MSK 7.2B Posterior Trunk

Question 1

Movements of Back and Neck

Answer 1

Question 2

Overview: Muscles of the Back
3 Layers: Origin, function, innervation

Answer 2

3 Layers: Superficial + Intermediate + Deep

Superficial + Intermediate = Extrinsic Muscles: originate from other areas in development. Not true back muscles. Help with respiration, move upper limb (trapezius, latissimus dorsi). Innervated by anterior rami. Except for trapezius, innervated by cranial nerve XI

Deep: Intrinsic Muscles: True back muscles. Develop in back. Move + stabalise vertebral column and head, control posture, innervated by psoterior rami

Question 3

Extrinsic vs Intrinsic back muscles summarised
Function, examples, innervation

Answer 3

Question 4

List the extrinsic muscles of the back.
Function and innervation

Answer 4

Question 5

Trapezius anatomy

Answer 5

SUPERFICIAL

Question 6

Latissimus dorsi

Answer 6

SUPERFICIAL

Question 7

Levator scapulae

Answer 7

SUPERFICIAL

Question 8

Rhomboid major

Answer 8

SUPERFICIAL

Question 9

Rhomboid minor

Answer 9

SUPERFICIAL

Question 10

Serratus posterior superior

Answer 10

Intermediate

Question 11

Serratus posterior inferior

Answer 11

Question 12

3 layers of deep intrinsic muscles:

Answer 12

Question 13

Deep superficial intrinsic muscles

Question 14

Splenius cervicis

Answer 14

Question 15

Splenius capitis

Answer 15

Question 16

Deep intermediate muscles of back

Answer 16

✅ This is the Erector Spinae group

Part of the deep intrinsic muscles

Innervated by: posterior rami

✅ 3 muscles (from lateral to medial):
Column Muscle Name Super simple way to remember
Lateral Iliocostalis “I” = lateral
Middle Longissimus “L” = longest one, in middle
Medial Spinalis “S” = spinal column, closest to spine
Mnemonic: “I Love Spine” (Iliocostalis - Longissimus - Spinalis)

✅ 🔑 Pure exam facts:

Erector spinae = intrinsic back muscles → posterior rami → extend & laterally flex spine.

Question 17

Erector spinae

Answer 17

Question 18

Deep Deep muscles of back

Answer 18

🔎 Deep Intrinsic Muscles — Deep group

✅ This group lies deep to erector spinae and forms the:

Transversospinalis group

✅ Main muscles:
Muscle Function
Semispinalis Extension, some rotation
Multifidus Stabilization, rotation
Rotatores Fine-tune rotation, proprioception

✅ 🔑 Actions overall:

Stabilize spine

Help with extension and rotation of vertebral column

✅ 🔑 Innervation:

All intrinsic deep muscles = posterior rami

🔥 PURE EXAM SUMMARY:

"Transversospinalis group = semispinalis, multifidus, rotatores → extension, rotation, stabilization → posterior rami."

Question 19

Transversospinal group

Answer 19

Question 20

Summary of back muscles
Extrinisic and Intrinsic

Answer 20

Question 21

Anatomy, function and innervation of
1. Trapezius
2. Latissimus Dorsi
3. Lavator scapulae
4. Rhomboid major and minor
5. Teres major

Answer 21

THESE ARE SUPERFICIAL AND INTERMEDIATE EXTRINSIC BACK MUSCLES

Question 22

Rotation of scapula for arm abduction

Answer 22

🔥 SUPER EXAM LINE:

"Full arm abduction needs scapular rotation — Trapezius (CN XI) + Serratus Anterior (long thoracic nerve)."

Trapezius  rotates scapula upwards
and outward on thoracic wall which
elevates Glenoid Cavity
* Serratus Anterior  aids in upward
rotation of scapula

Question 23

1) What is the scapulohomeral group?
2) Deltoid can bring all shoulder movements exvept

Answer 23

Deltoid + Rotator Cuff Muscles

ADDUCTION

Question 24

Rotator ccuff muscles anatomy

Answer 24

Question 25

1) What is the coracoacromial arch? 2) Painful arc syndrome

Answer 25

1) Roof of shoulder joint. Formed by acromion + coracoacrimial ligament Supraspinatus tendon passes underneath this arch during abduction 2) Arm abduction, supraspinatus tendon impinged under CAA Painful arc - pain specifically when moving through that 50–130° zone Painful arc (50–130° abduction) = supraspinatus impingement under coracoacromial arch. Tests: Positive Painful Arc Test = suggests rotator cuff problem. Classic cause of shoulder pain during abduction.