Thorax: Viscera (Mediastinum) Flashcards
mediastinum: general features
- central portion of thoracic cavity
- from superior thoracic aperture to diaphragm inferiorly
ant: sternum and costal cartilage
post: bodies of vertebrae
mediastinum: list divisions
- superior mediastinum
- inferior mediastinum
mediastinum: superior mediastinum
btw manubrium/sternum and T1-4 vertebrae
mediastinum: inferior mediastinum and list divisions
- manubriosternal j and lower T4 vertebrae to thoracic outlet
- ant, middle, post mediastinum
mediastinum: ant mediastinum
- inf mediastinum
- btw sternal body and pericardium
mediastinum: middle mediastinum
- inf mediastinum
- broadest part containing cardiovascular viscera
mediastinum: post mediastinum
- inf mediastinum
- btw trachea/ vessels/ pericardium/ diaphragm and thoracic vertebrae from T4 down
superior mediastinum: boundaries
- bound above by thoracic inlet, below sternal plane and laterally by lung pleura
superior mediastinum: contents
neck mm:
- sternohyoid
- sternothyroid
- longus colli
- thoracic viscera (exc lungs)
superior mediastinum: list major structures (10)
- thymus
- brachiocephalic v
- sup vena cava
- arch of aorta w branches
- trachea
- oesophagus
- phrenic n
- vagus n
- L recurrent laryngeal n
- thoracic duct
superior vena cava: forms where
- post to 1st costal cartilage on the R
superior vena cava: enters R atrium where
- 3rd level of costal cartilage
superior vena cava: formed by
junction of 2 brachiocephalic veins behind lower border of 1st R costal cartilage as it nears the sternum
arch of aorta: general features
- continues from ascending aorta located to R of upper border of 2nd sternocostal joint
- continues to arch to L over top of trachea and descends over T4 and continues as descending aorta
arch of aorta: location and branches
- entirely in superior mediastinum
- R brachiocephalic
- L common carotid
- L subclavian
arch of aorta: anatomical (normal) pattern seen in
65% of people
arch of aorta: ligamentum arteriosum
- remnant of ductus arteriosus -> allowed blood to bypass lungs during development in utero
- if doesn’t close after birth, causes congenital heart defect: patent ductus arteriosus which does not produce cyanosis intially
anterior mediastinum: bound by
- laterally: pleura
- post: pericardium
- ant: sternum
- costal cartilages of ribs 5,6,7
anterior mediastinum: contains (5)
- loose areolar tissue
- lymph vessels
- ant mediastinal lymph nodes
- mediastinal branches of int thoracic aa
- thymus (involuted in adults)
middle mediastinum: contains (4)
- pericardium
- heart
- roots of great vessels
- nerves
posterior mediastinum: contains (6)
- thoracic aorta
- thoracic duct
- post mediastinal lymph nodes
- azygos and hemiazygos veins
- oesophagus
- thoracic sympathetic trunks
vagus nerve: R
- enters thorax ant to R subclavian aa
- gives R recurrent laryngeal nn -> hooks around R subclavian aa
- R vagus nn passes post to R brachiocephalic v, SVC and root of R lung
vagus nerve: L
- enters mediastinum btw L common carotid aa and L subclavian aa
- gives L recurrent laryngeal nn (lateral to ligamentum arteriosum) -> hooks around arch of aorta
- L vagus nn continues descent and passes post to root of L lung
vagus nerve: both nn
- L and R vagus nn form post/ant vagal plexuses around oesophagus and leave thoracic cavity through oesophageal opening of diaphragm (at T10 vertebral level)
- enters ab cavity and supplies Psy fibres to ab viscera as far as 2/3 of transverse colon
vagus nerve: paralysis of recurrent laryngeal nn due to
- aortic arch aneurism (excessive localised swelling of aa wall)
- thyroid pathology/ surgery
- surgery in neck, oesophagus, heart and lungs
vagus nerve: symptoms and signs of recurrent laryngeal paralysis
- dysphagia (difficulty swallowing)
- dysphonia (difficulty speaking)
- aphonia (inability to speak) w inspiratory stridor (bilateral injury to recurrent laryngeal nn)
- anaesthesia of superior part of larynx
phrenic nerve: origin and border
- ventral rami of C3,4,5
- each phrenic nn forms at lateral border of ant scalene m at level of superior border of thyroid cartilage
phrenic nerve: L location
- lies on ant scalene mm and crosses ant to first part of subclavian aa
phrenic nerve: R location
- lies on ant scalene mm and crosses ant to second part of subclavian aa
phrenic nerve: enters superior mediastinum
- btw subclavian aa and origin of brachiocephalic vein
- pass ant to roots of lungs (vs vagus nn which pass post)
phrenic nerve: R passes
- along R side of pericardium over R atrium
- then passes through caval opening (T8) to supply inf diaphragm
phrenic nerve: L passes
- along L side of pericardium superficial to L atrium and ventricle
- pierces diaphragm laterally to pericardium
thoracic aorta: location
- lies post to root of L lung
thoracic aorta: branches
- bronchial
- pericardial
- post intercostal
- superior phrenic
- oesophageal
- mediastinal
- subcostal
eg. coarctation of aorta
narrowing of small section of aorta
azygos vein: features
- azygos sistem of veins drains the back, thoracoabdominal walls and mediastinal viscera
- forms collateral pathway btw SVC and IVC
thoracic duct: features
largest lymphatic channel conveys lymph from:
- lower limbs
- pelvic cavity
- abdominal cavity
- L side thorax
- L side of head, neck, upper limb
thoracic duct: drains into
- empties into venous system
- either subclavian v or brachiocephalic v
sympathetic trunks: features
- 2 parallel cords w 11-12 ganglia
- ganglia connected to adjacent spinal nn
sympathetic trunks: upper 5 ganglia supply
thoracic viscera
sympathetic trunks: lower 7 ganglia
give sympathetic n supply to abdominal viscera
oesophagus: features
- muscular tube in neck from C6 vertebra at junction of pharynx -> ends in abdominal cavity and cardiac opening in stomach at level T11 vertebra
- R and L vagus nn form post/ant vagal plexuses around oesophagus
oesophageal anatomical constrictions:
compressed at 4 levels:
- in neck at junction w pharynx
- superior mediastinum by aortic arch
- post mediastinum b L main bronchus
- at passage through diaphragm
- have clinical importance
eg. dissection of aorta
- injury to aorta causes wall layers to split
- allowing blood to flow btw layers
