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Axial Skeleton
Bones of the skull, vertebrae, and ribs
| Question | Answer |
|---|---|
| Cranial fossae | - anterior, middle, and posterior - compose the intracranial cavity |
| Coronal suture | - runs in the coronal plane - located where parietal bones meet frontal bone |
| Squamous suture | - occurs where each temporal bone meets a parietal bone inferiorly |
| Sagittal suture | - occurs where right and left parietal bones meet superiorly |
| Lambdoid suture | - occurs where the parietal bone meet the occipital bone posteriorly |
| Sutural bones | - small bones that occur within sutures - irregular in shape, size, location - not all people have them |
| Supraorbital margin | - superior margin of the orbits |
| Glabella | - smooth part of the frontal bone between superciliary (eyebrow) arches |
| Occipital bone | - forms posterior portion of the cranium and cranial base - articulates with temporal bones and parietal bones - forms posterior cranial fossa - foramen magnum located at its base |
| Frontal bone | - forms the forehead and roofs of orbits - contributes to anterior cranial fossa |
| Occipital bone features | - occipital condyles - hypoglossal foramen - external occipital protuberance - superior nuchal lines - inferior nuchal line |
| Temporal bones | - lie inferior to parietal bones - form the inferolateral part of skull - contributes to the middle and posterior cranial fossa |
| Mastoid process | - site for neck muscle attachment - contains air sinuses - part of the temporal bone |
| Petrous region | - projects medially, contributes to cranial base - appears as bony wedge b/w occipital bone posteriorly and sphenoid bone anteriorly - houses cavity of middle and internal ear |
| Foramina of the temporal bone | - jugular foramen: at boundary with occipital bone - carotid canal - foramen lacerum - internal acoustic meatus |
| Sphenoid bone | - spans width of cranial floor - has 3 pairs of processes - "keystone" of the cranium |
| Sella turcica | - saddle-shaped prominence in superior part of sphenoid bone - contains the hypophyseal fossa, which holds the pituitary gland |
| Sphenoid bone processes | - Greater wings - Lesser wings - Pterygoid process |
| Sphenoid bone openings | - optic canal - superior orbital fissure - foramen rotundum - foramen ovale - foramen spinosum |
| Ethmoid bone | - lies between nasal and sphenoid bones - forms most of the medial bony region between nasal cavity and orbits |
| Cribiform plate | - superior surface of the ethmoid bone - contain olfactory foramina |
| Crista galli | - attachment for falx cerebri (large vertical sheet between cerebral hemispheres |
| Perpendicular plate | - forms superior part of nasal septum |
| Mandible | - largest and strongest facial bone - 2 parts: horizontal body and two upright rami |
| Maxillary bones | - articulate with all facial bones except the mandible - contain maxillary sinuses - part of the interior orbital fissure - "keystone" facial bones |
| Zygomatic bones | - form lateral wall of the orbits |
| Nasal bones | - form bridge of the nose |
| Lacrimal bones | - located in medial orbital walls |
| Palatine bones | - complete the posterior part of the hard palate |
| Vomer | - forms inferior part of the nasal septum |
| Inferior nasal conchae | - thin, curved bones that project medially & form lateral walls of nasal cavity |
| Paranasal sinuses | - air filled sinuses within frontal, ethmoid, sphenoid, and maxillary bones - lined with mucous membrane - lighten the skull |
| Orbit walls | - roof - lateral wall - medial wall - floor - formed by frontal, sphenoid, zygomatic, maxillary, palatine, lacrimal, and ethmoid bones |
| Orbit wall openings | - superior orbital fissures - inferior orbital fissures - optic canals - lacrimal fossa |
| Hyoid bone | - inferior to mandible in anterior neck - acts as movable base for tongue - not directly in contact with any other bone |
| Vertebral curvatures | - concave: cervical and lumbar - develop when baby starts to walk - convex: thoracic and sacral - present at birth - increase resilience of spine - |
| Anterior longitudinal ligament | - attaches to bony vertebrae and intervertebral discs - prevents hyperextension |
| Posterior longitudinal ligament | - narrow and relatively weak - attaches to intervertebral discs |
| Nucleus pulposus | - gelatinous inner sphere of intervertebral disc - absorbs compressive stresses |
| Annulus fibrosus | - outer rings formed of ligament - inner rings formed of fibrocartilage - contain the nucleus pulposus |
| General structure of vertebrae | - body - vertebral arch - vertebral foramen - spinous process - transverse process - superior articular process - inferior articular process - intervertebral foramina |
| Atlas | - first cervical vertebrae - lacks body and spinous process - superior articular facets receive occipital condyles, supports skull - allows flexion and extension of neck |
| Axis | - has body and spinous process - second cervical vertebrae |
| Dens (odontoid process) | - formed from fusion of the body of atlas with the axis - acts as pivot for rotation of axis and skull - participates in rotating head from side to side |
| Vertebrae C3-C7 | - body: small and wide laterally - short & bifid spinous process extends posteriorly (except C7) - vertebral foramen: triangular and large - transverse processes have foramina |
| Thoracic vertebrae | - all articulate with ribs - body: larger than cervical bodies - spinous processes: long and point inferiorly - vertebral foramen are circular |
| Costal facets | - inferior, superior - transverse (except T11-T12) - present on both sides of vertebrae - head of rib attached to inferior costal facet of superior vertebra and superior costal facet of inferior vertebra |
| Connections between thoracic and vertebral bodies | - laterally, each side of vertebral body has 2 facets (demifacets) - demifacets interface with vertebral bodies above and below - superior articular facets point posteriorly - inferior articular processes point anteriorly |
| Thoracic cage | - forms framework of the chest - protects thoracic organs - supports shoulder girdle and upper limbs - 3 components: thoracic vertebrae (posteriorly), ribs (laterally), sternum & costal cartilage (anteriorly) |
| Manubrium | - superior section of sternum - articulates with medial end of clavicles |
| Body | - bulk of sternum - sides are notched at articulations for costal cartilage of ribs 2-7 |
| Xiphoid process | - inferior end of sternum - ossifies around age 40 |
| Jugular notch | - central indentation of superior border of manubrium |
| Sternal angle | - horizontal ridge where manubrium joins the body |
| Xiphisternal joint | - where sternal body and xiphoid process fuse - lies at level of T9 |
| Rib pairs 1-7 | - vertebrosternal ribs - superior 7 pairs of ribs which attach to sternum by costal cartilage |
| Rib pairs 8-10 | - vertebrochondral ribs - airs of ribs which attach to sternum indirectly |
| Rib pairs 11-12 | - floating ribs - are not attached to sternum |
| Lumbar vertebrae | - thick & robust bodies - thin & tapered transverse processes - spinous processes are thick, blunt, point posteriorly - triangular vertebral foramina |
| Sacrum | - shapes posterior wall of pelvis - formed from 5 fused vertebrae - superior surface articulates with L5 - inferiorly articulates with coccyx |
| Sacral promontory | - where the anterosuperior margin of first sacral vertebrae bulges into pelvic cavity - human body's center of gravity is 1 cm posterior to sacral promontory |
| Sacrum: anterior view | - sacral promontory - four transverse ridges cross anterior surface of the sacrum, marking the lines of fusion of sacral vertebrae - anterior sacral foramina transmit ventral divisions of sacral spinal nerves |
| Sacrum: posterior view | - median sacral crest: represents fused spinal processes of sacral vertebrae - posterior sacral foramina: transmit dorsal rami of sacral spinal nerves - lateral sacral crest - ala: develop from fused rib elements |
| Sacral foramina | - ventral foramina: passage for ventral rami of sacral spinal nerves - dorsal foramina: passage of dorsal rami of sacral spinal nerves |
| Coccyx | - tailbone - 3-5 fused vertebrae - offers only slight support to pelvic organs |
| Cleft palate | - common congenital disorder - right and left halves of palate fail to fuse medially |
| Stenosis of lumbar spine | - narrowing of the vertebral canal - can compress roots of spinal nerves |
| Abnormal spinal curvatures | - Scoliosis: abnormal spinal curvature - Kyphosis: exaggerated thoracic curvature - Lordosis: accentuated lumbar curvature |
| Axial skeleton throughout life | - flat membrane bones begin to ossify in 2nd month of development - bone tissue grows outward from ossification centers - at birth, skull bones are separated by still-unossified remnants of membranes |
| Fontanelles | - still-unossified remnants of membranes at birth - anterior, posterior, mastoid, sphenoidal - allows skull to be safely compressed & molded as infant passes thru birth canal - usually replaced about a year after birth |
Created by:
peckman12
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