MUSCLES OF THE BACK Extrinsic back muscles Superficial group Movements of the upper limb Intermediate group Attached to the ribs May serve as a respiratory function. Intrinsic (deep) back muscles Act on the vertebral column Its movements Maintain posture
SUPERFICIAL GROUP OF BACK MUSCLES Immediately deep to the skin and superficial fascia. Connected with the shoulder girdle. Attach the superior part of the appendicular skeleton (clavicle, scapula, and humerus) to the axial skeleton (skull, ribs, and vertebral column).
SUPERFICIAL GROUP OF BACK MUSCLES Produce and control limb movements. Trapezius Latissimus dorsi Rhomboid major Rhomboid minor Levator scapulae
Covers posterior aspect of neck & superior half of trunk trapezium (G. irregular four-sided figure)
muscle's origin: base of triangle situated along vertebral column muscle's insertion: apex pointing toward tip of shoulder Occipital bone Scapula Vertebral column
attaches the pectoral girdle to cranium & vertebral column assists in suspending the upper limb.
Descending (superior) fibers elevate the scapula (e.g., when squaring the shoulders). Middle fibers retract the scapula (i.e., pull it posteriorly). Ascending (inferior) fibers depress the scapula and lower the shoulder.
Superior fibers of trapezius from the skull and upper portion of the vertebral column descend to attach to lateral 1/3 clavicle & acromion of scapula.
Lateral 1/3 C7 to T12 Spine of scapula
Superior nuchal line External occipital protuberance Ligamentum nuchae Spinous processes of C7 to T12 Lateral 1/3 of clavicle Acromion Spine of scapula
Superior and inferior fibers work together to rotate the lateral aspect of the scapula upward, which needs to occur when raising the upper limb above the head.
The trapezius also braces the shoulders by pulling the scapulae posteriorly and superiorly, fixing them in position on the thoracic wall with tonic contraction; consequently, weakness of this muscle causes drooping of the shoulders.
Motor innervation of trapezius accessory nerve [XI] descends from the neck onto the deep surface of the muscle. Proprioceptive fibers from trapezius pass in the branches of the cervical plexus and enter the spinal cord at spinal cord levels C3 &C4.
LATTISIUMUS DORSI L. widest of back Begins in the lower portion of the back Tapers as it ascends to a narrow tendon that attaches to the humerus anteriorly.
LATTISIUMUS DORSI Posterior axillary fold
LATTISIUMUS DORSI Spinous processes of T7 to L5 Sacrum Iliac crest Ribs 10 to 12 Floor of intertubercular sulcus of humerus
LATTISIUMUS DORSI Passes from the trunk to the humerus. Acts directly on the glenohumeral joint. Acts indirectly on the pectoral girdle.
LATTISIUMUS DORSI Extend Adduct humerus (arm,upper limb) Medially rotate Apley scratch test. can also depress the shoulder, preventing its upward movement
LATTISIUMUS DORSI In combination with pectoralis major powerful adductor of the humerus plays a major role in downward rotation of the scapula in association with this movement.
LATTISIUMUS DORSI also useful in restoring the upper limb from abduction superior to the shoulder; important in climbing.
LATTISIUMUS DORSI In conjunction with pectoralis major, raises the trunk to the arm, performing chin-ups or climbing a tree
LATTISIUMUS DORSI Innervation: thoracodorsal nerve
LEVATOR SCAPULAE Superior 1/3 deep to sternocleidomastoid Inferior 1/3 deep to trapezius
Upper portion medial border of scapula superior to root of spine of scapula LEVATOR SCAPULAE
LEVATOR SCAPULAE
LEVATOR SCAPULAE acts with the descending part of the trapezius to elevate the scapula, or fix it! resists forces that would depress it, as when carrying a load.
LEVATOR SCAPULAE With rhomboids & pectoralis minor, rotates the scapula, depressing the glenoid cavity rotating the lateral aspect of scapula inferiorly
LEVATOR SCAPULAE Acting bilaterally (also with the trapezius), the levators extend the neck. Acting unilaterally, may contribute to lateral flexion of the neck toward the side of the active muscle.
RHOMBOID MAJOR RHOMBOID MINOR Deep to trapezius, inferior to levator scapulae Broad parallel bands Pass inferolaterally from vertebrae to medial border of scapulae
RHOMBOID MINOR Lower portion of ligamentum nuchae Spinous processes of C7 and T1 Medial border of scapula at the spine of scapula
RHOMBOID MAJOR Spinous processes of T3 to T5 Medial border of scapula between spine & inferior angle
RHOMBOID MAJOR ET MINOR Retract (adduct) and elevate scapula Assist serratus anterior in holding the scapula against the thoracic wall and fixing the scapula during movements of the upper limb.
Innervation: dorsal scapular nerve branch of brachial plexus C4 & C5
SERRATUS POSTERIOR SUPERIOR SERRATUS POSTERIOR INFERIOR Deep to the muscles in the superficial. group Related to the movements of the thoracic cage Superficial respiratory muscles More likely proprioceptive rather than motor in function
Serratus posterior superior lies deep to the rhomboids Serratus posterior inferior lies deep to the latissimus dorsi.
SERRATUS POSTERIOR SUPERIOR SERRATUS POSTERIOR INFERIOR. attached to the vertebral column and associated structures medially Either descend (fibers of serratus posterior superior) or Ascend (fibers of serratus posterior inferior) to attach to the ribs. These two muscles therefore elevate and depress the ribs
SERRATUS POSTERIOR SUPERIOR SERRATUS POSTERIOR INFERIOR. Lower portion of ligamentum nuchae Spinous processes of C7 to T3 Supraspinous ligaments Upper border of ribs 2 to 5 just lateral to their angles Spinous processes of T11 to L3 Supraspinous ligaments Lower border of ribs 9 to 12 just lateral to their angles
SERRATUS POSTERIOR SUPERIOR first four intercostal spinel nerves. SERRATUS POSTERIOR INFERIOR last four intercostal spinel nerves