Superior Vena Cava, Aorta and Pulmonary Trunk Question And Answers

Superior Vena Cava, Aorta and Pulmonary Trunk

• Superior Vena Cava Introduction: This is the large venous channel which collects the blood from the upper half of the body and drains into the right atrium.
• Superior Vena Cava Draining areas: It brings deoxygenated blood from all the regions above the diaphragm (head, neck, face, brain, both upper limbs and thorax).
• Superior Vena Cava Formation: It is formed by right and left brachiocephalic veins.
• Superior Vena Cava Site: It is formed behind the lower border of 1st right costal cartilage.
• Superior Vena Cava Length: 7 cm.

Read And Learn More: Anatomy Important Question And Answers

• Superior Vena Cava Termination: It terminates by opening into the upper part of the right atrium behind the 3rd costal cartilage.
• Relations
• Anterior
  • Chest wall,
  • Internal thoracic vessels,
  • Anterior margin of the right lung and pleura, and
  • Vessels are covered by pericardium in its lower half.
• Superior Vena Cava Posterior
  • Trachea and right vagus (posteromedial to the upper part of the vena cava), and
  • The root of the right lung (posterior to the lower part).
• Superior Vena Cava Medial
  • Ascending aorta, and
  • Brachiocephalic artery.
• Superior Vena Cava Lateral
  • Phrenic nerve (with accompanying vessels), and
  • Right pleura and lung.

• Azygos vein: It opens into the superior vena cava at the level of 2nd costal cartilage just before it enters the pericardium.
• Small mediastinal veins, and
• Pericardial veins.

• The upper half develops from a right anterior cardinal vein.
• The lower half develops from a right common cardinal vein.

• In the obstruction of the superior vena cava above the opening of the azygos vein, the venous blood of the upper half of the body is returned through the azygos vein. The superficial veins are dilated on the chest up to the costal margin.
• In the obstruction of the superior vena cava below the opening of the azygos vein, the blood is returned through the inferior vena cava via the femoral vein. The superficial veins are dilated on both the chest and abdomen.
• In cases of the mediastinal syndrome, the signs of the superior vena cava obstruction appear 1st.

• It begins behind the upper border of the 2nd right sternochondral joint.
• It runs upwards, backwards and to the left, across the left side of the bifurcation of the trachea. Then it passes downwards behind the left bronchus and on the left side of the body of the 4th thoracic vertebra. It thus arches over the root of the left lung.
• It ends at the lower border of the body of the 4th thoracic vertebra by continues as the descending aorta.
• Thus, the origin and termination of the aortic arch are at the same level, although it begins anteriorly and terminates posteriorly.

• Anteriorly and to the left
  • Nerves (from before backwards)
    • Left phrenic,
    • Lower cervical cardiac branch of the left vagus,
    • Upper cervical cardiac branch of left sympathetic chain, and
    • Left vagus.
  • Left superior intercostal vein, deep to the phrenic nerve and superficial to the vagus nerve,
  • Left pleura and lung, and
  • Remains of thymus

• Posterior and to the right
  • Trachea, with the deep cardiac plexus and the tracheobronchial lymph nodes, Oesophagus,
  • Left recurrent laryngeal nerve,
  • The thoracic duct, and
  • Vertebral column.
• Superior: Three branches of the arch of the aorta
  • Brachiocephalic trunk,
  • Left common carotid, and
  • Left subclavian artery.
  • All these arteries are crossed, close to their origin by the left brachiocephalic vein.
• Inferior
  • Bifurcation of the pulmonary trunk,
  • Left bronchus,
  • Ligamentum arteriosum with superficial cardiac plexus on it, and
  • Left recurrent laryngeal nerve.

4. Aortic arch Branches

• • The brachiocephalic artery which divides into the right common carotid and right subclavian artery,
  • Left common carotid artery, and
  • Left subclavian artery.

• Chronological age: It develops at the end of 4th week of intrauterine life (IUL).
• Germ layer: Mesoderm.
• Site: Ventral to the foregut.
• Sources: The arch of the aorta is developed from four sources (from before backward)

• The ventral part of the aortic sac: Part of the arch of the aorta beginning of the arch of the aorta to the brachiocephalic trunk.
• Left horn of the aortic sac (truncus arteriosus): It forms the part of the arch of the aorta between the brachiocephalic trunk and the left common carotid artery.
• Left 4th arch artery: It forms the part of the arch of the aorta between the left common carotid artery and ductus arteriosus.
• Left dorsal aorta: It forms the rest of the arch up to the descending aorta.

Anomalies

• Coarctation of the aorta: This is due to the congenital stenosis or atresia of the arch of the aorta. It is distal to the origin of the left subclavian artery. The stenosis is due to a defect of the tunica media which may be
• Products and
• Postductal.
• Right-sided aortic arch: This is common in birds. It is due to the persistence of the right dorsal aorta below the 7th intersegmental artery.
• Double aortic arch: It is common in frogs. It is due to the persistence of the left dorsal aortae.
• Patent ductus arteriosus
• It is a short wide channel that connects the left pulmonary artery with the arch of the aorta.

• It is immediately distal to the origin of the left subclavian artery.
• It conducts most of the blood from the right ventricle into the aorta, thus short-circuiting the lungs.
• After birth, it is closed functionally within a week and anatomically in 8 weeks.
• The remnants of the ductus form a fibrous band called the ligamentum
• arteriosum.
• The left recurrent laryngeal nerve hooks around the ligamentum arteriosum. The ductus may remain patent after birth. The condition is called patent ductus arteriosus and may cause serious problems. The condition can be surgically treated.

•  Aortic knuckle: A convex bulging known as aortic knuckle is found on the left side of the sternal angle in a plain X-ray chest. It is formed by the distal part of the arch of the aorta.
•  Aortic aneurysm: It is the dilatation of the aorta. It presses the mediastinal structures. It stretches the left recurrent laryngeal nerve and may cause injury to it. may
•  Manifestations
  •  A gross dilatation of the aorta (aneurysm) may manifest as a pulsatile swelling in the suprasternal notch.
  •  It manifests as tracheal tug.

• It is a short wide channel that connects the left pulmonary artery with the arch of the aorta.
• It is immediately distal to the origin of the left subclavian artery.
• It conducts most of the blood from the right ventricle into the aorta, thus short-circuiting the lungs.
•  After birth, it is closed functionally within a week and anatomically in 8 weeks.
• The remnants of the ductus form a fibrous band called the ligamentum arteriosum.
•  The left recurrent laryngeal nerve hooks around the ligamentum arteriosum. The ductus may remain patent after birth. The condition is called patent ductus treated. arteriosus and may cause serious problems. The condition can be surgically treated.

Ligamentum arteriosum

•  Left pulmonary artery to
•  Inferior surface of the arch of the aorta.

•  In pulmonary stenosis and aortic stenosis, the ductus arteriosus is patent.
• It is the most common site of coarctation of the aorta. It may be
  •  Preductal coarctation: It is proximal to the attachment of ductus arteriosus.
•  Postductal coarctation: It is distal to the attachment of ductus arteriosus.
• “Site: It usually develops between the proximal and distal parts of the aorta through the intercostal and internal thoracic arteries. This type of coarctation is compatible with many years of life because the collateral circulation carries blood to the thoracic aorta inferior to the stenosis.
•  Manifestations: The collateral vessels may become so large that they cause notable pulsations in the intercostal spaces and erode the adjacent surfaces of the ribs. It is visible in radiographs of the thorax.

Patent ductus arteriosus