Muscles of Back
Dr. Sama ul Haque
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.
Vertebral Column
 Cervical:
7
 Thoracic: 12
 Lumbar: 5
 Sacral:
5 (fused to form 1 sacrum)
 Coccygeal: 4
 Total=
(fused to form coccyx)
33 (counted as 26 in the total bones of
the body because of fusion.
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
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
Muscles of the Back
 Extrinsic
 Intrinsic
muscles
muscles
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.
Superficial
Extrinsic Back
Muscles
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboids major
& minor
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.
Intermediate
Extrinsic Back
Muscles
Serratus posterior
superior
&
Serratus
posterior inferior
Intrinsic Muscles of the Back
 Called
 Deep
 All
muscles of the back proper.
muscles of the back.
are supplied by the posterior primary
rami of spinal nerves.
 Act
to maintain posture and control
movement of the vertebral column.
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.
Superficial
Intrinsic Back
Muscles
Splenius cervices
&
splenius capitis
Superficial Intrinsic Back Muscles
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
 Spinalis
(forms intermediate column)
(forms medial column)
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.
Intermediate
Intrinsic Back
Muscles
Erecter Spinae
(Ilio-costalis
Longissimus
Spinalis)
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
Intrinsic Muscles of the Back
2.Deep intrinsic back muscles:

Major deep layer
Transversospinal
group consist of
semispinalis, multifidus & rotators.
N.S:Posterior
Actions:
rami of spinal nerves.
Extension and stabilization of
vertebral column.
Deep Intrinsic
Back Muscles
Transversospinal
group
(semispinalis,
multifidus &
rotators)
Intrinsic Muscles of the Back
2.Deep intrinsic back muscles:

Minor deep layer
 Interspinales
 Intertransversarii
 Levatores
 N.S:
costarum
Posterior rami of spinal nerves
 Actions:
Extension, rotation, lateral flexion and
stabilization of vertebral column.
Movements of Back and Neck
Muscles of the back are organized in layers
Extrinsic: Movements of upper limb and respiration.
1st layer:
2nd layer:
3rd layer:
Trapezius
Latissimus Dorsi
Levator Scapulae
Rhomboids (minor & major)
Serratus posterior (superior & inferior)
Intrinsic: Act on vertebral column and neck.
1st layer:
2nd layer:
3rd layer:
Splenius
Erector Spinae:
Iliocostalis
Longissimus
Spinalis
Transversospinal: Multifidus
Rotatores
Semispinalis
Thank You