Anatomy of the Thoracic Wall

Question 1

The endothoracic fascia creates a natural cleavage plain between which two layers of the thoracic wall?

Answer 1

It separates the parietal pleura from its costal attachments.

Question 2

Thoracic cage

Answer 2

Consists of 12 pairs of ribs and costal cartilages, sternum, 12 thoracic vertebrae and associated intervertebral discs.

Question 3

Rib classification

Answer 3

_True ribs _(1-7) - articulate with sternum

False ribs (8-10) - articulate with the rib above

_Floating ribs _(11-12)

Also may be classified as:

Typical* *(3-9)

Atypical (1,2, 10-12)

Question 4

Tubercle of typical rib

Answer 4

Facet for articulation with transverse process.

Question 5

Abnormalities of ribs

Answer 5

Abnormalities of ribs are fiarly common:

• Extra ribs (cervical or lumbar: cervical rib relatively common (0.5-2%) and may affect the brachial plexus and/or subclavian vessels.
• Rudimentary 12th rib
• Congenitally fused ribs

Question 6

Jugular notch

Answer 6

Level of vertebra T2

Question 7

Sternal angle of Louis

Answer 7

Manubriosternal joint.

• Site of articulation of second costal cartilage.
  
  • Level of T4/T5.
    *

Question 8

Kyphosis

Answer 8

Anatomically used to describe the natural anteiror concavity of the thoracic spine.

Clinically is used to describe an excessive anterior concavity which may result from compression fractures of vertebral bodies.

Question 9

Costovertebral joints

Answer 9

• Head of rib ‘x’ and thoracic vertebral bodies ‘x’ and ‘x-1’.
• Synovial plane joint.
• Ligament: mainly radiate ligament.
• Exceptions are irbs 1,11,12 (T1, T11, T12).

Question 10

Costotransverse joint

Answer 10

• Tubercle of rib ‘x’ and transverse process of thoracic vertebra ‘x’.
• Synovial plane.
• Liagment: costotransverse ligament

Question 11

Intervertebral T1-T12

Answer 11

• Symphysis (secondary cartilaginous) - vertebral bodies covered by hyaline cartilage united by fibrocartilage.
• Ligaments - anterior and posterior longitudinal.

Question 12

Joints of the thoracic cage

Answer 12

• Costovertebral joint
• Costotransverse joint
• Intervertebral joints

Question 13

Sternal joints

Answer 13

• Sternal angle of Louis/manubriosternal joint
• Sternoclavicular joint
• Sternocostal joints
• Costochondral junction
• Interchondral joint

Question 14

Sternal angle of Louis

Answer 14

Manubriosternal joint.

• Symphysis - fibrocaritlage, often ossifies later in life.

Question 15

Sternoclavicular joint

Answer 15

Synovial saddle

Question 16

Sternocostal joints

Answer 16

Cartilages of ribs 1-7.

• First is primary cartilaginous (synchondrosis) usually ossifies in later life.
• Ribs 2-7 synovial plane.

Question 17

Costochondral junction

Answer 17

Not really a joint. Degenerates with age so useful forensically.

Question 18

Interchondral joint

Answer 18

• Between cartilages 6-7, 7-8, 8-9.
• Synovial plane.
• Ribs 9-10 fibrous.

Question 19

Boundaries of thorax

Answer 19

• Superior thoracic aperture: rib 1, manubrium and T1.
• Inferiorly enclosed by diaphragm

Question 20

Diaphragm

Answer 20

Most important muscle of respiration. It is a musculotendinous sheet which separates thoracic and abdominal cavities.

Central portion is tendinous (central tendon - dense fibrous CT), outer portions are muscular.

Question 21

Diaphragm innervation

Answer 21

Phrenic nerve (C3-C5)

Question 22

Diaphragm attachments

Answer 22

• Ribs 7-12
• Lumbar vertebrae
• Xiphoid process
• Crura (right and left crus)
• Arcuate ligaments
  
  • Median
  • Medial
  • Lateral

Question 23

Diaphragm openings

Answer 23

• IVC at T8
• Oesophagus and vagal trunks at T10
• Aorta and thoracic duct as T12

Question 24

External intercostal membranes

Answer 24

External intercostal muscles do not continue all the way to the sternum.

Question 25

Internal intercostal membrane

Answer 25

Internal intercostal muscles do not continue all the way to the thoracic spine

Question 26

Subcostals

Answer 26

Similar to innermost intercostals except transverse more than one rib

Question 27

Changes upon inspiration

Answer 27

During inspiration: * The vertical, lateral and anteroposterior diameters of the thoracic cavity increase. * The upper ribs have a 'pump handle' action which increases A-P diameter. * The lower ribs have a 'bucket handle' action which increases the transverse diameter.

Question 28

The external intercostals

Answer 28

Mainly inspiration

Question 29

The internal intercostals

Answer 29

Mainly expiration - during normal respiration they mainly increase in tone and only during forced respiration do they create movement.

Question 30

Innermost intercostals and subcostals actions

Answer 30

## Footnote The innermost intercostals and subcostals probably act similar to internal intercostal muscles and transversus thoracis is probably active in forced expiration and is also involved in proprioception.

Question 31

Levator costarum

Answer 31

Probably elevate the ribs in forced inspiration

Question 32

Serratus posterior superior and inferior

Answer 32

Most likely only proprioceptive.

Question 33

Accessory muscles of respiration

Answer 33

* Pectoralis minor and major * Serratus anterior * Scalene muscles

Question 34

Forced expiration

Answer 34

During forced expiration the abdominals contract - increasing intra-abdominal pressure, forcing diaphragm superiorly.

Question 35

Location of intercostal VAN

Answer 35

Located between internal and innermost intercostals, deep to the costal groove. Smaller collateral branches are located above the rib below.

Question 36

Posterior intercostal arteries

Answer 36

Arise from the superior intercostal a (rib 1,2) and from the thoracic aorta (rib 3-11).

Question 37

Anterior intercostal arteries

Answer 37

Arise from the internal thoracic a (ribs 1-6) and musculophrenic artery (ribs 7-9). Anastamoses exist between anterior and posterior intercostal aa.

Question 38

Anterior intercostal veins

Answer 38

Drain to the musculophrenic and internal thoracic vein.

Question 39

Posterior intercostal veins

Answer 39

* _Right: 4-11_ drain to the azygos v then to the SVC. * _Left: 4-11_ drain to the hemiazygos vein and accessory hemiazygos vv then to the azygos vein. * Superiorly the _first_ intercostal vv drain into the right or left brachioephalic vv. * The _second and third_ (fourth) drain into the superior intercostal vv and then into the azygos v on the right or the brachiocephalic v on the left.

Question 40

Intercostal nn

Answer 40

Arise form the ventral rami of spinal nerve T1-T12 (T12 = subcostal n), remember most of T1 goes to the brachial plexus. T1-11 supply intercostal and abdominal mm and give off lateral and anterior cutaneous braches to skin of the trunk.

Question 41

Base of breast surface anatomy

Answer 41

Overlies ribs 2-6, most of pectoralis major, part of serratus anterior.

Question 42

Lateral mammary branches

Answer 42

From the lateral thoracic a, thoracoacromial a and posterior intercostal aa.

Question 43

Medial mammary branches

Answer 43

Arise from the internal thoracic a.

Question 44

Veins of the breast region

Answer 44

Veins drain mainly to the axillary v with some drainage to the internal thoracic v

Question 45

Breast innervation

Answer 45

Intercostal nerves 2-6 (anteiror and lateral cutaneous branches). Niiple and areola - T4 dermatome.

Question 46

Breast lymphatic drainage

Answer 46

Breast cancer commonly spreads via lymphatics. * Approximately 75% lymph drains to pectoral (anterior axillary) nodes, then to central axillary nodes and to apical axillary nodes. * Approximately 20% of lymph to parasternal (internal thoracic) nodes * 5% of lymph to interpectoral nodes, intercostal (posterior parietal) nodes, opposite breast and subdiaphragmatic nodes.