Anatomy of the Thorax

Question 1

Over what muscle does the long thoracic nerve run?

Answer 1

Serratus anterior

Question 2

What is the innervation to the intercostal muscles?

Answer 2

Innervated by the anterior rami of the thoracic spinal nerves

Question 3

Between which muscles do the neuromuscular bundles run in the intercostal margin?

Answer 3

Between the internal intercostal and the innermost intercostal muscles

Question 4

Describe the procedure of thoracocentesis

Answer 4

Where a needle is inserted just superior to the rib in the mid-axillary line of the 9th rice to avoid the inferior border of the lung and sample the pleural fluid

Question 5

What is thoracocentesis?

Answer 5

Where a sample of pleural fluid is taken using a needle

Question 6

Describe the procedure of chest drain insertion

Answer 6

A chest drain is inserted into the 5th intercostal space in the mid-axillary line in the ‘safe triangle’

Question 7

What is the ‘safe triangle’ formed by?

Answer 7

Medially: the lateral border of pectorals major
Laterally: anterior border of latissimus dorsi
Inferiorly: level of the nipple
Superiorly: apex is just below the axilla

Question 8

What muscles are involved in quiet inspiration?

Answer 8

Contraction of the diaphragm, external intercostals and the interchondral part of the internal intercostal

Question 9

What muscles are involved in deep inspiration?

Answer 9

Contraction of the diaphragm, external intercostals and the interchondral part of the internal intercostal as normal, with the addition of accessory muscles of respiration: sternocleidomastoid and scalene muscle contraction

Question 10

What muscles are involved in quiet expiration?

Answer 10

Elastic recoil of the diaphragm, external intercostals and interchondral part of internal intercostals

Question 11

What muscles are involved in forced expiration?

Answer 11

Elastic recoil of the diaphragm, external intercostals and interchondral part of internal intercostals alongside contraction of the internal intercostal muscle (except for interchondral aspect) and contraction of abdominal muscles

Question 12

What is fluid in the pleural cavity known as?

Answer 12

Pleural effusion

Question 13

How could you diagnose pleural effusion from a chest x-ray?

Answer 13

Severe blunting of the costophrenic recess and white at the base of the lungs

Question 14

Which type of pleura produces pleural fluid?

Answer 14

The parietal pleura, and this fills the pleural cavity

Question 15

What structures are covered by the parietal pleura?

Answer 15

Thoracic wall and superior surface of diaphragm

Question 16

What structures are covered by the visceral pleura?

Answer 16

External lung surface

Question 17

What is the neuromuscular supply to the parietal pleura?

Answer 17

The parietal pleura is sensitive to pressure, pain, and temperature. It produces a well localised pain, and is innervated by the phrenic and intercostal nerves.

The blood supply is derived from the intercostal arteries.

Question 18

What is the neuromuscular supply to the visceral pleura?

Answer 18

The visceral pleura is not sensitive to pain, temperature or touch. Its sensory fibres only detect stretch. It also receives autonomic innervation from the pulmonary plexus (a network of nerves derived from the sympathetic trunk and vagus nerve).

Arterial supply is via the bronchial circulation (internal thoracic arteries), which also supplies the parenchyma of the lungs.

Question 19

What is the difference in blood supply to the parietal and visceral pleura?

Answer 19

Visceral pleura is supplied by the bronchial circulation (internal thoracic artery) whereas the parietal pleura is supplied by the intercostal arteries

Question 20

Why may a lung tumour not cause any pain until it is very large?

Answer 20

As the visceral pleura doesn’t have sensory nerve fibres for pain, and therefore it is only when the tumour grows large enough to distort the parietal pleura that it will trigger referred pain via the phrenic or intercostal nerves

Question 21

Where is the apex of the lung located from surface anatomy?

Answer 21

About 2cm above the clavicle

Question 22

Where is the cardiac notch approximately located from surface anatomy?

Answer 22

Approximately at the 4th rib

Question 23

How would COPD/emphysema appear on chest x-ray?

Answer 23

Lung hyper expansion (can see more than 8 ribs)

Question 24

How many lobes are there in the left lung?

Answer 24

Two, superior and inferior

Question 25

How many lobes are there in the right lung?

Answer 25

Three; superior, middle and inferior

Question 26

What is the horizontal fissure in the lungs?

Answer 26

This is the fissure that separates the superior lobe from the middle lobe in the right lung

Question 27

What four structures pass through the lung hilum?

Answer 27

Pulmonary ligament, pulmonary veins, bronchus and pulmonary arteries

Question 28

Outline the progressive segmentation of the airways

Answer 28

Trachea –> main bronchus –> lobar bronchus –> segmental bronchi –> terminal bronchioles –> conducting bronchioles –> respiratory bronchioles –> alveolar ducts –> alveolar sacs

Question 29

What is emphysema?

Answer 29

A condition that involves the destruction of alveolar walls leading to the permanent enlargement of air spaces and reduction of surface area and loss of elastic tissue. This leads to reduced recoil of the lungs and narrowed bronchioles (due to mucus aggregation and plugging). The mucus aggregation and plugging alongside bronchiole narrowing leads to ‘air trapping’ which leads to hyperinflation of the lungs

Question 30

Why do you get lung hyperinflation in COPD and emphysema?

Answer 30

Due to ‘air trapping’ as a result of mucus plug formation and bronchiole narrowing

Question 31

How may a lung tumour lead to unilateral pupillary constriction?

Answer 31

A tumour in the apex of the lung that is compressing the stellate ganglion of the sympathetic trunk can cause Horner’s syndrome leading to pupillary constriction ipsilaterally due to reduced sympathetic innervation.

Question 32

How may a lung tumour lead to a hoarse voice?

Answer 32

If there is a tumour in the apex of the lung it may compress the recurrent laryngeal nerve and therefore affect phonation

Question 33

Where is the superior mediastinum found?

Answer 33

Above the sternal angle

Question 34

What structures are in the superior mediastinum?

Answer 34

The great vessels, oesophagus, trachea, thymus, phrenic nerves, vagus nerves, recurrent laryngeal nerves and the thoracic duct

Question 35

Where is the posterior mediastinum found?

Answer 35

Anterior to the T5-T12 vertebra

Question 36

What structures are found in the posterior mediastinum?

Answer 36

Contains the azygos (and hemi-azygos) vein, vagus nerve, oesophagus, thoracic duct and thoracic aorta

Question 37

Which nerve supplies the vocal cords?

Answer 37

The recurrent laryngeal nerve

Question 38

Which structure does the left recurrent laryngeal nerve loop around?

Answer 38

Descending aorta

Question 39

Which structure does the right recurrent laryngeal nerve loop around?

Answer 39

Right subclavian artery

Question 40

What is the sympathetic trunk?

Answer 40

This is formed by the sympathetic chain ganglia from T1 to L2 and is involved in facilitating the fight or flight response

Question 41

What is the role of the sympathetic trunk?

Answer 41

Is involved in initiating the fight or flight response and is therefore involved in:
pupil dilation, bronchodilator, cardiac acceleration, digestive inhibition, bladder filling, peripheral vasoconstriction and piloerection.