Muscles of the Muscles of the BackBack

ByBy

Prof Saeed A. Abouel Prof Saeed A. Abouel MakaremMakarem

Cutaneous Nerves of the Back Cutaneous Nerves of the Back of the Neckof the Neck

Back of the neck is supplied by dorsalBack of the neck is supplied by dorsal

rami of the rami of the cervical nervescervical nerves

EXCEPT the 1EXCEPT the 1stst & 8 & 8thth (which has no (which has no cutaneous branches).cutaneous branches).

N.B.N.B.

Dorsal Dorsal ramusramus

of of C1C1 & C 8& C 8

has nohas no

CutaneousCutaneous

Branches.Branches.

Muscles of back are arranged in Muscles of back are arranged in 4 layers.4 layers.

11stst. Layer. Layer : : 1- Trapezius.1- Trapezius. 2- Latissimus Dorsi.2- Latissimus Dorsi. 2nd2nd Layer: Layer: 1- Levator Scapulae.1- Levator Scapulae. 2- Rhomboideus minor.2- Rhomboideus minor. 3- Rhomboideus major.3- Rhomboideus major. Also the 2Also the 2ndnd layer contains 2 other muscles: layer contains 2 other muscles: 4- Serratus posterior superior.4- Serratus posterior superior. 5- Serratus posterior inferior5- Serratus posterior inferior

33rdrd Layer Layer : : Erector spinae (Sacrospinalis) & Semispinalis.Erector spinae (Sacrospinalis) & Semispinalis.

44thth Layer Layer : : Number of small muscles called multivators, rotators, interspinalis, Number of small muscles called multivators, rotators, interspinalis,

intertransverses & muscles forming the suboccipital triangle.intertransverses & muscles forming the suboccipital triangle.

TrapeziusTrapezius Origin:Origin: From Occipital bone (Medial From Occipital bone (Medial

1/3 of superior nuchal line), external 1/3 of superior nuchal line), external occipital protuberance, Ligamentum occipital protuberance, Ligamentum nuchae, spines of all cervical & all nuchae, spines of all cervical & all thoracic vertebrae and supraspinous thoracic vertebrae and supraspinous ligamentligament

Insertion Insertion : posterior border of : posterior border of lateral 1/3 of the clavicle, medial lateral 1/3 of the clavicle, medial margin of acromion upper lip of the margin of acromion upper lip of the crest of the spine of the clavicle.crest of the spine of the clavicle.

Nerve supplyNerve supply: Spinal : Spinal accessory cranial accessory cranial nerve & C 3,4nerve & C 3,4

Actions:Actions: upper fibers: elevate upper fibers: elevate

the shoulderthe shoulder Lower fibers: depress Lower fibers: depress

the shoulder.the shoulder. Middle fibers: brace Middle fibers: brace

back (retraction) of back (retraction) of shouldershoulder

It also, helps in raising It also, helps in raising the arm above 90the arm above 90° ° with (serratus with (serratus anterior).anterior).

LatissimusLatissimus DorsiDorsi Origin:Origin: 1- Lower 6 thoracic spine. 1- Lower 6 thoracic spine. 2- Thoracolumbar fascia.2- Thoracolumbar fascia. 3- Iliac crest. 3- Iliac crest. 4- Lower 3 or 4 ribs.4- Lower 3 or 4 ribs. 5- Back of the inferior angle of the 5- Back of the inferior angle of the

scapula.scapula. Insertion:Insertion: floor of the bicipital groove. floor of the bicipital groove. Nerve supplyNerve supply: Nerve to Latissimus dorsi : Nerve to Latissimus dorsi

(thoracodorsal nerve).(thoracodorsal nerve). Action: adduction, medial rotation.Action: adduction, medial rotation. It also helps in extension and climbing.It also helps in extension and climbing.

11stst layer: layer: TrapeziusTrapezius Latissimus Latissimus

dorsidorsi 22ndnd layer: layer: Levator Levator

scapulaescapulae Rhomboid Rhomboid

minorminor Rhomboid Rhomboid

major.major.

Levator scapulaeLevator scapulae Origin: TransverseOrigin: Transverse processes of upper 4 cervical processes of upper 4 cervical

vertebrae.vertebrae. InsertionInsertion: Medial border of scapula.: Medial border of scapula. Nerve supplyNerve supply: C3,4 & 5: C3,4 & 5 Action:Action: Elevate the medial border of the Elevate the medial border of the

scapula.scapula. Rhomboid minorRhomboid minor

Origin:Origin: Ligamentum nuchae & spines of C 7& T1 Ligamentum nuchae & spines of C 7& T1 InsertionInsertion: Medial border of the scapula.: Medial border of the scapula. Nerve supplyNerve supply: C4& 5: C4& 5 Action:Action: Raises the medial border of scapula Raises the medial border of scapula

upward & medially.upward & medially.

Rhomboid MajorRhomboid Major Origin:Origin: Spines of T2,3,4 & 5. Spines of T2,3,4 & 5. InsertionInsertion: Medial border of : Medial border of

scapula.scapula. Nerve supplyNerve supply: C4 & 5.: C4 & 5. ActionAction:: Raises the medial border Raises the medial border

of the scapula upward and of the scapula upward and medially.medially.

Origin:Origin: 1- Lower 6 thoracic 1- Lower 6 thoracic

spine, spine, 2- Thoracolumbar 2- Thoracolumbar

fascia,fascia, 3- Iliac crest 3- Iliac crest 4- Lower 3 or 4 ribs 4- Lower 3 or 4 ribs

andand 5- Back of the 5- Back of the

inferior angle of the inferior angle of the scapulascapula

Insertion:Insertion: floor of the bicipital floor of the bicipital

groovegroove

DeltoidDeltoid

Muscles connecting scapula to Muscles connecting scapula to the Humerusthe Humerus

SupraspinatusSupraspinatusOrigin: supraspinous fossa.Origin: supraspinous fossa.Insertion: top of greater Insertion: top of greater

tubercle.tubercle.Nerve: Suprascapular N. Nerve: Suprascapular N. Action: Starts abduction Action: Starts abduction

fromfrom 0 to 15.0 to 15. Steadies head of humerus.Steadies head of humerus.

InfraspinatusInfraspinatusOrigin: infraspinous fossaOrigin: infraspinous fossaInsertin: middle impression Insertin: middle impression

of greater tubercle.of greater tubercle.Nerve: Suprascapular nerve.Nerve: Suprascapular nerve.Action: adduction & Action: adduction &

Steadies head of humerus Steadies head of humerus

Teres minorTeres minor Origin: Upper 2/3 of lateral border of scapulaOrigin: Upper 2/3 of lateral border of scapula Insertion: lower impression of the greater Insertion: lower impression of the greater

tubercle.tubercle. Nerve AxillaryNerve Axillary Action: adduction & Lateral rotation.Action: adduction & Lateral rotation. Teres MajorTeres Major Origin: lower 1/3 of lateral border of scapula.Origin: lower 1/3 of lateral border of scapula. Insertion: Medial lip of intertubercular grooveInsertion: Medial lip of intertubercular groove Nerve: lower subscapular n.Nerve: lower subscapular n. Action: Adduction, medial rotation and Action: Adduction, medial rotation and

extension.extension.

SubscapularisSubscapularisOrigin:Origin: Subscapular Subscapular

fossafossaInsertionInsertion: Lesser : Lesser

tubercle tubercle (tuberosity) of (tuberosity) of Humerus.Humerus.

Nerve:Nerve: Upper & lower Upper & lower subscapular nerve.subscapular nerve.

Action:Action: adduction & adduction & medial rotation of medial rotation of shoulder.shoulder.

The tendons of The tendons of Suprasinatus, & Suprasinatus, & infraspinatus, & infraspinatus, & teres minor, and teres minor, and subscapularis subscapularis

form rotator-cuff.form rotator-cuff.

Rotator cuff:Rotator cuff: 1-1-

Supraspinatus.Supraspinatus. 2- infraspinatus2- infraspinatus 3- Teres minor.3- Teres minor. 4- 4-

SubscapularisSubscapularis