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Respiratory Anatomy
Organisation of the Body
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 |