1. Muscles of Back
Dr. Sama ul Haque

2. Objectives
Identify the superficial and deep muscles of the back in terms of their location, nerve supply and actions.
Understand the muscle support of the trunk.
Explain the mechanism of body weight transmission.

3. Vertebral Column Cervical: 7 Thoracic: 12 Lumbar: 5
Sacral: 5 (fused to form 1 sacrum)
Coccygeal: 4 (fused to form coccyx)
Total= 33 (counted as 26 in the total bones of the body because of fusion.

5. Movements at the Vertebral Column
Flexion: bending forward
Extension: bending backwards
Lateral flexion: bending side-wards
Rotation: Twisting the trunk
Circumduction:
The axis of movement passes through the center of the vertebral bodies, so that the bodies do not move. Movements are mostly permitted by the cervical & lumbar spines. Thicker the intervertebral disc, greater the degree of movement

6. Functions of the Vertebral Column
Protects the spinal cord & spinal nerves.
Supports the weight of the body superior to the level of the pelvis.
Provides a partly rigid & flexible axis for the body & an extended base on which the head is placed and rotates.
Plays an important role in posture & locomotion

7. Muscles of the Back
Extrinsic muscles
Intrinsic muscles

8. Extrinsic Muscles of the Back
1. Superficial extrinsic back muscles:
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboids major & minor
They all connect the upper limb to the trunk.

9. Superficial Extrinsic Back Muscles
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboids major & minor

10. Extrinsic Muscles of the Back
2. Intermediate extrinsic back muscles:
Serratus posterior superior
Serratus posterior inferior
They are superficial respiratory muscles and
are supplied by intercostal nerves.

11. Intermediate Extrinsic Back Muscles
Serratus posterior superior
&
Serratus posterior inferior

12. Intrinsic Muscles of the Back
Called muscles of the back proper.
Deep muscles of the back.
All are supplied by the posterior primary rami of spinal nerves.
Act to maintain posture and control movement of the vertebral column.

13. Intrinsic Muscles of the Back
1. Superficial intrinsic back muscles:
Splenius cervices & splenius capitis
N.S: Posterior rami of spinal nerves.
Actions: Acting alone; laterally flex neck &
rotate head to side of active muscle.
Acting together; extend head & neck.

14. Superficial Intrinsic Back Muscles
Splenius cervices
&
splenius capitis

15. Superficial Intrinsic Back Muscles

16. Intrinsic Muscles of the Back
2. Intermediate intrinsic back muscles:
Erector spinae is the chief extensor of the vertebral column & is divided into three columns (also called as the long muscle of the back).
Ilio-costalis (forms lateral column)
Longissimus (forms intermediate column)
Spinalis (forms medial column)

17. Intrinsic Muscles of the Back
2. Intermediate intrinsic back muscles:
N.S: Posterior rami of spinal nerves
Actions: Acting bilaterally, extend head & neck
from a position of flexion.
Acting unilaterally, laterally flex vertebral
column.

18. Intermediate Intrinsic Back Muscles
Erecter Spinae
(Ilio-costalis
Longissimus
Spinalis)

20. Intrinsic Muscles of the Back
2. Deep intrinsic back muscles:
This is a group of muscles that lie deep to erector Spinae.
It can be divided into two groups:
Major deep layer
Minor deep layer

21. Intrinsic Muscles of the Back
2. Deep intrinsic back muscles:
Major deep layer
Transversospinal group consist of semispinalis, multifidus & rotators.
N.S:Posterior rami of spinal nerves.
Actions: Extension and stabilization of vertebral column.

22. Deep Intrinsic Back Muscles
Transversospinal group
(semispinalis, multifidus & rotators)

23. Intrinsic Muscles of the Back
2. Deep intrinsic back muscles:
Minor deep layer
Interspinales
Intertransversarii
Levatores costarum
N.S: Posterior rami of spinal nerves
Actions: Extension, rotation, lateral flexion and stabilization of vertebral column.

25. Movements of Back and Neck

26. Muscles of the back are organized in layers
Extrinsic: Movements of upper limb and respiration.
1st layer: Trapezius
Latissimus Dorsi
2nd layer: Levator Scapulae
Rhomboids (minor & major)
3rd layer: Serratus posterior (superior & inferior)
Intrinsic: Act on vertebral column and neck.
1st layer: Splenius
2nd layer: Erector Spinae: Iliocostalis
Longissimus
Spinalis
3rd layer: Transversospinal: Multifidus
Rotatores
Semispinalis

27. Thank You