Extrinsic Back Muscles

Back Objectives Describe the gross anatomy for each system (circulatory, muscular, nervous, and skeletal) in the region of the back. Integrate the systems to discuss the vertebral column functions. Analyze common dysfunctions in the vertebral column. For each muscle, describe how the attachment sites result in an action around a joint. For each muscle, identify the innervation (peripheral nerve and nerve roots). Objectives pulled from syllabus

Intermediate layer of intrinsic back muscles Erector Spinae Spinalis Longissimus Iliocostalis Erector spinae – extensors of the spine (slow twitch aka Type I, postural) Tendons – long, stringy, length of contractibility is low (they don’t contract very far but can contract for long periods of time, it’s more energy efficient to be mostly tendon) Spinalis – SP L2 -> SP T1 spinalis cervicis highly variable spinalis thoracis Longissimus – erector spinae tendon (posterior iliac crest and sacrum) -> ribs (medial to angle), TP, mastoid process longissimus thoracis longissimus cervicis longissimus capitis Iliocostalis – erector spinae tendon -> angles of ribs & TP of cervicals iliocostalis lumborum iliocostalis thoracis iliocostalis cervicis

Superficial layer of intrinsic back muscles Splenius Latin for bandaid – in its own layer of fascia wrapping the erectors and deep muscles Explained earlier in relation to the neck

Cross section Thoracolumbar fascia Quadratus Lumborum Tight, thick fascia that holds muscles in place 3 layers: anterior, middle, posterior Iliac crest to lower ribs Between anterior and middle is quadratus lumborum Between middle and posterior are intrinsic muscles of the back (review intrinsic muscles)

The semispinalis capitis: is part of the erector spinae group of muscles. when acting unilaterally, rotates the head so that the face points to the ipsilateral side. when acting bilaterally, flexes the neck. is innervated by cervical and upper thoracic posterior rami. is superficial to the splenius capitis. D

The rotatores: have a relatively large mechanical advantage for producing trunk rotation. possibly function primarily as "kinesiological monitors" or organs of proprioception. are part of the erector spinae group of muscles. are attached to the transverse processes of a pair of consecutive vertebrae. when acting bilaterally, can produce trunk flexion. B

The following lateral radiograph of the thoracic part of the vertebral column is from a patient with severe osteoporosis. Which of the following conditions does it demonstrate? kyphosis scoliosis lordosis IV disc herniation vertebral body hypertrophy A

Intermediate extrinsic back muscles Serratus Posterior Superior Serratus Posterior Inferior Serratus comes from root serrated (like a knife) – describes the appearance of the attachments to ribs SPS – superficial to erectors, thin, courses inferolaterally SP C7-T3 -> ribs 2-4 elevates ribs, proprioceptive intercostal nerves 2-4 SPI – superficial to erectors, thin, courses superiolaterally SP T11-L2 -> ribs 8-12 depresses ribs, proprioceptive intercostal nerves 8-12

Superficial extrinsic back muscles NOT TRUE BACK MUSCLES Axio-appendicular muscles Trapezius Latissimus Dorsi Rhomboids Levator Scapulae Not all true back muscles – attach to scapula or humerus! UE muscles Reason to discuss now = functionally not back muscles, but anatomically they are. We will learn them on the cadavers with the back, so we will learn them in lecture with the back. Protective features spinal accessory nerve deep to trapezius dorsal scapular nerve & dorsal scapular artery deep to rhomboids thoracodorsal nerve & lateral thoracic artery deep to latissimus

Trapezius Superior (descending) superior nuchal line & cervical SP -> lateral 3rd of clavicle fibers twist from origin to insertion elevates scapula along with levator scap doesn’t truly contract alone upward rotation (discuss later with inferior part) Middle upper thoracic SP -> acromion process & part of spine of scap horizontal fibers, thickest part of muscle retraction (horizontal abduction) Inferior (ascending) lower thoracic SP -> spine of scap (wraps around to inferior surface) angle of muscle fibers produces superior rotation of scap

Scapular motions Elevation / depression Protraction / retraction Upward rotation / downward rotation

Upward rotation of scapula Descending Trapezius Ascending Trapezius Serratus Anterior (TBD) Draw in muscle fibers Discuss how axis of rotation can shift since there is no bony articulation Pic on left: all upper trap and serratus anterior (lower trap not contracting) Pic on right: all lower trap and serratus (upper trap not contracting)

Latissimus Dorsi thoracolumbar fascia & lower thoracic SP -> intertubercular groove of humerus no attachment to scapula crosses 2 “joints” – scapulothoracic and glenohumeral extends, internally rotates, and adducts humerus (whole muscle) indirectly depresses and downwardly rotates scapula (lower, vertical fibers) fibers twist – upper fibers are posterior in axilla, inferior at insertion; lower fibers are anterior in axilla, superior at insertion *show with theraband Rhomboid Major SP T2-T5 -> medial border of scap below spine retraction and downward rotation of scap Rhomboid Minor SP C7-T1 -> medial border of scap at spine Levator Scapulae posterior tubercles of C1-C4 TP -> medial border of scap above spine why is origin not on scap? while running how to breathe easier story elevation and downward rotation

Downward rotation of scapula Rhomboids Levator Scap Latissimus When could downward rotation be useful for daily life? example: crutches

Triangles and spaces Reference points Neurovasculature Like landmarks to help find structures and identify muscles Many have neurovasculature that passes through them Suboccipital triangle – suboccipital nerve Triangle of auscultation and lumbar triangle do not – just connective tissue Lumbar triangle – different sources say different things (thanks AJ and Sarah!) not important – we will use it as a simple reference point in surface anatomy

Back musculature General muscle functions: movement, sensation, protection, metabolism General tendon functions: transfer muscle forces efficiently, sensation Actions Interactions Protective features Sensory features

What muscle attaches immediately superior to the Rhomboid minor on the scapula? Rhomboid major Inferior trapezius Middle trapezius Levator Scapulae Serratus Posterior Superior D

Your patient has difficulty flexing his shoulder past 90 degrees and no other difficulties. Which muscle is least likely to be weak? Superior Trapezius Rhomboid Major Inferior Trapezius Middle Trapezius Serratus Anterior B

Your patient has a weak latissimus dorsi Your patient has a weak latissimus dorsi. Which activity would she likely have the most difficulty with? Juggling Jumping jacks Push ups Supermans Rowing E

Sensorimotor peripheral nervous system Peripheral nerves as highways Nerve roots as one-ways Gray vs White Matter Basics of neuroanatomy Peripheral nerves have sensory and motor (two directions) within each nerve neurons are all one way but the nerve has mixed neurons Rami – are peripheral nerves (split after nerve root) Define and differentiate nerve root, dorsal root, and ventral root Dorsal root ganglion is bodies of sensory neurons Gray matter is cell bodies, dendrites, and synapses White matter is myelinated axons (we are all fat heads!)

sensations Skin: touch, pressure, temperature, pain Muscles and tendons: pressure, pain, proprioception Specialized receptors in dermis and subcutaneous tissue respond to touch, pressure, temperature and pain Muscles, tendons and joint capsules contain proprioceptors “In the limbs, the proprioceptors are sensors that provide information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the limb in space. The muscle spindle is one type of proprioceptor that provides information about changes in muscle length.” http://courses.washington.edu/conj/bess/spindle/proprioceptors.html

Spina bifida “Bifid spine” Three types: Occulta Meningocoele Myelomeningocoele Occulta – least problematic, may be some surface indicator but few symptoms Meningocoele – sac of fluid present Myelomeningocoele – (shown in pic above) sac of fluid with displaced spinal cord co-morbidities include tethered cord syndrome & hydrocephalus & latex allergy reduced walking ability, reduced bowel and bladder control Failure of neural tube to close during first month of development Known risks include: medications, diabetes, obesity, increased core body temp from fever or hot tubs

The neural tube forms from which layer of tissue? Ectoderm Endoderm Mesoderm A

Tethered cord syndrome Various dorms that all result in a spinal cord tethered to sacrum May go undiagnosed until adulthood As vertebrae grow, spinal cord becomes stretched Symptoms may not arise until late because amount of stretching will be gradual with growth Symptoms: pain, muscle weakness, loss of sensation, issues with bowel and bladder control, scoliosis, gait abnormalities

Lumbar puncture Into CSF of Lumbar cistern For spinal anesthesia

Epidural Into epidural space of Lumbar cistern Blocks nerves where they exit the dura mater – results in anesthesia at the level of application and below

Deep -> superficial rotatores, multifidus, interspinales, semispinalis cervicis, semispinalis cap, splenius (both), rhomboid minor, levator Notes: thickness of muscles (levator is strong!), start with bony landmarks to determine vertical location, side picture will not be given

Lat -> med QL, intertransversarii ilicostalis, longissimus, spinalis, rotatores Purple = disc Yellow = spinal nerves Orange = ligamentum flavum Peach = epidural space Mint green = thoracolumbar fascia

What is this muscle? Rotatores Multifidus Semispinalis Longissimus B

Back essay Discuss marked up exemplars Meet with groups to discuss ideas 5 minutes per person (?) Explain ideas and thoughts so far Group members ask questions to clarify – try to understand their thought process Group members give feedback or ask challenge questions How does this idea relate to PT? Why is this topic worth writing about? How will you incorporate descriptive anatomy with a functional limitation? Etc. -> really challenge each other (respectfully) to improve Summarize new ideas Discussions: premise – ideas and plans should be adaptable knowledge is gained in a messy way – updating is required constantly Discussion framework

Next class 2 presentations! Bring your essay draft to class! (printed copies for your group members) Study for some unit wrap up questions in class (like a group quiz!)