Week 19 Anatomy

Aorta.

  • 2.5cm diameter
  • Ascending is intrapericardial, middle mediastinum
  • Arch – begins posterior to 2nd R sternocostal joint, arches superiorly, posteriorly and to left then inferiorly. Rise ant to trachea and R pulm art, apex at L of trachea and oesophagus, descends posterior to root of L lung, ending posterior to L 2nd sternocostal joint. (next to body of T4 vertebra)
  • Branches – brachiocephalic trunk, L common carotid, L subclavian.
  • Aorta passes diaphram at T12

 

Oesophagus.

  • Passes at T10 with vagal trunks, oes branches of L gastric artery, veins and lymphatics.
  • 18-25cm long, stratified squamous epithelium. Starts at C6 vertebra(inf border of cricoid cartilage). Enters cardia of stomach at T11.
  • Innervated by vagus(parasympathetic) and cervical and thoracic sympathetic plexus.
  • Narrowest at top sphincter – cricopharyngeal

 

Lymphatics.

  • Pulmonary lymphatic plexus in viscera. Superficial drain parenchyma and visceral pleura–>bronchopulmonary LN in Hilum.
  • Deep lymphatic plexus are in submucosa of bronchi–> pulmonary LNs–>bronchopulmonary(hilar) LNs–> both superficial and deep then drain into superior and inferior tracheobronchial LNs. –> R and L bronchomediastinal Lymph trunks–> terminate at venous angles.

 

Azygous veins.

  • Starts at T12 when lumbar veins and R subcostal vein join.
  • Runs on R side of thoracic vertebral column arches over R main bronchus and drains into SVC.
  • Drains posterior thoracic wall, abdomen , R bronchial vein
  • L bronchial vein drains into accessory hemiazygos
  • IVC passes diaphragm at T8 – with R phrenic nerve

 

Lungs:

Lung roots/hila.

Right

  • Veins – most anterior and inferior
  • Bronchus usually middle of posterior.

 

Left

  • Artery is most superior
  • Veins – most anterior and inferior
  • Bronchus usually middle of posterior.

 

Pulmonary ligament – sleeve for expansion of vessels.

 

Arrangements of lobes and segments

  • R bronchus is wider, shorter and more directed inferior so can get aspirations.
  • L bronchus – passes inferolaterally, inferior to arch of aorta, anterior to oesophagus and thoracic aorta.
  • Bronchopulmonary segments – seperated by connective tissue, supplied independently by bronchus and pulmonary artery.  Surgically resectable. 18-20 all up

 

Blood supply of the lungs

  • Pulmonary arteries – deoxygenated blood
  • 2 left and one R bronchial arteries – arise from aorta and supply lung parenchyma.
  • Pleura supplied by arterial supply of thoracic wall.

 

Trachea.

  • Bifurcates at trans thoracic plane or sternal angle.
  • C shaped cartilage
  • Trachea is 10cm long and 2.5cm in diameter. In the first year of life it is 3mm in diameter.
  • Starts at cricoid C6

 

Vagus and phrenic nerves.

  • Vagus – carotid sheath posterior most –> R loops under R subclavian artery to give Recurrent laryngeal, L loop under arch of aorta next to ligementum arteriosum. Vagus runs down medially to aorta and form network around oesophagus and has a anterior and posterior trunk.
  • Phrenic decends on anterior scalene passes anterior to subclavian artery and posterior to subclavian vein and passes anterior to hilum–> pericardium and via vena cava hiatus T8.

 

Transverse thoracic plane

  • From T4/T5 disc to manubriosternal angle.
  • Seperates mediastinum into superior and inferior.
  • Inferior mediastinum is divided into anterior, posterior and middle (Discussed in Week 18)

 

Coronary arteries

  • Just deep to epicardium in fat.
  • Aortic valve cusps have R and L coronary arteries – fills during diastole
  • R coronary artery –> gives sinoatrial nodal branch –> R marginal branch–> goes posteriorly –> gives atriventricular nodal branch–> often giving posterior interventricular artery(if R dominant in 67%)
    • R supplies SA node in 60% and AV node in 80% of people.
    • R atrium and ventricle, L diaphragmatic area of ventricle, part of IV septum.
  • L coronary emerge and split into L anterior descending and L circumflex artery. LAD gives off diagonal branch. Circumflex gives off L marginal arteries.
    • L atrium, Most of L ventricle, most of IV septum, part of R ventricle.

 

Coronary Veins

  • Great cardiac vein – drain ant IV septum and groove
  • Middle cardiac vein – drain posterior IV groove
  • Small cardiac vein – drain R atrium and ventricle
  • All drain into coronary sinus and into IVC