachiocephalic vein is connected to the right venous vein, forming the upper hollow vein.

The right brachiocephalic vein 3 cm long forms behind the right sternoclavicular joint. Then the vein descends almost vertically behind the right edge of the sternum and adjoins the dome of the right pleura.

In each arm, the vein of the veins are covered with small veins from the internal organs: thymus veins (vv. Thymicae); pericardial veins (v. Pericardiacae); pericardial diaphragmatic veins (v. Reisardiacophrenicae); bronchial veins (vv. Bronchiales); esophageal veins (v. Oesophageales); mediastinal veins (vv. Mediastinales) - from the lymph nodes and connective tissue of the mediastinum. The larger influxes of brachiocephalic veins are the lower thyroid veins (vv. Thyroideae inferiores, only 1-3), through which blood flows from the unpaired thyroid plexus (plexus tliyroideus impar), and the lower laryngeal vein (v. Laryngea inferior), which brings blood from the larynx and anastomosing with upper and middle thyroid veins.

The vertebral vein (v. Vertebralis) passes along with the vertebral artery through the transverse apertures of the cervical vertebrae to the brachiocephalic vein, taking along the veins of the internal vertebral plexuses.

The deep cervical vein (v. Cervicalis profunda) starts from the outer vertebral plexuses, collects blood from the muscles and fascia located in the occipital region. This vein passes behind the transverse processes of the cervical vertebrae and flows into the brachiocephalic vein not far from the mouth of the vertebral vein or directly into the vertebral vein.

The internal thoracic vein (v. Thoracica interna) is paired, accompanies the internal thoracic artery. The roots of the internal thoracic veins are the superior epigastric vein (v. Epigastrica superioris) and the muscular-diaphragmatic vein (v. Musculophrenica). The upper epigastric vein anastomoses in the thickness of the anterior abdominal wall with the lower epigastric vein flowing into the external iliac vein. In the inner thoracic vein, anterior intercostal veins (vv. Intercostales anteriores) lying in the anterior intercostal spaces intersect, which anastomose with the posterior intercostal veins flowing into the unpaired or semi-unpaired vein.

In each brachycephalic vein, right and left, the highest intercostal vein (v. Intercostalis suprema) flows , collecting blood from 3-4 upper intercostal spaces.