2ObjectivesIdentify 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.
3Vertebral 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.
5Movements at the Vertebral Column Flexion: bending forwardExtension: bending backwardsLateral flexion: bending side-wardsRotation: Twisting the trunkCircumduction: Combined movements
6MUSCLES 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 backSupplied by posterior rami of spinal nervesExtrinsic muscles:Not developed in the backSupplied by anterior rami of spinal nerves.
7Extrinsic Muscles of the Back 1. Superficial extrinsic back muscles:TrapeziusLatissimus dorsiLevator scapulaeRhomboids major & minorThey all connect the upper limb to the trunk.Supplied by anterior rami of spinal nerves
8Superficial Extrinsic Back Muscles TrapeziusLatissimus dorsiLevator scapulaeRhomboids major & minor
10LEVATOR SCAPULAE; RHOMBOID MINOR & MAJOR Origin:Levator scapulae: cervical transverse processesRhomboid minor & major: thoracic spinesInsertion: back of medial border of scapula.Nerve supply: dorsal scapular nerve.Actions:Levator scapulae: elevates scapula.Rhomboid minor & major: retract scapula.
11LATISSIMUS DORSI Origin: Spinous processes of T7 - L5 vertebrae. Iliac crest of sacrum.Thoracolumbar fascia.Inferior angle of the scapula.Lower three or four ribs.Insertion:floor of bicipital groove of humerus.Nerve supply:thoracodorsal nerve.Actions:extension, adduction & medial rotation of humerus (arm, shoulder joint).
12Extrinsic Muscles of the Back 2. Intermediate extrinsic back muscles:Serratus posterior superiorSerratus posterior inferiorThey are superficial respiratory muscles andare supplied by intercostal nerves.
13Intermediate Extrinsic Back Muscles It includes:Serratus posterior superior (rib elevator).Serratus posterior inferior (rib depressor).Nerve supply: anterior rami of thoracic spinal nerves.
14Intrinsic 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.
15Intrinsic Muscles of the Back 1. Superficial intrinsic back muscles:Splenius cervices & splenius capitisN.S: Posterior rami of spinal nerves.Actions: Acting alone; laterally flex neck &rotate head to side of active muscle.Acting together; extend head & neck.
16Superficial Intrinsic Back Muscles Splenius cervices&splenius capitis
182. 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)
19They 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.
21Intrinsic Muscles of the Back 3. Deep intrinsic back muscles:It can be divided into two groups:Major deep layerMinor deep layer
22Deep Intrinsic Muscles of the Back 1-Major deep layerTransversospinal group consist of semispinalis, multifidus & rotators.N.S: Posterior rami of spinal nerves.Actions: Extension and stabilization of vertebral column.
23Transversospinal group Deep Intrinsic Back MusclesTransversospinal group(semispinalis, multifidus & rotators)
24Deep Intrinsic Muscles of the Back 2- Minor deep layerInterspinalesIntertransversariiLevatores costarumN.S: Posterior rami of spinal nervesActions: Extension, rotation, lateral flexion and stabilization of vertebral column.
27MUSCULAR TRIANGLES OF BACK Auscultatory Triangle:2.Boundaries: latissimus dorsi, trapezius, and medial border of scapula.2. Importance: breath sounds are most easily heard with a stethoscope.Lumbar Triangle: (Triangle of Petit)1.Boundaries : latissimus dorsi, posterior border of external oblique muscle of the abdomen and iliac crest.2. Importance: Site of an abdominal hernia
28Extrinsic: Movements of upper limb and respiration. Muscles of the backExtrinsic: Movements of upper limb and respiration.1st layer: Trapezius - Latissimus Dorsi2nd layer: Levator Scapulae- Rhomboids (minor & major)3rd layer: Serratus posterior (superior & inferior)Intrinsic: Act on vertebral column and neck.1st layer: Splenius2nd layer: Erector Spinae: IliocostalisLongissimusSpinalis3rd layer: Transversospinal: MultifidusRotatoresSemispinalis