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ANATOMY: thorax > Posterior mediastinum > Flashcards

Posterior mediastinum Flashcards

1
Q

At what level does the descending aorta start?

A

T4/5

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2
Q

In what direction does the aorta descend?

A

It descends, first to the left of the vertebral column, and then in the midline in front of the vertebral bodies

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3
Q

At what level does the aorta pass the diaphragm?

Does it pass in front or behind the diaphragm?

A

T12

Behind

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4
Q

What are the main branches of the descending thoracic aorta?

A

Bronchial, oesophageal, posterior intercostal, and subcostal arteries

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5
Q

Where does the oesophagus begin?

A

In the neck opposite C6 just below the cricoid cartilage

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6
Q

At what point does the oesophagus pass through the diaphragm?

A

T10

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7
Q

Where does the oesophagus lie?

A

Initially, it lies in the midline, following the curve of the vertebral column. In the posterior mediastinum, it passes to the left, anterior to the aorta, so that it pierces the diaphragm to the left of the midline with the anterior and posterior vagal trunks

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8
Q

How does the right crus of the diaphragm interact with the oesophagus?

A

The right crus of the diaphragm forms a sling round the oesophagus and provides some sphincteric action at the lower end

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9
Q

What lines the oesophagus?

A

Stratified squamous (“wear and tear”) epithelium with mucous glands for lubrication

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10
Q

How is blood supplied to the oesophagus?

A

The upper part is supplied by branches of the inferior thyroid artery, the middle part directly by aortic branches, and the lower part by a branch of the left gastric artery ascending through the diaphragm

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11
Q

How is blood returned to the veins from the oesophagus?

A

Veins from the upper part drain to the systemic circulation via the azygos vein, but the lower third drains via the left gastric vein to the portal vein.

These veins anastomose freely in the submucous layer and constitute a site of portosystemic anastomosis

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12
Q

How is the oesophagus innervated?

A

Nerve supply in the upper third is from recurrent laryngeal and sympathetic nerves from the middle cervical ganglion via the inferior thyroid artery. The lower part is supplied by the vagi and sympathetic nerves in the oesophageal plexus

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13
Q

Where does the azygous vein start?

A

In the abdomen to the right of the first or second lumbar vertebra as the union of the right subcostal vein and ascending lumbar veins inferior to the diaphragm

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14
Q

What is the path taken by the azygous vein as it leaves the abdomen?

A

It ascends to pass through the aortic opening in the diaphragm to the right of the aorta and thoracic duct. It arches over the right lung hilum to enter the superior vena cava

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15
Q

Where are the hemiazygous veins?

A

To the left of the thorax

both cross the midline and join the azygos vein

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16
Q

How many hemiazygous veins are there?

A

2

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17
Q

How is blood returned to the venous system from the thoracic walls, oesophageal and bronchial veins?

A

The posterior intercostal veins on the left drain to the hemiazygos veins, and into the azygos on the right

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18
Q

What region does the superior intercostal vein drain?

A

The second and third intercostal spaces

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19
Q

What is the asymmetry in the azygous system?

A

The superior intercostal vein drains into the azygous vein on the right

On the left it drains anteriorly, across the ascending aorta, in between the vagus and phrenic nerves, to empty into the left brachiocephalic vein

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20
Q

How is blood from the first intercostal space returned to the venous system?

A

The supreme intercostal veins which drain into their respective brachiocephalic veins

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21
Q

What is the main lymph trunk of the body?

A

The thoracic duct

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22
Q

Where does the thoracic duct start?

A

In the abdomen as a continuation of the cisterna chyli which receives the lumbar and intestinal lymph trunks

23
Q

What path does the thoracic duct take as it leaves the abdomen?

A

It passes up on the right, behind the median arcuate ligament, ascending on the vertebral column behind the oesophagus, between the aorta and the azygos vein

24
Q

At what level does the thoracic duct pass the oesophagus?

In what direction does it pass?

A

T4/5

Behind the oesophagus and to the left

25
Q

What path does the thoracic duct take in the neck?

A

It arches forwards, at first medial to the apex of the lung and then over the subclavian artery to enter the junction of the left subclavian and internal jugular veins

26
Q

Why may variations occur in the thoracic duct?

A

It may divide into a number of branches to enter the venous junction

27
Q

What type of valve is present at the terminal end of the thoracic duct?

Why is this necessary?

A

Bicuspid

To avoid or reduce reflux of blood

28
Q

Why might the proximal part of the thoracic duct look like a vein after death?

A

There may be backflow of blood after death

29
Q

Where does the thoracic duct receive lymph from?

A

Both lower limbs, abdomen, left half of the thorax, left upper limb, and left side of the head and neck

30
Q

Which part of the spine does the thoracic sympathetic chain?

A

The thoracolumbar part of the spinal cord (T1-L2)

31
Q

Where do preganglionic neurones in the sympathetic chain come from?

A

The ventral root of the spinal nerve

32
Q

What do sympathetic fibres leave spinal roots as in order to enter the sympathetic chain?

A

White rami communicantes

33
Q

What forms the basic structure of the sympathetic chain?

A

A chain of ganglia connected by nerve fibres

34
Q

What happens to preganglionic nerves after entering the sympathetic chain?

A

They may synapse immediately on the cell bodies in the ganglion, or run up or down the chain and synapse at different points

35
Q

What do the cell bodies in the ganglia of the sympathetic chain give rise to?

A

Postganglionic or secondary sympathetic neurones, some of which pass onto the spinal nerves as grey rami communicantes. These come off the whole length of the sympathetic chain to join all the spinal nerves

36
Q

How many splanchnic nerves are there?

Where do they arise from?

A

3: greater, lesser and least

Emerge from T5 to 12 and are preganglionic

37
Q

What path do the splanchnic nerves take after emerging from the thorax?

A

They pass through the crura of the diaphragm to the coeliac plexus where they synapse in the coeliac ganglia, sending postganglionic neurones to supply abdominal structures

38
Q

How are the ribs connected?

A

A typical rib has a head which articulates with its own vertebral body and the one above. The neck of the rib is angled for its tubercle to articulate with the transverse process of its own vertebra

39
Q

What direction does the body of each rib follow?

A

The shaft sweeps downwards around the thorax, first laterally then medially

40
Q

Why is the angle of the neck and the slope of the shaft of the ribs important?

A

They are both major factors in chest expansion

41
Q

Which ribs are atypical?

A

The 1st, 11th, and 12th

42
Q

How much mobility does the first rib have?

A

Relatively immobile

43
Q

Why is the first rib atypical?

A

Its shaft is flat and its head articulates with its own vertebral body only (T1)

44
Q

Why are the 11th and 12th ribs atypical?

A

They articulate with their own vertebral bodies only.

They are tethered to their own transverse processes by fibrous tissue, without forming synovial joints

45
Q

What type of joint forms between each rib and its costal cartilage?

A

Primary cartilaginous

46
Q

What type of joint forms between the first costal cartilage and the manubrium?

A

Primary cartilaginous

47
Q

What type of joint forms between most costal cartilages and the manubrium?

A

Synovial

48
Q

Why are the joints between the costal cartilages and the sternum described as atypical?

A

Fibrocartilage is found on their joint surfaces instead of hyaline cartilage

49
Q

How is the costal margin created?

A

The costal cartilages of the 8th to 10th ribs join the costal cartilage of the rib above

50
Q

What are the “true ribs”?

What are the “false ribs”?

What are the “floating ribs”?

A

1st to 7th

8th to 12th

11th and 12th

51
Q

Which ribs are connected to the sternum via their costal cartilages?

A

1st to 7th (true ribs)

52
Q

Where is the costal groove?

A

The inferior border of each rib

53
Q

What is found in each costal groove?

A

The intercostal neurovascular bundle

The nerve is the appropriate spinal nerve,

The artery is formed from the posterior intercostal artery which anastomoses with an anterior intercostal branch of the internal thoracic artery

The veins drain posteriorly to the azygos or hemiazygos veins, or anteriorly to the internal thoracic veins

ANATOMY: thorax (5 decks)

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