Spinal Muscles

Professor Emeritus Moira O’Brien FRCPI, FFSEM, FFSEM (UK), FTCD Trinity College Dublin MOB TCD

Thoracolumbar Fascia

• • Three layers of fascia enclosing the muscles of the posterior abdominal wall Laterally fascia is fused and is continuous with internal oblique and transversus abdominis

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Thoracolumbar Fascia Posterior layer

• • • • Covers the erector spinae is very strong three layers It is reinforced by the aponeurosis of latissimus dorsi Medially it is attached to lumbar and sacral spinous processes Superiorly it extends over the back muscles to be continuous with the deep fascia of the neck

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Thoracolumbar Fascia

• • • • • Partial origin to internal oblique Transversus abdominus Latissimus dorsi Tensile strength of 2000 psi Most important non-contractile structure

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Thoraco-Lumbar Fascia

• • • Anterior layer Covering quadratus lumborum muscle, separating it from the psoas major Attaches in front of lumbar transverse processes and from iliac crest to12th rib

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Thoraco-Lumbar Fascia

• • • • • Middle layer Between erector spinae and quadratus lumborum Attached to tips of transverse processes of lumbar vertebrae Extending in a vertical plane between the iliac crest and the 12th rib Posterior layer attached to spinous process covers sacrospinalis

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Superficial Muscles

• • • • • • Superficial layer Trapezius Latissimus dorsi Levator scapulae Rhomboid minor and major Connect upper limb to trunk

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Trapezius

• • • • The trapezius is a large, flat, triangular muscle, covering the posterior aspect of the neck and superior half of the trunk.

It attaches the pectoral girdle to the skull and the vertebral column. It also helps in suspending the shoulder girdle and rotates the scapula.

The trapezius is supplied by the spinal part of the accessory, the eleventh cranial nerve.

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Trapezius

• • Origin Medial third superior nuchal line Ligamentum nuchae and spines and inter spinous ligaments of all thoracic vertebrae • • Insertion Upper third to lateral third of posterior border of clavicle Middle third to medial border of acromion and the superior lip of the crest of the spine of the scapula

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Trapezius

• • • • • • Lower third fibres insert into the medial end of spine of scapula Nerve supply

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pinal accessory nerve (C1 - 5) Proprioceptive fibres from the C3 - 4 cervical plexus.

Actions

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upper fibres elevate and extension of the neck Middle fibres retract scapula Upper and lower fibres rotation of scapula

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Trapezius

• • • • The upper fibres elevate the scapula, shrug shoulders.

The intermediate fibres draw the medial border of the scapula near to the midline and press against the chest wall.

The lower fibres pull the scapula downward and depress the tip of the shoulder.

The three parts of the trapezius, acting together, draw the scapula medially and rotate the glenoid fossa superiorly in abduction of the shoulder.

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Trapezius

• • • • • The trapezius muscle is involved in throwing events In racquet sports and in overhead movements Middle fibres help to stabilise the scapula in rowing and swimming It prevents the glenoid fossa being pulled down when lifting heavy objects with your arms It also helps when you are holding an object overhead

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Latissimus Dorsi

• • • • • The latissimus dorsi is a large, wide fan-shaped muscle covering the inferior part of the back It arises from the spines of the lower six thoracic vertebrae The lumbar fascia The posterior third of the outer lip of the iliac crest The lower three ribs and the inferior angle of the scapula

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Latissimus Dorsi

• • • • It spirals around the teres major Forms medial part of the posterior fold of the axilla It is inserted by a flat white bilaminated tendon into the floor of the bicipital groove Nerve supply

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thoracodorsal nerve C6,7,8

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Latissimus Dorsi

• • • • • • Extends the shoulder Powerful adductor of the arm (climbing muscle) Rotates the humerus medially at the shoulder joint The latissimus dorsi is an accessory muscle of respiration if humerus is fixed It is supplied by the thoracodorsal nerve C6,7,8 It is involved in activities such as paddling a canoe, climbing and swimming

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Latissimus Dorsi

• • In freestyle swimming, the latissimus dorsi is a prime mover in the down stroke of the arm, mainly an extension movement and some medial rotation In canoeing, the muscle is a prime mover in the down stroke of the paddle, a movement of extension, adduction and medial rotation

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Superficial Muscles

• • • Deep to trapezius Levator scapulae Rhomboid minor and major They connect upper limb to trunk

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Levator Scapulae

• • • The levator scapulae muscle lies under the trapezius It has its origin from the transverse processes of the upper four cervical vertebrae (C1 to C4) Inserted into the superior part of the medial border of the scapula

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Levator Scapulae

• • The action of the levator scapulae is to raise the medial margin of the scapula and in doing so rotate it so as to produce downward rotation of the glenoid cavity The nerve supply is C5 via the nerve to the rhomboids from the roots of the brachial plexus

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Rhomboid Major and Minor

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• • • • • The rhomboid major and minor muscles lie deep to the trapezius and are not always distinct from each other Rhomboid minor arises from C7 and T1 vertebrae The major is about twice as wide as the minor Arises from T2-5 Appearing as parallel bands, they both pass inferiolaterally from the vertebrae

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Rhomboid Major and Minor

• • • • • The rhomboid major and minor muscles work together Retract the scapula and rotate it to depress the glenoid cavity Help the serratus anterior muscle to hold the scapula against the thoracic wall Fix the scapula during movements of the upper limb The nerve supply is C5 via the nerve to the rhomboids from the roots of the brachial plexus

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Intermediate

• Serratus posterior is an accessory muscle of respiration

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Superficial Layer: Splenius Capitis and Cervicis

• • • • • Inferior half of ligamentum nuchae and all the spinous processes of T1-T6 Insertion: lateral aspect of mastoid process Lateral third of superior nuchal line of occipital bone deep to sternocleidomastoid Splenius cervicis Posterior tubercles of transverse processes C1-C4 posterior to levator scapulae

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Splenius Capitis and Cervicis

• • Acting alone – – Lateral flexion Rotation of head and neck to same side Acting together – – Extension of neck and head Nerve supply: dorsal rami inferior cervical nerves.

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Intrinsic Muscles of Back

• • • • Deep layer of postural muscles attached to vertebral column and the back of head Anatomically in three layers: superficial, intermediate and deep Deep layer of muscles is responsible for movement of vertebral column Represents the intrinsic group of back muscles

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Intermediate Layer: Erector Spinae

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• • • • • • Lies between anterior and posterior layers of thoraco-lumbar fascia Three vertical columns: – – – medial = spinalis intermediate = longissimus lateral = iliocostalis Origin: a common broad band from posterior aspect of iliac crest Sacrum Sacroiliac ligaments Sacral and inferior lumbar spines

Erector Spinae: Iliocostalis and Longissimus

• • Iliocostalis Forms lateral column of erector spinae Inserts into angles of the ribs • • • Longissimus Forms the intermediate column of erector spinae Attached to transverse processes of thoracic and cervical vertebrae Mastoid process of temporal bone (muscle has a herring bone appearance)

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Erector Spinae: Spinalis

• • Narrow medial column of erector spinae (relatively insignificant) Extending to spinous processes of superior lumbar and inferior thoracic region

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Deep Layer: Transversospinal

• • • • • • In the groove between transverse processes and spines of vertebrae Collectively termed the transversospinal muscles Consists of several short muscles Semispinalis Acting bilaterally: extend and stabilise spine Acting unilaterally: rotate spine to opposite side and laterally flex

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Semispinalis

• • • Three part muscle – – – Thoracis Cervicis Capitis Acting bilaterally it will extend head, neck and thoracic spine Acting unilaterally it rotates head and neck to the opposite side

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Rotatores

• • • • • Short muscle Attached from transverse processes of one vertebra To the base of the spinous process of the vertebra superiorly Action: rotates the spine to opposite side Mainly in thoracic region

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Multifidus

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