Thoracic Wall Flashcards
Thoracic Wall
Is segemental, composed of skeletal elements & muscles
Boundaries:
* the superior thoracic aperture bordered by vertebra T1, rib 1, & the manubrium of sternum
-contains: axillary artery/vein, brachial plexus, & subclavian art/vein
* The inferior border thoracic aperture bordered by vertebra T12, rib 12, the end of rib 11, the costal margin, & the xiphoid process of sternum
Skeletal framework
consists of:
* thoracic vertebrae
* intervertebral discs
* ribs
* sternum
Ribs
- 12 pairs of ribs, each terminating anteriorly in a costal cartilage
- classifications
-true ribs (1-7)
-false ribs (8-12)
-typical (3-9)
-atypical (1,2, 10-12)
-floating ribs (11 &12)
Typical ribs: 3-9
- 2 articular facets on head
- 1 articular facet for transverse process on the tubercle
- costal groove accomodates vessels
Pair of ribs that can be classified as false & typical: 8 &9
Distinct features of atypical ribs
1, 2, and 10-12
Rib 1
* wide, flat, shortest
* only 1 attachment on vertebral segement (T1)
* scalene tubercle for anterior scalene muscle
* posterior groove (small): caused by subclavian artery, sharply curved groove
* anterior groove (large): caused by subclavian vein, sharply curved groove
Rib 2:
* flat & tuberosity for serratus anterior muscle
Ribs 10, 11, & 12
* Rib 10 (selfish has own vertebra): the head of rib 10 has a single facet for articulation with its own vertebra
* rib 11 &12: articulate only with the bodies of their own vertebrae & have no tubercle. Both ribs are short, have little curve, & are pointed anteriorly. no artculation with sternum.
Sternum
Consists of:
* manubirum of sternum
* body of sternum
* xiphoid process
Sternocostal, intercondral, manubriosternal joint
- sternocostal joints: ribs and sternal notch
- interchondral joint: costal cartilage of false ribs for gliding movement
- Why only rib 1 has a fibrocartilaginous joint? Don’t want movement due to all the structures passing
- Manubriosternal joint: only allows small angular movements anteriorly
- sternal angle of Louis with the rib next to manubriosternal joint
Sternal angle as a clinical landmark
- it is at level T4-T5 intervetebral disc
- Marks the level of the transverse thoracic plane which divides the mediastrium into superior and inferior mediastrium
- it overlies the aortic arch on the left and the superior vena cava on the right
- the pericardium extends from just superior to the angle of Louis to the level of xiphisternal joint
- it is roughly at the level of bicurfation of the trachea
- the tracheal carina is deep to the sternal angle
- it is roughly at the level of bifurcation of the pulmonary trunk
Intercostal space
- lie between adjacent ribs & are filled by intercostal muscles
- intercostal nerves & associated major arteries & veins lie in the costal groove along the inferior margin of the superior rib & pass in the plane between the inner two layers of muscles
- In each space, the vein is the most superior structure, the artery is inferior to the vein, and the nerve is inferior to the artery (vein, artery, nerve)
- nerve located outside the costal groove-can be damaged. located betwen internal intercostal and innermost intercostal (between 2nd and 3rd layer)
Intercostal muscles
3 flat muscles found in each intercostal space that pass between adjacent ribs
* individual muscles in this group are named according to their positions
* external intercostals muscles are most superficial (help with inspiration, front pockets)
* internal intercostal muscles are between the external & innermost muscles (internal and innermost help with expiration, back pockets)
Blood supply: arteries
- posterior intercostal artery: from aorta, overlap with ribs 3-12
- internal thoracic artery: aka mammary: lateral to the sternum
- anterior intercostal artery: from internal thoracic artery ribs 6-10
- musculophrenic artery: runs obliquely downward behind the cartilages of false ribs
Blood supply: azygos system
Right
* Azygos vein: on the right side, goes to inferior vena cava
* Right superior intercostal vein: goes to azygos vein
Left: all go to the right to drain to inferior vena cava
* Left superior intercostal vein: goes to accessory hemiazygos
* Acessory hemiazygos vein: goes to azygos vein (superior)
* hemiazygos vein: goes to azygos (inferior)
Both: internal thoracic vein
Intercostal nerve
- What are they? segmentally supply motor innervation to muscles in the intercostal space and sensory innervation to underlying parietal pleura and overlying skin
- innervation of the thoracic wall is mainly by the intercostal nerves, which are the anterior rami of spinal nerves T1-T11.
- The anterior ramus of spinal nerve T12 (the subcostal nerve) is inferior to rib 12. Innervates the abdominal wall.
- Sensory: skin (from dermatomes)
-posterior branch
-lateral cutaneous branch
-anterior branch
-lateral branch
-anteior cutaneous branch
-medial branch
