Muscles of the thoracic wall

Question 1

External intercostal muscles

Answer 1

Origin:

• Inferior margin of the rib above

Insertion:

• Superior margin of the rib below

Innervation:

• Intercostal nerves

Function:

• Most active during inspiration
• Supports intercostal space
• Moves ribs superiorly

Question 2

Internal intercostal muscles

Answer 2

Origin:

• Lateral edge of costal groove of rib above

Insertion:

• Superior margin of rib below deep to the attachment of the related external intercostal

Innervation:

• Intercostal nerves

Function:

• Most active during epiration
• Sipports intercostal space
• Moves ribs inferiorly

Question 3

Innermost intercostal muscles

Answer 3

Origin:

• Medial surface of costal groove of rib above

Insertion:

• Internal aspect of superior margin of rib below

Innervation:

• Intercostal nerves

Function:

• Acts with internal intercostal muscles

Question 4

Subcostals

Answer 4

Origin:

• Internal surface (near angles) of lower ribs

Insertion:

• Internal surface of second or third rib below

Innervation:

• Related intercostal nerves

Function:

• May depress ribs

Question 5

Transversis thoracis

Answer 5

Origin:

• Inferior margins and internal surfaces of costal cartilages of second to sixth ribs

Insertion:

• Inferior aspect of deep surface of body of sternum
• Xiphoid process
• Costal cartilages of ribs 4-7

Innervation:

• Related intercostal nerves

Function:

• Depress costal cartilages