Muscles of Back Dr. Sama ul Haque Dr Rania Gabr

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 (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 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 They are organized into 3 groups: Deep group: attached to & involved in the movement of vertebral column & head. Intermediate group: attached to ribs & serve respiratory functions. Superficial group: attached to & involved in the movements of upper limb. Intrinsic muscles: Develop in the back Supplied by posterior rami of spinal nerves Extrinsic muscles: Not developed in the back Supplied by anterior rami of spinal nerves.

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. Supplied by anterior rami of spinal nerves

Superficial Extrinsic Back Muscles Trapezius Latissimus dorsi Levator scapulae Rhomboids major & minor

TRAPEZIUS Origin: Spines of cervical & thoracic vertebrae Insertion: lateral 1/3 of clavicle + acromion & spine of scapula. Action: rotation of scapula during abduction of humerus above horizontal. Upper fibers: elevate scapula. Middle fibers: retract scapula Lower fibers: depress scapula. Nerve supply: Spinal part of accessory (11th cranial) nerve. Insertion Action Origin

LEVATOR SCAPULAE; RHOMBOID MINOR & MAJOR Origin: Levator scapulae: cervical transverse processes Rhomboid minor & major: thoracic spines Insertion: medial border of scapula. Nerve supply: dorsal scapular nerve. Actions: Levator scapulae: elevates scapula. Rhomboid minor & major: retract scapula.

LATISSIMUS DORSI Origin: a. Spinous processes of T7 - L5 vertebrae. b. Iliac crest of sacrum. c. Thoracolumbar fascia. d. Inferior angle of the scapula. e. Lower three or four ribs. Insertion: 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: Serratus posterior superior Serratus posterior inferior They are superficial respiratory muscles and are supplied by intercostal nerves.

Intermediate Extrinsic Back Muscles It is separated from the deep group by thoracolumbar fascia. It includes: Serratus posterior superior (rib elevator). Serratus posterior inferior (rib depressor). 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: 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

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 (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 N.S: Posterior rami of spinal nerves Actions: Acting bilaterally, extend head & neck from a position of flexion. Acting unilaterally, laterally flex vertebral column.

Intrinsic Muscles of the Back 3. 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

Deep Intrinsic Muscles of the Back 1-Major deep layer Transversospinal group consist of semispinalis, multifidus & rotators. N.S:Posterior rami of spinal nerves. 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 layer Interspinales Intertransversarii Levatores costarum N.S: Posterior rami of spinal nerves Actions: Extension, rotation, lateral flexion and stabilization of vertebral column.

Movements of Back and Neck

MUSCULAR TRIANGLES OF BACK Auscultatory Triangle: Boundaries: latissimus dorsi, trapezius, and medial border of scapula. Site where breath sounds are most easily heard with a stethoscope. Lumbar Triangle: (Triangle of Petit) Boundaries : latissimus dorsi, posterior border of external oblique muscle of the abdomen, and iliac crest. Site of an abdominal hernia; or where pus may emerge from the abdominal wall.

Muscles of the back are organized in layers Extrinsic: 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: Splenius 2nd layer: Erector Spinae: Iliocostalis Longissimus Spinalis 3rd layer: Transversospinal: Multifidus Rotatores Semispinalis

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