Mediastinum Anatomy

Question 1

chylothorax

Answer 1

• accumulation of lymph in the pleural cavity
• can result from surgery error or trauma to thorax
• a right chylothorax suggests damage in the inferior ½ of the thorax, while a left chylothorax suggests damage in the superior ½ of the thorax.

Question 2

Contents of the Inferior Mediastinum – Anterior Mediastinum

Answer 2

Anterior Mediastinum: mostly fat, lymph nodes, and branches of the internal thoracic artery. The most clinically important of these structures are the retrosternal lymph nodes that are situated along the internal thoracic vessels. In the female, these nodes receive lymphatic drainage from the medial quadrant of the breast and, as a consequence, may be sites of metastases

Question 3

location and boundaries of mediastinum

Answer 3

location: The mediastinum is the region in the thorax between the two pleural sacs

boundaries: The boundaries of the mediastinum are the thoracic inlet superiorly, sternum anteriorly, diaphragm inferiorly, vertebral column posteriorly and the mediastinal pleurae laterally

Question 4

divisions of mediastinum

Answer 4

• divided into the superior mediastinum and inferior mediastinum by a horizontal plane that intersects the T4-5 vertebra posteriorly and the sternal angle (manubriosternal joint) anteriorly (at level of carina)
• inferior mediastinum is further divided into three regions: middle, anterior, posterior

Question 5

carotid sheath

Answer 5

a condensation of cervical fascia. It runs from the base of the skull to the root of the neck. It contains the internal jugular vein, common carotid artery, and the vagus nerve (CN X)

Question 6

posterior intercostal arteries

Answer 6

• supply the thoracic and abdominal walls
• travel between the ribs with the intercostal veins and arteries

Question 7

azygos vein

Answer 7

main channel of venous drainage system in thoracic wall; connects the inferior and superior venae cavae; azygos vein ascends on the right side of the vertebral column and receives blood from the right side of the abdominal and thoracic walls, mainly through the posterior intercostal veins

Question 8

ALL ventral and dorsal rami of spinal nerves carry ___ fibers

Answer 8

ALL ventral and dorsal rami of spinal nerves carry somatomotor, general sensory and postganglionic sympathetic fibers

Question 9

how does the azygous system provide alternative venous drainage?

Answer 9

If the inferior vena cava were obstructed, venous blood from the lower half of the body could be shunted to the superior vena cava. Alternatively, if the superior vena cava were occluded, blood from the head and upper extremities could be shunted to the inferior vena cava for return to the heart

Question 10

The union of the ____ forms the brachiocephalic veins

Answer 10

internal jugular and subclavian veins

Question 11

hemiazygos vein

Answer 11

ascends on the left side of the vertebral column, posterior to the aorta as far as vertebral body T9

Question 12

Contents of Posterior Mediastinum (Inferior Mediastinum)

Answer 12

Contains the descending aorta, thoracic duct, azygos vein, hemiazygos vein, esophagus, vagus nerves and sympathetic chains

Question 13

descending aorta’s visceral branches include:

Answer 13

the bronchial arteries, which deliver oxygenated blood to the lungs, and the esophageal arteries

Question 14

Neurovasculature of the Thoracic Wall

Answer 14

Neurovascular bundles travel parallel to the ribs through the intercostal between the second and third layers of intercostal muscles

The arteries in the intercostal space are the anterior and posterior intercostal arteries, branches of the internal thoracic and thoracic aorta, respectively.

Each has a corresponding vein, and is accompanied by the ventral ramus of a thoracic spinal nerve

Question 15

ansa cervicalis

Answer 15

a loop of somatomotor nerves that innervate the infrahyoid muscles, lies along the anterior surface of the carotid sheath

Question 16

Contents of the Superior Mediastinum

Answer 16

• Digestive layer – the esophagus
• Respiratory layer – the trachea
  
  • Note that the trachea bifurcates at about T4-5 and therefore does not descend below the superior mediastinum.
• Arterial layer - the aortic arch and its branches:
  
  • brachiocephalic arter
  • left common carotid artery
  • left subclavian artery
• Venous layer - the superior vena cava and its tributaries: right and left brachiocephalic veins
• Glandular layer - the thymus

Question 17

order of vessels running along ribs

Answer 17

The vein is closest to the rib, followed by the artery and nerve (use the mnemonic VAN)

Question 18

Thoracic Duct

Answer 18

• largest lymphatic vessel in the body
• originates in the upper abdomen at the cisterna chyli
• enters the thorax through the aortic hiatus in the diaphragm
• ascends on the right side of the midline in the lower half of the thorax and then shifts to the left side of the midline in the upper half of the thorax

Question 19

although the ___recurrent laryngeal nerve is within the mediastinum, the ___ recurrent laryngeal nerve is never in the mediastinum

Answer 19

left; right

Question 20

thoracentesis consideration of vessels around ribs

Answer 20

needle is inserted through an intercostal space to obtain a sample of pleural fluid, or to remove blood, the needle is usually introduced just above the rib to avoid injuring the main neurovascular bundle

Question 21

Contents of the Middle Mediastinum (Inferior mediastinum)

Answer 21

Contains the heart within the pericardial sac

Question 22

three major regions of the thoracic aorta

Answer 22

ascending aorta: exits the left ventricle and gives rise to the right and left coronary arteries

arch of the aorta: branches asymmetrically to form the brachiocephalic trunk and the left common carotid and left subclavian arteries

descending aorta: has both parietal and visceral branches to supply the body wall and the internal organs, respectively