What is Superior Vena Cava?
Blood from all body parts enters the heart through this vein. There are two parts to the vena cava: the superior vena cava and the inferior vena cava. From the head, neck, arms, and chest, blood flows into the superior vena cava. The inferior vena cava on the other hand is responsible for carrying blood from the legs, feet, and abdominal and pelvic organs. Here, we will discuss questions like what is superior vena cava and superior vena cava branches.
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Located in the anterior right superior mediastinum, the superior vena cava is short but is a large diameter vein. The Latin name, cava, means 'hollow' in reference to its large pipe appearance in cadavers. As it contributes largely to the input of blood to the right atrium, the superior vena cava is relatively important for the function of the cardiovascular system. The heart's superior and inferior venae cavae are affected by any hypertensive process occurring in the right side of the heart. Consequently, the veins cannot withstand high pressure, resulting in aneurysms or even ruptures of the SVC.
Superior Vena Cava Anatomy
In embryology, the SVC is composed of the brachiocephalic (or innominate) veins (also known as the brachiocephalic veins) that receive blood from the upper limbs, head (including the eyes), and neck.
The SVC does not have a valve that separates it from the right atrium, which conducts blood upward into the internal jugular vein (seemed as jugular venous pressure) and sternocleidomastoid muscle. At the second costal cartilage level, the SVC penetrates the fibrous pericardium covering its lower half. At the 3rd costal cartilage level, the SVC is located directly behind the lower border of the first right costal cartilage, then descends vertically behind the second and third intercostal spaces to empty into the right atrium.
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Superior Vena Cava
The superior vena cava is formed of the right and left brachiocephalic veins, sometimes called the innominate veins, behind the inferior border of the first right costal cartilage. Blood is carried through these veins from the chest wall, the esophagus, the lungs, the neck, and the pericardium. At the third intercostal space and the second intercostal space, the superior vena cava descends vertically downwards. By means of the azygos arch, the azygos vein drains into the superior vena cava at the point where it penetrates the fibrous pericardium opposite the right second costal cartilage. This fibrous pericardium covers the lower portion of the superior vena cava. At the level of the third costal cartilage, it drains into the right atrium. Within the right atrium, the superior vena cava terminates in the sinus venarum. The superior vena cava does not have valves at the point where it drains into the right atrium. The superior vena cava measures approximately 7 centimeters in length and 2 centimeters in width.
Superior Vena Cava Location
Both the inferior vena cava and the superior vena cava of humans drain into the right atrium. On the right side of the human body, they are slightly off-center. Through two large veins called venae cavae, deoxygenated blood flows into the right atrium.
Superior Vena Cava Tributaries
Tributaries create superior vena cava from the head, neck, arms, and part of the chest. The venous sinuses lie between the two layers of dura mater, the brain's outer covering; they do not have valves. Through these sinuses and communicating vessels, the brain receives venous drainage. A few centimeters below the collarbone, the innominate veins of each side converge to form the subclavian vein of that side. Continuing this vein downward into the neck, the internal jugular vein carries blood from parts of the face, neck, and brain.
In the lower jaw or mandible, there is a junction of tributaries of the external jugular vein. The subclavian and some of the head and neck structures drain into the innominate vein on the same side. A tributary of the subclavian vein of that side runs through all the veins of the arm. These veins are found both superficially and deeply and have valves. The deep veins are typically arranged in pairs and connected crosswise.
Thus, the well-written has explained all the vital information unrelated to superior vena cava.
FAQs on Superior Vena Cava
1. What is the superior vena cava and where is it located in the body?
The superior vena cava (SVC) is a large, major vein located in the upper chest, specifically in the anterior right superior mediastinum. It is one of the two main veins that bring deoxygenated blood from the body back to the heart. Its primary role is to channel blood from the upper half of the body into the right atrium.
2. What is the main function of the superior vena cava?
The main function of the superior vena cava is to collect deoxygenated blood from the head, neck, arms, and upper portions of the chest and deliver it to the right atrium of the heart. This is the first step in the pulmonary circulation circuit, where the blood will be sent to the lungs to get oxygenated.
3. How is the superior vena cava formed from its major tributaries?
The superior vena cava is formed behind the first right costal cartilage by the convergence of two major veins:
- The right brachiocephalic vein
- The left brachiocephalic vein
These brachiocephalic veins, in turn, collect blood from the head, neck, and upper limbs. The azygos vein, which drains blood from the posterior chest wall, is another significant tributary that joins the SVC.
4. What are the key differences between the superior vena cava and the inferior vena cava?
The primary difference between the two largest veins in the body lies in the regions they drain:
- The Superior Vena Cava (SVC) carries deoxygenated blood from the upper half of the body (head, neck, arms, and upper chest) to the right atrium.
- The Inferior Vena Cava (IVC) carries deoxygenated blood from the lower and middle body (legs, feet, abdomen, and pelvis) to the right atrium.
5. Why doesn't the superior vena cava have valves like other veins?
The superior vena cava lacks valves primarily because the flow of blood from the upper body towards the heart is assisted by gravity. This downward flow, combined with the low-pressure system and the suction effect of the relaxing right atrium, is generally sufficient to prevent significant backflow of blood, making valves unnecessary for its function.
6. What is Superior Vena Cava Syndrome (SVCS) and what causes it?
Superior Vena Cava Syndrome (SVCS) is a medical condition resulting from the partial or complete obstruction of the SVC. This blockage slows down blood flow from the upper body to the heart, causing symptoms like swelling in the face, neck, and arms, as well as shortness of breath. The most common cause of SVCS in adults is an external mass, such as a cancerous tumour from the lung or lymph nodes, compressing the vein.
7. How does the anatomy of the superior vena cava impact medical procedures?
The superior vena cava's thin walls and low-pressure nature make it vulnerable during medical procedures. Since it is the main drainage route for the brain, any obstruction or surgical clamping can dangerously increase intracranial pressure. Therefore, surgeons must take extreme care during thoracic surgeries or when placing long-term central venous catheters to avoid damaging or blocking this critical vessel.
