Station 9: Muscles Of The Trunk

Question 1

Erector Spinae

Origin, Insertion, Actions

What 3 muscles make up this group? What is their role?

Answer 1

Origin: Sacrum and Thoracic Vertebrae

Insertion: Ribs 1-12

Actions: Extension

3 Muscles:

• Illiocostalis
• Longissimus
• Spinalis

Role: Prime movers of trunk extension, eccentric movement (bending down)

Question 2

Quadratus lumborum

Origin, Insertion, Actions

Answer 2

Origin: Illiac Crest

Insertion: 12th Rib

Actions: Lateral Flexion

Question 3

Abdominal Group:

Rectus abdominis

Origin, Insertion, Actions

Answer 3

Origin: Pubic Symphysis

Insertion: Xyphoid Process

Actions: Flexion

Question 4

Abdominal Group:

External Oblique

Origin, Insertion, Actions

Answer 4

Origin: Ribs 5-12

Insertion: Linea Alba

Actions: Flexion, Lateral Flexion

Note:

• “Hands in Pocket” (V)
• Layer closest to skin

Question 5

Abdominal Group:

Internal Oblique

Origin, Insertion, Actions

Answer 5

Origin: Illiac Crest, Inguinal Ligament

Insertion: Ribs 8-12

Actions: Flexion, Lateral Flexion

Note:

• (^)
• Middle Layer of muscle

Question 6

Abdominal Group:

Transverse abdominis

Origin, Insertion, Actions

Answer 6

Origin: Lumbar Vertebrae

Insertion: Linea Alba

Actions: Compression

Note:

• Horizontal (=)
• Deepest layer of muscle