Mediastinum Flashcards
Mediastinum is occupied by…
- Mass of tissue between 2 pulmonary/pleural cavities
- contains all thoracic viscera, nerves, and vessels except the lungs and those in thoracic wall
Mediastinum is covered by…
- Mediastinal pleura
- surrounded by blood & lymphatic vessels, lymph nodes, nerves & fat
Mediastinum extends from…
- superior thoracic aperture to diaphragm
- sternum & costal cartilages to bodies of thoracic vertebrae
Mediastinum primarily consists of hollow visceral structures united by…
Loose CT (often adipose)
Mediastinum is divided by…
Transverse thoracic plane at level of sternal angle & junction of T4-T5 (at IVD)
Name the divisions of the mediastinum
- superior
- inferior: anterior, middle, posterior
Contents of middle mediastinum
- pericardium
- heart
- roots of great vessels
What is the pericardium?
- Fibroserous membrane
- closed sac covering heart and beginning of great vessels
Name the layers of the pericardium
Fibrous
Parietal serous
Visceral serous
Superior attachments of fibrous pericardium
- continuous with tunica adventitia of great vessels
- continuous with pretracheal layer of cervical fascia
Anterior attachments of fibrous pericardium
To posterior surface of sternum by sternopericardial ligaments
Posterior attachments of fibrous pericardium
Loose CT to structures of posterior mediastinum
Inferior attachments of fibrous pericardium
Continuous with central tendon of diaphragm
Pericardial cavity
- space between opposing layers of parietal & visceral serous pericardium
- contains fluid that enables heart to move & beat in frictionless environment
Visceral serous pericardium forms the ____
Epicardium
Visceral serous pericardium attachments
Extends onto beginning of great vessels, continuous with parietal layer of serous pericardium:
- where aorta & pulmonary trunk leave heart
- where superior vena cava (SVC) and inferior vena cava (IVC) and pulmonary veins leave atria
Blood supply of pericardium
- pericardiacophrenic a. (Branch of internal thoracic a)
- musculophrenic a
- bronchial, esophageal, superior phrenic aa of thoracic aorta
- coronary aa (visceral serous pericardium only)
Pericardium venous drainage
- pericardiacophrenic vv = tributaries of brachioceophalic v or internal thoracic vv
- various tributaries of azygous venous system
Nerve supply to pericardium
- phrenic nerves (C3-C5) = sensory, pain
- vagus nerve (CN X) = parasympathetic
- sympathetic trunks = vasomotor functions
Location of superior mediastinum
Superior to transverse thoracic plane
Contents of superior mediastinum
- thymus
- great vessels & veins
- vagus, phrenic nerves
- cardiac plexus
- trachea
- esophagus
- recurrent laryngeal nerves
- thoracic duct & lymphatic trunks
Location of thymus
- inferior neck & anterior portion of superior mediastinum anterior to fibrous pericardium
- largely replaced by fat after puberty
Great vessels of superior mediastinum
- R & L brachiocephalic vv
- SVC
- ascending aorta
- arch of aorta
- thoracic (descending) aorta
- arch of azygous v
- brachiocephalic trunk
- L common carotid a
- L subclavian a
Ligamentum arteriosum
- remnant of fetal ductus arteriosus
- passes from root of L pulmonary a to inferior surface of arch of aorta
Where does Right vagus nerve enter the thorax?
Anterior to right subclavian a
R vagus nerve gives rise to the ____
R. Recurrent laryngeal nerve
Where does R vagus nerve travel in the superior mediastinum?
Posterior to R brachiocephalic vein, SVC, and root of lung
Where does L vagus nerve enter mediastinum?
Between carotid and subclavian aa
Where does L vagus nerve travel in the superior mediastinum?
- Descends in neck posterior to left common carotid a.
- at arch of aorta, diverges posterior to left phrenic nerve
L vagus nerve gives rise to the ____
Left recurrent laryngeal nerve
R recurrent laryngeal nerve
- Hooks around R subclavian artery
- ascends between trachea & esophagus to supply larynx
L recurrent laryngeal nerve
- passes inferior to arch of aorta, lateral to ligamentum arteriosum
- ascends to larynx
R phrenic nerve pathway
- Passes along right side of R brachiocephalic vein, SVC, and pericardium over the R atrium
- descends on right side of SVC to diaphragm
L phrenic nerve pathway
- descends between L subclavian & common carotid aa
- crosses left surface of aortic arch to vagus nerve
- runs along fibrous pericardium superficial to L atrium & ventricle to diaphragm
Cardiac plexus
- nerve network lies anterior to bifurcation of trachea
- supplies sympathetics & parasympathetics to heart
Trachea
- respiratory structure
- divides into L & R bronchus at level of sternal angle
Esophagus
- fibromuscular tube that extends from pharynx (back of throat)
- enters mediastinum between trachea & vertebrae
Location of thoracic duct
Lies on left side of esophagus, deep to arch of aorta
Where does thoracic duct drain?
Into L brachiocephalic vein by confluence of L subclavian & internal jugular veins
