Introduction[edit | edit source]
- Superior vena cava (SVC) conveying blood from the head, chest, and upper extremities.
- Inferior vena cava) conveying blood from all parts of the body below the diaphragm.
As with other arteries and veins, the vena cava are made up of three total layers of muscle. The innermost endothelial lining of the superior vena cava is known as the tunica intima. The middle layer, comprised of smooth muscle tissue, is known as the tunica media. This is the layer that receives input from the nervous system. The outermost layer is the tunica adventitia. It consists of collagen and elastic connective tissue. It is this outmost layer that is primarily responsible for the superior vena cava’s flexibility.
Superior Vena Cava (SVC)[edit | edit source]
The superior vena cava is a large (measures .78 inches in diameter and 2.7 inches in length.), significant vein responsible for returning deoxygenated blood collected from the body back into the heart.
- The superior vena cava starts at the lower border of the first costal cartilage. It is located posterior (behind) this first costal cartilage on the right side and descends vertically to the right of the trachea (windpipe) and the aorta (the largest artery in the body). This large vein drains into the right atrium of the heart at the superior cavoatrial junction (located at the level of the third costal cartilage).
- The lower half of the superior vena cava is covered by pericardium—a sac that encloses the heart. The superior vena cava ends at the junction of the superior vena cava and the left atrium, emptying into the upper aspect of the right atrium at the level of the third costal cartilage.
- The superior vena cava handles the venous return of blood from structures located superior to the diaphragm. The superior vena cava is a commonly used site for central venous access.
Inferior Vena Cava (IVC)[edit | edit source]
The IVC’s job is to drain all the blood from the lower half of the body including the feet, legs, thighs, pelvis, and abdomen.
The IVC starts in the lower back where the right and left common iliac veins (two major leg veins) have joined together. Once the IVC is formed it runs under the abdominal cavity along the right side of the spinal column. It goes into the right atrium of the heart, in through the back side.
What makes the IVC different from other veins is that there are no valves within the vein to keep blood moving forward instead of backward, which is how the typical anatomy of a vein works. The IVC veins anatomy is slightly different. Instead of valves, the pressure from breathing and the contraction of the diaphragm as the lungs fill with air helps to pull the blood forward from the IVC all the way up to the heart.
Clinical Significance[edit | edit source]
Complete or partial obstruction of the superior vena cava can occur, resulting in a condition known as superior vena cava syndrome. Causes of the obstruction may include intrinsic stenosis, extrinsic compression, or thrombosis of the vein. Malignancy is the single most common cause with cancer of the lung, lymphoma, or metastatic cancers resulting in the majority of superior vena cava obstructions.
The IVC is most commonly used for IVC filter placement, which can help reduce the risk of pulmonary embolisms (a blockage in the lung which can prevent blood flow). An IVC filter stops blood clots that form in the veins of the lower half of the body, or someone who suffers from deep vein thrombosis, from having those clots reach the lungs.
References[edit | edit source]
- Dictionary Vena Cava Available:https://www.dictionary.com/browse/vena-cava (accessed 16.7.2021)
- Very Well health IVC Available:https://www.verywellhealth.com/inferior-vena-cava-anatomy-4688365 (accessed 16.7.2021)
- White HJ, Soos MP. Anatomy, Thorax, Superior Vena Cava. [Updated 2020 Aug 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan- Available:https://www.ncbi.nlm.nih.gov/books/NBK545255/ (accessed 16.7.2021)
- Very Well health The Anatomy of the Superior Vena Cava Available:https://www.verywellhealth.com/superior-vena-cava-5097375 (accessed 16.7.2021)