Mediastinum & Superficial Anatomy of the Heart Flashcards
What is the mediastinum?
It is a broad central partition that separates the two laterally placed pleural cavities.
Describe the boundaries of the mediastinum
Anteriorly – Body of sternum
Posteriorly – Vertebral bodies of thoracic vertebrae
Inferiorly – Diaphragm
Superiorly – Thoracic aperture
What divides the mediastinum into superior and inferior mediastinum?
A transverse plane that passes between the sternal angle and the intervertebral disc at T4/T5
Describe the boundaries of the superior mediastinum
Superior Boundary: Oblique plane passing from jugular notch to superior border of T1.
Inferior Boundary: Transverse plane between sternal angle and intervertebral disc at T4/T5.
Lateral Boundary: Pleural cavities on either side.
Anterior boundary – Posterior surface of manubrium.
Posterior boundary – Body of first four thoracic vertebrae.
List the contents of the superior mediastinum
Thymus
Left and Right Brachiocephalic veins
Left Superior Intercostal vein
Superior vena cava
Arch of Aorta
Trachea and Oesophagus
Phrenic and Vagus nerves
Left recurrent branch of vagus nerve
Thoracic Duct
Superior
Describe the thymus in terms of it’s position in the mediastinum and it’s function
-Most anterior component of superior mediastinum.
-Immediately posterior to manubrium.
-Asymmetrical, bilobed structure.
-Involved in early development of immune system
Position of left and Right Brachiocephalic veins in the mediastinum
Immediately posterior to the thymus
Position of the left superior intercostal veins
-Passes over left side of aortic arch.
-Situated lateral to the vagus nerve and medial to the phrenic nerve.
Which structure is palpable in jugular notch as it enter the superior mediastinum?
Trachea
Position of the oesophagus in the mediastinum
Oesophagus is posterior to the trachea and immediately anterior to the vertebral bodies.
Which vessel crosses the both the trachea and oesophagus laterally on the right and the arch of the aorta on the left?
Azygos vein
Position of the thoracic duct on the superior mediastinum
This is the major lymphatic vessel in the body.
Enters superior mediastinum inferiorly.
Continues upward posterior to the arch of aorta between oesophagus and parietal pleura.
Describe the boundaries of the anterior mediastinum
Superior Boundary: Transverse plane between sternal angle and intervertebral disc at T4/T5.
Inferior Boundary: Diaphragm
Lateral Boundary: Pleural cavities on either side.
Anterior boundary – Body of sternum
Posterior boundary – Pericardial sac.
What are the contents of the anterior mediastinum?
- Inferior extension of thymus gland.
- Mediastinal branches of internal thoracic vessels.
- Sternopericardial ligaments. (This attaches the mediastinum to the posterior surface of the sternum)
What are the boundaries of the middle mediastinum?
Superior Boundary: Transverse plane between sternal angle and intervertebral disc at T4/T5.
Inferior Boundary: Diaphragm
Lateral Boundary: Pleural cavities on either side.
Anterior boundary – Anterior margin of pericardium.
Posterior boundary – Posterior margin of pericardium.
What are the contents of the middle mediastinum?
Pericardium, heart, great vessels and nerves.
What are the borders of the posterior mediastinum?
Superior Boundary: Transverse plane between sternal angle and intervertebral disc at T4/T5.
Inferior Boundary: Diaphragm
Lateral Boundary: Pleural cavities on either side.
Anterior boundary – Pericardial sac.
Posterior boundary – Bodies of T5-T12 Vertebrae.
What are the contents of the posterior mediastinum?
Oesophagus and oesophageal nerve plexus.
Descending aorta and its branches.
Azygos system of veins.
Thoracic duct and lymph nodes.
Sympathetic trunk and thoracic splanchnic nerves.
Where does the oesophagus begin and end?
Begin: Level of C6, behind the cricoid cartilage
Ends: level of T11
Describe the course of the oesophagus as it descends
Descends on anterior aspect of vertebral bodies, in midline.
Moves slightly to the left inferiorly to lie anterior to descending aorta.
Right side of the oesophagus is covered with____________, left side in contact with
aorta.
parietal pleura