Chapter 7
The Skeletal System:The Axial Skeleton
Axial Skeleton
80 bones
lie along longitudinal axis
skull, hyoid, vertebrae, ribs, sternum, ear ossicles
Appendicular Skeleton
126 bones
upper & lower limbs and pelvic & pectoral girdles
Types of Bones
5 basic types of bones:
long = compact
short = spongy except surface
flat = plates of compact enclosing spongy
irregular = variable
sesamoid = develop in tendons or
ligaments (patella)
Sutural bones = in joint between
skull bones
Bone Surface Markings
Surface features-- rough area, groove, openings, process
Specific functions
passageway for blood vessels and nerves
joint formation
muscle attachment & contraction
Bone Surface Markings
from Table 7.2
Foramen = opening
Fossa = shallow depression
Sulcus = groove
Meatus = tubelike
passageway or canal
Condyle = large, round
protuberance
Facet = smooth flat articular
surface
Trochanter = very large projection
Tuberosity = large, rounded,
roughened projection
Learning the terms found in this Table will simplify your
study of the skeleton.
The Skull
8 Cranial bones
protect brain & house ear ossicles
muscle attachment for jaw, neck & facial muscles
14 Facial bones
protect delicate sense organs -- smell, taste, vision
support entrances to digestive and respiratory systems
The 8 Cranial Bones
Frontal
Parietal (2)
Temporal (2)
Occipital
Frontal Bone
Forehead, roof of orbits,
& anterior cranial floor
Frontal suture gone by age 6 (metopic
suture)
Supraorbital margin and frontal
sinus
Parietal & Temporal Bones
Parietal
sides & roof of
cranial cavity
Temporal
temporal squama
zygomatic process
forms part of arch
external auditory meatus
mastoid process
styloid process
stylomastoid foramen(VII)
mandibular fossa
(TMJ)
petrous portion (VIII)
Temporal and Occipital bones
Temporal
carotid foramen
(carotid artery)
jugular foramen
(jugular vein)
Occipital
foramen magnum
occipital condyles
external occipital protuberance attachment for ligamentum nuchae
superior & inferior nuchal
lines
Sphenoid bone
Base of skull
Pterygoid processes are attachment
sites for jaw muscles
Sphenoid in Anterior View
Body is a cubelike portion holding
sphenoid sinuses
Greater and lesser wings
Pterygoid processes
Sphenoid from
Lesser wing & greater wing
Sella turcica
holds pituitary gland
Optic foramen
Ethmoid Bone
Cranial floor, lateral nasal walls & nasal septum
Cribriform plate & olfactory
foramina
Crista galli
for attachment of membranes cover the brain
Ethmoid bone
Lateral masses contain ethmoid
sinuses
Perpendicular plate is upper part of nasal septum
Superior & middle nasal concha
or turbinates
filters & warms air
14 Facial Bones
Nasal (2) Maxillae (2) Zygomatic
(2)
Mandible (1) Lacrimal
(2)
Inferior nasal conchae (2) Vomer (1)
Maxillary bones
Floor of orbit, floor of nasal cavity or hard palate
Maxillary sinus
Alveolar processes hold upper teeth
Cleft palate is lack of union of maxillary bones
Zygomatic Bones
Cheekbones
Lateral wall of orbit along with sphenoid
Part of zygomatic arch along with
part of temporal
Lacrimal and Inferior Nasal Conchae
Lacrimal bones
part of medial wall of orbit
lacrimal fossa
houses lacrimal sac
Inferior nasal concha or turbinate
(not part of ethmoid)
Palatine & Vomer
L-shaped : one end is back part of hard palate, other end is
part of orbit (see previous picture)
Vomer
posterior part of nasal septum
Mandible
Body, angle & rami
Condylar & coronoid
processes
Alveolar processes for lower teeth
Mandibular & mental foramen
Sutures
Lambdoid suture unites parietal
and occipital
Sagittal suture unites 2 parietal
bones
Sutures
Coronal suture unites frontal and both parietal bones
Squamous suture unites parietal
and temporal bones
Paranasal Sinuses
Paired cavities in ethmoid,
sphenoid, frontal and maxillary
Lined with mucous membranes and open into nasal cavity
Resonating chambers for voice, lighten the skull
Sinusitis is inflammation of the membrane (allergy)
Fontanels of the Skull at Birth.
Dense connective tissue membrane-filled spaces
(soft spots)
Unossified at birth but close
early in a child's life.
Fetal skull passes
through the birth
canal.
Rapid growth of the
brain during infancy
Bones of the Orbit
Roof is frontal and sphenoid
Lateral wall is zygomatic and
sphenoid
Floor is maxilla, zygomatic and
sphenoid
Medial wall is maxilla, lacrimal, ethmoid and sphenoid
Orbital fissures and optic foramen
Nasal Septum
Divides nasal cavity into left and right sides
Formed by vomer, perpendicular
plate of ethmoid and septal
cartilage
Deviated septum does not line in the midline
developmental abnormality or trauma
Hyoid Bone
U-shaped single bone
Articulates with no other bone of the body
Suspended by ligament and muscle from skull
Supports the tongue & provides attachment for tongue,
neck and pharyngeal muscles
Vertebral Column
Backbone or spine built of 26 vertebrae
Five vertebral regions
cervical vertebrae (7)
in the neck
thoracic vertebrae ( 12 ) in the thorax
lumbar vertebrae ( 5 ) in the low back region
sacrum (5, fused)
coccyx (4, fused)
Intervertebral Discs
Between adjacent vertebrae absorbs vertical shock
Permit various movements of the vertebral column
Fibrocartilagenous ring with a
pulpy center
Normal Curves of the Vertebral Column
Typical Vertebrae
Body
weight bearing
Vertebral arch
pedicles
laminae
Vertebral foramen
Seven processes
2 transverse
1 spinous
4 articular
Vertebral notches
Intervertebral Foramen &
Spinal Canal
Spinal canal is all vertebral foramen together
Intervertebral foramen are 2
vertebral notches together
Typical Cervical Vertebrae (C3-C7)
Smaller bodies
Larger spinal canal
Transverse processes
shorter
transverse foramen for vertebral artery
1st and 2nd cervical vertebrae are unique
atlas & axis
Atlas & Axis (C1-C2)
Atlas -- ring of bone, superior facets for occipital condyles
nodding movement at atlanto-occipital
joint signifies “yes”
Axis -- dens or odontoid process
is body of atlas
pivotal movement at atlanto-axial joint signifies “no”
Thoracic Vertebrae
(T1-T12)
Larger and stronger bodies
Longer transverse & spinous
processes
Facets or demifacets on body for
head of rib
Facets on transverse processes (T1-T10) for tubercle of rib
Lumbar Vertebrae
Strongest & largest
Short thick spinous &
transverse processes
back musculature
Sacrum
Union of 5 vertebrae (S1 - S5) by age 30
median sacral crest was spinous
processes
sacral ala is fused transverse processes
Sacral canal ends at sacral hiatus
Auricular surface & sacral tuberosity
of SI joint
Coccyx
Union of 4 vertebrae (Co1 - Co4) by age 30
Caudal or epidural anesthesia during delivery
into sacral hiatus anesthetize sacral & coccygeal nerves
sacral and coccygeal cornu are important landmarks
Thorax
Bony cage flattened from front to back
Sternum (breastbone)
Ribs
1-7 are true ribs (vertebrosternal)
8-12 are false ribs (vertebrochondral)
11-12 are floating
Costal cartilages
Bodies of the thoracic vertebrae.
Sternum
Manubrium
1st & 2nd ribs
clavicular notch
Body
costal cartilages of 2-10 ribs
Xiphoid
ossifies by 40
CPR position
abdominal mm.
Sternal puncture
biopsy
Ribs
Increase in length from ribs 1-7, thereafter decreasing
Head and tubercle articulate with facets
Body with costal groove containing nerve & blood vessels
Intercostal spaces contain intercostal muscles
Rib Articulation
Tubercle articulates with transverse process
Head articulates with vertebral bodies
Herniated (Slipped)
Disc
Protrusion of the nucleus pulposus
Most commonly in lumbar region
Pressure on spinal nerves causes pain
Surgical removal
of disc after laminectomy
Clinical Problems
Abnornal curves of the spine.
scoliosis (lateral bending of the column)
kyphosis (exaggerated thoracic
curve)
lordosis (exaggerated lumbar
curve)
Spina
bifida is a congenital defect
failure of the vertebral laminae
to unite
nervous tissue is unprotected
paralysis