Mediastinum Flashcards
whats the mediastinum ?
media = middle
stinum = between 2 objects
mediastinum is the area between the 2 lungs
from anterio posterior view where does it extend from?
Anteriorly sternum
the 12 T vertebrae posteriorly
from a superior inferior view where does it extend from?
thoracic inlet to the diaphragm
how is the mediastinum divided into superior and inferior?
an imaginary line between the sternal angle ( manubrio sternal joint ) to the lower body of T4
above the line is superior
below it is inferior
what divides the inferior mediastinum ?
its divided by the pericardium sac
divides it into : anterior , middle , posterior
whats the superior boundary of the superior mediastinum?
superiorly by the thoracic inlet
whats the inferior boundary of the superior mediastinum?
inferiorly by the imaginary line ( from sternal angle to disk between T4, T5)
whats the anterior boundary of the superior mediastinum?
manubrium sterni
whats the posterior boundary of the superior mediastinum?
upper 4 thoracic vertebrae ( T1-T4)
what do forms the sides of the superior mediastinum?
mediastinal pleura
what are the anterior muscles that are found in the superior mediastinum?
Sternohyoid
sternothyroid
what are the posterior muscles that are found in the superior mediastinum?
longus coli posteriorly
what are the contents of superior mediastinum from anterior to posterior?
Manubrium
Thymus gland ( found also in the anterior mediastinum ) its directly manubrium sterni
Right and left brachiocephalic vein (unit to form SVC ) + LEFT SUPERIOR INTERCOSTAL VEIN
Aortic arch and its branches ( Brachiocephalic artery , left common carotid artery and then left subclavian )
Trachea ( Formed of hyaline cartilage + divides at the upper border of 5th thoracic , or lower border or 4th thoracic حسب مصادرك )
Esophagus ( enters the diaphragm at T10 , eggs at 10 )
whats the relation between the branches of the aortic arch?
the aortic arc is bending backwards so the branches are parallel to each others like the brachiocephalic is the most anterior one then the left common carotid and its behind the brachiocephalic and then behind it is the left subclavian and its the most posterior one
what are the nerves on the RIGHT side of the superior mediastinum ?
Right vagus –> directly on the right side of the trachea
Right phrenic nerve –> اقصى اليمين runs on the right side of the right brachiocephalic vein and SVC
what are the nerves on the LEFT side of the superior mediastinum?
Left vagus : Left side of the subclavian then to the left side of aortic arch
Left phrenic nerve : Descends on the LEFT side of left common carotid and then left side of aortic arch
Left recurrent laryngeal nerve : branch from left vagus and curves below aortic arch to go back to the larynx
Cardiac branches : from the 2 vagus nerves
which duct runs in the superior mediastinum?
thoracic duct runs on the left side of esophagus ( also runs in the posterior mediastinum )
which lymph nodes are found in the superior mediastinum?
brachiocephalic
Paratracheal and superior tracheobronchial groups
whats the origin of ascending aorta?
aortic orifice at the level of LEFT 3rd intercostal space (SVC was right 3rd costal cartilage )
whats the termination of ascending aorta?
Right 2nd costal cartilage by becoming the arch of aorta? ( 2nd costal cartilage cuz thats the sternal angle and the beginning of the superior mediastinum and we know that aortic arch is in the superior mediastinum
what are the branches of ascending aorta?
right coronary artery ( from the anterior sinus )
left coronary artery ( from the left posterior sinus )
whats the beginning of the aortic arch?
it begins at the termination of the ascending aorta ( right 2nd costal cartilage , sternal angle, superior mediastinum )
whats the termination of aortic arch?
the same level except its that the aortic arch is bending backward so it will go from anterior ( right 2nd costal cartilage ) to the posterior (LOWER BORDER OF 4TH thoracic vertebrae ,on the same level as sternal angle but posteriorly ) then it continue as descending aorta
whats the course of the aortic arch?
upward and backward then to the left infront the trachea
curves on the left side of trachea
curves downwards on the left side of the lower border or the body of the 4th thoracic vertebra
what are the branches of the aortic arch?
1- brachiocephalic artery
2- left common carotid artery
3- left subclavian artery
whats the common sites of aortic aneurysm?
the distal part of the the ascending aorta
the abdominal aorta
why is the distal part of the ascending aorta is common part for aneursym but not the proximal?
because its not reinforced by fibrous pericardium
at what level does the SVC will form?
its formed by the joining of the left and right brachiocephalic veins at the 1ST RIGHT COSTAL CARTILAGE
where does the SVC terminate?
right 3rd costal cartilage where it empty in the right atrium
what are the tributaries of SVC?
azygos vein –> right 2nd costal cartilage b4 it pierces pericardium ( sternal angle level )
several small veins
whats the beginning of trachea?
6th cervical vertebrae
whats the termination of trachea?
5th thoracic vertebrae OR 4th thoracic , حسب مصادرك
bs its the imaginary line, like the end of the superior mediastinum
what happens to the trachea as it goes down?
the lower part of it deviates to the right side
what constitutes the trachea?
hyaline cartilage
16-20 rings of hyaline cartilage
the ring is incomplete posteriorly and its separated from the esophagus by muscle and C.T
whats the differences between the right and left bronchus?
right bronchI : short, wider, more vertical ( in line with the trachea ), enter hilium at T5
Left bronchi : longer, narrower, oblique , enter the hilium at T6
NO BRONCHUS OUTSIDE THE LUNGS
wheres the left vagus nerve located?
between left common carotid and left subclavian
the LEFT recurrent laryngeal nerve is hooked around which ligament?
ligamentum arteriosum
The right recurrent laryngeal nerve is hooked under what?
artery that ascends between the trachea and esophagus to the larynx
why doesnt the left recurrent laryngeal moves up?
because the LEFT 6th aortic arch presists as ductus arteriosus and then ligamentum arteriosum but the RIGHT one disappears so its get hooked around the 4th aortic arch ( subclavian artery)
what happens at the sternal angle?
1- 2nd costal cartilage lie at this level so ribs can be counted from here
2- Ascending aorta end at this level
3- arch of aorta start and end here ( remember it ends in the posterior T4 compartment )
4- descending aorta begins
5- bifurcation of trachea into two bronchi
6- bifurcation of pulmonary trunk into 2 pulmonary arteries
7- azygos vein opens in SVC
8- thoracic duct crosses the esophagus to reach the left side
9- medial margins of pleura and the lungs on each side oppose each others in the middle line
whats the site of the anterior mediastinum?
below the imaginary line and infront of the pericardium sac
anteriorly –> body of the sternum
posteriorly –> the middle mediastinum ( pericardium )
on the sides –> mediastinal layer of pleura
whats the content of the anterior mediastinum?
- superior and inferior sternopericardial ligaments
- part of the thymus gland
- internal mammary artery
- two or 3 lymph nodes and lymphatic
-areolar tissue
- sternocostalis muscle ( the muscle that anchors the sternocostal joints )
whats the site of middle mediastinum?
below the imaginary line and its at the pericardium sac
anterior : anterior mediastinum
posterior : posterior mediastinum
superiorly : imaginary line
inferiorly : diaphragm
whats the content in the mediastinum ?
pericardium of the heart and the heart and its vessels :
ascending aorta
pulmonary trunk
bifurcation of pulmonary trunks
lower half the superior vena cava
upper part of the inferior vena cava
4 pulmonary veins
right and left phrenic nerves along side the pericardium ( NOT THE VAGUS CUZ ITS POSTERIORLY)
-inferior tracheobronchial lymph nodes
whats the site of posterior mediastinum?
between the pericardium and the thoracic vertebrae
superiorly –> imaginary horizontal plane
inferiorly : diaphragm
anteriorly : pericardium sac
posterior :lower 8 vertebrae ( 5-12 ), the upper 4 are in the superior
what are the contents of posterior mediastinum?
- descending aorta
- esophagus
-azygos and hemiazygos veins ( they are on the vertebrae )
- 2 vagus nerves forming the esophageal plexus
- splanchnic nerves
- thoracic duct runs on the right side ( LEFT IN THE SUPERIOR MEDIASTINUM )
- posterior mediastinal lymph nodes
when does the esophagus begin?
6th cervical vertebrae
when does the esophagus end?
enters the diaphragm at T10 and stomach at T11
whats the course of esophagus?
lies on the median plane
descending vertically in the superior mediastinum and posterior mediastinum and it has 2 curvatures to the left side :
1ST curvature : deviate to the left and reach the midline again at T5
2nd curvature : shifts towards the left again as it enters the diaphragm
what reflex does the esophagus has?
anteroposterior flexures
what are the constrictions of the esophafus
every 3 inches after the 6th inchs
1- beginning of the esophagus ( 6 inches from the incisor teeth )
2- opposite to the arch of aorta ( 9 inches from the incisor teeth )
3- opposite to the point of crossing of the left principle bronchus ( 12 inches from the incisor teeth )
4- at esophagus opening of diaphragm ( 15 inches from the incisor teeth )
whats the importance of these constriction of the esophagus?
gastroscope
where does the thoracic duct drain from?
all the body except the right upper limbs and the head and the SUPERIOR SURFACE OF THE LIVER
whats the origin of thoracic duct?
cristerna chyli
what are the course and relations?
pass through the aortic opening of the diaphragm
ascends in the posterior mediastinum on vertebral bodies on the right side of esophagus ( in the posterior mediastinum its right )
Crosses the left side of the esophagus ( in the superior mediastinum its left )
arches above the clavicle in the neck
where does the thoracic duct terminate ?
the junction of the left subclavian and internal jugular veins
how does the right lymphatic duct form?
union of the right jugular lymph trunk
right subclavian lymph trunk and RIGHT bronchomedistinal lymph trunk
