The Heart and Mediastinum Flashcards Preview

Block 2 > The Heart and Mediastinum > Flashcards

Flashcards in The Heart and Mediastinum Deck (54)
Loading flashcards...

What is the mediastinum?

Where does it extend from/to?

Broad central region that separates the two laterally placed pleural cavities

Extends from the thoracic inlet (aperture) at rib 1 to the diaphragm (T12) and from the sternal manubrium to the vertebral bodies


Is the patient on this x-ray in inspiration or expiration?


  • Flattening out of costodiaphragmatic recess
  • Large lung fields 


Label the features of the x-ray 

Top arrow: arch of aorta

Bottom arrow: Pulmonary trunk

Line: hilum 


What is the mediastinum divided by?

Sternal plane (T4/T5) divides the mediastinum into inferior and superior parts.

Inferior part divided into:

  • Anterior 
  • Middle
  • Posterior
  • Divided by the pericardial sac 





What can collect in the costodiaphragmatic recess?

Effusion fluid



What does the anterior mediastinum contain?

What are its borders?

  • Anterior border: sternum
  • Posterior border: pericardial sac
  • Superior border: sternal plane
  • Inferior border: diaphragm 


  • Thymus (part of)
  • Internal thoracic arteries
  • Fat
  • Connective tissue 


What can the internal thoracic arteries be used for?

Which arteries branch off them?

Which arteries do these meet?

Coronary Artery Bypass Graft (CABG)

Anterior intercostal arteries branch off them

  • Form anastamotic relationship with posterior intercostal arteries in each intercostal space. 


Label the structures on the diagram 


Where is the thymus normally located?

What is the thymic sail sign?

What happens to the thymus with age?

In the anterior and/or superior mediastinum

The thymus is relatively large in children therefore can be seen on x-ray 

Thymus shrinks with age 


What does the superior mediastinum contain?

Label them on the diagram 

Arch of aorta

Great vessels



Thoracic duct

Phrenic and Vagus nerves 


Where does the trachea normally bifurcate?

Around T4


Where do the great veins sit in relation to the arteries?

Label the vessels on the diagram 



What is the ligamentum arteriosis?

What happens if it stays open?

Was previously the ductus arteriosis vessel, fuses soon after birth. Open in utero to help blood bypass the lungs which are not fully developed. 

If it stayed open, it would create a mix of high O2 and low O2 blood from the arch of aorta and pulmonary trunk 


Where do the phrenic and vagus nerves travel in lungs?

Which important branch comes off the vagus? Where does it branch?

Phrenic nerve passes anterior to the hilum of the lung and the great vessels 

Vagus nerve passes posterior to the hilum of the lung, recurrent laryngeal artery.

  • Right recurrent laryngeal branches off around the right subclavian artery in the superior mediastinum
  • Left recurrent laryngeal branches off around the arch of the aorta behind the ligamentum arteriosum. 


What do the recurrent laryngeal nerves do?

Sensory below vocal chords

Motor to all extrinsic and intrinsic muscles of the larynx except cricothyroid (external laryngeal nerve) 


On which side would a hilar lymph node cause a hoarse voice? Why?

On which side could a pancoast tumour cause a hoarse voice? Why?

Hilar lymph node enlargement on the left side

  • Could compress the left laryngeal nerve 

Pancoast apical tumour could on the right side could compress the right recurrent laryngeal nerve against the right subclavian artery 


Describe the route of the vagus nerve in the mediastinum

Vagus nerves form a plexus around the trachea and oesophagus and give off anterior and posterior vagal plexuses on the surface of the oesophagus:

  • Left vagus: anterior plexus
  • Right vagus: posterior plexus 


Where does the left atrium of the heart sit against?

What can this anatomical relationship be used for?

Sits against the oesophagus 

Can be used for trans-oesophageal ultrasound of the heart 


What does the posterior mediastinum contain?

What are its borders?

  • Superior border: sternal plane
  • Posterior border: vertebral column
  • Anterior border: pericardial sac
  • Inferior border: diaphragm 


  • Oesophagus and vagal plexus
  • Descending aorta
  • Thoracic duct
  • Sympathetic chain
  • Azygous system 


What type of muscle is the oesophagus made up of?

What type of motor supply do they have?

Upper 1/= skeletal muscle

  • Somatic control

Lower 2/3 = smooth  muscle

  • Autonomic control



What does the middle mediastinum contain?

What are its borders?

  • Superior border: sternal plane
  • Lateral borders: parietal pleura of the lungs
  • Inferior borders: pericardial sac against diaphragm
  • Anterior and posterior: paricardial sac 


  • Heart and paricardium 
  • Lower superior vena cava
  • Lower ascending aorta
  • Lower pulmonary trunk 
  • Phrenic nerves (run along edges of fibrous pericardium)
  • Cardiac plexus 



What attaches the heart to the diaphragm?

Fibrous pericardium via the central diaphragmatic tendon 


Describe the surfaces of the heart

Posterior surface: base 

Inferior surface: diaphragmatic surface




Which chambers of the heart can be viewed anteriorly?

Why is this?

  • Right ventricle
  • Right atrium
  • Small amount of left ventricle

Due to the left rotation of the heart during embryological development


What are the atrial appendages?

What is their clinical significance?

Small pouches in the atria

During atrial fibrillation, blood flow becomes turbulent and in atrial appendages can become static where clots can form. 


What is the pericardium composed of?

Where is the pericardial cavity?

Fibrous outer pericardium: tough, fibrous layer surrounding entire heart and anchors to diaphragm.

Serous pericardium: 2 layers:

  • Parietal (outer): lines internal surface of pericardium
  • Visceral (inner): lines external surface of heart, forms the epicardium

Pericardial cavity between the parietal and visceral paricardium

  • Filled with pericardial fluid for lubrication



What is cardiac tamponade?

What can it be caused by?

What is inflammation of the pericardium?

Pericarditis: inflammation of the pericardium

  • Can result in pain if it affects the parietal layer

Cardiac tamponade: caused by increased pressure in the pericardial cavity caused by air, fluid e.t.c. Compresses heart allowing less room for contraction. This impairs contractility and prevents adequate refilling of the heart. 

  • Can be caused by haemopericardium (blood in pericardial space)


How is the pericardium formed embryologically?

What pockets are formed from this process?

During development heart tube becomes surrounded by pericardial sac with reflections at great vessels.

Folding of heart tube creates a passageway (transverse pericardial sinus) between arterial outflows & venous input

Reflection of serous layer creates blind ended oblique pericardial sinus posterior to heart


What can the transverse pericardial sinus be used for surgically?


To clamp off the arterial outflow from the heart


What are the atrioventricular valves?

What are they formed from?

What is the role of the papillary muscles?

Lie between atria and ventricles and allow for unidirectional flow of blood.

Formed from flap-like cusps that are anchored to the ventricle wall by tendons (chordae tendinae) which are anchored to papillary muscles.  

Papillary muscles contract to prevent the cusps from being blown back into the atria during ventricular systole. 

  • Note they do not contract to open valves, only contract to prevent vales being forced backwards during systole