Lecture 19 - Throacic Cavity: Mediastinum and Respiratory Diaphragm

Question 1

What are the divisions and subdivisions of the mediastinum?

L19 S5

Answer 1

Superior mediastinum (above plane through sternal angle and IV disc T4-5):

• retrosternal
• prevertebral

Inferior mediastinum:

• anterior
• middle
• posterior

Question 2

What are the contents of the superior mediastinum?

L19 S6

Answer 2

Retrosternal:

• great vessels and branches
• thymus

Prevertebral:

• trachea
• esophagus
• thoracic duct
• sympathetic trunks
• vagus nerve

Question 3

What are the contents of the inferior mediastinum?

L19 S7

Answer 3

Anterior:

• thymus
• fat
• lymph nodes

Middle:

• pericardium
• phrenic nerves
• pericardiophrenic artery
• heart and great vessels

Posterior:

• esophagus
• thoracic duct
• aorta and branches
• vagus nerve
• sympathetic trunk
• azygos system of veins

Question 4

What is the path of the esophagus?

L19 S12

Answer 4

• left of midline at base of neck
• midline at the aortic arch
• left of midline passing trough the diaphragm (level of T10)
• travels posterior to the trachea
• travels anterior to the spinal column
• travels to the right of the thoracic aorta

Question 5

What is the blood supply and innervation of the esophagus?

L19 S13

Answer 5

Blood supply:

• bronchial artery
• thoracic aorta
• left gastric artery
• left inferior prhenic artery

Innervation:
-upper third (voluntary muscle)
—recurrent laryngeal nerve
-lower two-thirds (involuntary muscle)
—vagus nerve and sympathetic chain

Question 6

What is the path of the thoracic aorta?

L19 S14-15

Answer 6

• continuation of aortic arch beginning at at level of T4/sternal angle
• travels left of midline
• pierces the diaphragm at the level of T12

Question 7

What are the branches of the thoracic aorta?

L19 S14

Answer 7

• posterior pericardial
• left bronchus (x2)
• esophageal
• posterior mediastinum
• intercostal arteries (9 pairs)
• subcostal arteries (1 pair)
• superior phrenic artery

Question 8

What forms the azygos vein and what path does it take?

L19 S15

Answer 8

Union of right ascending lumbar vein and right subcostal vein

• pierces diaphragm
• ascends along right of thoracic vertebrae
• arches over root of right lung
• enters superior vena ceva

Question 9

What forms the hemiazygos vein and what path does it take?

L19 S16

Answer 9

Union of left ascending lumbar vein and left subcostal artery

• pierces diaphragm
• ascends along left side of thoracic vertebrae to level of T9
• crosses vertebrae and empties into azygos vein

Question 10

What forms the accessory hemiazygos vein and what path does it take?

L19 S16

Answer 10

• runs along the left side of upper thoracic vertebrae
• receives blood form superior intercostal vein and left intercostal veins 4-8
• crossed vertebral body and empties into azygos vein

Question 11

What lymph nodes are present in the thoracic cavity?

L19 S18-19

Answer 11

Parasternal

Posterior intercostal

Diaphragmatic

Posterior mediastinal

Brachiocephalic

Tracheobroncial

• paratracheal
• superior/inferior tracheobroncial
• bronchopulmonary
• pulmonary

Question 12

What are the origins of the diaphragm?

L19 S36

Answer 12

Sternal:
-xiphoid

Costal:
-lower 6 ribs and cartilages

Lumbar:
-L1-3 (right crura) and L1-2 (left crura)

Question 13

What are the openings in the respiratory diaphragm?

L19 S38

Answer 13

T8 caval foramen:

• inferior vena cava
• right phrenic nerve

T10 esophageal hiatus:

• esophagus
• vagus nerve

T12 aortic hiatus:

• aorta
• greater splanchnic nerve

Question 14

What are the tendons and ligaments of the diaphragm?

L19 S42

Answer 14

Crura:

• right originate2 from L3
• left originates from L2

Arcuate:
-median
—aortic opening
—connects crura
-medial
—deep fascia of psoas major
—transeveres process to body of L1
-lateral
—deep fascia of quadratus lumborum
-transverse processes of L1 to rib 12