9 - Thorax

Question 1

Boundaries of Thorax:

- Superior and inferior thoracic aperture

Answer 1

> Superior thoracic aperture
Posterior (T1)
Lateral (R1 and costal cartilages 1)
Anterior (manubrium)

> Inferior Thoracic Aperture
Posterior (T12)
Lateral (R12 + costal margin)
Anterior (xiphisternal)

Question 2

Sternum Facts

Answer 2

• 3 parts (manubrium, sternum + xiphoid process)
• Males: body of sternum is longer
• Females: bottom of body of sternum is broader

Question 3

Joints of Sternum

Answer 3

1) Sternocostal
2) Manubriosternal
3) Xiphisternal

Question 4

Sternocostal Joint:

Answer 4

Sternocostal Joint: between sternum and rib
1st Rib: primary cartilaginous (synchondrosis) > fibrous joint w/ little movement
2-7th Rib: plane synovial > gliding motion, moveable

Question 5

Manubriosternal Joint

Answer 5

Manubriosternal Joint: between manubrium + body 
Secondary cartilaginous (symphysis) > has a disc within midline.

Question 6

Xiphisternal Joint

Answer 6

Xiphisternal Joint: between body and xiphoid process
 Primary cartilaginous (synchondrosis) > little movement 
Usually fuses at age 40

Question 7

Sternum Variation

Answer 7

Rib 1 attaching higher = rib 2 attaching on manubrium instead of sternal angle.

Question 8

Ribs (true, false, floating)

Answer 8

• 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.

Question 9

Atypical Ribs Characteristics

Answer 9

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.

Question 10

Typical Ribs Characteristics

Answer 10

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.

Question 11

Thoracic Outlet Syndrome

Answer 11

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.

Question 12

Joints of Thorax:

Answer 12

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)

Question 13

Ligaments of Thorax

Answer 13

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

Question 14

Muscles of Thorax:

Levator Costarum

Answer 14

Attach: transverse process C7-T11 > rib below vertebrae between tubercle and angle
Action: elevate ribs
Innervation: posterior rami (8-1T1)

Question 15

Muscles of Thorax:

Transverse Thoracis

Answer 15

Attach: posterior surface of inferior sternum > internal surface of costal cartilage
Action: weakly depressed ribs + proprioception
Innervation: intercostal nerves

Question 16

Muscles of Thorax:

Intercostal Muscles

Answer 16

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

Question 17

Diaphragm Attachments:

Answer 17

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)

Question 18

Structures Passing Diaphragm:

Answer 18

Aorta (T12)
Esophagus (T10)
Inferior Vena Cava (T8)

Question 19

Diaphragm Action

Answer 19

Diaphragm Action: as muscle fibres contract, domes of diaphragm descend, causing intrathoracic pressure to decrease = air enters lungs

Question 20

5 Arcuate Ligaments:

Answer 20

Lateral Quadratus Lumborum (x2)
Psoas Major (x2)
Median over Aorta (x1)

Question 21

Rib Movements:

Answer 21

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.

Question 22

Pump Handle Movement:

Answer 22

Pump Handle Movement: between ribs 2-6

Question 23

Bucket Handle Movement:

Answer 23

Bucket Handle Movement: expansion of thoracic cavity from medial to lateral.

Question 24

Muscles of Respiration:

Answer 24

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.

Question 25

Flail Chest:

Answer 25

Flail Chest: multiple rib fractures = segment of thoracic wall being unable to move independently of the rest of the wall, resulting in paradoxical movement of the segment.

Question 26

Pectus Excavatum

Answer 26

Pectus Excavatum: indentation of chest, sternum is positioned further back, compresses heart = decreased efficiency, heart wall muscle becomes bigger and chambers become smaller = reduced blood entering heart.

Question 27

Pleura:

Answer 27

Parietal
Visceral
Pleura space

Question 28

Pneumothorax

Answer 28

Pneumothorax: damage to the outer thoracic cage = ripper parietal pleura (air collects in pleural space = lungs cannot expand.

Question 29

Factors affecting viscera position:

Answer 29

Factors affecting viscera position:
Postural position
Phase respiratory cycle
Thoracic trauma.