Arteries and Veins of the Thorax

Arteries of the Thorax

• The arteries of the thorax stem from the aorta.

Parts of the Aorta in the Thorax

• The aorta is the largest artery in the body.
• It arises from the left ventricle of the heart, arches backward over the heart, and descends through the thorax and abdomen, where it eventually divides into the common iliac arteries, which enter the pelvis.
• The aorta is described in four parts; three are found in the thorax.

Ascending Aorta

• The ascending aorta ascends 5 cm, next to the pulmonary trunk.
• Branches include:
  • Coronary arteries
  • Arch of aorta

Arch of Aorta

• The arch of aorta follows the ascending aorta and arches posteriorly over the left principal bronchus.
• There are three major branches of the aortic arch:
  • The brachiocephalic artery
  • The left common carotid artery
  • The left subclavian artery
• Each of these vessels is classified as an elastic artery.
• The brachiocephalic artery is located only on the right side of the body; there is no corresponding artery on the left.
• The brachiocephalic artery branches into the right subclavian artery and the right common carotid artery.
• The left subclavian and left common carotid arteries arise independently from the aortic arch but otherwise follow a similar pattern and distribution to the corresponding arteries on the right side.

Descending Thoracic Aorta

• The thoracic aorta begins at the level of vertebra T5 and continues through to the diaphragm at the level of T12, initially traveling within the mediastinum to the left of the vertebral column.
• The thoracic aorta gives rise to several branches, which are collectively referred to as visceral branches and parietal branches.

Visceral Branches

• Supply blood primarily to visceral organs.
• Include:
  • Bronchial arteries
  • Pericardial arteries
  • Esophageal arteries
  • Mediastinal arteries

Bronchial Artery

• Typically two on the left and one on the right.
• Supplies systemic blood to the lungs and visceral pleura, in addition to the blood pumped to the lungs for oxygenation via the pulmonary circuit.
• Follow the same path as the respiratory branches, beginning with the bronchi and ending with the bronchioles.
• Considerable, but not total, intermingling of the systemic and pulmonary blood at anastomoses in the smaller branches of the lungs.
• The systemic vessels also deliver nutrients to the lung tissue.
• The mixed blood drains into typical pulmonary veins, whereas the bronchial artery branches remain separate and drain into bronchial veins.

Pericardial Artery

• Supplies blood to the pericardium.

Esophageal Artery

• Provides blood to the esophagus.

Mediastinal Artery

• Provides blood to the mediastinum.

Parietal Branches (Somatic Branches)

• Include the intercostal and superior phrenic arteries.

Intercostal Artery

• Provides blood to the muscles of the thoracic cavity and vertebral column.

Superior Phrenic Artery

• Provides blood to the superior surface of the diaphragm.

Right Coronary Artery

• Passes along the coronary groove between the right atrium and right ventricle to supply the heart muscle itself.

Branches of the Descending Thoracic Aorta

• Bronchial Artery: Supplies the bronchial tree.
• Esophageal Artery: Several branches run over the esophagus.
• Posterior Intercostal Arteries: Supply the posterior intercostal spaces.
• Subcostal Artery: Travels below the twelfth rib.

Abdominal Aorta

• The abdominal aorta descends over the lumbar vertebrae and terminates at the level of L4 by dividing into the common iliac arteries.
• Branches include:
  • Celiac trunk
  • Inferior/superior mesenteric
  • Inferior phrenic
  • Lumbar
  • Median sacral
  • Middle suprarenal
  • Ovarian/testicular
  • Renal
  • Common iliac

Veins

• The right atrium receives all of the systemic venous return.
• Most of the blood flows into either the superior vena cava or inferior vena cava.
• Systemic venous circulation from above the diaphragm generally flows into the superior vena cava; this includes blood from the head, neck, chest, shoulders, and upper limbs.
• Most venous blood flow from the coronary veins flows directly into the coronary sinus and, from there, directly into the right atrium.
• Beneath the diaphragm, systemic venous flow enters the inferior vena cava, that is, blood from the abdominal and pelvic regions and the lower limbs.

The Superior Vena Cava

• The superior vena cava drains most of the body superior to the diaphragm.
• On both the left and right sides, the subclavian vein forms when the axillary vein passes through the body wall from the axillary region.
• It fuses with the external and internal jugular veins from the head and neck to form the brachiocephalic vein.
• Each vertebral vein also flows into the brachiocephalic vein close to this fusion.
• These veins arise from the base of the brain and the cervical region of the spinal cord and flow largely through the intervertebral foramina in the cervical vertebrae.
• They are the counterparts of the vertebral arteries.
• Each internal thoracic vein, also known as an internal mammary vein, drains the anterior surface of the chest wall and flows into the brachiocephalic vein.
• The remainder of the blood supply from the thorax drains into the azygos vein.
• Each intercostal vein drains muscles of the thoracic wall, each esophageal vein delivers blood from the inferior portions of the esophagus, each bronchial vein drains the systemic circulation from the lungs, and several smaller veins drain the mediastinal region.
• Bronchial veins carry approximately 13% of the blood that flows into the bronchial arteries; the remainder intermingles with the pulmonary circulation and returns to the heart via the pulmonary veins.
• These veins flow into the azygos vein, and with the smaller hemiazygos vein (hemi- = “half”) on the left of the vertebral column, drain blood from the thoracic region.
• The hemiazygos vein does not drain directly into the superior vena cava but enters the brachiocephalic vein via the superior intercostal vein.
• The azygos vein passes through the diaphragm from the thoracic cavity on the right side of the vertebral column and begins in the lumbar region of the thoracic cavity.
• It flows into the superior vena cava at approximately the level of T2, making a significant contribution to the flow of blood.
• It combines with the two large left and right brachiocephalic veins to form the superior vena cava.

Veins of the Thoracic Region