CVS 1

• Mediastinum


  A visceral compartment between two lungs, includes mediastinal parietal pleura
• Mediastinum


  • Asymmetry
  • Merges into lung interstitium & bronchial trees
• Boundaries of mediastinum


  • Thoracic inlet (superiorly)
  • Diaphragm (thoracic outlet) (inferiorly)
  • Sternum & costal cartilages (anteriorly)
  • Bodies of 12 thoracic vertebrae (posteriorly)

  
• Mediastinum may shift in respiration & pathological condition
• Transverse thoracic plane


  An imaginary horizontal plane from sternal angle (anteriorly) to superior half of T5 (posteriorly)
• Divisions of mediastinum


  • Superior mediastinum
  • Anterior mediastinum
  • Middle mediastinum
  • Posterior mediastinum
• Superior mediastinum


  • Superiorly - Thoracic inlet
  • Inferiorly - Transthoracic plane
  • Anteriorly - Manubrium sternum
  • Posteriorly - 1st - 4th/5th thoracic vertebrae
  • Laterally - mediastinal parietal pleura

  
• Content of superior mediastinum

  • Thymus or its remnant
  • Trachea, oesophagus
  • Superior vena cava
  • Aortic arch, brachiocephalic trunk, left common carotid, subclavian arteries, internal thoracic vessels
  • Left and right brachiocephalic veins, forming SVC
  • Sympathetic trunk, cardiac nerves, phrenic nerve (lateral), vagus nerve (medial), left recurrent laryngeal nerve
  • Supreme intercostal, left superior intercostal
  • Accessory hemiazygos, inf thyroid vein
  • Lymph nodes
  • Origin of sternothyroid and sternohyoid attached posterior manubrium
  • Terminal part of thoracic duct- between left subclavian & left internal jugular vein
• Anterior mediastinum

  • Superiorly - Transverse thoracic plane
  • Inferiorly - Diaphragm
  • Anteriorly - Body of sternum
  • Posteriorly - Fibrous pericardium
• Content of anterior mediastinum

  • Sternopericardial ligaments
  • Branches of internal thoracic vessels
  • Lymph nodes & lymphatic vessels
  • Thymus (or its remnant)
  • Fat, loose connective tissue
  • Sternocostal triangles (of Morgagni)
• Sternocostal triangles (of Morgagni)

  • Filled with areolar tissue
  • Crossed by superior epigastric vessels and lymph vessels
  • Site for retrosternal hernia
• Middle mediastinum


  • Broadest part of inferior mediastinum
  • Superiorly - Transverse thoracic plane
  • Inferiorly - Diaphragm
  • Anteriorly - Anterior border of pericardium
  • Posteriorly - Posterior border of pericardium
  • Laterally - Mediastinal parietal pleura
• Content of middle mediastinum

  • Heart & pericardium
  • Great vessels: Ascending aorta, Pulmonary trunk with left and right pulmonary arteries & veins, Inferior half of superior vena cava
  • Nerves: Phrenic nerve, Deep part of cardiac plexus
  • Tracheal bifurcation & main bronchi
  • Root of the lungs
  • Subcarinal & lower paratracheal (tracheobronchial) lymph nodes
• Posterior mediastinum


  • Longest and narrowest inferior mediastinum
  • Superiorly - Transverse thoracic plane
  • Inferiorly - Posterior 1/3rd diaphragm
  • Anteriorly - Tracheal bifurcation, fibrous pericardium, pulmonary vessels
  • Posteriorly - 4th/5th - 12th thoracic vertebrae
  • Laterally - Mediastinal pleura
• Aorto-oesophageal and azygo-oesophageal recesses are medially in the posterior mediastinum
• Posterior mediastinum opens into the diaphragm
• Content of posterior mediastinum

  • Posterior mediastinal lymph nodes & thoracic duct
  • Descending aorta & its branches
  • Azygos, hemiazygos, accessory hemiazygos veins
  • Oesophagus (thoracic part)
  • Vagus nerve & eosophageal nerve plexus
• Mediastinal communication with the neck

  • Via parapharyngeal space (retropharyngeal and pretracheal spaces) into sup mediastinum and later inferior mediastinum
  • Via danger space
  • Via carotid sheath
• Pulmonary trunk


  • About 5cm length, 3cm diameter
  • Conveys deoxygenated blood from the right ventricle of heart to the lungs
  • Origin: Pulmonary annulus of right ventricle
  • Course: Incline posterosuperior
  • Terminates into right and left pulmonary arteries (equal size) at T6, 2-3cm inf to sternal plane, inf to aortic arch left to midline
  • Bifurcation lies anteroinferior and left of tracheal bifurcation

  
• Ascending aorta


  • 5cm length, origin: Aortic orifice of left ventricle
  • Course: Begins at left 3rd costal cartilage (lower border), Traverses superiorly, curve anteriorly and to the right, Terminates: Right 2nd sternocostal joint (sternal angle level) & continues as arch of aorta
  • Enclosed in a sheath of serous pericardium, together with pulmonary trunk
• Relations of ascending aorta

  • Anteriorly: Right auricle, infundibulum of right ventricle, root of pulmonary trunk
  • Posteriorly: Right pulmonary artery, left atrium, right main bronchus
  • To the left side: Pulmonary trunk above and left atrium below
  • To the right side: Superior vena cava, right atrium
  • Para-aortic body
• Aortic arch


  • Origin: Continuation of ascending aorta at the level of sternal angle
  • Course: Arches superiorly, posteriorly & to the left, then inferiorly, Ascend anterior to right pulmonary artery & bifurcation of the trachea; then passes over the hilum of the left lung, thereby descend posterior to left T4 vertebra
  • Termination: Lower border of 4th thoracic vertebra & continues as the descending aorta
• Relations of aortic arch

  • Anteriorly: Left lung & pleura, remains of thymus, left superior intercostal vein, left phrenic nerve, left vagus nerve & its branches
  • Posteriorly: Trachea, oesophagus, thoracic duct, vertebrae column
  • Superiorly: Brachiocephalic trunk, left common carotid & left subclavian arteries
  • Inferiorly: Bifurcation of pulmonary trunk, left bronchus, ligamentum arteriosum, left recurrent laryngeal nerve
• Descending thoracic aorta


  • Origin: Continuation from arch of aorta at left lower border of 4th thoracic vertebra
  • Course: Descends on the left side of T5 - T12 vertebrae. Lies posterior to root of left lung, pericardium & oesophagus
  • Terminate: Aortic opening of diaphragm in midline
• Relations of descending thoracic aorta

  • Anterior- hilum left lung, oesophagus
  • Posterior- vertebral column, accessory hemiazygos, hemiazygos
  • Right- thoracic duct, azygos vein
  • Inferior- mediastinal pleura both lungs
• Branches of descending thoracic aorta

  • Posterior intercostal arteries (3rd - 11th post. intercostal arteries on each side)
  • Subcostal arteries (Both sides, run along the lower border of the 12th rib)
  • Pericardial branches (Posterior pericardium)
  • Oesophageal branches (Distal thoracic oesophagus)
  • Bronchial arteries (Pulmonary areolar tissue, visceral pleura)
  • Mediastinal branches (Posterior mediastinum)
  • Superior phrenic branches (Supply superior aspect of diaphragm)
• Brachiocephalic trunk


  • First and largest branch of aortic arch, 4 - 5 cm length
  • Anterior to trachea & posterior to left brachiocephalic vein
  • Course: Ascend superolaterally to the right of trachea. It divides into right subclavian & right common carotid arteries behind right sternoclavicular joint

  
• Right common carotid artery

  • Origin: Brachiocephalic trunk, posterior to sternoclavicular joint
  • Course: Ascend superolaterally to 1st rib (posterior to sternal end clavicle & scalenus anterior), then inferolaterally across superior 1st rib becoming axillary artery at its external border
• Right subclavian artery


  • Origin: Brachiocephalic trunk, posterior to sternoclavicular joint
  • Course: Ascend superolaterally to 1st rib (posterior to sternal end clavicle & scalenus anterior), then inferolaterally across superior 1st rib becoming axillary artery at its external border
• Left subclavian artery


  • Origin: Third branch of the arch aorta & lies posterior to left common carotid artery
  • Course: Ascends into neck (post to scalenus muscle), then inferolaterally to external border 1st rib to become left axillary artery
• Left common carotid artery

  • Origin: Second branch of aortic arch; lies posterior & to the left of the brachiocephalic trunk
  • Course: Ascends anterior to left subclavian artery to the left of trachea, then passes posterior to left sternoclavicular joint to enter the neck
  • Thoracic part - 2 - 2.5cm long, anterior to trachea, moves to the left eventually
  • Cervical part (including whole right CCA)

  
• Brachiocephalic veins


  • Forms at posterior to sternoclavicular joint by union of internal jugular vein & subclavian vein on both sides of neck
  • Drains blood from head, neck & upper limb
  • Right side- 2.5cm long, descend almost vertical, anterolateral to brachiocephalic trunk
  • Left side is longer (6cm) - passes anterior to the root of 3 major branches of aortic arch & trachea

  
• Superior vena cava


  • Large vein of thorax, 7cm length
  • Forms by union of right & left brachiocephalic veins
  • Descend vertically, slight right convex, ends in the right atrium
  • Its inferior half within fibrous pericardium & covered anterolaterally by visceral serous pericardium

  
• Relations of superior vena cava

  • Posteromedially- trachea & right vagus
  • Posterior- hilum right lung
  • Superior (left)- brachiocephalic trunk & ascending aorta
  • Inferior (anteromedial)- aorta
  • Laterally- right phrenic nerve
  • Joins by azygos vein on posterior aspect just before it enters the pericardium

  
• Inferior vena cava


  • Return blood to inferoposterior atrium from infradiagphragmatic tissue
  • Passes caval foramen in diaphragm
  • Thoracic part is short, partly outside and within pericardial sac
• Azygos venous system


  • "a-zygos" means "un-paired"
  • Made up of: azygos vein, Hemiazygos vein, Accessory hemiazygos vein
  • Drains the back, thoraco-abdominal walls & mediastinal viscera

  
• Azygos vein


  Union of right ascending lumbar vein & right subcostal vein
• Brachiocephalic veins


  • Descend vertically, slight right convex, ends in the right atrium
  • Its inferior half within fibrous pericardium & covered anterolaterally by visceral serous pericardium

  
• Superior vena cava


  • Posteromedially- trachea & right vagus
  • Posterior- hilum right lung
  • Superior (left)- brachiocephalic trunk & ascending aorta
  • Inferior (anteromedial)- aorta
  • Laterally- right phrenic nerve
  • Joins by azygos vein on posterior aspect just before it enters the pericardium

  
• Superior vena cava obstruction

  Clinical application