Muscles of the Abdomen & Back

Question 1

External oblique OIA

Answer 1

Origin: Ribs 5-12

Insertion:
- Linea alba
- Iliac crest
- Pubic crest

Actions:
- Bilateral contraction:
○ flexion of the vertebral column
○ Abdominal compression
- Unilateral contraction:
○ Lateral flexion (right oblique means lean right)
○ Trunk rotation ()

Question 2

Internal oblique OIAI

Answer 2

Origin:
- Thoracolumbar fascia
- Iliac crest

Insertion:
- Linea alba
- Pubis
- Inferior ribs and costal cartilage

Actions:
- Bilateral contraction:
○ Flexion of vertebral column
○ Abdominal compression
- Unilateral
○ Lateral flexion

Question 3

Rectus Abdominis OIA

Answer 3

Origin: Pubic Crest

Insertion:
- Xiphoid process
- Costal cartilage of ribs 5-7

Actions:
- Flexion of the trunk
- Abdominal compressions

Features:
- Tendinous intersection (what gives you the six pack)
○ Allows us to contract rectus abdominis in a segmental fashion.

Question 4

Transversus Abdominis OIA

Answer 4

Deepest layer of abdominal muscles
Fibres run transversely

Origin:
- Costal cartilage of inferior ribs
- Iliac crest
- Thoracolumbar fascia

Insertion:
- Linear alba
- Pubis

Actions:
Abdominal compression

Question 5

Rectus Sheath

Answer 5

• Formed by the aponeuroses of external oblique, internal oblique and transverse abdominis.
• Encloses the rectus abdominis
• Converge centrally

Question 6

Linea alba

Answer 6

• Midline fibrous band
• formed by the union of the anterior abdominal wall aponeuroses
• Separates the two rectus abdominis muscles

Question 6

Trapezius OIA

Answer 6

Origin:
- Occipital bone of the skull
- Spinous processes of thoracic vertebrae

Insertion:
- Scapular (acromion and scapular spine)
- Lateral aspect of clavicle

Action:
- Upper: elevate scapula
- Middle: retract scapula & upward rotation of scapula (arm abduction)
- Lower: depress scapular & upward rotation of scapula (arm abduction

Question 7

Latissimus dorsi OIAI

Answer 7

Origin:
- Spinous processes of lower thoracic vertebrae & lumbar vertebrae
- Iliac crest

Insertion:
- Intertubercular groove of the humerus

Actions:
- Adduction of arm
- Extension of arm
- Medial rotation of arm

Innervation: Thoracodorsal nerve (brachial plexus)

Question 8

Levator scapulae OIAI

Answer 8

Origin: Transverse processes superior cervical vertebrae

Insertion: Medial border of scapula

Actions: Elevation of the scapula

Innervation: Dorsal scapular nerve (brachial plexus)

Question 9

Rhomboids, major and minor

Answer 9

Origin: Spinous processes of C7-T5

Insertion: Medial border of the scapula

Actions:
- Retraction of the scapula
- Downward rotation of the scapula (arm adduction)

Innervation: Dorsal scapular nerve (Brachial plexus)

Question 10

Teres major OIAI

Answer 10

Origin: posterior aspect of the inferior angle of scapula

Insertion: Medial lip of intertubercular groove

Actions:
- Adduction of arm
- Internal rotation of arm

Innervation: Lower subscapular nerve (brachial plexus)

Question 11

Insertions of the intertubercular groove of the humerus. Miss between two majors

Answer 11

Pectoralis major: inserts on the lateral lip of the intertubercular groove

Latissimus Dorsi: Inserts on the floor of the intertubercular groove

Teres major: inserts on the medial lip of the intertubercular groove

Question 12

Erector spinal muscles (I like standing)

Answer 12

Deep 3 paired muscles running along the vertebral column

Lateral to medial
1. Iliocostalis
2. Longissimus
3. Spinalis

Actions:
- Bilateral: extension of the vertebral column
- Unilateral: lateral flexion of vertebral column