Muscles of The Thorax

Question 1

External Intercostals

Answer 1

O: Lower border of a rib

I: Upper border of rib below

A: Elevate ribs during inspiration

Inv: Intercostal nerves

Question 2

Internal Intercostals

Answer 2

O: Inner surface of a rib and costal cartilages

I: Upper borders of the adjacent ribs below

A: Draw ribs downward during forced Expiration

Inv: Intercostal nerves

Question 3

Transversus Thoracis

Answer 3

O: Inner surfaces of the lower third of the body of the sternum and adjacent surfaces of the xiphoid process

I: Internal surfaces of the sternocostal joints associated with the second (or third) through the sixth ribs

A: Depresses the ribs

Inv: Intercostal nerves

Question 4

Quadratus Lumborum

Answer 4

O: Iliolumbar ligament and crest of the ilium

I: Rib 12 and tips of the transverse processes of the L1 to L4

A: Extension and side flexion of lumbar spine, expiration

Inv: Ventral ramus of spinal nerve roots T12-L3

Question 5

Psoas Major

Answer 5

O: Transverse processes and lateral bodies of the last thoracic and all lumbar vertebrae including the intervertebral discs

I: Lesser trochanter of femur

A: Forward flexion and side flexion of lumbar spine, Flexion of the hip joint

Inv: Branches of ventral rami L1-L3

Question 6

Iliacus

Answer 6

O: Superior two thirds of the iliac fossa, inner lip of the iliac crest

I: Lesser trochanter of femur

A: Flexion of hip joint

Inv: Femoral nerve

Question 7

Rectus Abdominis

Answer 7

O: Pubic crest and anterior pubic ligament

I: On the front of the wall of the thorax, along a horizontal line passing laterally from the xiphoid process, and cutting in that order, the 7th, 6th and 5th costal cartilages

A: Expiration, Flexion of the spine

Inv: Lower six or seven thoracic nerves

Question 8

External Oblique

Answer 8

O: Lateral side of ribs 4-12

I: Iliac crest, linea alba, and contralateral rectus sheaths

A: Bilaterally: flexion of the trunk and posterior tilt of the pelvis Unilaterally: lateral flexion and contralateral rotation of the trunk

Inv: Lower six thoracic nerves

Question 9

Internal Oblique

Answer 9

O: Iliac crest, inguinal ligament, and thoracolumbar fascia

I: Ribs 9-12, linea alba, and contralateral rectus sheaths

A:
- Unilaterally: lateral flexion and ipsilateral rotation of the trunk

• Bilaterally: flexion of the trunk and
  posterior tilt of the pelvis

Inv: Lower six thoracic nerves and the first lumbar nerve

Question 10

Transversus Abdominis

Answer 10

O: Iliac crest, thoracolumbar fascia, inner surface of the cartilages of ribs 6-12 and the inguinal ligament

I: Linea alba

A: Bilaterally: stabilization of attachment sites for other abdominal muscles; compression of the abdominal cavity

Inv: Lower six thoracic nerves and the first
lumbar nerve