Lecture 2: Superior mediastinum Flashcards
What is the division between the superior and inferior mediastinum?
Transverse thoracic plane
Level of the sternal angle - junction of vertebrae T4/5
What are the three divisions of the inferior mediastinum?
Anterior
Middle
Posterior
What is the superior limit of the superior mediastinum?
The superior thoracic aperture - manubrium, 1st rib and costal cartilage, T1 vertebra
What is the anterior boundary of the superior mediastinum?
Manubrium
What is the posterior boundary of the superior mediastinum?
T1-T4/5 vertebral bodies
What is the lateral boundary of the superior mediastinum?
Mediastinal pleura
What is in the superior mediastinum?
Arteries (arch of aorta and branches)
Veins (brachiocephalic veins, superior vena cava)
Trachea
Oesophagus
Thoracic duct
Phrenic and Vagus nerves
Thymus gland (part)
Where is the thymus gland?
Located immediately deep to the sternum in Superior AND Anterior Mediastinum
What is the thymus gland?
Lymphoid organ
T and B lymphocytes are produced in bone marrow.
Bs mature in bone marrow, Ts mature in Thymus.
What is the blood supply of the thymus?
Internal thoracic arteries
What replaces the thymus gland when it atrophies at puberty?
Fat
Where does lymph drain from the thymus gland?
Through from parasternal, brachiocephalic and tracheobronchial nodes
What are the three branches of the aortic arch?
Brachiocephalic trunk
Left common carotid artery
Left subclavian artery
Which vessel branches into the right common carotid & right Subclavian arteries?
The brachiocephalic trunk
What are the 1st arteries branching from the ascending aorta?
Left & right coronary arteries
What branches from the descending aorta?
Intercostal, bronchial & lumbar arteries
What % of people have the normal pattern of aortic branching?
65%
Which two veins come together to form the superior vena cava?
Left and right brachiocephalic veins
Which two veins come together to form the brachiocephalic veins?
An internal jugular vein and a subclavian vein
What drains into the venous angle?
Lymph
What artery runs along with the internal jugular?
The common carotid
What is the name of the structure that becomes the ligamentum arteriorsum?
Ductus arteriosus
What two structures are connected by the ligamentum arteriosum?
The pulmonary trunk and the arch of the aorta
What is the purpose of the ductus arteriosus?
Important in foetal circulation allowing blood to bypass the immature lungs
After birth, the ductus arteriosus closes and becomes what?
The ligamentum arteriosum
Where does the oesophagus run from and to?
Pharynx to stomach
Where does the trachea run from and to?
Larynx to bronchi
Where do the phrenic nerve originate from?
C3, C4 and C5
Where do the phrenic nerves enter the superior mediastinum?
Between the brachiocephalic veins and the subclavian arteries
Do the phrenic nerves run anterior or posterior to the main bronchi?
Anterior
What structures do the phrenic nerves provide motor and sensory supply to?
Motor - diaphragm
Sensory - diaphragm and pleura (diaphragmatic and mediastinal)
How many phrenic nerves are there?
2
Where do the vagus nerves originate?
CNX - brainstem
Where do the vagus nerves enter the superior mediastinum?
Close to but medial to the phrenic nerve
How many vagus nerves are there?
2
What branches from the vagus nerves?
Recurrent laryngeal nerves to supply the larynx
Do the vagus nerves travel anterior or posterior to the main bronchi?
Posterior
What type of supply do the vagus nerves provide?
Parasympathetic supply via pulmonary, cardiac and oesophageal plexi
What is present in the anterior mediastinum?
Thymus gland/fatty tissue
Pericardial-sternal ligaments
Lymph nodes and vessels
Internal thoracic artery
What are the boundaries of the anterior mediastinum?
Sternum anteriorly
Pericardial sac posteriorly
Diaphragm inferiorly
What layer do the angiogenic clusters form from?
Mesoderm
What are the two large blood vessels called that form in the cardiogenic area?
Heart tubes
By which day does the single heart tube begin to fold?
Day 23
Which chambers are anterior and posterior?
Anterior - ventricles
Posterior - atria
What is the name of the primitive outflow vessel?
Truncus arteriosus
What is the name of the primitive inflow vessel?
Sinus venosus
What are the two features of the foetal heart that allow blood to bypass the lungs?
Foramen ovale
Ductus arteriosus
What is the foramen ovale?
Opening between the right and left atria in the foetus and allows oxygenated blood to by-pass lungs
When the foramen ovale closes, what does it become?
Fossa ovalis
Where is the fossa ovals located in the adult heart?
In the inter-atrial septum
