Lecture 14: Skeletal Muscles Trunk Flashcards
Muscles of the back
3 layers: superficial, intermediate, deep
Superficial and intermediate layers = extrinsic back muscles
Deep layer = intrinsic back muscles
Superficial back muscles
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboid
Function: connects upper limb to trunk and positions pectoral girdle and upper limb
Innervated by anterior/ventral rami of spinal nerves
Intermediate back muscles
Serratus posterior superior
Serratus posterior inferior
Function: accessory respiratory muscles
Innervated by ventral rami of spinal nerves
Deep back muscles
Erector spinae
Transversospinalis
Segmental muscle groups
Splenius wapitis
Cervicis
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, extends/laterally flexes vertebral column, elevates ribs, extends and rotates head/neck
Innervated by dorsal rami of spinal nerves
Trapezius
Origin: occipital bone, spinous process from all cervical and thoracic vertebrae
Insertion: clavicle, acromian, spine of scapula
Function: upper fibers (down and lateral) elevate shoulders, middle fibers (horizontal) retract/adduct scapula, lower fibers (superior and lateral) depress scapula
Nerve: CNXI (accessory)
Latissimus dorsi
Origin: spinous process of lower thoracic and lumbar vertebrae, sacral and iliac crests
Insertion: intertubercular groove of humerus
Function: prime mover of shoulder extension; adduction, medial rotation of shoulder
Nerve: thoracodorsal nerve of brachial plexus
Levator scapulae
Origin: upper cervical vertebrae
Insertion: superior angle of scapula
Function: elevation of scapula
Nerve: branch of brachial plexus
Rhomboid (major and minor)
Origin: thoracic vertebrae
Insertion: medial border of scapula
Function: retraction and elevation of scapula
Nerve: branch of brachial plexus
Erector spinae
3 longitudinal bundles of muscles fibers (from lateral to medial): iliocostalis, longissimus, spinalis
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, stabilizes vertebral column
Nerve: dorsal rami of spinal nerves
Transversospinalis
Between transverse process and spinous process of vertebrae
Subdivided (from superficial to deep): semispinalis, multifidus, rotatores
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, stabilizes vertebral column
Nerve: dorsal rami of spinal nerves
Segemental group
From medial to lateral: interspinales, intertransversarii, elevator costarum
Function: extends or laterally flexes vertebral column, elevates ribs
Nerve: dorsal rami of spinal nerves
Splenius capitis and cervicis
Extend and rotates the neck/head
Nerve: dorsal rami of spinal nerves
Muscles of thorax (extrinsic and intrinsic)
2 groups:
Extrinsic muscles originate in thorax, and insert to upper limb: pectoralis major, pectoralis minor, serrates anterior, subclavius muscle
Intrinsic muscles originate and insert to thorax: intercostal muscles and diaphragm
Pectoralis major
Origin: clavicle and costal cartilage of upper fibers
Insertion: proximal end of humerus
Function: medial rotation and adduction of shoulder; accessory respiratory muscle
Nerve: branch of brachial plexus
Pectoralis minor
Origin: ribs 3-5
Insertion: corocoid process of scapula
Function: brings tip of shoulder anteriorly and inferiorly
Nerve: branch of brachial plexus
Serratus anterior
Origin: ribs 1-9
Insertion: anterior medial border of scapula
Function: prime mover for protraction of scapula, stabilizes scapula against chest wall (if paralyzed, scapula will be unstable and 7-8 other muscles that depend on scapula will also lose function)
Nerve: long thoracic nerve of brachial plexus (close to breast gland)