thorax Flashcards
What is the transverse thoracic plane?
Imaginary horizontal plane at the level of sternal angle/rib 2 & T4/5
What happens at the level of the transverse thoracic plane?
Sternal angle
Trachea bifurcates
Pulmonary trunk birfucates
Aortic arch concavity
What are the different components of the mediastinum?
Superior
Inferior - anterior, middle, posterior
What are the boundaries of the mediastinum?
Anterior: sternum and costal cartilages
Posterior: Tx vertebrae
Inferior: diaphragm
Superior: superior Tx aperture (manubrium, ribs 1, T1)
What are the contents of the mediastinum?
All Tx viscera and structures except the lungs
What are the features of the mediastinum?
Central compartment in thoracic cavity between the lungs and above the diaphragm
Covered by mediastinal pleura
Very mobile region to accomodate movement, pressure and volume changes
What are the contents of each mediastinal compartment?
Superior:
- trachea
- oesophagus
- aortic arch & branches
- phrenic & vagus n
Inferior (anterior):
- thymus
Inferior (middle):
- heart
- great vessels
- phrenic n
Inferior (posterior):
- oesophagus
- Tx aorta
- vagus n
- Tx duct & lymph nodes
What are the 4 types of muscles in the thoracic cage?
Respiration (1)
Intercostal (3)
Internal Cage (2)
External Cage (3)
What are the muscles of the thoracic cage?
There are 9 muscles in the thoracic cage:
Respiration:
- diaphragm
Intercostal:
- external
- internal
- innermost
Internal Cage:
- subcostal
- transverse thoracis
External Cage:
- serratus posterior superior
- serratus posterior inferior
- levator costorum
Describe the diaphragm
PA:
- xiphoid process
- internal surfaces of ribs and costal cartilages 1-6
- Lx vertebrae and IVDs
DA:
- central tendon
NS:
- motor: phrenic (C3-5)
- sensory (central): phrenic (C3-5)
- sensory (peripheral): intercostal nerves 5-11, subcostal nerve
A:
- contraction pulls dome inferiorly and increases thoracic cavity
Describe the anatomy of the intercostals:
3 layers:
- external
- internal
- innermost
PA:
- inferior border of ribs
DA:
- superior border of inferior rib
NS:
- intercostal nerve of same level
Fibres:
- external: anteriorly and inferiorly
- internal and innermost: posteriorly and inferiorly
A:
- external: elevates ribs during forced inspiration
- internal: interossesous part depresses ribs and interchondral part elevates ribs
Describe the crura of the diaphragm
There are two crura (right and left).
Musculotendinous bundles that connect the diaphragm to L1-4 vertebrae, the IVDs, and the ALL.
Right:
- longer, attaches to L1-4, contains oesophagal hiatus
Left:
- shorter, attaches to L1-3
What are the 4 bony elements of the thoracic cage?
Ribs (12)
Costal cartilages (12)
Sternum
Thoracic vertebrae (12)
What are the 3 types of ribs?
1-7: true ribs (attach directly to sternum)
8-10: false ribs (attach to sternum via costal connection to superior rib)
11-12: floating ribs (no anterior attachment)
What are the 3 components of the sternum?
Manubrium (superior)
Body (middle)
Xiphoid process (inferior)
Which are the typical and atypical thoracic vertebrae?
T2-9: typical
T1, T10-12: atypical
What are the characteristics of a typical thoracic vertebrae?
Body - heart shaped
Foramen - circular
Spinous processes - long and sharp, project inferiorly and overlap inferior vertebrae
Transverse processes - project posteriorly as well as laterally to accomodate ribs; T1-10 have costal facets for articulation with ribs
Articular facets:
- superior facets face posteriorly, inferior facets face anteriorly
Describe the costal facets on the typical thoracic vertebrae
On typical vertebrae (T2-9):
Superior demifacet: large semicircle, articulates with same rib (head)
Inferior demifacet: small semicircle, articulates with inferior rib (head)
Transverse costal facet: articulates with tubercle of same rib
Which vertebrae have a single circular facet to articulate with ribs?
T1, T10-12
Which vertebrae have costal facets on the transverse processes to articulate with tubercle of ribs?
T1-10
Which are the typical and atypical ribs?
Typical: 3-9
Atypical: 1, 2, 10, 11, 12
Describe a typical rib
Ribs 2-9:
- wedge shaped head posteriorly made up of superior and inferior demifacets (articulate with facets of vertebrae) and crest of head for attachment of intra-articular ligament
- neck (lateral to head)
- tubercle (articulates with costal facets on transverse processes)
- angle (where rib slants inferiorly)
- costal groove (internal surface, for passage of neurovascular vessels)
- costal cartilage anteriorly
What are the 3 components of the sternum and their features?
Manubrium, body and xiphoid process
Manubrium:
- widest and thickest part
- suprasternal notch
- clavicular notoch
- costal notch for rib 2 at sternal angle
Body:
- costal notches for ribs 3-7
Xiphoid process:
At what levels of the Tx spine are the components of the sternum located?
Manubrium: T3-4 level
Body: T5-9 level
Xiphoid: T10 level
Which nerves innervate the thoracic wall?
The intercostal and subcostal nerves:
Source: ventral rami of Tx spinal nerves T1-11 (intercostal) and T12 (subcostal)
Course:
- arise from ventral rami of spinal nerves to run between pleura and internal intercostal membrane
- at angle of ribs, enters costal groove between innermost and internal intercostals
- runs length of intercostal space (with intercostal artery and vein) in costal groove
Which two major arteries does the thoracic cage receive blood supply from?
Subclavian
(Anterior Intercostal 1-9)
Thoracic Aorta
(Posterior Intercostal & Subcostal)
What are the branches of the subclavian artery in the thoracic cage?
Subclavian - Internal Thoracic - Anterior Intercostal 1-6 (direct branches)
musculophrenic
- Anterior Intercostal 7-9
What is the venous drainage of the thoracic cage?
Venous drainage via:
- posterior & anterior intercostal veins (anastamose and drain into azygos venous system & superior vena cava)
- internal thoracic veins drain into braciocephalic veins, which unite to form superior vena cava)
What is the transverse thoracic plane?
Imaginary horizontal line between:
T4/5 & IVD posteriorly
Rib 2 / sternal angle anteriorly
At this level:
- divides superior and inferior mediastinum
- trachea bifurcates
- pulmonary trunk bifurcates
- aortic arch
- azygous vein drains into SVC
Describe the mediastinum
Central compartment in the thoracic cavity
Divided into superior and inferior mediastinum at the level of the sternal angle / transverse thoracic plane
Inferior mediastinum further divided into anterior, middle and posterior sections
Mobile compartment to accommodate volume and pressure changes of contents (structures accomodate fluid and air)
What are the contents of the mediastinum (overall)?
All thoracic viscera and structures except the lungs:
- heart (middle)
- trachea (superior)
- oesophagus (superior and posterior)
- arch or aorta and branches (superior)
- superior vena cava (superior)
- descending aorta (posterior)
- vagus nerves (superior and posterior)
- phrenic nerves (superior and anterior)
- thymus (superior and anterior)
