9 - Thorax Flashcards
Boundaries of Thorax:
- Superior and inferior thoracic aperture
> Superior thoracic aperture
Posterior (T1)
Lateral (R1 and costal cartilages 1)
Anterior (manubrium)
> Inferior Thoracic Aperture
Posterior (T12)
Lateral (R12 + costal margin)
Anterior (xiphisternal)
Sternum Facts
- 3 parts (manubrium, sternum + xiphoid process)
- Males: body of sternum is longer
- Females: bottom of body of sternum is broader
Joints of Sternum
1) Sternocostal
2) Manubriosternal
3) Xiphisternal
Sternocostal Joint:
Sternocostal Joint: between sternum and rib
1st Rib: primary cartilaginous (synchondrosis) > fibrous joint w/ little movement
2-7th Rib: plane synovial > gliding motion, moveable
Manubriosternal Joint
Manubriosternal Joint: between manubrium + body Secondary cartilaginous (symphysis) > has a disc within midline.
Xiphisternal Joint
Xiphisternal Joint: between body and xiphoid process Primary cartilaginous (synchondrosis) > little movement Usually fuses at age 40
Sternum Variation
Rib 1 attaching higher = rib 2 attaching on manubrium instead of sternal angle.
Ribs (true, false, floating)
- True (1-7) Attach to costal cartilage - has a direct attachment to sternum
- False (8-10) Attach to costal cartilage of ribs 1-7 (no direct attachment)
- Floating (11-12) Don’t attach to costal cartilage.
Atypical Ribs Characteristics
Atypical Ribs (1-2, 10-12) Rib 1: scalene tubercle of anterior scalene, subclavian vein and artery pass scalane tubercle Rib 2: defined angle Rib 10: one articular facet on head Rib 11-12: floating ribs, one on articular facet on head.
Typical Ribs Characteristics
Typical Ribs (3-9)
Head, neck, shaft
Inferior articular facet: articulates w/ vertebrae of same number.
Superior facet articulates with vertebrae one less
Inferior surface of typical rib is where neurovascualr bundle is.
Thoracic Outlet Syndrome
Thoracic Outlet Syndrome: compression of structures passing through thoracic inlet. Structures include:
Compression of subclavian artery = weakness of pulse in upper limb. Inadequate blood supply can result in cyanosis and gangrene of distal upper limb.
Compression of brachial plexus = pain, paraesthesia and muscle atrophy.
Joints of Thorax:
Manubrium (symphysis)
Xiphisternal (primary cartilaginous)
Sternocostal (1st primary, 2-7th synovial)
Intercostal (9-10th fibrous - others synovial)
Costochondral (primary cartilaginous)
Costovertebral (synovial)
Costotransverse (ribs 1-10 only - synovial)
Ligaments of Thorax
Sternocostal radiate lig: begins at costal cartilage and radiates around sternum
Radiate ligament: blends into joint capsule
Superior costotransverse ligament (ribs 6 to vertebrae 5, running obliquely)
Intra Articular ligament
Muscles of Thorax:
Levator Costarum
Attach: transverse process C7-T11 > rib below vertebrae between tubercle and angle
Action: elevate ribs
Innervation: posterior rami (8-1T1)
Muscles of Thorax:
Transverse Thoracis
Attach: posterior surface of inferior sternum > internal surface of costal cartilage
Action: weakly depressed ribs + proprioception
Innervation: intercostal nerves
Muscles of Thorax:
Intercostal Muscles
Attach: (external, internal, innermost) attach inferior and superior borders of adjacent ribs
(sternocostal muscles) attach internal surface of lower ribs > sup border of 2-3rd rib.
Action: difficult to interpret
Innervation: intercostal bundle
Diaphragm Attachments:
Xiphoid process (posterior aspect) Costal cartilages 5-10 (internal aspect_ L1-L3 anterior aspect body ** Consists of 2 domes (singular = L and R crura) (together = via crura)
Structures Passing Diaphragm:
Aorta (T12)
Esophagus (T10)
Inferior Vena Cava (T8)
Diaphragm Action
Diaphragm Action: as muscle fibres contract, domes of diaphragm descend, causing intrathoracic pressure to decrease = air enters lungs
5 Arcuate Ligaments:
Lateral Quadratus Lumborum (x2)
Psoas Major (x2)
Median over Aorta (x1)
Rib Movements:
Inspiration (diaphragm moves down) and expiration (diaphragm moves up)
Pump Handle Movement: between ribs 2-6
Bucket Handle Movement: expansion of thoracic cavity from medial to lateral.
Pump Handle Movement:
Pump Handle Movement: between ribs 2-6
Bucket Handle Movement:
Bucket Handle Movement: expansion of thoracic cavity from medial to lateral.
Muscles of Respiration:
Quiet inspiration: diaphragm and intercostals
Quiet expiration: passive elastic recoil of the lungs + muscles of thorax
Forced Inspiration: scalenes, sternocleidomastoid, pec major, minor and elevator sternum
Forced Expiration: quadratus lumborum, fibers rib 12, anterolateral abdominal wall muscles > depress lower ribs and increased intraabdominal pressure, internal intercostals, depression of sternum.
