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Trachea, Bronchial Tree, Lungs and Pleurae Lorcán McBrideLearning Outcomes • Trachea • Bronchial Tree • Lungs (surfaces, borders, fissures, lobes and surface markings) • Lung hila • Pleura • Diaphragm vClinical relevance will be covered throughout T racheobronchial T ree • Upper respiratory tract = nasal cavity and pharynx • Lower respiratory tract = larynx and tracheobronchial tree • The trachea begins at C6 vertebral level and bifurcates at the carina (T4 vertebra/sternal angle) • The trachea lies anterior to the oesophagus • Respiratory portion is from the terminal bronchioles to the alveoli where there is no cartilage • Resection of bronchopulmonary segments is possible as each segment has its own segmental artery and bronchusQ: Aspirated foreign bodies are more likely to end up in which primary bronchus and why?Q: Aspirated foreign bodies are more likely to end up in which primary bronchus and why? A: Right primary bronchus because it is wider, shorter and runs more vertically than the left primary bronchusLungs • Two lungs: right lung (larger) and left lung (smaller) • Three surfaces: costal, diaphragmatic and mediastinal • Three borders: anterior, posterior and inferior • Each lung has an apex and a base • Fissures: o Right lung – right oblique fissure and horizontal fissure o Left lung – left oblique fissure • These fissures divide the right lung into three lobes (superior, middle and inferior) and two lobes (superior and inferior) • accommodate the apex of the heart on its anterior border and a lingula to • Clinical relevance – apical lung cancers can compress the recurrent laryngeal nerves and cause hoarseness, and lung cancer involving a phrenic nerve can cause paralysis of a hemidiaphragm Lung Hila • Pulmonary artery - superiormost on left (the superior lobar/eparterial bronchus may be superiormost on the right) • Superior and inferior pulmonary veins - anteriormost and inferiormost, respectively • Main bronchus - against and approximately in the middle of the posterior boundary, with the bronchial vessels coursing on its outer surface • Nerves from the pulmonary plexus • Lymphatics • Inferior to the root of the lung, the lung is connected to the mediastinum by the pulmonary ligamentPleurae • Two components: parietal pleura (lines the pulmonary cavities) and visceral pleura (lines the lungs) • These layers are continuous with each other because they derive embryologically from invagination of the lungs into the pleural sac • There is a potential space between these layers – the pleural cavity • The pleural cavity is filled with pleural fluid for lubrication • The parietal pleura has four parts, named according to the structures they overly: costal, diaphragmatic, mediastinal and cervical• There are two pleural recesses: costodiaphragmatic recess and costomediastinal recess • Fluid can collect here in pleural effusion • Arterial supply: o Visceral pleura = bronchial arteries and pulmonary arteries (branches of thoracic aorta) o Parietal pleura = intercostal arteries (anterior and posterior) • Venous supply: o Visceral pleura = bronchial veins and pulmonary veins o Parietal pleura = intercostal veins (anterior and posterior) • Innervation: o Visceral pleura = visceral afferent nerves travel with sympathetic nerves to the sensory ganglia of upper thoracic spinal nerves o Parietal pleura = intercostal nerves supply costal and peripheral diaphragmatic pleura, and phrenic nerves (C3-C5) supply the central diaphragmatic and mediastinal part o The visceral pleura is insensitive to pain, but the parietal pleura is very sensitive to painClinical Relevance • bronchopulmonary fistulae pleural cavity caused by a penetrating wound of the parietal pleura or • There are two types of pneumothorax: spontaneous (primary and secondary) and traumatic • Tension pneumothorax can develop – life-threatening emergency • Hydrothorax - fluid in the pleural cavity caused by pleural effusion • Haemothorax – blood in the pleural cavity caused by chest wounds • If there is air and fluid present, there will be an obvious air-fluid level on radiograph • Treatment – thoracocentesis (9 ICS, MAL) or chest drain (5 – 6 ICS, MAL) • Pleuritis – inflammation of the pleurae causing a pleural rub on auscultation • Atelectasis – collapse of a lung • Two types: primary (failure of lung to inflate at birth) and secondary (collapse of a previously inflated lung)Tension pneumothorax Pleural effusionDiaphragm • Innervation – phrenic nerves (C3-C5) • Contracts for inspiration and relaxes for expiration