Mediastinum Flashcards
superior mediastinum
contains neural, vascular and respiratory structures passing from the adjacent regions of the neck and abdomen (via the inferior mediastinum).
superior mediastinum in children
contains the thymus
thymus
- contributes to the development and maintenance of the immune system.
- It is large in childhood, but involutes after puberty and is replaced by fatty tissue.
thymus location
- located: meck lower part and anterior part of the superior mediastinum.
- It lies posterior to the manubrium and in children can extend into the anterior mediastinum to lie anterior to the pericardium.
thymus blood supply
from the internal thoracic arteries
thymus venous drainage
via the internal thoracic and brachiocephalic veins.
great vessels
great systemic blood vessels of the heart lie within the superior mediastinum and their main branches arise before passing thru the superior thoracic aperture
types of great vessels (3)
- arch of aorta
- pulmonary trunk
- superior vena cava
the following veins are assoicated with the superior vena cava within the superior mediastinum (4):
- brachiocephalic veins
- left superior intercost vien
- supremem intercostal vien
- azygos vein
Brachiocephalic veins
draining blood from the upper body.
Left superior intercostal vein
- collects blood from the left 2nd and 3rd intercostal vein.
- It drains into the left brachiocephalic vein.
supereme intercostal vein
drains the vein from first intercostal space directly into the brachiocephalic veins.
azygos vein
receiving blood from the right posterior intercostal veins.
where the SVC do not return blood to?
lungs and heart
where does the hemizazygos vein empty into?
azygos vien
hemizygous vein
= vena azygos minor inferior
- a vein running superiorly in the lower thoracic region
where does the pulmonary trunk exit?
from right ventricle
pulmonary trunk location
- Initially anterior to the aorta it moves medially & posteriorly.
- Bifurcates into the L/R pulmonary arteries
branches of the aorta
L/R coronary arteries
what are the 3 major branches of the aortic arch within the superior mediastinum?
- brachiocephalic artery
- left common carotid artery
- left subclavian artery
brachiocephalic artery
supplying the right side of the head & neck and the right upper limb.
left common carotid artery
to the left side of the head & neck
left subclavian artery
to the left upper limb
where does the ascending aorta start?
aortic orifice (T4/T5), then reach to T3/T4 and ends T4/T5 sternal angle
what nerve is in the superior/ posterior mediastinum?
vagus nerve
vagus nerve
in the superior mediastinum and has 2 paths: Right and left vagus nerve
right vagus nerve
runs parallel to the trachea and passes posteriorly to the superior vena cava and the right primary bronchus.
left vagus nerve
enters the superior mediastinum between the left common carotid and the left subclavian arteries. It descends anteriorly to the aortic arch (9), before traveling posterior to the left bronchus.
overall flow of vagus nerve
- Travels through the neck with the internal jugular veins and the common carotid arteries.
- Right and left vagus nerves give off parasympathetic branches that contribute to the cardiac and pulmonary plexuses.
- After the nerves pass behind the main bronchi, they converge on the esophagus and form the esophageal plexus.
- Plexus gives rise to two vagal trunks (the anterior and posterior vagal trunks).
what do the vagi give off?
recurrent laryngeal branches that scend to larynx to innervate all but one larynx muscle
right recurrent laryngeal nerve
does not enter the mediastinum–it hooks around the right subclavian artery before ascending to the right side of the larynx
the spatial relation of right recurrent laryngeal nerve
to the apex of the right lung.
left recurrent laryngeal nerve
hooks around the aortic arch and ascends in the groove between the trachea and esophagus
the spatial relation of left recurrent laryngeal nerve
spatially related to the lymph nodes of the aortic arch.
how can the recurrent laryngeal nerve be injured and what is the result?
- from trauma, during surgery, or other means
- result in unproductive cough, a weakened voice (hoarseness) or loss of voice (aphonia) and cause problems in the respiratory tract
ligamentum arteriosum
A fibrous remnant of the ductus arteriosus extending between the aortic arch and the pulmonary trunk
ductus arteriosus
a fetal blood vessel that connects the left pulmonary artery to the descending aorta.
In utero, the ductus arteriosus serves as what?
bypass for lungs
phrenic nerve (8)
- phrenic nerves (roots C3, C4 and C5) enter the superior mediastinum lateral to the great vessels.
- They then descend anteriorly into the middle mediastinum, passing anteriorly to the hilum of the lungs.
where do cardiac nerves originate and what do they form?
- originate from the superior, middle and inferior cardiac ganglia
- form the superficial and deep cardiac plexuses in the superior mediastinum.
location of superior plexus
sits between the aortic arch and right pulmonary vein.
location of deep plexus
lies on the surface of the trachea at the point of bifurcation.
sympathetic trunk
runs bilaterally to the vertebral bodies along the entire length of the vertebral column.
trachea location
- Descends anterior to the esophagus
- Posterior surface is flat where applied to the esophagus
- Ends at the level of the sternal angle
- Divides into L/R primary bronch
where does the thoracic aorta begin?
- Begins inferior border of T4
- Descends on the left side of the T5-T12 vertebrae
when does the thoracic aorta become the abdominal aorta?
when it passes through the aortic hiatus (thoracic duct & azygos vein)
function of the thoracic aorta
Supplies intercostal spaces and thoracic viscera
esophagus
- Posterior to arch of aorta, pericardium/left atrium)
- Passes through esophageal hiatus
- Anterior & posterior vagal trunks
what is the largest lymphatic channel in the body?
thoracic duct
where does the thoracic duct originate?
- originates from the cisterna chyliin the abdomen
- ascends thru posterior and superior mediastina to drain into the union of the left internal jugular and subclavian veins
what does the thoracic duct drain?
drains lymph from the whole body
what does the thoracic duct NOT drain?
- right side of the head
- neck
- right upper limb
- right side of the thorax and upper surface of the liver
WHERE does the thoracic duct drain?
drain into the right jugular, subclavian, and bronchomediastinal trunks which enter the veins on the right side of the neck as the right lymphatic duct.
