Thorax Flashcards
What forms the sternal angle and at what vertebral level is it?
Manubrium articulating with body of the sternum (Level of the 2nd rib) is the sternal angle.
This occurs at T4/5 vertebral level
Describe the costovertebral and costotransverse joints in the rib cage.
Costovertebral - Head of rib articulates with articular facets its own vertebrae and the vertebrae superior to it. Reinforced by the radiate ligament.
Costotransverse - Between the tubercle of the rib and the transverse process of its own vertebrae.
- Medial faces articulates with the transverse process (synovial joint)
- Lateral facet gives rise to lateral costotransverse ligament to the transverse process
Which ribs attach to the sternum, costal cartilages above and which are floating?
Ribs 1-7 attach to the sternum
Ribs 8-10 attach to costal cartilage above
Ribs 11-12 are floating ribs
How does the 12th rib differ from the other ribs
Has no neck, tubercle or costal groove
Only contains one facet which articulates with corresponding vertebra
Describe the Outer, Middle and Inner Layer of thoracic muscles (Including innervation and action)
All innervated by intercostal nerves (Anterior rami of spinal nerves)
Outer Layer
- External Intercostal (Pass obliquely forwards, action to elevate ribs)
- Serratus posterior Superior (Spinous Process C6-T2 to ribs 2-5, elevates ribs)
- Serratus posterior inferior (SP T11-L2 to ribs 9-12, depresses ribs)
Middle Layer
- Internal Intercostal (Pass obliquely backwards, depress ribs)
Inner Layer
- Transversus thoracic (Continuous with transverses abdominis, from inferior sternum to costal cartilages 2-6, weak depressor)
- Innermost intercostal
- Subcostals (inner surface lower ribs then arch to superior border of rib 2 or 3)
Between what muscle layers does the intercostal space lie and what are its contents
Between middle and innermost muscular layers.
Consists of intercostal vein, artery and nerve (Superior to Inferior)
Located on the lower border of the rib.
What are the two branches of the intercostal nerves
Intercostal nerves arise from anterior rami of spinal nerves T1-11.
Give off:
i. Lateral cutaneous branch
ii. Anterior cutaneous branch
What is special regarding the lower 5 intercostal nerves, and especially the 12th intercostal nerve?
The lower 5 intercostal nerves slope downward before exiting their intercostal rib space to supply anterior abdominal wall.
The 12th intercostal nerve is referred to as the subcostal nerve and it passes into the abdominal cavity behind the lateral arcuate ligament and lies behind the kidney
Describe the Posterior and Anterior intercostal arteries that supply the thoracic wall
Posterior intercostal arteries
- Intercostal Space 1&2 from costocervical trunk (subclavian)
- Intercostal spaces 3-11 from Thoracic Aorta
Anterior intercostal arteries
- Intercostal spaces 1-6 from Internal thoracic artery (subclavian)
- Intercostal spaces 7-9 my musculophrenic artery (Branch of internal thoracic a.)
Diaphragm - What Levels do the crura anchor the diaphragm to the vertebrae?
Both are very strong tendons
- Right Crura form L1-3
- Left Crura from L1-2
Diaphragm - Describe the 2 major ligaments of the diaphragm
Median arcuate ligament
- Between both crura and in front of the aorta
- It is a thickening of the psoas fascia
- Sympathetic trunks pass behind the medial arcuate ligament
Lateral arcuate ligament
- Anterior thickening of the lumbar fascia
- Subcostal nerve and vessels pass behind the lateral arcuate ligament
Diaphragm - What is its nerve supply
Phrenic Nerve (C3-5) to each side
Motor supply mainly C4
Diaphragm - What is the blood supply
Right and left inferior phrenic arteries
Lower 5 intercostal arteries and subcostal arteries
Diaphragm - Describe the Major Openings of the diaphragms, what passes through them and the respective vertebral levels
T12 - Aortic Hiatus (Aorta, Azygos vein, thoracic duct)
T10 - Oesophageal Opening (Oesophagus, vagus nerves)
T8 - Vena Caval Opening (IVC, right phrenic nerve)
Others:
*Left phrenic pierces muscular dome
*Hemiazygos vein passes through left crus
*Splanchnic nerves pieces the crura
* Subcostal nerve and vessels pass behind lateral arcuate ligament
Describe the main muscles involved in inspiration and expiration
Inspiration
- Mainly due to diaphragm
- External intercostals also active
- Accessory muscles can also be used including scalenes, sternocleidomastoid, erector spine
Expiration
(largely passive)
- Internal intercostals most active
- Assisted by external oblique, internal oblique and transverses abdomens muscles, latissimus doors
List some of the anatomical landmarks that occur at the sternal angle (T4/5) [Division of superior mediastinum to inferior mediastinum]
- Bifurcation of the trachea
- Beginning and end of the aortic arch
- Just above the bifurcation of the pulmonary trunk
- Azygos vein enters SVC
- Thoracic duct moves from left to right of the oesophagus
- Ligamentum arteriosum attaches from left pulmonary artery to aortic arch
Superior Mediastinum: What two structures does the aortic arch pass over and what are the major branches of the aortic arch?
Passes over:
- Left bronchus
- Pulmonary trunk
Major Branches
- Brachiocephalic a.
- Left common carotid a.
- Left subclavian a.
SM: At what anatomical landmark doe the brachiocephalic a. divide into the right common carotid a. and rich subclavian a.?
behind the right sternoclavicular joint