Skeletal System:Skeletal System:The Axial The Axial SkeletonSkeleton

SkullSkullVertebral ColumnVertebral Column

RibsRibsSternumSternum

The SkullThe Skull 22 separate bones, 22 separate bones,

many fused many fused togethertogether

Two divisions:Two divisions: Cranial Bones (8 Cranial Bones (8

bones)bones) Facial Bones (14 Facial Bones (14

bones)bones)

Bones of the CraniumBones of the Cranium Enclose and Enclose and

protect the brainprotect the brain Bones:Bones:

Frontal (1)Frontal (1) Parietal (2)Parietal (2) Temporal (2)Temporal (2) Occipital (1)Occipital (1) Sphenoid (1)Sphenoid (1) Ethmoid (1)Ethmoid (1)

Sphenoid bone

Ethmoidbone

Ethmoid and Sphenoid Ethmoid and Sphenoid BonesBones

Ethmoid BoneEthmoid Bone: anterior : anterior part of the cranium basepart of the cranium base Forms the floor of the craniumForms the floor of the cranium Makes up the medial wall of Makes up the medial wall of

the orbits (eye sockets)the orbits (eye sockets) The major supporting The major supporting

structure for the nasal cavitystructure for the nasal cavity Sphenoid BoneSphenoid Bone: medial : medial

base of the skullbase of the skull Connects the frontal, Connects the frontal,

temporal, and parietal bonestemporal, and parietal bones Sella Turcica: a “saddle” for Sella Turcica: a “saddle” for

the pituitary gland in the brainthe pituitary gland in the brain

Sutures in the SkullSutures in the Skull Suture:Suture: An immovable An immovable

joint found only in the joint found only in the skull bonesskull bones Coronal SutureCoronal Suture: between : between

the frontal and two parietalsthe frontal and two parietals Sagittal Suture:Sagittal Suture: between between

the two parietalsthe two parietals Lambdoid Suture:Lambdoid Suture:

between the two parietals between the two parietals and the occipitaland the occipital

Squamous SuturesSquamous Sutures: : between the parietals and between the parietals and temporal bonestemporal bones

FontanelsFontanels Membrane-filled spaces Membrane-filled spaces

found between cranium found between cranium bones in infantsbones in infants

““Soft Spots”Soft Spots” Eventually become ossified Eventually become ossified

(replaced by bone)(replaced by bone) Allow for:Allow for:

The babies skull to The babies skull to compress, thus allowing compress, thus allowing childbirthchildbirth

The brain to grow before the The brain to grow before the skull is completely fusedskull is completely fused

Facial BonesFacial Bones Your face grows the most in Your face grows the most in

the first two years; then the first two years; then stops by the age of 16.stops by the age of 16. Nasal BonesNasal Bones MaxillaeMaxillae: form the lower orbit : form the lower orbit

and upper jawand upper jaw Zygomatic BonesZygomatic Bones: cheekbones: cheekbones MandibleMandible: lower jawbone: lower jawbone Lacrimal Bones:Lacrimal Bones: smallest smallest

bones in the face; have a bones in the face; have a foramen for the tear duct to foramen for the tear duct to passpass

Palatine BonesPalatine Bones: form the : form the hard palate in the roof of the hard palate in the roof of the mouthmouth

Hyoid BoneHyoid Bone A U-shaped bone A U-shaped bone

located in the neck located in the neck between the between the mandible and the mandible and the larynx (voicebox) larynx (voicebox)

Does not articulate Does not articulate with any other bonewith any other bone

Supports the tongueSupports the tongue Provides attachment Provides attachment

for muscles to allow for muscles to allow for neck movement for neck movement and swallowingand swallowing

Vertebral ColumnVertebral Column Protects the Spinal CordProtects the Spinal Cord Allows the major nerves Allows the major nerves

to enter and exit the to enter and exit the spinal cordspinal cord

Usually 33 BonesUsually 33 Bones 7 Cervical7 Cervical 12 Thoracic12 Thoracic 5 Lumbar5 Lumbar 5 Sacral (fused to form 5 Sacral (fused to form

the sacrum)the sacrum) 4 Coccygeal (fuse to form 4 Coccygeal (fuse to form

one or two fused = one or two fused = coccyx)coccyx)

Typical VertebraTypical Vertebra Body: Body: the thick weight the thick weight

bearing portionbearing portion Vertebral foramenVertebral foramen: the : the

hole that holds the spinal hole that holds the spinal cord cord

Spinous ProcessSpinous Process: a single : a single projection for muscle projection for muscle attachmentattachment

Transverse ProcessTransverse Process: two : two lateral projections for lateral projections for muscle attachmentmuscle attachment

Articular ProcessesArticular Processes: the : the facets that allow the facets that allow the vertebrae to move with the vertebrae to move with the vertebrae superior and vertebrae superior and inferior to theminferior to them

Atlas and AxisAtlas and Axis Atlas (C1):Atlas (C1): supports supports

the headthe head Articulates with the Articulates with the

occipital condyles of occipital condyles of the skull (nod your the skull (nod your head “yes”)head “yes”)

Axis (C2): Axis (C2): The The “peglike” dens makes “peglike” dens makes a pivot for the head a pivot for the head to rotate (move your to rotate (move your head “no”)head “no”)

Sacrum and CoccyxSacrum and Coccyx SacrumSacrum (holy bone): (holy bone):

5 fused vertebrae5 fused vertebrae Usually starts to fuse Usually starts to fuse

at age 16-18 and end at age 16-18 and end in mid 20s)in mid 20s)

Provides a foundation Provides a foundation for the pelvis and for the pelvis and allows nerves to passallows nerves to pass

Coccyx: Coccyx: Usually 4 Usually 4 vertebrae that fusevertebrae that fuse Fusion occurs Fusion occurs

between 20-30 years between 20-30 years of ageof age

Epidural AnesthesiaEpidural Anesthesia

Numbing medicine is delivered near the spinal cordthrough the sacrum

SternumSternum Aka: BreastboneAka: Breastbone Three separate Three separate

bones:bones: ManubriumManubrium BodyBody Xiphoid ProcessXiphoid Process

Articulates with the Articulates with the ribs, provides ribs, provides attachment point for attachment point for some abdominal some abdominal muscles, hemopoiesismuscles, hemopoiesis

Fuses in late teens; Fuses in late teens; completely by age completely by age 40.40.

RibsRibs 12 pairs (24 total)12 pairs (24 total) True RibsTrue Ribs: pairs 1-7 : pairs 1-7

directly attach to the directly attach to the sternum by costal sternum by costal cartilagecartilage

False Ribs:False Ribs: pairs 8- pairs 8-12, their cartilage 12, their cartilage attaches to the 7attaches to the 7thth rib cartilagerib cartilage

Floating RibsFloating Ribs: pairs : pairs 11-12; don’t attach 11-12; don’t attach to the sternumto the sternum