1. Muscles of Back
Dr. Sama ul Haque Dr Rania Gabr

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 They are organized into 3 groups:
Deep group: attached to & involved in the movement of vertebral column & head.
Intermediate group: attached to ribs & serve respiratory functions.
Superficial group: attached to & involved in the movements of upper limb.
Intrinsic muscles:
Develop in the back
Supplied by posterior rami of spinal nerves
Extrinsic muscles:
Not developed in the back
Supplied by anterior rami of spinal nerves.

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.
Supplied by anterior rami of spinal nerves

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

10. TRAPEZIUS Origin: Spines of cervical & thoracic vertebrae
Insertion: lateral 1/3 of clavicle + acromion & spine of scapula.
Action: rotation of scapula during abduction of humerus above horizontal.
Upper fibers: elevate scapula.
Middle fibers: retract scapula
Lower fibers: depress scapula.
Nerve supply: Spinal part of accessory (11th cranial) nerve.
Insertion
Action
Origin

11. LEVATOR SCAPULAE; RHOMBOID MINOR & MAJOR
Origin:
Levator scapulae: cervical transverse processes
Rhomboid minor & major: thoracic spines
Insertion: medial border of scapula.
Nerve supply: dorsal scapular nerve.
Actions:
Levator scapulae: elevates scapula.
Rhomboid minor & major: retract scapula.

12. LATISSIMUS DORSI Origin: a. Spinous processes of T7 - L5 vertebrae.
b. Iliac crest of sacrum.
c. Thoracolumbar fascia.
d. Inferior angle of the scapula.
e. Lower three or four ribs.
Insertion:
bicipital groove of humerus.
Nerve supply:
thoracodorsal nerve.
Actions:
extension, adduction & medial rotation of humerus (arm, shoulder joint).

13. 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.

14. Intermediate Extrinsic Back Muscles
It is separated from the deep group by thoracolumbar fascia.
It includes:
Serratus posterior superior (rib elevator).
Serratus posterior inferior (rib depressor).
Nerve supply: anterior rami of thoracic spinal nerves.

15. 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.

16. 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.

17. Superficial Intrinsic Back Muscles
Splenius cervices
&
splenius capitis

18. Superficial Intrinsic Back Muscles

19. 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)

20. They extend from sacrum to skull.
They include extensors and rotators of head & vertebral column.
Their tone is responsible for maintenance of normal curvature of vertebral column.

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

23. Intrinsic Muscles of the Back
3. 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

24. Deep Intrinsic Muscles of the Back
1-Major deep layer
Transversospinal group consist of semispinalis, multifidus & rotators.
N.S:Posterior rami of spinal nerves.
Actions: Extension and stabilization of vertebral column.

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

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

28. Movements of Back and Neck

29. MUSCULAR TRIANGLES OF BACK
Auscultatory Triangle:
Boundaries: latissimus dorsi, trapezius, and medial border of scapula.
Site where breath sounds are most easily heard with a stethoscope.
Lumbar Triangle: (Triangle of Petit)
Boundaries : latissimus dorsi, posterior border of external oblique muscle of the abdomen, and iliac crest.
Site of an abdominal hernia; or where pus may emerge from the abdominal wall.

30. 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

31. Thank You