2- anatomy of mediastinum Flashcards
what area is the mediastinum?
area that lies between the lungs
what are divisions of mediastinum?
- superior
- inferior = anterior, middle, posterior
at what point is the superior & inferior mediastinum split?
at transverse thoracic plane between sternal angle & T4/T5 intervertebral disc
what is the thymus?
in a child = part of lymphatic system that produces T lymphocytes
- regresses in adults so usually just fat
what structures are in anterior mediastinum?
anterior mediastinum = between sternum & fibrous pericardium
- just thymus
what does middle mediastinum contain?
- pericardium
- heart
- parts of the great vessels that connect with the heart (inferior part of SVC, superior part of IVC, pulmonary trunk & arteries, pulmonary veins, ascending aorta)
what does posterior mediastinum contain?
- vagus nerves
- sympathetic chains/trunks
- thoracic aorta
- oesophagus
- thoracic duct
- azygous veins
- trachea & 2 main bronchi
where is oesophagus?
posterior mediastinum directly behind heart
what runs along surface of oesophagus?
vagal plexus (intertwining of R&L vagal nerves)
*vagal plexus then gives rise to vagal trunks that pass into diaphragm into abdomen to supply viscera in abdomen
where is thoracic aorta?
= also called descending aorta
- behind oesophagus in posterior mediastinum
what is function of azygous vein?
drains venous blood from intercostal veins in intercostal spaces to superior vena cava and ultimately to Right Atrium (can be ruptured in chest trauma)
what is route of azygous veins?
goes up posterior mediastinum then crosses over root of lung and into superior vena cava then RA
when does aorta referred to as
a) ascending
b) arch
c) thoracic
d) abdominal
it’s first referred to ascending as it leaves heart and then when it curves it’s called arch of aorta then it bends down and is known as descending aorta/thoracic aorta and finally once it enters diaphragm is referred to as abdominal aorta
what are the branches coming off the ARCH of the aorta?
- brachiocephalic trunk = supplies right hand side of neck (right carotid) & right upper limb (right subclavian)
- left common carotid artery = supplies left hand side of head & neck
- left subclavian artery = supplies left upper limb
what branches come off descending aorta?
posterior: bilateral intercostal arteries (1 for each intercostal space)
anterior:
- bronchial arteries (arterial blood for lung tissue)
- oesophageal arteries
- mediastinal arteries
- pericardial arteries
- phrenic arteries (for diaphragm)
what is aortic hiatus?
small opening in the diaphragm
what areas drain back to thoracic duct?
lymph produced in lower limbs, abdomen and left thoracic area, left upper limb, left side of head
where does thoracic duct drain into?
thoracic duct is on the left side of body and drains lymph back to left venous angle
*venous angle = in between internal jugular vein & subclavian vein
where does lymphatic duct drain to?
lymphatic duct is on right side of body and drains lymph into right venous angle
*venous angle = in between internal jugular vein & subclavian vein
what areas drain lymph into lymphatic duct?
right hand side of thoracic area and right upper limb and right hand side of head
what side of body is
a) lymphatic duct?
b) thoracic duct?
a) right
b) left
where does lymph from lung tissue drain to?
will drain back to bronchopulmonary lymph nodes and from there to midline area which have tracheobronchial lymph nodes→they then travel to thoracic duct for left hand side and lymphatic duct on right hand side
where are bronchopulmonary lymph nodes?
surrounding the main bronchus at root of lung
where are tracheobronchial lymph nodes?
around bifurcation of the trachea
what is the exception to the rule about what areas drain to each duct in lymphatic system?
in some patients the lymph from left inferior lobe drains into right lymphatic duct
what is the cisterna chyli?
swollen start of thoracic duct in abdomen = origin of thoracic duct
what is route of thoracic duct?
originates at cisterna chyli in abdomen then travels up through posterior mediastinum between azygous vein & oesophagus in order to drain into left venous angle
why would patient with mass at tracheobronchial lymph nodes have difficulty swallowing?
because oesophagus sits right where tracheobronchial lymph nodes are so if mass in the nodes then it could push on oesophagus and cause difficulty swallowing
where is oesophageal hiatus?
in the diaphragm (gap)
what is route of right vagus nerve? (From superior to inferior)
along right lateral border of trachea, passes posterior to root of lung and forms plexus on surface of oesophagus
what is route of left vagus nerve?
along surface of arch of aorta, then posterior to root of lung, forming plexus on surface of oesophagus and then into diaphragm to supply viscera
what is recurrent laryngeal branch and where is it?
= branch of vagus nerve that supplies the larynx
Left recurrent laryngeal nerve: Hooks around the ligamentum arteriosum. (which connects pulmonary trunk & aorta) - DOES ENTER CHEST
Right recurrent laryngeal nerve: Loops around the right subclavian artery. - DOESN’T enter chest
what are the structures/vessels in superior mediastinum - listed from anterior → posterior?
- brachiocephalic veins & superior vena cava
- arch of aorta
- trachea
- oesophagus
- thoracic duct
what are the nerves in superior mediastinum from lateral →medial?
- phrenic nerves
- vagus nerves
- recurrent laryngeal nerves
what makes up the right brachiocephalic vein?
right subclavian vein & right internal jugular vein
what do brachiocephalic veins come together to make?
superior vena cava -> drains to RA
what is link between pressure in central veins and pressure in right atrium?
- large veins are close enough to the heart so that the pressure within them is said to approximately reflect pressure within RA
*depends on posture
what are the most common points of access in central venous cannulation/catheterisation?
- internal jugular veins
- femoral veins
which recurrent laryngeal branch hooks lower down?
Left Lower
what referred pain could be felt with liver abscess or inflammation of gallbladder and why?
could have shoulder tip pain as the brain refers the pain to the more superficial structure, the skin over shoulder tip
- it irritates parietal perineum lining inferior surface of diaphragm which is supplied by phrenic nerve (C3,4,5)
- the supraclavicular nerves (C3,4) supply the dermatomes over shoulder & enter spinal cord at same level as phrenic nerve
