A: Mediastinum Flashcards
Superior mediastinum major contents:
Thymus glands
Veins: right + left brachiocephalic veins, superior vena cava, arch of azygous vein
Arteries: aortic arch + its branches (brachiocephalic, left common carotid, left subclavian arteries)
Nerves: left + right vagus, left recurrent laryngeal branch of left vagus, left + right phrenic nerves
Viscera: trachea, oesophagus and its plexus derived from left + right vagus nerves + branches from sympathetic chain
Thoracic duct
Posterior mediastinum major contents
DATES:
D - descending aorta
A - azygous venous system
T - thoracic duct
E - Oesophagus
S - sympathetic nerves + trunk
Anterior mediastinum contents
thymus gland
Fat
Lymph nodes
Connective tissue
Sternopericardial ligaments
Left brachiocephalic vein in children?
Rises above upper border of manubrium, so is less protected from injury as opposed to passing behind manubrium.
Right and left brachiocephalic veins unite to form what and where?
superior vena cava, behind lower edge of 1st RCC close to sternum
Path of superior vena cava - at what point does it enter right atrium?
Descends in front of lung root to open into right atrium behind lower edge of 3rd RCC. Receives azygous vein immediately before entering pericardial sac.
Azygous veins
- Arise at L1/L2.
- Passes through aortic hiatus to enter posterior mediastinum.
- Continues up along right side of bodies of thoracic vertebrae.
- Receives posterior intercostal veins
- Azygous vein forms arch that passes over root of right lung + enters posterior aspect of superior vena cava, immediately before superior vena cava enters pericardial sac
- Drains mediastinum + posterior thoracic + abdominal walls on right.
Hemiazygous veins
- Drains mediastinum + lower posterior thoracic wall + abdominal wall on left.
- Arises in abdomen by junction of veins
- Passes through aortic hiatus to enter posterior mediastinum
- Continues up on left side of bodies of thoracic vertebrae
- Receives posterior intercostal veins
- Hemiazygous crosses to right side to enter azygous vein, posterior to thoracic aorta.
Patent ductus arteriosus
Congenital heart defect where ductus arteriosus fails to close at birth. Oxygenated + deoxygenated blood mix.
Branches of ascending aorta
Right & left coronary arteries
Branches of aortic arch
- Brachiocephalic artery. Divides into right subclavian + common carotid artery behind right sternoclavicular joint
- Left common carotid artery: ascends through superior mediastinum and supplies left side of head and neck
- Left subclavian artery: ascends through superior mediastinum, on left side of trachea. Enters neck + curves laterally on dome of pleura. Passes between anterior scalene + middle scalene.
Branches of descending aorta
- posterior intercostal arteries. Supply intercostal spaces & thoracic wall
- Oesophageal branches to oesophagus.
Vagus nerves innervations + where does it enter?
- Provide parasympathetic innervation to thoracic viscera + carry sensory fibres from thoracic viscera about normal physiology processes + reflex activities.
- Do not carry pain sensations
- Enters superior mediastinum posterior to brachiocephalic veins.
Branches of vagus nerves
Lung - pulmonary plexus
Heart - cardiac plexus
Oesophagus
Origin of left recurrent laryngeal nerve
Left vagus close to aortic arch, loops under it
Origin of right recurrent laryngeal nerve
Loops around right subclavian artery in root of neck.
Consequences of anatomy of right + left recurrent laryngeal nerves
- Diseases of thorax (enlarged lymph nodes associated with lung cancer) more likely to involve LRLN rather than right, resulting in paralysis of left vocal cord, leading to hoarseness of voice.
- Cancer of apex of right lung may affect RRLN, resulting in paralysis of right vocal cord, leading to hoarseness of voice.
What do phrenic nerves arise from
C3,4,5
What do phrenic nerves innervate
Motor to diaphragm
Sensory to central diaphragm, fibrous pericardium + parietal serous pericardium
How are right and left sympathetic trunks connected to thoracic spinal nerves
White + gray rami communicans.
Sympathectomy
Division of sympathetic trunks.
Can be used to reduce bp + hypertension by preventing vasoconstriction.
Branches of sympathetic trunks
greater, lesser + least splanchnic nerves
Convey preganglionic sympathetic fibres from thoracic ganglia to preertebral ganglia of abdomen
Carry visceral afferent nerves from abdomen.
Thoracic duct origin
Lymphatic duct that begins in abdomen as cisterna chyli.
Diaphragm openings
I ate 10 eggs at 12
inferior Vena Cava = T8
Oesophagus, vagus trunks = T10 oesophageal hiatus
Aortic hiatus for aorta, thoracic duct = T12
What structure is directly behind ductus arteriosus
Left recurrent laryngeal nerve
Identify this vessel + its origin
Right coronary artery, right aortic sinus.
Identify this vessel
Left coronary artery
Name this vessel + its divisions
Brachiocephalic trunk.
Behind the right sternoclavicular joint.
Branches: right subclavian & right common carotid arteries
Name the dilatation at the end of the right common carotid artery
Carotid sinus
Identify this nerve and what it arises from.
Left recurrent laryngeal nerve –branch of Left vagus nerve
Identify this nerve
Phrenic nerve
Identify this vein + its course
hemiazygous
Arises in abdomen
Passes through diaphragm (left crus/aortic hiatus) –> posterior mediastinum.
Runs upward along left side of vertebral bodies
It receives left posterior intercostal veins.
crosses to right side, posterior to thoracic aorta,
empties into azygos vein.
What kind of nerve fibres are found within vagus nerve?
Parasympathetic nerves and visceral afferent nerve fibers
What is the relationship of the phrenic nerves to the aortic arch and
superior vena cava?
Left phrenic n: just lateral to aortic arch
Right phrenic n: just lateral to superior vena cava
A sudden deceleration (e.g. road traffic accident) may cause injury to the
aorta at certain locations. List these locations
Aortic valve, attachment of ligamentum arteriosum, as it passes
through the diaphragm.
Identify this nerve
Right recurrent laryngeal nerve
Branches of descending aorta
Right and left bronchial arteries (to bronchi and lungs)
Oesophageal branches
Where does the thoracic duct drain into the venous system?
At the junction of left internal jugular and left subclavian veins
Identify this - which division of mediastinum is it located
Thoracic duct. Located in posterior & superior mediastinum.
