Axial Skeleton

axial skeleton is composed of

vertebral column, ribs, skull, and sternum

functions of axial skeleton

-supports and protects organs

-transfer and absorb forces

-directly involved with swallowing, breathing, and chewing

-support of HAT

-stability and mobility

vertebral column is made up of

7 cervical

12 thoracic

5 lumbar

5 sacral

4 coccygeal

intervertebral discs

fibrocartilage pads that separate and cushion the vertebrae

intervertebral discs function

protect facet joints, shock absorption, mobility, limit motion, force distribution

nucleus pulposis

inner gelatinous nucleus, gives disc its elasticity and compressibility

annulus fibrosis

outer layer of intervertebral disc; provide structure, shape, and protects nucleus pulposis

vertebral end plates

help anchor together, thin layers of fibrocartilage cover inferior / superior aspects of the vertebral body

body of vertebrae

changes throughout day and life

different planes of vertebral levels

-influence angle and amount of motion

-help transfer loads across multiple vertebrae, reduce shear and force on intervertebral discs

lordotic curve

anterior curve of vertebral column

kyphotic curve

posterior curve of vertebral column

curves of vertebral column

decrease impact of forces

at birth curve is

kyphotic

lifting head and sitting develop

lordotic curve

standing and walking develop

both a lordotic and kyphotic curve

development of normal spinal curve

full curvature of spine develops by age 10

infants and spinal curvature

need to put them in different positions while young to help development of curves

line of gravity passes cervical spine

slightly posteriorly

line of gravity passes thoracic spine

anteriorly

line of gravity passes lumbar spine

posteriorly

motions of spine

flexion, extension, lateral flexion, axial rotation

bony structures that influence vertebral motion

facet joints, spinous processes, presence of ribs

ligaments influence vertebral motion by

assist in limiting/preventing excessive motions of the spine

ligamentum flavum

between laminae, limits flexion

supraspinous and interspinous ligaments

connect tips of spinous processes; between spinous processes

-limits flexion

intertransverse ligament

between transverse process. limit lateral flexion

anterior longitudinal ligament

connects anterior surfaces of adjacent vertebral bodies

-limits extension

-supports intervertebral discs

posterior longitudinal ligament

Connects all the posterior surfaces of the vertebral bodies

-limits flexion

-supports intervertebral discs

osteokinematics of cervical region

large amounts of flexion/extension, rotation, and lateral rotation occur here

atlanto-occipital joint

between skull and C1

-2 degrees of freedom: flexion/extension and small amount of lateral rotation

atlanto-axial joint

between atlas (c1) and axis (c2)

-rotation (50% of cervical rotation occurs at this joint)

C2-C7 articulations

flexion/extension, lateral flexion, and rotation occur here

osteokinematics of thoracic region

limited flexion/extension, lateral flexion, rotation all occur here

ribs and sternum

limit motion at costovertebral, costotransverse, and sternocostal joints

extension in thoracic region is limited by

spinous process

flexion in thoracic region is limited by

facet joints

osteokinematics of lumbar region

have large vertebral bodies due to large compression forces

flexion/extension, lateral flexion, rotation is

allowed but limited

facet joints in lumbar region

limit rotation

lumboscaral articulation

between lumbar and sacrum, provides stability to pelvis

bilateral

both sides cause pure flexion or extension

unilateral

one-sided, can be flexion or extension PLUS some degree of lateral flexion and rotation

gravity exerts an

external torque on vertebral column

many muscles of vertebral column act

isometrically: stabilize function

eccentrically: prevent excessive motion

axial skeleton stability depends on

what part of the axial skeleton is fixed vs. what part is free to move

ipsilateral

muscle causes rotation towards the SAME SIDE that the muscle is on

contralateral

muscle causes rotation towards the OPPOSITE side that the muscle is on

sternocleidomastoid bilateral

flexes head and neck and assist elevation of ribs during inhalation

sternocleidomastoid unilateral

contralateral head rotation and ipsilateral lateral flexion

scalenes bilateral

flexes head and neck (anterior scalene) and elevates ribs during inhalation (all)

scalenes unilateral

ipsilateral lateral flexion and contralateral head rotation

longus colli and longus capitis function

stabilizes head and neck

longus colli and longus capitis bilateral

flexion

longus colli and longus capitis unilateral

ipsilateral lateral flexion and ipsilateral rotation

rectus capitis anterior and rectus capitis lateralis muscles functions

stabilize head and neck

flexion and lateral flexion

suboccipital muscles

rectus capitis posterior major & minor AND superior & inferior oblique capitus

suboccipital muscles bilateral

extend head and neck

suboccipital muscles unilateral

ipsilateral lateral flexion and ipsilateral rotation

splenius capitis and cervicis bilateral

extend head and neck

splenius capitis and cervicis unilateral

ipsilateral rotation and ipsilateral lateral flexion

transversospinal/transversospinalis group

rotares, multifidi, semispinalis capitis

transversospinal/transversospinalis group bilateral

extend neck

transversospinal/transversospinalis group unilateral

contralateral rotation

erector spinae muscles

spinalis, longissimus, iliocostalis

erector spinae muscles bilateral

extend neck

erector spinae muscles unilateral

ipsilateral lateral flexion

what happens if posterior neck muscles are weak

Mo.A. from head to jaw is bigger which increases external torque which makes it harder for person to overcome to move their head

guy wire function of muscles

muscles groups on posterior, anterior and lateral surfaces work together to provide balance

intertransversarii, interspinous/interspinales function

contribute to stabilizing, lateral flexion, and extension of trunl

transversospinal/transversospinalis group bilateral trunk function

extend trunk

transversospinal/transversospinalis group unilateral trunk function

contralateral trunk rotation

erector spinae group bilateral trunk function

extend trunk

erector spinae group unilateral trunk function

ipsilateral lateral trunk flexion

quadratus lumborum bilateral

fix last rib during forced inhalation and exhalation

quadratus lumborum unilateral

laterally tilt/elevate pelvis, ipsilateral lateral trunk flexion, assist trunk extension

rectus abdominis

bilateral trunk flexion and posterior pelvis tilt

external oblique biltaeral

trunk flexion

external oblique unilateral

contralateral rotation and ipsilateral lateral flexion

internal oblique bilateral

trunk flexion

internal oblique unilateral

ipsilateral rotation and ipsilateral lateral flexion

transverse abdominis

abdominal compression

how to reduce force demands while lifting

lift slow

reduce weight of load

reduce length of E Mo.A to decrease external torque

increase I Mo.A so less force is used by back muscles

abnormal lateral curve of spine

scoliosis

abnormal kyphotic curve of spine

excessive curvature of the thoracic region, hunched back

spondylosis

a degenerative disorder that can cause the loss of normal spinal structure and function, small break in vertebrae

spondylolisthesis

forward slipping of one vertebra over another

herniated disc

Nucleus pulposus breaks through anulus fibrosus

Presses on spinal cord or nerves