Anatomy 3 Flashcards
What are the Borders of the Superior Mediastinum?
- superior border: the superior thoracic arpeture (clinical name thoracic outlet), the upper opening of the thorax
- inferior border: the transverse thoracic plane, a slightly oblique plane passing posteriorly from the sternal angle to the junction of the 4th and 5th thoracic vertebra
- lateral border: the pleurae
- anterior border: the manubrium of the sternum
- posterior border: the first four vertebral bodies
What are the Contents of the Superior Mediastinum:
Muscles
Arteries
Veins
Nerves
Other structures
- Muscles:
- origins of the Sternohyoidei and Sternothyreoidei
- lower ends of the Longi colli
- aortic arch
- brachiocephalic artery
- thoracic portions of the left common carotid and the left subclavian
- brachiocephalic veins and
- upper half of the superior vena cava
- left highest intercostal vein
- Nerves:
- vagus nerve
- cardiac nerve
- superficial and deep cardiac plexuses
- phrenic nerve
- left recurrent laryngeal nerve
- Other Structures:
- trachea
- esophagus
- thoracic duct
- remains of the thymus
- some lymph glands
- anterior longitudinal ligament
What are the Borders of the Anterior Mediastinum?
- anterior border: the sternum, the left Transversus thoracis and the fifth, sixth, and seventh left costal cartilages
- lateral border: the pleurae
- posterior border: the pericardium
- superior border: the transverse thoracic plane
- inferior border: the diaphragm
What are the Contents of the Anterior Mediastinum?
- a quantity of loose areolar tissue.
- some lymphatic vessels which ascend from the convex surface of the liver.
- two or three anterior mediastinal lymph nodes.
- the small mediastinal branches of the internal mammary artery.
- thymus (in infants and young children)
What are the Borders of the Middle Mediastinum?
Borders of the Middle Mediastinum:
all borders: the pericardium
What are the Contents of the Middle Mediastinum? (9)
- the heart enclosed in the pericardium
- the ascending aorta
- the lower half of the superior vena cava with the azygos vein opening into it
- the bifurcation of the trachea and the two bronchi
- the pulmonary artery dividing into its two branches
- the right and left pulmonary veins
- the phrenic nerves
- some bronchial lymphatic glands
- pericardiocophrenic vessels
What are the Borders of the Posterior Mediastinum?
- anterior border: the pericardium
- inferior border: the thoracic surface of the diaphragm
- superior border: the transverse thoracic plane
- posterior border: the bodies of the vertebral column from the lower border of the fifth to the twelfth thoracic vertebra
- lateral border: the mediastinal pleura
What are the Contents of the Posterior Mediastinum? (8)
- thoracic part of the descending aorta
- azygos vein
- the hemiazygos vein and the accessory hemiazygos vein
- vagus nerve
- splanchnic nerves (but not the sympathetic chain)
- oesophagus
- thoracic duct
- some lymph glands
What level is the transverse thoracic plane and what structures do you find there? (9)
Notable features at level T4/T5
- The start (where the aortic arch comes out of the heart) and end of the arch of the aorta (where the arch of the aorta becomes the descending aorta)
- The upper margin of the superior vena cava
- The crossing of the thoracic duct
- The bifurcation of the trachea
- The bifurcation of the pulmonary trunk
- The level of the sternal angle (angle of Louis)
- The level of Rib 2 where it attaches to the sternum
- Vertebrae T4/T5
- The drainage of the azygos vein into the SVC
Describe the course of the vagus nerve
Vagus: cranial nerve 10. Leaves the medulla, extends through the jugular foramen, then passes into the carotid sheath between the internal carotid artery and the internal jugular vein down the neck. The right vagus passes anterior to the subclavian artery then runs posterior to the SVC. The left vagus nerve enters the thorax between the left subclavian and left common carotid and runs posterior to the trachea. Both nerves continue down and enter the diaphragm at the oesophageal hiatus.
What are the branches of the vagus nerve? (12)
- Auricular nerve
- Pharyngeal nerve
- Superior laryngeal nerve
- Superior cervical cardiac branches of vagus nerve
- Inferior cervical cardiac branch
- Recurrent laryngeal nerve
- Thoracic cardiac branches
- Branches to the pulmonary plexus
- Branches to the esophageal plexus
- Anterior vagal trunk
- Posterior vagal trunk
- Hering-Breuer reflex in alveoli
Where does the vagus nerve run in comparison to the jugular vein?
The vagus runs posterior to the common carotid artery and internal jugular vein inside the carotid sheath
Where does the phrenic nerve originate?
The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves (C3-C5) in humans.
What kind of nerve fibres does the phrenic nerve contain (3) and what does it supply (4)?
The phrenic nerves contain motor, sensory, and sympathetic nerve fibers. These nerves provide
- the only motor supply to the diaphragm
- sensation to the central tendon
- the mediastinal pleura
- the pericardium
