| Question | Answer |
| Overview | Lungs extend to top of thoracic cavity
Extends a long way posteriorly - T10
Pleural space extends to T12 |
| Sternum and Ribs | Protective for blunt force trauma
Less useful in penetrating wounds due to gaps
Generates negative pressure for breathing
Ribs articulate posteriorly with spinal vertebrae and anteriorly with sternum |
| Anterior attachments of the ribs | 1-7 = sternum via costal cartilage
8-10 = costal cartilage joins to one above
11-12 = no anterior attachment |
| Intercostal muscles | External
Internal
Innermost
Costal groove - blood and nervous supply runs within the groove under each rib |
| Pump and bucket handles | Pump - ribs move up and out
Bucket - elevation of the ribs
This generates negative pressures for ventilation |
| Influences on ventilation | Reduced FVC in supine posture - harder to breathe lying down due to increased weight on ribs
Worse in obesity and at night
Mechanical disadvantage to lying down and all muscles paralysed except diaphragm
Also in kyphoscoliosis |
| Diaphragm | Attaches to costal cartilage of ribs 7-10
Inferior margin at 12th rib
Slightly higher on right - presence of liver
IVC perforates at T8, Oesophagus at T10 and Aorta at T12 |
| Phrenic nerve | Innervates diaphragm from C3,4,5
Runs through mediastinum outside pleural sac
Ramifies over surface of diaphragm
Spinal injury below C3,4,5 is likely to leave respiration intact |
| Diaphragmatic paralysis | Presents as one side of the diaphragm being too high'
e.g. tumour at apex of the lung damaging phrenic nerve |
| Accessory muscles | Trapezius, Scalenus and Sternomastoid used in help inflate the lungs when struggling with ventilation
Tripod position brings these into play |
| Pleura | Visceral pleura surround the lung directly
Parietal pleura is attached to the inside of the chest wall
Separated by pleural cavity - a potential space
Pressure in here is slightly negative compared to lungs - negative intrapleural pressure |
| Pneumothorax | Loss of negative pressure due to communication between pleural cavity and outside
Lung cannot inflate
Tension pneumothorax - pressure increases as air moves into cavity but cannot leave
Release of air helps
Bullae -connections between lungs and cavity |
| Flail chest | Ribs broken in two spaces and usually multiple ribs
Free floating chest wall makes no contribution to ventilation
As pressure decreases the chest wall is sucked in |
| Vascular supply of the chest wall | Segmental anterior and posterior intercostal arteries
Arise from descending aorta and anastomose at front with internal thoracic arteries
Intercostal veins and thoracic veins drain into azygous vein |
| Vascular supply of the lungs | Receive all the blood in pulmonary circulation under low pressure
Also have a systemic component in bronchial arteries
These are at higher pressure - bleeding in lungs is most likely from here |
| Hilar structures | Where pulmonary artery and vein move in and out of the lungs
Bronchi enter through here |
| Lobes and segments of the lung | Right - three lobes (upper, middle and lower) separated by the horizontal and oblique fissures
Left - two lobes (upper and lower) separated by oblique fissure |
| Trachea and bronchi | Carries gas into the lungs
Cartilaginous rings support these and prevent collapse
Smooth muscle around these contracts in asthma to constrict the airways
Foreign bodies most likely to enter right bronchi |
| Bronchoscopy | A flexible camera is inserted into the trachea to look down into the lungs
Can be used with an ultrasound probe to direct needles into lymph ducts to take biopsy |
| Terminal bronchioles and alveoli | Blood vessels run over the surface of alveoli to allow gas exchange to occur |
| Lymphatic drainage | Mainly drain into thoracic ducts
Through hilar areas to lymph nodes in mediastinum
Bi-hilar lymphadenopathy - enlarged lymph nodes |
| Chylothorax | A collection of chylo (lymphatic drainage) in the pleural space
Similar to pneumothorax |
| Autonomic innervation | Both sympathetic and parasympathetic innervation
Sympathetic - chain ganglia
Parasympathetic - vagus nerve
Sympathetic chains run alongside vertebrae |
| Damage to lung innervation | Pancoast syndrome - bronchogenic carcinoma of the apex of the lung which may damage sympathetic chain ganglia
Horner's syndrome - loss of SNS innervation due to damage to chain ganglia - wasting, pain and paralysis of arm and hand |
| Emphysema | COPD
Damage to structure of the lung
Alveoli break down to form large pockets of air
Loss of gas exchange surface |
