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Skeletal system: Axial
Type of bones
humerus
• Long
Bones that are longer than wide
Humerus, femur
• Short
carpals
Cube shaped, wide as tall
Carpals (wrist)
• Flat
Smooth, thin bones
Some cranial, parietal
• Irregular
No distinct shape
Vertebrae
parietal
• Sutural
Bones found between the bones of the
skull, within the sutures.
Sometimes absent.
• Sesamoid
Found within tendons; act to re-enforce the
tendon.
– Patella
Knee cap; within the tendon of the
quadriceps.
Surface markings
• Condyle
A smooth surface, usually found at either epiphysis,
which articulates with another bone
• Epicondyle
A large prominence near a condyle; muscle attachment
• Crest
A prominent ridge on a bone; muscle attachment, illiac crest
• Head
A large rounded condyle; head of the femur
• Line
A thin ridge on a bone; muscle attachment, linea aspera
• Ramus
A large bony extension from the body of a bone;
mandibular ramus
• Spine
A thin bony extension from the body of a bone
• Trochanter
A large prominence on the femur; muscle attachment
• Fissure
A slit-like opening; vessels and nerves pass through
• Foramen (foramina, pl.)
A circular opening; vessels and nerves pass
• Fossa
A shallow depression; muscle attachment
• Meatus
A tube-like opening through a bone; vessels and nerves
pass through
• Sinus
A cavity within a bone; frontal sinuses
• Sulcus
A shallow groove on the surface of a bone
Divisions of the
skeletal system
• appendicular skeleton
– 126 bones
– appendages and girdles
•
80 bones
•
skull
•
hyoid
•
vertebral column
•
thorax
•
auditory ossicles
Axial
•
Skull
– 22 bones in 2 regions
– 8 Cranial bones
– 14 facial bones
Frontal
• frontal squama
Smooth, flat area; anterior surface
• frontal sinuses
Cavity within the frontal bone
• supraorbital foramen
Hole above the orbit
Parietal-2
• sagittal suture
The joint between the two parietal bones
Temporal-2
• zygomatic process (zygomatic arch)
This process forms the posterior part of the zygomatic arch
• petrous portion
Large wedge-like mass on the medial side of the temporal
bone; contains the middle and inner ear
• external auditory meatus
The external ear canal;
Occipital
• foramen magnum
“large hole” passing through the occipital bone; brain stem and spinal cord passes
through.
• occipital condyles
Smooth points of articulation on the inf. surface of the bone; articulates with the first
cervical vertebra.
Sphenoid
• sella turica
“Turk’s saddle”; pituitary gland
sits here.
Also, called the hypophyseal
fossa
• optic foramen
Hole through which the optic nerve passes.
Ethmoid
• cribriform plate
A horizontal shelf of bone filled with tiny holes
called the olfactory foramina; allows the olfactory
nerves to pass through.
• superior nasal concha
A bump-like extension of bone within the
nasal cavity; causes air turbulence and slows
air flow during breathing.
14 Facial bones
Nasal-2
Maxillae-2
• alveolar process
An extension of bone containing alveoli;
holes or sockets for teeth.
Zygomatic-2
• temporal process
The process forming the anterior part of the zygomatic
arch.
!
• zygomatic arch
Two parts: "
"
"
temporal process of the zygomatic bone
zygomatic process of the temporal bone
Mandible
• condylar process
The process holding the mandibular condyles.
• coronoid process
One of two coronoid processes in
the body; muscle attachment site.
Lacrimal-2
Part of the orbit of the eye; medial;
Contains the nasolacrimal duct
Palatine-2
Post. to the maxilla; part of the hard palette
Inferior nasal conchae-2
Similar to sup nasal concha. More inf in the nasal
cavity.
vomer
Forms part of the nasal septum.
Sutures
• Coronal
Between the frontal and two parietal bones.
• Lamboidal
Between the two parietal bones and the
occipital bone.
• Squamosal
Between the parietal and the temporal bone.
Fontanels
CT found between the developing cranial bones in the fetus.
Allows increase in cranial volume as the brain grows during
development.
Hyoid
The only bone in the body that does not articulate (forms
a joint) with another bone.
Anchors some of the muscle of the tongue, amongst
others.
Vertebral column
•
•
•
•
•
•
approx. 30 vertebrae
cervical-7
throacic-12
lumbar-5
sacral-5
coccygeal-3 to 5
Intervertebral discs
A cushion between the vertebrae
• annulus fibrosus
A donut shaped ring of fibrous cartilage; acts as a
tough outer cover for the discs.
• nucleus pulposus
A jelly-like inner pulp; acts as a cushion for the disc.
• Intervertebral foramina
A space between each vertebra through which
the spinal nerves pass.
A ruptured disc occurs when the outer annuls
breaks open, allowing the pulposus to bulge out.
A dislocated disc occurs when the entire disc
shifts sideways .
Curves
The vertebral column is not straight.
The curves give the column a
“springiness”, which allows it to absorb
compressive forces without damage.
Curves are cervical, thoracic, lumber and
sacral.
Typical structure of vertebrae
• Body
The thick, cylindrical part of the vertebra; lies
in-between the vertebral discs.
• vertebral (neural) arch
An arch of bone which encloses the vertebral foramen; made of
the pedicles and the laminae
• Pedicles
The base of the arch; attaches to the
body.
• Laminae
Top part of the arch; joins it’s mate
on the other side.
• vertebral foramen
The space formed by the neural arch; the foramen of the other vertebrae, stacked on
top of each other forms the spinal cavity.
processes
• Spinous
The process that projects posteriorly. One. Muscle and ligament attachment.
• Transverse
Projects laterally. Two.
Muscle and ligament
attachment.
• superior articular!
Projects superiorly; contains a articular facet; articulates with the vertebra just superior
to it. Two
• inferior articular!
Projects inferiorly; contains an articular facet; articulates with the vertebra just inferior
to it.
Cervical 7
There are seven cervical vertebrae in the cervical (neck) region
• small body
The body is reduced in size in all these vertebrae
• bifid spinous process (exp. C7)
The spinous process is bifid, is split into two parts.
• transverse foramina
This is the identifying feature of the cervical
vertebrae.
All these vertebrae have a foramen passing
through the transverse process.
Allows the vertebral vessels to pass up and
down the neck.
Atlas C1!
The first cervical vertebra.
Articulates with the occipital bone above and the axis (C2) below.
• superior articular facets
The point of contact between the atlas and the occipital bone.
Allows you to nod your head: flexion and extension.
Axis C2
Articulates with C1 above and the C3 below.
• dens (odontoid process)
A peg-like process about which the atlas ( and the head) rotates.
Allows you to shake your head.
Thoracic 12
Located within the thoracic region.
12 vertebrae with associated ribs.
long spinous process
rib facets on body
Attachment points for the ribs.
Identifying feature.
no transverse foramina
Intact transverse process.
Lumbar 5
Located in the lumbar region: 5 large, heavy vertebrae.
• no rib facets
• spinous process heavy
Sacrum (5)
Consists of 5 fused vertebrae, which
produces the features seen on the surface.
sacral canal
A bony channel formed by the fusion
of the vertebral foramen of each
sacral vertebrae.
auricular surface
Articulation areas on either side of the sacrum that joins with the pelvic bones.
Coccyx (3-5)
Tail bone; sometimes fused
Thorax
Sternum
Breast bone; anterior structure on the rib cage and anchors the ribs via
costal cartilage. Three parts.
manubrium!
Most superior part: clavicles attach here.
Body
Middle structure.
xiphoid process
Most inferior structure structure. Sometimes not calcified.
Ribs 12 pair
Posterior end attach to the thoracic vertebrae and the sternum
on the anterior end.
costal cartilage
The ribs do not attach directly, but through costal cartilage.
true ribs 1-7
Each rib attaches through its own cartilage.
false ribs 8-10
Costal cartilage for these ribs is fused and attached to the 7th
rib.
floating ribs 11, 12
No costal cartilage for these ribs.