How does the sternum develop?
- as a series of separate bones called sternebrae
- small bones fuse to become body of the sternum
- first becomes manubrium, most inferior becomes xiphoid process
Role of the costal groove on the rib bone
- protects the intercostal nerve and vessels
Features of the first rib
- atypical rib
- one articular facet for first thoracic vertebra
- scalene tubercle
What does the osseocartilaginous thoracic skeleton consist of?
- 12 pairs of ribs and their costal cartilages
- 12 thoracic vertebrae and intervertebral discs between them
- sternum
What is the superior thoracic aperture?
- major transition site between neck, upper limb and thoracic cavity
- anterior aspect of body of first vertebrae
- medial border of first ribs
- jugular notch of the manubrium
Where is the inferior thoracic aperture?
- enclosed by the diaphragm forming the inferior border of the thoracic cavity
- contains openings which provide continuity with abdominal cavity
What is a thoracocentesis?
- positioning of a chest drain tube
Origins of the intercostal nerves
- T1-11
Origin of the subcostal nerve
- T12
Significance of the ventral ramus of T1
- gives large branch which joins the brachial plexus
- smaller branch passes round the 1st intercostal space as the first intercostal nerve
What do the intercostal nerves supply?
- intercostal muscles (motor)
- parietal pleura (sensory)
- skin over the anterior and lateral side of the thoracic wall
What arteries supply the intercostal spaces?
- two arteries supply each: anterior/posterior intercostal artery
- anastomose with intercostal space and provide each space with dual blood supply
What is the mediastinum?
- region of the thorax between the two pleural cavities
- contains several important anatomical structures
Where is the anterior mediastinum?
- narrow space between the sternum and pericardium
- contains few lymph node, lymphatic vessels, internal thoracic arteries and veins
Where is the middle mediastinum?
- contains the heart, roots of the great vessels
- fibrous pericardium forms boundary of this space
Where is the posterior mediastinum?
- space behind the pericardium, anterior to bodies of T5-12
What is the thoracic duct?
- largest lymphatic channel of the body
- carries lymph from entire body and returns it to venous system
Where is the thoracic duct located?
- arise in the abdomen just below the diaphragm from the cistern chyli
- enters thorax through aortic hiatus
Where are the lymph nodes of the thoracic wall located?
- parasternal nodes along the internal thoracic artery
- posterior intercostal nodes are in the posterior intercostal spaces
Where are the posterior mediastinal nodes located?
- behind the heart
- drain oesophagus, posterior diaphragm, pericardium and surrounding posterior intercostal spaces
How is the lymph from the lung and visceral pleura drained?
- by superficial and deep lymphatic vessels to bronchopulmonary nodes at hilum of each lung
Where does the vagus nerve travel between?
- through the neck in the carotid sheath between common carotid artery and internal jugular vein
What type of nerve fibres does the vagus nerve carry?
- parasympathetic nerve fibres to thoracic and abdominal viscera
What does the vagus nerve innervate?
- smooth muscle and glands of the bronchial tree
- pulmonary vessels
