The superior vena cava is a thick and short vein trunk, formed by the left and right cephalbrachial veins, converging behind the junction of the right first costal cartilage and the sternum, and flowing down to the lower edge of the third sternal joint and into the right atrium.
Chinese name
Superior vena cava
Foreign name
precava;venaecavasuperior;
Location
Right front of upper mediastinum
Structure
The left and right cephalbrachial veins are in the right first thoracic rib
It mainly collects venous blood from head and neck, upper limbs and chest wall.When the superior vena cava is compressed, it may cause facial and upper limb edema, and the veins in the neck, upper limbs, and chest wall become engorged, which is called superior vena cava obstruction syndrome.
anatomic structure
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1. Superior vena cava
Collect the venous blood of the upper body back to the right atrium. It is a thick and short vein trunk, which is formed by the confluence of the left and right unnamed (cephalobrachial) veins behind the right first sternocostal joint.It descends vertically along the right side of the ascending aorta to the lower edge of the right third sternocostal joint and flows into the upper part of the right atrium.The total length of the superior vena cava is about 7 cm, without valves, and slightly convex to the right.The anterior septum thymus or adipose tissue and part of the right pleura are adjacent to the anterior chest wall.At the rear is the right lung root.The left side is close to the ascending aorta, and the right side has part of the right pleura and phrenic nerve.The azygos vein was injected into the right atrium before injection.The lower segment is located in the fibrous pericardium, and the front and both sides are covered by the serous layer of the pericardium.
The superior vena cava and its branches constitute the superior vena cava system.All the veins from the head, neck, upper limbs and chest (except the heart) belong to the superior vena cava system, which finally flows into the right atrium through the superior vena cava.
2. Inferior vena cava
The inferior vena cava is the largest vein trunk in the human body that collects the venous blood of the lower body back to the right atrium. The level of the 4th to 5th lumbar vertebrae is formed by the confluence of the left and right common iliac veins.It rises on the right side of the abdominal aorta, passes through the vena cava fossa of the liver, and then goes up through the vena cava hole of the diaphragm to reach the chest cavity, and flows into the posterior lower part of the right atrium.There is a less obvious inferior vena cava valve at the left front of its entrance.
The front of the inferior vena cava is adjacent to the right common iliac artery, the root of the small intestine mesentery, the right internal spermatic artery, the third segment of the duodenum, the pancreas, the portal vein and the liver from bottom to top;The rear is adjacent to the lumbar segment of the spine, the right renal artery, the right lumbar artery, the right adrenal artery and the right inferior phrenic artery;The left lower part is adjacent to the abdominal aorta, and the upper part is adjacent to the caudate lobe of the liver and the right foot of the diaphragm.
The inferior vena cava and its branches constitute the inferior vena cava system.All the veins from the lower limbs, pelvis and abdomen belong to the inferior vena cava system, and finally all flow into the right atrium through the inferior vena cava.
3. Right ventricle
The right ventricle is a triangular pyramid with the bottom right atrial orifice and the tip downward.There is a muscular ridge in the ventricular cavity from the right atrioventricular orifice to the pulmonary artery orifice, which is called supraventricular ridge.This ridge divides the right ventricle into two parts: inflow and outflow.
Inflow passage is the main part of the right ventricle. There are many cross muscular protuberances on the inner surface of the ventricular wall, which are called meat pillars.There are several thick and conical meat pillars, called papillary muscles, which are generally three in front, back and inside.The inlet of the inflow passage is the right atrioventricular orifice. There are three triangular valves at the front, back and medial edges of the orifice, called tricuspid valves.The bottom of each valve is attached to the fibrous ring (cardiac skeleton) around the right atrioventricular orifice, and its tip or free edge is connected to the two adjacent papillary muscles by the tendon.When the ventricle contracts, the blood pushes the valve and closes the atrioventricular orifice. Because of the contraction of the papillary muscle and the pulling of the tendon, the valve will not turn over into the right atrium, preventing the blood from flowing back to the atrium, and ensuring the directional flow of blood.If the valve, tendon, papillary muscle and annulus fibrosus function is abnormal, it will have a serious impact on blood dynamics.
The outflow tract is the protruding part of the right ventricle to the upper left, called the arterial cone or funnel, and its inner wall is smooth without meat column.The outlet of the outflow tract is the pulmonary artery orifice.There are three half moon shaped valves around the mouth, called pulmonary artery valves.The free edge of the valve is consistent with the direction of blood flow and faces the pulmonary artery.When the heart chamber relaxes, because the blood that has been pressed into the pulmonary artery pushes the valve against the flow, the free edges of the three valves are closed and the pulmonary artery orifice is closed to prevent the blood from flowing back to the right ventricle.
