S2: chest & lung anatomy Flashcards
Describe how the structure of the nose and paranasal sinuses is conducive to warming, humidifying and filtering/trapping particles in inspired air
Humidification is achieved by transudation of fluid through the epithelium & to a lesser extent mucous secretion
Each nostril is lined with coarse hairs -> trap large particles in inhaled air
-mucous secreted by the goblet cells traps almost all particles >5mm
Explain how the larynx protects the airway during swallowing
During swallowing, the laryngeal inlet becomes narrowed, the epiglottis folds downwards over the laryngeal inlet and the vocal cords come together -> acts as a sphincter closing off the entrance to the trachea
Explain why hoarseness of voice/voice change may be a sign of intra-thoracic disease
Movements of the vocal cords are caused by the action of the intrinsic laryngeal muscles
Recurrent laryngeal nerve supplies all the intrinsic muscles
-on the left side has a long course -> intra thoracic disease compressing/infiltrating the nerve can result in a hoarse voice – paralysis of the left vocal cord
Describe the features of a typical rib
Has a head, neck, tubercle and shaft
Head – two articular facets that articulate with the body of the corresponding vertebrae
Tubercle – one articular facet for articulation with the transverse process of the corresponding thoracic vertebra
Shaft – has a groove in which the intercostal vessels and nerve run
Describe rib movements during respiration
Elevation of lateral aspect of ribs in inspiration
Sternum moves forward in inspiration because of rib elevation
Diaphragm descends to increase thoracic capacity in inspiration
Opposite movements in expiration
Describe the nerve supply and actions in respiration of the external intercostal muscles
Run downwards & anteriorly from the inferior margin of the rib above to superior margin of the rib below
Responsible for about 30% of chest expansion during quiet respiration
Contraction of these muscles = increase the anteroposterior and transverse diameters of the chest
Innervation = intercostal nerves
Describe the nerve supply and actions in respiration of the internal intercoastal muscles
Fibres of these muscles run downwards and posteriorly from the rib above to rib below
Action = pulls the ribs down from the position of chest expansion
Active during forced expiration
Innervation = intercostal nerves
Describe the nerve supply and actions in respiration of the innermost intercostal muscles
Similar to the internal intercostal muscle, but less well developed
Act along with the internal intercostal muscles during forced expiration
Innervation = intercostal nerves
Describe the nerve supply and actions in respiration of the diaphragm
Main muscle of inspiration = responsible for > 70% of chest expansion in quiet respiration
Dome shaped and bulges into the thorax
Innervation = right and left phrenic nerves (C3, C4 & C5)
NB: damage to the phrenic nerve causes paralysis of the affected side of the diaphragm & appears as an elevated hemi-diaphragm on a chest x-ray
Describe the course of the intercostal nerves, arteries and veins
The intercostal arteries course between the intercostal vein superiorly and the intercostal nerve inferiorly
Intercostal nerves arise from the anterior rami of the thoracic spinal nerves from T1 to T11
Intercostal veins drain into the azygos vein
Describe the pleural cavity & pleura, including its nerve supply and the role of the pleural fluid and the pleural seal in lung expansion
Parietal pleura lines the inside of each hemi-thorax and is continuous at the hilum of the lung with the visceral pleura which lines the outside of lung
Pleura links the movement of the chest wall and lungs (surface tension between the molecules of pleural fluid creates a seal that connects the two pleurae -> ensures that when the thorax expands in respiration the lungs expand along with it)
Parietal pleura – innervated by the phrenic and intercostal nerves
Visceral pleura – innervated by the pulmonary plexus
Describe the trachea and bronchial tree
Trachea commences at the lower border of the cricoid cartilage of the larynx in the neck & terminates by dividing into the right and left main bronchi at the level of the sternal angle (costal cartilage of 2nd rib articulates with sternum)
Primary bronchi divide into lobar bronchi for each lobe – 3 on the right and 2 on the left -> divide into segmental bronchi each of which supply a bronchopulmonary segment
-bronchopulmonary segment: area of lung supplied by a segmental bronchus & the accompanying segmental branch of the pulmonary artery
Describe the lungs
Left lung is divided into 2 lobes – upper and lower by oblique fissure
Right lung is divided into 3 lobes – upper, middle and lower by oblique fissure and horizontal fissure
Describe structures in the root of the neck and mediastinum
Apex is closely related to the subclavian vessels and the brachial plexus
Left side – lung is adjacent to the heart, aortic arch, descending aorta, oesophagus and several nerves -> left phrenic nerve, vagus nerve and its left recurrent laryngeal branch
Right side – lung is adjacent to the SVC, azygous vein, right atrium, oesophagus, right phrenic nerve, vagus nerve & sympathetic trunk
Explain the effects of involvement of the structures in the root of the neck and mediastinum by pathological processes in the lung or thoracic cavity
Tumours of the apex of the lung can cause neurological and vascular problems in the upper limb
Stab wounds of the lower neck may puncture the lung causing a pneumothorax
Mediastinal structures may be involved/damaged by pathologies such as lung cancers, enlarged hilar lymph nodes or aortic aneurysm
-phrenic nerve -> causes paralysis of the affected hemi diaphragm -> breathlessness
-left recurrent laryngeal nerve -> causes paralysis of intrinsic laryngeal muscles on affected side -> vocal cord paralysis & hoarseness of voice
-SVC -> causes SVC obstruction
