Tx Muscles

Question 1

What are the 4 types of muscles in the thoracic cage?

Answer 1

Respiration (1)
Intercostal (3)
Internal Cage (2)
External Cage (3)

Question 2

What are the muscles of the thoracic cage?

Answer 2

There are 9 muscles in the thoracic cage:

Respiration:
- diaphragm

Intercostal:

• external
• internal
• innermost

Internal Cage:

• subcostal
• transverse thoracis

External Cage:

• serratus posterior superior
• serratus posterior inferior
• levator costorum

Question 3

Describe the diaphragm

Answer 3

PA:

• xiphoid process
• internal surfaces of ribs and costal cartilages 1-6
• Lx vertebrae and IVDs

DA:
- central tendon

NS:

• motor: phrenic (C3-5)
• sensory (central): phrenic (C3-5)
• sensory (peripheral): intercostal nerves 5-11, subcostal nerve

A:
- contraction pulls dome inferiorly and increases thoracic cavity

Question 4

Describe the anatomy of the intercostals:

Answer 4

3 layers:

• external
• internal
• innermost

PA:
- inferior border of ribs

DA:
- superior border of inferior rib

NS:
- intercostal nerve of same level

Fibres:

• external: anteriorly and inferiorly
• internal and innermost: posteriorly and inferiorly

A:

• external: elevates ribs during forced inspiration
• internal: interossesous part depresses ribs and interchondral part elevates ribs

Question 5

Describe the internal cage muscles:

Answer 5

Subcostals:

PA: internal surface of lower ribs (near angle)
DA: superior borders of ribs 2-3 spaces below
NS: intercostal nerve of same level
A: elevates ribs
(fibre direction anterior and inferior)

Transverse Thoracis:
(4-5 muscular slips)
PA: internal surface of lower sternum
DA: internal surface of costal cartilages 2-6
NS: intercostal nerves 2-6
A: weakly depresses ribs

Question 6

Describe the external cage muscles:

Answer 6

Serratus Posterior Superior:

PA: nuchal ligament, SPs of C7-T3
DA: superior borders of ribs 2-4
NS: intercostal nerves 2-5
A: elevates ribs

Serratus Posterior Inferior:
PA: SPs of T11-L2
DA: inferior borders of ribs 8-12 near angles
NS: ventral rami T9-12
A: depresses ribs

Levator Costarum:
(12 pairs of fan shaped muscles with fibres running infero-laterally between TPs and ribs)
PA: TPs of T7-11
DA: Adjacent ribs between tubercle and angle
NS: dorsal rami of C8-T11
A: elevates ribs
(also considered part of the deep minor accessory spinal muscles)

Question 7

Describe the openings of the diaphragm

Answer 7

Openings:
1) Caval opening: in central tendon, passage of inferior vena cava and branches of right phrenic nerve, level T8. Expands when diaphragm contracts

2) Oesophagal hiatus: opening in right crus for oesophagus and vagus nerves, level T10. Constricts with diaphragm contraction

3) Aortic hiatus:
posterior to diaphragm at median arcuate ligament, passage for aorta, azygous vein and thoracic duct, level of T12. Posterior to diaphragm and not affected by contraction

Question 8

Describe the ligaments of the diaphragm

Answer 8

Median arcuate ligament (unilateral / central)- arches over aorta

Medial arcuate ligament (bilaterally) - arches over psoas

Lateral arcuate ligament (bilaterally) - arches over QL

Question 9

Describe the crura of the diaphragm

Answer 9

There are two crura (right and left).

Musculotendinous bundles that connect the diaphragm to L1-4 vertebrae, the IVDs, and the ALL.

Right:
- longer, attaches to L1-4, contains oesophagal hiatus

Left:
- shorter, attaches to L1-3