Muscles of back

D.Rania GabrD.Sama.D.Elsherbiny

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 ColumnCervical: 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.

Movements at the Vertebral Column

Flexion: bending forward

Extension: bending backwards

Lateral flexion: bending side-wards

Rotation: Twisting the trunkCircumduction: Combined movements

MUSCLES OF THE BACKMUSCLES OF THE BACK

Intrinsic musclesIntrinsic muscles: : Develop in the backDevelop in the back Supplied by posterior

rami of spinal nerves

Extrinsic muscles:Extrinsic muscles: Not developed in the Not developed in the

backback Supplied by anterior

rami of spinal nerves.

Extrinsic Muscles of the Back

1. Superficial extrinsic back muscles: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

Superficial Extrinsic Back

Muscles

TrapeziusLatissimus dorsiLevator scapulaeRhomboids major & minor

TRAPEZIUS TRAPEZIUS

Action

LEVATOR SCAPULAE; RHOMBOID MINOR & MAJORLEVATOR SCAPULAE; RHOMBOID MINOR & MAJOR

Origin:

1. Levator scapulae: cervical transverse processes

2. Rhomboid minor & major: thoracic spines

Insertion: back of medial border of scapula.

Nerve supply: dorsal scapular nerve.

Actions:

1. Levator scapulae: elevates scapula.

2. Rhomboid minor & major: retract scapula.

LATISSIMUS DORSILATISSIMUS DORSI• Origin: Spinous processes of T7 - L5

vertebrae. Iliac crest of sacrum. Thoracolumbar fascia. Inferior angle of the scapula. Lower three or four ribs. Insertion: floor of bicipital groove of humerus. Nerve supply: thoracodorsal nerve. Actions: extension, adduction & medial

rotation of humerus (arm, shoulder joint).

Extrinsic Muscles of the Back

2. Intermediate extrinsic back muscles: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 It includes:It includes:

• Serratus posterior Serratus posterior superiorsuperior (rib elevator).

• Serratus posterior Serratus posterior inferior inferior (rib depressor).

Nerve supply: Nerve supply: anterior rami of thoracic spinal nerves.

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.

Intrinsic Muscles of the Back

1. Superficial intrinsic back muscles:Superficial intrinsic back muscles:

Splenius cervices & splenius capitis

N.S: Posterior rami of spinal nerves.

Actions: Acting alone; Acting alone; laterally flex neck &

rotate head to side of active muscle.

Acting together; Acting together; extend head & neck.

Superficial Intrinsic Back

Muscles

Splenius cervices &

splenius capitis

Superficial Intrinsic Back Muscles

2. Intermediate intrinsic Intermediate intrinsic back muscles: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)

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.

Intrinsic Muscles of the Back

3. Deep intrinsic back muscles:Deep intrinsic back muscles:

It can be divided into two groups:

Major deep layer

Minor deep layer

Deep Intrinsic Muscles of the Back1-Major deep layer

Transversospinal group consist of semispinalis, multifidus & rotators.

N.S: N.S: Posterior rami of spinal nerves.

Actions:Actions: Extension and stabilization of vertebral column.

Deep Intrinsic Back Muscles

Transversospinal group

(semispinalis, multifidus &

rotators)

Deep Intrinsic Muscles of the Back

2- Minor deep layerInterspinalesIntertransversariiLevatores costarum

N.SN.S: : Posterior rami of spinal nerves

ActionsActions: Extension, rotation, lateral flexion

and stabilization of vertebral column.

Movements of Back and Neck

MUSCULAR TRIANGLES OF MUSCULAR TRIANGLES OF BACKBACK

Auscultatory Triangle:

2.Boundaries: latissimus dorsi, trapezius, and medial border of scapula.

2. Importance: breath sounds are most easily heard with a stethoscope.

Lumbar Triangle: (Triangle of Petit)

1.Boundaries : latissimus dorsi, posterior border of external oblique muscle of the abdomen and iliac crest.

2. Importance: Site of an abdominal hernia

Muscles of the backExtrinsic: 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: Splenius2nd layer: Erector Spinae: Iliocostalis

LongissimusSpinalis

3rd layer: Transversospinal: MultifidusRotatoresSemispinalis