MOINA of Thoracic Wall

Question 1

External Intercostals

Answer 1

Origin: inferior border of the rib
Insertion: superior border of the rib below
Nerve: intercostal nerve
Action: stabilizes the rib cage; with first rib fixed they raise the ribs during inspiration thus increase the anteroposterior and transverse diameters of thorax

Question 2

Internal Intercostals

Answer 2

Origin: inferior border of the rib
Insertion: superior border of the rib below
Nerve: intercostal nerve
Action: stabilizes the rib cage; with last rib fixed by abdominal muscles; they lower ribs during expiration

Question 3

Innermost Intercostals

Answer 3

Origin: adjacent ribs
Insertion: adjacent ribs
Nerve: intercostal nerve
Action: supports external and internal intercostals

Question 4

Diaphragm

Answer 4

Origin: xiphoid process, lower 6 costal cartilages, first three lumbar vertebrae
Insertion: central tendon
Nerve: phrenic nerve
Action: most important muscle of inspiration; increases vertical diameter by pulling central tendon downward; assists in raising lower ribs; also used in abdominal straining and weightlifting

Question 5

Levatores Costarum

Answer 5

Origin: transverse process of C7 and T1-T11 vertebrae
Insertion: rib below
Nerve: posterior rami of thoracic spinal nerves
Action: elevates ribs; possibly proprioception

Question 6

Serratus Posterior Superior

Answer 6

Origin: lower cervical and upper thoracic spines
Insertion: upper ribs
Nerve: intercostal nerves
Action: proprioception; possibly raises ribs and therefore an inspiratory muscle

Question 7

Serratus Posterior Inferior

Answer 7

Origin: lower thoracic and upper lumbar spines
Insertion: lower ribs
Nerve: intercostal nerves
Action: proprioception; possibly depresses ribs and therefore is an expiratory muscle