Superior vena cava anatomy

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Veins are hollow, tubular structures that are part of the body's circulatory system; In most cases, the veins carry deoxygenated blood to the heart. The superior vena cava (SVC) is one of the two largest veins in the body and is considered one of many systemic veins. Systemic veins are those through which deoxygenated blood from various areas of the body to the heart is vital for the functioning of the cardiovascular system .

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Meaning of the name

Vena cava is Latin for "vena cava", which describes the appearance of its large tube.

Anatomy

The importance of the superior vena cava lies in its role in the cardiovascular system. In particular, the superior vena cava carries non-oxygenated blood from the upper half of the body to the right atrium of the heart. The blood then circulates through the heart to the right ventricle and is then pumped out of the heart through the pulmonary arteries into the lungs for oxygenation .

Why is blood important?

To fully understand the meaning of the superior vena cava, it is important to know a little about what blood is made of and why it is so important. Blood :

  • Carry oxygen to and from the lungs.
  • Eliminate waste products like carbon dioxide.
  • It acts as a medium for the delivery of nutrients from the digestive system.
  • Disease-fighting objects (such as white blood cells), which are an important part of the immune system, circulate.

The body could not live without continuous circulation. The vena cava plays a vital role in the circulation of deoxygenated blood from the upper body, draining it towards the heart so that blood can travel to the lungs to be re-oxygenated.

Composition

The superior vena cava is relatively large: 0.78 inches in diameter and 2.7 inches long .

All blood vessels, including veins and arteries, have basically the same structure. That is, these are hollow tubes with a lumen (open interior space). The width and length of each blood vessel may be different, but they all have a hollow opening through which blood flows.

Artery and vein walls have the same three layers, including :

  • Inner lining: The innermost, thinnest layer of a vein, made up of a single layer of endothelial cells (a type of cell found within the lining of the heart, lymphatic vessels, and blood vessels). The function of this layer is to reduce the friction within the vessel caused by the transfer of blood.
  • Sheath environment: middle layer of veins; In the artery, this layer is the thickest, because it is made up of muscle tissue, but in the veins there is much less elastic tissue and more collagen fibers. Collagen fibers are composed of a fibrous protein that constitutes the supporting element of connective tissue.
  • Outer sheath (also called adventitia): the outermost layer of a vein, made up of connective tissue and nerves; in the veins, this is the thickest layer. Protects and strengthens the vein and serves to attach the vein to surrounding structures.

Most veins have valves that help blood move toward the heart, preventing blood from flowing from the heart. However, the superior vena cava is one of the few valveless veins in the body .

The mechanism that prevents blood from flowing into the superior vena cava from the right atrium during contraction (called systole) is the part of the muscle that includes the atrial walls that surround the entry point to the vena cava. When the heart contracts, this muscle closes almost completely over the opening of the superior vena cava, preventing backflow of blood from the atrium.

Location

The superior vena cava is forming Left and right brachiocephalic veins, also called anonymous veins, on the right side of the upper chest, posterior (posterior) to the lower border of the first costal cartilage.

The superior vena cava is located in the thorax (thorax), more precisely, in the right, superior anterior (anterior) mediastinum (above).

The superior vena cava begins at the lower border of the first costal cartilage. It lies behind (behind) this first costal cartilage on the right side and descends vertically to the right of the trachea (windpipe) and aorta (the largest artery in the body). This large vein flows into the right atrium of the heart at the superior cavoauricular junction (located at the level of the third costal cartilage).

The lower half of the superior vena cava is covered by the pericardium, the sac that surrounds the heart. The superior vena cava ends at the junction of the superior vena cava and the left atrium, flowing into the upper part of the right atrium at the level of the third costal cartilage .

Anatomical variations

Anatomical variations of the superior vena cava include:

Congenital malformations of the superior vena cava.

Congenital malformation is an abnormality that occurs during the intrauterine development of the fetus. They are present at birth, but can be diagnosed prenatally (before birth). It is also possible that these defects are not diagnosed until a later age.

Heart defects (such as those that generally occur at the same time as SVC abnormalities) are among the most common and serious birth defects, according to the World Health Organization (WHO) .

There are several common congenital anomalies of the superior vena cava, including :

  • Persistent Left Superior Vena Cava (Persistent LSVC): A common systemic venous abnormality. It occurs more frequently with congenital heart disease. (CHD) .
  • Superior vena cava syndrome (ACLS): a condition that involves a partial or compressed blockage of the superior vena cava. Often the underlying cause is lung cancer, non- Hodgkin lymphoma , or cancer that has spread to the chest .

Function

The superior vena cava is a vital structure in the human circulatory system that helps drain large amounts of deoxygenated blood from the head, eyes, neck, and upper extremities to the upper left chamber (atrium) of the heart.

Clinical relevance

The superior vein cavern is a thin-walled, low-pressure vessel that makes it susceptible to conditions that increase venous pressure. This is an important factor when it comes to superior vena cava conditions. Anything that causes hypertension (high blood pressure) in the vessels on the right side of the heart or in the pulmonary circulation can seriously affect the superior vena cava.

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