Anatomy: back - muscles

Question 1

HYPAXIAL MUSCLES
- What are they?
- How did these end up in the back (an epaxial location)?

Answer 1

They developed ventrally and are innervated by ventral rami (hence, hypaxial). But, the muscle + nerves have migrated dorsally to the back

Question 2

HYPAXIAL MUSCLES
Trapezius:
- Attachments
- Innervation

Answer 2

Skull, nuchal ligament, spinous processes in cervical and thoracic regions
Cranial nerve 11

Question 3

HYPAXIAL MUSCLES
Levator scapulae
- Innervation
- Actions

Answer 3

Cervical innervation (including the dorsal scapular nerve)
Draws scapula superomedially - elevates and retracts the scapula

Question 4

HYPAXIAL MUSCLES
Rhomboideus major and minor
- Attachments?
- Innervation
- Actions

Answer 4

Nuchal ligament, spinous processes C7-T5, medial border of the scapula
Dorsal scapular nerve
Draws scapula superomedially - elevates and retracts the scapula

Question 5

HYPAXIAL MUSCLES
Latissimus dorsi
- Attachments
- Innervation
- Actions

Answer 5

Thoracolumbar fascia, humerus
Thoracodorsal nerve
Arm extension, internal rotation, adduction

Question 6

HYPAXIAL MUSCLES
2 inferior hypaxial muscles of the back?

Answer 6

Quadratus lumborum and transversus abdominus

Question 7

TRIANGLE OF AUSCULTATION
- What are its borders?
- Under what circumstances is it exposed? Why would you want to expose it?

Answer 7

Trapezius, latissimus dorsi, medial morder of scapula

When the arm is lifted. Makes it easier to hear lung sounds - as no muscles are covering it

Question 8

EPAXIAL MUSCLES
Describe their development and innervation

Answer 8

The muscles have developed dorsally
They are innervated by dorsal rami

Question 9

SUPERFICIAL EPAXIAL MUSCLES
What are the 2 groups?

Answer 9

• Erector spinae group
• Splenius muscles

Question 10

SUPERFICIAL EPAXIAL MUSCLES
Erector spinae muscles
- Mnemonic
- What are the muscles, and their subdivisions?

Answer 10

I like standing (from lateral to medial)

Iliocostalis lumborum/thoracis/cervicis (attaches at iliac crest (ilio) and ribs (costalis))
Longissimus thoracis/cervicis/capitis
Spinalis

Question 11

SUPERFICIAL EPAXIAL MUSCLES
Erector spinae muscles
- Common attachment?
- Innervation?
- Actions (bilaterally and unilaterally?)

Answer 11

Thoracolumbar fascia
Dorsal rami of spinal nerves, sequentially
Bilaterally: extension of spine (keeps the spine erect - name)
Unilaterally: laterally bending of the spine

Question 12

SUPERFICIAL EPAXIAL MUSCLES
Splenius muscles
- What does splenius mean?
- What direction are the fibres orientated?
- What are the two splenius muscles?

Answer 12

Bandage
Superolaterally
Splenius capitis and splenius cervicis

Question 13

SUPERFICIAL EPAXIAL MUSCLES
Splenius capitis
- Attachments
- Innervation
- Actions (unilaterally and bilaterally)

Answer 13

Mastoid process of temporal bone, spinous processes of C7-T3
Segmental innervation by the dorsal rami of spinal nerves
Bilaterally: extends the head
Unilaterally: rotates the head

Question 14

SUPERFICIAL EPAXIAL MUSCLES
Splenius cervicis
- Attachments
- Innervation
- Actions (bilaterally and unilaterally)

Answer 14

Transverse processes of C1-C3, T3-T6
Segmental innervation by the dorsal rami of spinal nerves
Bilaterally: extends the neck, unilaterally: rotates the neck

Question 15

INTERMEDIATE EPAXIAL MUSCLES
What are the 6 intermediate epaxial muscles?

Answer 15

TRANSVERSOSPINALIS GROUP
- Rotatores
- Multifidus
- Semispinalis thoracis/cervicis/capitis
- Levatores costarum

OTHER MUSCLES
- Interspinalis
- Intertransversarius muscles

Question 16

INTERMEDIATE EPAXIAL MUSCLES
Transversospinalis group
- What structures do they run between?
- What is the direction of the muscle fibres?

Answer 16

Run from the transverse processes to spinous processes, superomedially

Question 17

INTERMEDIATE EPAXIAL MUSCLES
How many segments do the following muscles span across?
- Rotatores brevis
- Rotatores longus
- Multifidus brevis
- Multifidus longus
- Semispinalis thoracis/cervicis/capitis

Answer 17

• Rotatores brevis: runs across 1 segment
• Rotatores longus: runs across 2 segments
• Multifidus brevis: runs across 2 segments
• Multifidus longus: runs across 4 segments
• Semispinalis thoracis/cervicis/capitis: runs across 6 segments

Question 18

TRANSVERSOSPINALIS GROUP
Levatores costarum
- What actions does it perform?
- Is it technically a part of the transversospinalis group? Why/why not?

Answer 18

Elevates (levatores) the ribs (costarum)

Technically not part of the transversospinalis group – as attachments from the angles of ribs to tranverse process

Question 19

INTERMEDIATE EPAXIAL MUSCLES
Label the following

Answer 19

Question 20

THORACOLUMBAR FASCIA
The anterior layer is found around what muscle?
The middle layer is found around what muscles?
The posterior layer is found around what muscles?

Answer 20

Anterior layer: around the quadratus lumborum

Middle layer: between the quadratus lumborum and erector spinae/multifidus muscles

Posterior layer: around the erector spinae and multifidus muscles

Question 21

DEEP EPAXIAL MUSCLES
What is the muscle group involved?
How many muscles are there (per side?)

Answer 21

Suboccipital muscles
4 (per side)

Question 22

DEEP EPAXIAL MUSCLES
Label the suboccipital muscles

Answer 22

Question 23

DEEP EPAXIAL MUSCLES
Rectus capitis posterior minor:
- Attachments
- Innervation
- Actions

Answer 23

Question 24

DEEP EPAXIAL MUSCLES
Rectus capitis posterior major:
- Attachments
- Innervation
- Actions

Answer 24

Question 25

DEEP EPAXIAL MUSCLES
Obliquus capitis superior:
- Attachments
- Innervation
- Actions

Answer 25

Question 26

DEEP EPAXIAL MUSCLES
Obliquus capitis inferior:
- Attachments
- Innervation
- Actions

Answer 26

Question 27

DEEP EPAXIAL MUSCLES
Suboccipital triangle
- Label the additional structures

Answer 27

Question 28

SUBOCCIPITAL TRIANGLE
- What are the muscular borders?
- What are the contents?

Answer 28

Rectus capitis major, obliquus capitis superior + inferior
Suboccipital nerve (dorsal ramus of C1) and the vertebral artery