Anatomy of the Thorax Flashcards
Over what muscle does the long thoracic nerve run?
Serratus anterior
What is the innervation to the intercostal muscles?
Innervated by the anterior rami of the thoracic spinal nerves
Between which muscles do the neuromuscular bundles run in the intercostal margin?
Between the internal intercostal and the innermost intercostal muscles
Describe the procedure of thoracocentesis
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
What is thoracocentesis?
Where a sample of pleural fluid is taken using a needle
Describe the procedure of chest drain insertion
A chest drain is inserted into the 5th intercostal space in the mid-axillary line in the ‘safe triangle’
What is the ‘safe triangle’ formed by?
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
What muscles are involved in quiet inspiration?
Contraction of the diaphragm, external intercostals and the interchondral part of the internal intercostal
What muscles are involved in deep inspiration?
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
What muscles are involved in quiet expiration?
Elastic recoil of the diaphragm, external intercostals and interchondral part of internal intercostals
What muscles are involved in forced expiration?
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
What is fluid in the pleural cavity known as?
Pleural effusion
How could you diagnose pleural effusion from a chest x-ray?
Severe blunting of the costophrenic recess and white at the base of the lungs
Which type of pleura produces pleural fluid?
The parietal pleura, and this fills the pleural cavity
What structures are covered by the parietal pleura?
Thoracic wall and superior surface of diaphragm
What structures are covered by the visceral pleura?
External lung surface
What is the neuromuscular supply to the parietal pleura?
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.
What is the neuromuscular supply to the visceral pleura?
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.
What is the difference in blood supply to the parietal and visceral pleura?
Visceral pleura is supplied by the bronchial circulation (internal thoracic artery) whereas the parietal pleura is supplied by the intercostal arteries
Why may a lung tumour not cause any pain until it is very large?
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
Where is the apex of the lung located from surface anatomy?
About 2cm above the clavicle
Where is the cardiac notch approximately located from surface anatomy?
Approximately at the 4th rib
How would COPD/emphysema appear on chest x-ray?
Lung hyper expansion (can see more than 8 ribs)
How many lobes are there in the left lung?
Two, superior and inferior
How many lobes are there in the right lung?
Three; superior, middle and inferior
What is the horizontal fissure in the lungs?
This is the fissure that separates the superior lobe from the middle lobe in the right lung
What four structures pass through the lung hilum?
Pulmonary ligament, pulmonary veins, bronchus and pulmonary arteries
Outline the progressive segmentation of the airways
Trachea –> main bronchus –> lobar bronchus –> segmental bronchi –> terminal bronchioles –> conducting bronchioles –> respiratory bronchioles –> alveolar ducts –> alveolar sacs
What is emphysema?
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
Why do you get lung hyperinflation in COPD and emphysema?
Due to ‘air trapping’ as a result of mucus plug formation and bronchiole narrowing
How may a lung tumour lead to unilateral pupillary constriction?
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.
How may a lung tumour lead to a hoarse voice?
If there is a tumour in the apex of the lung it may compress the recurrent laryngeal nerve and therefore affect phonation
Where is the superior mediastinum found?
Above the sternal angle
What structures are in the superior mediastinum?
The great vessels, oesophagus, trachea, thymus, phrenic nerves, vagus nerves, recurrent laryngeal nerves and the thoracic duct
Where is the posterior mediastinum found?
Anterior to the T5-T12 vertebra
What structures are found in the posterior mediastinum?
Contains the azygos (and hemi-azygos) vein, vagus nerve, oesophagus, thoracic duct and thoracic aorta
Which nerve supplies the vocal cords?
The recurrent laryngeal nerve
Which structure does the left recurrent laryngeal nerve loop around?
Descending aorta
Which structure does the right recurrent laryngeal nerve loop around?
Right subclavian artery
What is the sympathetic trunk?
This is formed by the sympathetic chain ganglia from T1 to L2 and is involved in facilitating the fight or flight response
What is the role of the sympathetic trunk?
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.
