Thorax Flashcards
Communication with the neck and upper limb is through the superior thoracic aperture. What does the aperture consist of?
The first thoracic vertebra.
The first pair of ribs
The superior surface of the manubrium of the sternum.
The thorax is separated from the abdomen by the muscular sheet of the diaphragm and communicates with the abdomen via the inferior thoracic aperture. What does the aperture consist of?
The twelfth thoracic vertebra
The eleventh and twelfth pairs of ribs
The inferior costal cartilages.
What three bones make up the sternum?
Manubrium, main sternal body and xiphoid process
What is the angle of louis?
The palpable landmark, formed by the manubriosternal joint, also called the sternal angle.
What spinal level does the angle of louis lie at?
Lower border of the T4 vertebral body or the intervertebral disc between the fourth and fifth thoracic vertebrae (T4/T5).
What divides the superior and inferior mediastinum?
T4 / The angle of louis
Which costal cartilage articulates with the sternal angle?
The second rib
Which spinal level is the jugular (suprasternal) notch at?
T2
Which spinal levels does the sternum span?
T5-T9
Under what circumstances might extra ribs be clinically significant?
If there is a pair of cervical ribs at the superior thoracic aperture, which may compress neurovascular structures traversing this narrow space.
What are the three groups of ribs and why are they grouped?
The upper seven pairs of ribs (1-7) articulate directly via their costal cartilages with the sternum (sternocostal joint) : the vertebrosternal or ‘true’ ribs
Rib pairs 8 to 10 articulate with the costal cartilage of the rib above: the vertebrocostalor ‘false’ ribs
Finally, the most inferior two ribs, 11 to 12, have no anterior articulation and are called floating ribs.
Where does the muscular part of the diaphragm attach?
Xiphoid process of the sternum, the eleventh and twelfth ribs, lower costal cartilages and the first to third lumbar vertebrae(L1-3)
How does the diaphragm attach to the vertebrae?
its vertebral attachments are via muscular slips called crura, the right arising from L1-3 and the left from L1-2 vertebral bodies.
How is the central tendon of the diaphragm formed?
Muscle fibres come together to from the central tendon.
When we inspire, how does the central tendon move?
Inferiorly
What passes through the diaphragm at T8?
Inferior vena cava
What passes through the diaphragm at T10?
Oesophagus and vagus nerves
What passes through the diaphragm at T12?
Aorta and thoracic duct (lymphatics). Sympathetic chain at a similar level.
Which nerve innervates the diaphragm?
Phrenic nerves which originate from the third, fourth and fifth cervical spinal nerves (C3,4 and 5), (sensory and motor). The peripheral edge of the diaphragm receives some sensory innervation from intercostal nerves.
Describe the course of the phrenic nerve
The phrenic nerves descend though the thorax on either side of the mediastinum to reach the diaphragm, where they penetrate its substance to innervate it.
Why does referred pain occur? Give an example in context of the phrenic nerve.
Irritation of the phrenic nerves supplying the diaphragm may generate pain referral to the shoulder region because of the distal origin of these diaphragmatic nerves (C3, 4 and 5). For example, an enlarged gallbladder pressing upon the diaphragm may refer pain to the right shoulder of a patient.
Where do the external intercostals run and what action do they provide?
Fibres of the external intercostal muscles run forwards and downwards from the tubercles of the ribs. Key for inspiration.
Where do the internal intercostals run and what action do they provide?
Internal intercostals are thickest close to the sternum, their fibres running at right angles to those of the external intercostals. Mainly exhalation
Describe neurovasculature of thoracic wall, where is it found?
Order is VAN
Found on inferior surface of rib (costal groove)
Where would you puncture during a chest drain?
The lower region of the intercostal space, to avoid laceration of an intercostal artery.
Where do the intercostal nerves arise?
Ventral rami of the second to eleventh thoracic spinal nerves (T2-T11).
What do the intercostal nerves innervate?
Intercostal muscles and provide branches to the parietal pleura and their respective dermatomes.
A lateral cutaneous branch pierces the intercostal muscles to provide sensation to the skin of the lateral thoracic wall while an anterior cutaneous branch provides sensation to the skin of the anterior thorax and abdomen.
Describe the arterial supply to the thoracic cage.
The anterior intercostal arteries are vessels from the internal thoracic arteries, which are branches of the subclavian arteries.
(7-9 anterior intercostal arteries are derived from musculophrenic branch of the internal thoracic artery)
The posterior intercostal arteries are mainly derived as segmental branches of the descending thoracic aorta.
Describe the venous return from the thoracic cage
Anterior and posterior intercostal veins, return venous blood to the internal thoracic veins and azygos system of veins respectively.
Intercostal veins of the right side drain into the azygos vein which drains into the superior vena cava.
The intercostal spaces of the left side are drained by the accessory hemiazygos vein and the lower hemiazygos vein, both of which usually cross the midline to join the azygous vein.
What nodes drain the thoracic cage? Lymph from what other clinically important location drains here?
Parasternal nodes
Lymphatic vessels from the medial half of each breast also drain to parasternal nodes. Thus, metastases from a breast tumour may drain to the thoracic wall.
What is significant clinically about apex of lung?
Compression of the sympathetic chains as they traverse the posterior thoracic wall, typically close to the superior thoracic aperture by a tumour in the apex of a lung (Pancoast’s tumour) can cause Horner’s syndrome.
The external intercostal muscles are active in …
Forced inspiration
The intercostal space in which a normal apex beat is typically located ?
5th intercostal space
How many vertebrae does the first rib articulate with compared with other ribs?
One compared with two
Pleura and diaphragm levels round the full thorax
T8 8th rib at mid clavicular line, 10th rib T10 and mid axillary line and T12 posteriourly
Where does the pleura follow the sternum down to?
4th costal cartilage
On the left side where does the pleura pass, why?
Due to the presence of the heart it passes from 4th costal cartilage to the left 6th costochondral joint
Right and left heart border
Right 3rd costal cartilage to 6th costal cartilage
Left 2nd IC space to 5th IC space (apex)
Where are lung apices?
3cm above the medial third of the clavicles
Movement of lower and upper ribs?
Lower, bucket handle (out and in) and upper pump handle ( up and down)
Location of caval opening of the diaphragm?
Central tendon
Location of oesophageal hiatus of the diaphragm?
Right crus
Location of aortic hiatus of the diaphragm?
Posterior
What passes through the diaphragm with the vena cava?
Branches of right phrenic nerve
What passes through the diaphragm with the oesophagus?
Vagus
Minor oesophageal arteries
What passes through the diaphragm with the aorta?
Thoracic duct
Azygous vein
Accessory muscles of respiration and roles
Sternocleidomastoid - inhalation
Scalene - inhalation
Abdominal wall - exhalation
Where is the VAN bundle found?
Between the internal and innermost layers of IC muscle
VAN bundle superior to inferior
VAN
Dermatome at sternal angle?
T2
Dermatome at nipples?
T4
Dermatome at Xiphoid?
T6
