The venous angle (angulus venosus) is formed by the internal jugular vein and the subclavian vein, which join to form the brachiocephalic vein. The left venous angle also contains the largest lymphatic vessel in humans, the thoracic duct. Diseases of the lymphatic system include lymphedema and lymphangitis.
What is the venous angle?
The venous angle is also known in technical language as the angulus venosus. It is located in the chest area of humans and refers to the angle where the internal jugular vein (internal jugular vein) and subclavian vein (subclavian vein) meet and merge into a common blood vessel. This united vein is the brachiocephalic vein, also known as the vena anonyma or vena innominata. In front of the heart, the venae brachiocephalicae of both sides bend into the superior vena cava (superior vena cava) and reach the right atrium by this route. The venous angle belongs to the vascular system of the systemic circulation, colloquially known as the great circulation. The veins carry blood toward the heart, which has previously supplied other organs with oxygen, energy and nutrients. By the time this blood reaches the heart, it is deoxygenated.
Anatomy and structure
The internal jugular vein drains blood from the cranial cavity, which it receives at the zygomatic vein or orifice (foramen jugulare). The passage is located in the posterior fossa of the skull (fossa cranii posterior) next to the petrous bone. In addition to the jugular vein, the ninth cranial nerve (glossopharyngeal nerve) and the tenth (vagus) and eleventh (accessorius) nerves also pass through the foramen jugulare. The deoxygenated blood initially drains from the brain through finer vessels and collects in the superior petrosal sinus, inferior petrosal sinus, and transverse sinus. All three blood conduits drain into the sigmoid sinus, which eventually flows into the internal jugular vein. The vein runs along the internal carotid artery to the bifurcation where the artery branches off from the common carotid artery. From there, it follows the carotid artery to the angle of the vein, where it joins the subclavian vein. This originates from the strong axillary vein, which runs in the axillary region and has valves that prevent the blood from flowing back into it. Its destination is the broad brachiocephalic vein. The venous angle is symmetrical in both halves of the body.
Function and tasks
The main function of the venous angle is to bring together blood from the internal jugular vein and subclavian vein and unite them into the brachiocephalic vein. In addition, the lymphatic system directs its fluid into the bloodstream at this point. Medicine also uses the vein angle to record the relative position of anatomical structures to each other. The vein angle serves as a spatial landmark. On the left is the brachiocephalic sinistra vein, which at 6 cm is about two to three times as long as its right counterpart. Behind the angle of the vein, this powerful blood vessel takes in further deoxygenated blood from other veins. Via the heart, the oxygen-poor blood from the veins finally reaches the pulmonary circulation, where the red blood cells (erythrocytes) in the lungs are loaded with oxygen. In the right side of the body, the venous angle also exists, but it is slightly smaller. The brachiocephalic vein dextra also receives blood from other veins and eventually joins the brachiocephalic vein sinistra. Other functionally important structures in the venous angle are the lymphatic vessels. The thoracic duct is a lymphatic duct in the left angle of the vein. It forms part of the immune system and has the task of transporting lymphocytes. These specialized white blood cells fight potential cancer cells and invading pathogens such as bacteria and viruses. Furthermore, the lymphatic system prevents fluid and proteins from being deposited in the tissue between the cells. At the angle of the vein, the thoracic duct returns the collected fluid to the vascular system. On the opposite side is the right lymphatic duct (Ductus lymphaticus dexter). However, the lymphatic duct in this half of the body is much smaller than in the left.
Diseases
The thoracic duct plays a central role in the function of the lymphatic system by releasing collected fluid and proteins contained in it into the blood at the angle of the vein. Disturbances in the drainage of lymph can cause lymphedema.Lymphedema manifests as swelling of the tissue and may cause pain. Hereditary lymphedema is due to a design defect in the drainage system, while in other cases the clinical picture occurs after a mastectomy or radiation treatment for breast carcinoma. However, not every swelling of the tissue indicates lymphedema: Many different causes can be considered for edema, from excessive salt intake through diet to electrolyte imbalances and heart failure. Inflammation of the lymphatic channels is referred to in medicine as lymphangitis. Bacteria, insect bites, parasites, drugs and other substances can cause the inflammation with its characteristic red streaks that rise in the lymph vessels and are visible externally. In addition, palpitations, fever and chills may appear. Often the red streak feels warm, throbs, and is accompanied by pain. Accompanying symptoms sometimes include swelling of the lymph nodes and blood poisoning (sepsis) if the infection also spreads to these vessels. Symptoms of sepsis, in addition to the lymphangitis signs, include diarrhea, vomiting, nausea, decreased urine output (oliguria), decreased blood pressure, rapid breathing (tachypnea), circulatory shock, and impaired consciousness (predominantly quantitative).
