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Skeletal System
Axial Skeleton
Axial Skeleton
Includes 80 bones of the skull, vertebral
column and bony thorax
 Functions:

– Supports head, neck & trunk
– Protects brain, spinal cord and thoracic
organs
Skull
Composed of flat bones
 Function:

– Used for attachment of head muscles &
protects the brain
Sutures of the Skull

Sutures: interlocking joints that unite
skull bones
– Coronal: where parietal bones meet frontal
– Sagittal: where 2parietal bones meet
superiorly
– Squamos: where parietal and temporal
bones meet on lateral aspects of skull
– Lambdoidal: where parietal bones meet
occipital bones meet posteriorly
Vertebral Column aka the Spine
Location: runs from the base of the
skull to the coccyx (tailbone)
 Function:

– Surrounds and protects the spinal cord
– Provides attachment sites for ribs and back
muscles
Vertebral Column

Characteristics
– 26 interconnected
irregular bones
– Provides a flexible,
curved structure
– Serves as axial
support of the trunk
Vertebral Column

Curvatures of the Spine:
–
–
–
–

S-shaped to prevent shock to head in motion
Allows for trunk flexibility
Increases resiliency & flexibility of the spine
Functions like a spring, not a rod
Cervical & Lumbar Curves: concave
posteriorly
 Thoracic & Sacral Curves: convex
posteriorly
Curvatures of the Spine
Abnormal Curvatures of the
Vertebral Column

Lordosis: aka
sway back
– An accentuated
lumbar curve

Kyphosis: aka
hunchback
– An exaggerated
thoracic curve

Scoliosis: the
twisted disease
– An abnormal lateral
curvature in the
thoracic region
– Typical in girls in late
childhood
Lordosis & Kyphosis
Scoliosis
Cervical Vertebrae

7 total extending from base of skull to ~
shoulder line
 Numbered C1-C7
 Smallest & lightest vertebrae
 Unique vertebrae
– Atlas or C1: no body; holds the occipital bone,
allows nodding motion (“yes”)
– Axis or C2: acts as a pivot for rotation; shake
head (“no”)
Thoracic Vertebrae
12 total; runs through mid-back
 Numbered T1-T12
 Larger than cervical
 Longer, palpable spinous processes
 Ribs attach here posteriorly

Lumbar Vertebrae

5 total
 Numbered L1-L5
 Huge bodies and
short spinous
processes
 Holds most of body
weight & stress; very
sturdy
Sacrum &
Coccyx

Sacrum
– Formed from 5 fused
vertebrae
– Numbered S1-S5
– Makes up posterior
wall of pelvis
– Strengthens &
stabilizes pelvis

Coccyx
– 4 fused vertebrae
Ligaments of the Spine

There are several; only 2 you need to
know
– Anterior Longitudinal Ligament: resists
back hyperextension
– Posterior Longitudinal Ligament: resists
back flexion
Intervertebral Discs
Cushion-like pads between vertebrae
 Asts as shock absorbers during motion
 Makes up ~25% of length of column
 Flattens during the day

Intervertebral Discs
Ribs




Flat bones
12 total pairs
Attach posteriorly to thoracic spine
Function:
– Protect thoracic organs

True Ribs: the superior 7 pairs
– Attach directly to sternum by costal cartilage

False Ribs: the inferior 5
– 8-10: join each other by cartilage and indirectly attach to
sternum
– 11& 12: the floating ribs, no anaterior attachment
Rib Cage
Pelvis
Has 2 regions: true and false pelvises
 False pelvis superior to true pelvis
 True pelvis dimensions are a concern
to child-bearing women
 Pelvic structure differs between men
and women

Gender Difference of Pelvis

Men
– Narrow outlet
– Heavier & thicker bone
structure
– Ilia less flared, more
vertical
– Sacrum long and curved
– Ischia close together
– Less rounded pubic arch

Women
– Inlet circular & large
– Pelvis shallow, lighter &
thinner
– Ilia flare laterally
– Sacrum shorter & less
curved
– Ischia farther apart &
shorter
– Pubic arch is more
rounded
Female vs. Male Pelvis
Female vs. Male Skulls
FUNTION OF JOINTS
They hold bones together.
 Allow the rigid skeleton mobility

Joints are classified in 2 ways:
1. Functionally –amount of movement
2. Structurally – type of tissue
Functionally- amount of
movement
1. Synarthrosis- immovable
 Ex) sutures in skull

2. Amphiarthrosis- slightly movable
 Ex) intervertebral joints

3. diarthrosis-freely movable
 Ex) limbs

Structurally- tissue type between
bones
1) Fibrous- connected by fibrous tissue
 - sutures skull
 2) Cartilaginous- connected by cartilage
 -pubic symphysis
 3) Synovial- separated by a joint
containing fluid
 -6 types based on articulating bone
surface

Types of Synovial Joints
1. Plane Joint-wrist
 2. Hinge Joint- elbow
 3. Pivot Joint- ulna & radius
 4. Condyloid Joint- metacarpels
 5. Saddle Joint- thumb
 6. Ball & Socket- shoulder or hip

Stress Fracture of the Tibia
STAGES OF BONE REPAIR