Expiratory muscles

Question 1

M. serratus dorsalis caudalis

Answer 1

o Origin: caudally on superficial layer of fascia thoracolumbalis
o Insertion: proximal part of ribs 11–13.
o Action: expiration

Question 2

M. retractor costae ultimae

Answer 2

o Origin: transverse processes of L1–4 vertebrae, caudal part of thoracolumbar fascia over lumbar site
o Insertion: caudal border of last rib
o Action: expiration

Question 3

M. transversus thoracis

Answer 3

o Origin: inner surface of sternum, close to midline o Insertion: 2–8th costal cartilages,
ventral to costochondral junctions o Action: expiration

Question 4

Mm. intercostales

Answer 4

Two muscle-groups can be distinguished: m. intercostalis externus and internus
o Origin and insertion:
- m. intercostalis externus: muscle fibres run caudoventrally (\)
- from caudal border of one rib to cranial border of the next rib - m. intercostalis internus: muscle fibers run cranioventrally (///)
- from cranial border of one rib to caudal border of the previous rib
o Action:
- m. intercostalis externus: inspiration
- m. intercostalis internus: expiration

Question 5

M. subcostalis

Answer 5

o Origin and insertion: crossing medial surface of ribs 9–11. in a cranioventral direction (///), inside thoracic cavity
o Action:expiratorymuscle