Muscles of Back Dr Sama ul Haque Objectives

Muscles of Back Dr. Sama ul Haque

Objectives l Identify the superficial and deep muscles of the back in terms of their location, nerve supply and actions. l Understand l Explain the muscle support of the trunk. the mechanism of body weight transmission.

Vertebral Column Ø Cervical: 7 Ø Thoracic: 12 Ø Lumbar: Ø Sacral: 5 5 (fused to form 1 sacrum) Ø Coccygeal: Ø Total= 4 (fused to form coccyx) 33 (counted as 26 in the total bones of the body because of fusion.

Movements at the Vertebral Column Ø Flexion: bending forward Ø Extension: bending backwards Ø Lateral flexion: bending side-wards Ø Rotation: Twisting the trunk Ø 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 Ø Protects the spinal cord & spinal nerves. Ø Supports the weight of the body superior to the level of the pelvis. Ø Provides a partly rigid & flexible axis for the body & an extended base on which the head is placed and rotates. Ø Plays an important role in posture & locomotion

Muscles of the Back Ø Extrinsic Ø Intrinsic muscles

Extrinsic Muscles of the Back 1. Superficial extrinsic back muscles: Ø Trapezius Ø Latissimus dorsi Ø Levator scapulae Ø Rhomboids major & minor They all connect the upper limb to the trunk.

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

Extrinsic Muscles of the Back 2. Intermediate extrinsic back muscles: Ø Serratus posterior superior Ø Serratus posterior inferior They are superficial respiratory muscles and are supplied by intercostal nerves.

Intermediate Extrinsic Back Muscles Serratus posterior superior & Serratus posterior inferior

Intrinsic Muscles of the Back Ø Called Ø Deep Ø All muscles of the back proper. muscles of the back. are supplied by the posterior primary rami of spinal nerves. Ø 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

Intrinsic Muscles of the Back 2. Intermediate intrinsic back muscles: Ø Erector spinae is the chief extensor of the vertebral column & is divided into three columns (also called as the long muscle of the back). Ø Ilio-costalis (forms lateral column) Ø Longissimus Ø Spinalis (forms intermediate column) (forms medial column)

Intrinsic Muscles of the Back 2. Intermediate intrinsic back muscles: Ø N. S: Posterior rami of spinal nerves Ø Actions: Acting bilaterally, extend head & neck from a position of flexion. Acting unilaterally, laterally flex vertebral column.

Intermediate Intrinsic Back Muscles Erecter Spinae (Ilio-costalis Longissimus Spinalis)

Intrinsic Muscles of the Back 2. Deep intrinsic back muscles: Ø This is a group of muscles that lie deep to erector Spinae. Ø It can be divided into two groups: ØMajor deep layer ØMinor deep layer

Intrinsic Muscles of the Back 2. Deep intrinsic back muscles: Ø Major deep layer ØTransversospinal group consist of semispinalis, multifidus & rotators. ØN. S: Posterior ØActions: rami of spinal nerves. Extension and stabilization of vertebral column.

Deep Intrinsic Back Muscles Transversospinal group (semispinalis, multifidus & rotators)

Intrinsic Muscles of the Back 2. Deep intrinsic back muscles: Ø Minor deep layer Ø Interspinales Ø Intertransversarii Ø Levatores Ø N. S: costarum Posterior rami of spinal nerves Ø Actions: Extension, rotation, lateral flexion and stabilization of vertebral column.

Movements of Back and Neck

Muscles of the back are organized in layers Extrinsic: Movements of upper limb and respiration. 1 st layer: 2 nd layer: 3 rd layer: Trapezius Latissimus Dorsi Levator Scapulae Rhomboids (minor & major) Serratus posterior (superior & inferior) Intrinsic: Act on vertebral column and neck. 1 st layer: 2 nd layer: 3 rd layer: Splenius Erector Spinae: Iliocostalis Longissimus Spinalis Transversospinal: Multifidus Rotatores Semispinalis

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