Superior Mediastinum Flashcards
What is the mediastinum and where is it located?
Central compartment of the thorax Located between left and right pleural cavities
Where does the mediastinum divide into the superior and inferior mediastinum?
T4/5
What are the other names for T4/5?
The sternal angle Transverse Thoracic Plane
Complete the diagram of the mediastinum
What 3 parts is the inferior mediastinum divided into?
- Anterior mediastinum
- Middle mediastinum
- Posterior mediastinum
What are the boundaries of the superior mediastinum?
Superior
Inferior
Anterior
Posterior
Lateral
Superior: superior thoracic aperture (manubrium, 1st rib and costal cartilage, T1 vertebra)
Inferior: transverse thoracic plane (sternal angle to vertebral level T4/T5)
Anterior: Manubrium
Posterior: T1-T4/5 vertebral bodies
Lateral: Mediastinal pleura
What are the boundaries of the anterior mediastinum?
Anteriorly
Posteriorly
Inferiorly
Superiorly
Anteriorly - Sternum
Posteriorly - Pericardial sac
Inferiorly - Diaphragm
Superiorly - Level T4/5
What 7 structures reside in the superior mediastinum?
- Arteries (arch of aorta and branches)
- Veins (brachiocephalic veins, superior vena cava)
- Phrenic and Vagus nerves
- Oesophagus
- Trachea
- Thoracic duct
- Thymus gland (part)
Where is the thymus gland located?
Immediately deep to the sternum in Superior AND Anterior Mediastinum
What type of organ is the thymus gland?
Lymphoid organ
Where are T and B lymphocytes produced and matured?
T and B lymphocytes are produced in bone marrow. Bs mature in bone marrow, Ts mature in Thymus.
Which 3 nodes does lymph drain from at the thymus gland?
Parasternal nodes
Brachiocephalic nodes
Tracheobronchial nodes
At what stage of life does the thymus gland atrophy and turn into fat?
Adolescence
Which artery supplies the thymus gland?
Internal thoracic arteries
What is 1,2, and 3?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
What is 1,2 and 3?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
What are the 3 branches of the aortic arch?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
What does the brachiocephalic trunk branch into?
Right common carotid & Right Subclavian arteries
What are the 2 branches of the ascending aorta?
- Left coronary artery (LCA)
- Right coronary artery (RCA)
What are the 3 branches of the descending aorta?
- Posterior intercostal
- Bronchial arteries
- Lumbar arteries
Complete the diagram
What percentage of people have normal branches of the aorta? (no anatomical variation)
65%
Label the diagram
- Superior vena cava
- Left brachiocephalic vein
- Right brachiocephalic vein
- Internal jugular vein
- Subclavian vein
What is this structure?
Ligamentum Arteriosum
What is the embryological version of ligamentum arteriosum?
Ductus ateriosus
What is ductus arteriosus and how does it work?
An open duct connecting the pulmonary trunk and the arch of aorta.
Important in fetal circulation allowing blood to bypass the immature lungs.
When does ductus arteriosus close?
At birth
Where does the trachea run?
From larynx to bronchus
What is the oesophagus made of?
Muscular tube
Where does the oesophagus run from?
From pharynx to stomach
What is this structure?
Thoracic duct
What is the function of the thoracic duct?
Transports lymph to venous system
Where does the thoracic duct recieve lymph from?
- Receives multiple branches throughout thorax
- Numerous lymph nodes associated with thoracic (descending) aorta
Which 2 structures pass the thorugh the superior and inferior mediastinum?
Thoracic duct
Oesophagus
Which nerves are these?
Left and right phrenic nerves
Where do the phrenic nerves originate from?
The anterior rami of spinal nerves C3, C4, C5
Where do the phrenic nerves enter the superior mediastinum?
Between brachiocephalic veins and subclavian arteries
Do the phrenic nerves pass anterior or posterior to the main bronchi?
Anterior
Where does the phrenic nerves supply -
Motor supply
Sensory supply
Motor supply to diaphragm
Sensory supply to diaphragm (central region) and parietal pleura (diaphragmatic and mediastinal)
Complete the diagram
Do the vagus nerves pass anterior or posterior to the main bronchus?
Posterior
What type of nerves are the vagus nerves and where do they originate from?
Cranial nerves so originate from brainstem
Where do the vagus nerves enter the superior mediastinum?
Just medial to the phrenic nerve
Where does the recurrent laryngeal branch supply?
Larynx
What type of nervous supply does the vagus nerve provide?
Parasympathetic supply via pulmonary, cardiac and oesophageal plexi
What 4 things does the anterior mediastinum contain?
- Thymus gland in children which atrophies in the adult and is replaced by fatty tissue
- Pericardial-sternal ligaments
- Lymph nodes (parasternal) and vessels
- Internal thoracic artery
Complete the diagram of the developing heart (part 1)
How does the heart develop?
- Angiogenic clusters form in the mesoderm and these canalise to form early blood vessels.
- Two large blood vessels known as the heart tubes form in the cardiogenic area
At how many days in foetal development do the heart tubes grow and fuse?
21 days
Complete the diagram of the developing heart (part 2)
What 4 regions is a newly developed heart tube made up of in foetal heart development?
- Sinus venosus
- Primordial atrium
- Primordial ventricle
- Truncus arteriosus
At how many days does the pericardial cavity become too long and need to fold in foetal heart development?
Day 23
What does folding of the heart tube in foetal heart development result in?
Ventricles and outflow tracks positioned anteriorly
Atria and veins posteriorly
What happens after the heart tube folding in foetal heart development?
Septa then grow to divide the heart into 4 chambers
Which 2 structures in the foetal heart allow it to bypass the lungs?
- Foramen Ovale
- Ductus Arteriosus
Why is a small amount of blood still needed at the lungs in a foetus?
For lung development
What is foramen ovale?
Opening between the right and left atria in the foetus and allows oxygenated blood to by-pass lungs
Complete the diagram on foramen ovale
What is fossa ovalis?
The embryological remnant of the Foramen Ovale which closes after birth
What does the diagram show?
Fossa Ovalis in the adult inter-atrial septum
Complete the diagram
