The Axial Skeleton

consists of: bones, cartilage, joints and ligaments -composed of 206 named bones grouped into 2 divisions: axial skeleton and appendicular skeleton

-upper and lower limbs -126 bones

-consists of the skull, vertebral column, and thoracic cage -total of 80 bones

-body's most complex bony structure -formed by cranial and facial bones

-enclose and protect the brain -provide attachment sites for some muscles of the head and neck -formed from 8 large bones (2 paired and 4 unpaired)

-form framework of the face -form cavities for sense organs which provides blood vessel and innervation -provides open passageway for air and food -hold teeth in place -anchor muscles of face

-middle and inner ear cavities -nasal cavity (posterior to nose) -orbits -air-filled sinuses (occur in several bones around the nasal cavity)

-on both sides of the skull -temporal bones -parietal bones

-frontal bones -occipital bone -sphenoid bone -ethmoid bone

-form the superior and lateral parts of the skull -sites of articulation (joints) with other bones create 4 sutures

-small bones that occur within sutures -irregular in shape, size, and location -not all people have sutural bones

-coronal suture: runs in the coronal plane, located where parietal bones meet frontal bone -squamous suture: occurs where each parietal bone meets a temporal bone inferiorly -sagittal suture: occurs where right and left parietal bones meet superiorly -lambdoid suture: occurs where the parietal bones meet the occipital bone posteriorly

-lies inferior to the mandible -the only bone with no direct articulation with any other bone -acts as moveable base and forms anchoring structures for the tongue -consists of landmarks: greater horn, lesser horn, and body

-in adult is formed from 26 bones -transmit weight of the trunk to the lower limb -surrounds & protects the spinal cord -serves as attachment sites for muscles of the neck and back

-5 major regions -7 cervical vertebrae -12 thoracic vertebrae -5 lumbar vertebrae -sacrum (five fused bones) -coccyx

-cushion-like pads between vertebrae -composted of 2 parts: nucleus pulposus and anulus fibrosus

-gelatinous inner sphere that absorbs compressive stresses -shock absorber

-outer rings formed of ligament (dense regular) -inner rings formed by fibrocartilage -contains the nucleus pulpous -holds everything together

-aka slip disc -may be caused by trauma to the spine by repeated stress, wear&tear, or lifting heavy objects that causes rupture of anulus pulposus followed by protrusion of nucleus pulposus -aging could also be a contributing factor where nucleus purposes loses cushioning properties and annulus fibrosis weakens -can cause neurological problems of the spinal nerves that will cause inflammation, pain, and deficit in motor and sensory neurons that will block signals causing numbness or weakness in muscles

-body -vertebral arch -vertebral foreamen -spinous process -transverse process -superior and inferior articular processes (where vertebral connect to each other -intervertebral foramina (spinal nerves passes thru)

-flexion and extension -lateral flexion -rotation in the long axis

-are the smallest and lightest vertebrae -C3-C7 are typical that have wider body laterally and have a spinous process that is short and bifid (except for C7) -vertebral foramen are large and triangular -transverse processes contain transverse foramina that are little holes to hold blood vessels and nerves -superior articular facets face superioposteriorly

-lacks a body and spinous process -supports the skull because it has very wide and large superior articular facets that receive the occipital condyles -contains a transverse ligament that surrounds the dens that constrains amount of rotation you can get -allows flexion and extension of the neck (nodding the head "yes")

-has a body and spinous process -contains a dens which projects superiorly

-aka odontoid process -part of C2 that acts as a pivot for rotation of the atlas and skull -participates in rotation the head from side to side (no)

-all articulate with the ribs -heart-shaped bodies from superior view -each side of the body of T1-T10 bears demifacts (costal facets) for articulation with ribs - flexion and extension and lateral flexion, and a little rotation

-where the head of the rib is attached to

-where the tubercle of rib is attached to

-bodies are thick and robust -transverse process are thin and tapered -spinous processes are thick and blunt and point posteriorly -superior and inferior articular facets directly medially -allows flexion and extension - rotation prevented

-shapes the posterior walls of pelvis -formed from 5 fused vertebrae during embryo stage -superior surface articulates with L5 and inferior articulates with coccyx

-where the first sacral vertebrae bulges into pelvic cavity -center of gravity is 1 cm posterior to this area

-upper lateral sides of the sacrum -develops from fused rib elements

-aka tailbone -formed from 3-5 fused vertebrae -offers only slight support to pelvic organs but not necessarily, so therefore a vestigial structure

-forms the bony framework of the chest -components: thoracic vertebrae (posteriorly), ribs (laterally), sternum and costal cartilage (anteriorly) -functions: protects thoracic organs, supports shoulder girdle and upper limbs, provides attachment sights for many back muscles

-has 3 sections -manubrium: superior section that contains a clavicular notches articulate with the medial end of clavicles -body: bulk of sternum where sides are notched at articulations for costal cartilage of ribs 2-7 -xiphoid process: inferior end of sternum that ossifies around age 40, might break during Heimlich maneuver if it ossified

-Jugular Notch: central indentation at superior border of the manubrium -Sternal angle: a horizontal ridge where the manubrium joins the body -Xiphisternal joint- where sternal body and xiphoid process fuse; lies at the level of the 9th thoracic vertebra

-all ribs attach to vertebral column posteriorly contains: true ribs (7) that have their own cartilage and attach to sternum by costal cartilage. false ribs (8-10) that share cartilage. floating ribs (11-12) do not attach to sternum

-an abnormal lateral curvature

-an exaggerated thoracic curvature, hunchback

-an accentuated lumbar curvature; 'swayback', -can happen temporarily in pregnancy