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Skeletal System
Chapter 7
Introduction
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Skeletal tissues form bones – the organs of the
skeletal system
The adult skeleton is composed of 206
separate bones
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Axial Skeleton
Divisions of Skeleton
A.
Axial skeleton – the 80 bones of the head,
neck, and torso; composed of 74 bones that
form the upright axis of the body and six tiny
middle ear bones

Appendicular Skeleton
Divisions of Skeleton (Figure 8-1;
A.
Appendicular skeleton – the 126 bones that
form the appendages to the axial skeleton;
the upper and lower extremities
A.
Skull – made up of 28 bones in two major
divisions: cranial bones and facial bones
(Figures 8-2 to 8-7; Table 8-3)
Cranial bones
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Frontal bone (Figure 8-8, C)
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Forms the forehead and anterior part of the top of the cranium
Contains the frontal sinuses
Forms the upper portion of the orbits
Forms the coronal suture with the two parietal bones
Cranial Bones
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Parietal bones (Figure 8-8, A)
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Form the bulging top of the cranium
Form several sutures: lambdoidal suture
Cranial Bones
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Temporal bones (Figure 8-8, B)
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Form the lower sides of the cranium and part of the cranial
floor
Contain the inner and middle ears
Mastoiditis – inflammation of a sinus with in the temporal
bones
Cranial Bones
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Occipital bone (Figure
8-8, D)
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Forms the lower,
posterior part of the
skull
Forms immovable
joints with three other
cranial bones and a
movable joint with the
first cervical vertebra
Omit 3 and 4 on
outline
Cranial Bones
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Sphenoid bone (Figure
8-8, E)
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A bat – shaped bones
located in the central
portion of the cranial
floor.
Keystone of the
cranium
Contains the sphenoid
sinuses
Cranial Bones
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Ethmoid bone (Figure
8-8, F)
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A complicated,
irregular bone that lies
anterior to the
sphenoid and posterior
to the nasal bones
If damaged, infectious
materials can pass
form the nose to the
brain
Facial bones (Table 8-4)
Maxilla (upper jaw) Figure 8-8, H
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Two maxillae form the keystone of
the face (upper jaw)
Maxillae articulate with each other
and with nasal, zygomatic, inferior
concha, and palatine bones
Forms parts of the orbital floors,
roof of the mouth, and floor and
sidewalls of the nose
Contains maxillary sinuses
(paranasal sinuses)
Facial Bones
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Mandible (lowerjaw)
Figure 8-8, M
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Largest, strongest
bone of the face
Forms the only
movable joint of the
skull with the
temporal bone
Lower jaw
Facial Bones
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Zygomatic bone (Figure
8-8, I) (malar)
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Shapes the cheek and
forms the outer margin
of the orbit
Forms the zygomatic
arch with the
zygomatic process of
the temporal bones
Facial Bones
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Nasal bone (Figure 8-8,
L)
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Both nasal bones form
the upper part of the
bridge of the nose,
whereas cartilage
forms the lower part
Articulates with the
ethmoid, nasal
septum, frontal,
maxillae, and the other
nasal bone
Facial Bones
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Lacrimal bone (Figure
8-8, K)
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Paper – thin bone that
lies just posterior and
lateral to each nasal
bone
Forms the nasal cavity
and medial wall of the
orbit
Contains groove for the
nasolacrimal (tear) duct
Articulates with
maxilla, frontal, and
ethmoid bones
Facial Bones
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Palatine bone (Figure 88, J)
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Two bones form the
posterior part of the
hard palate
Vertical portion forms
the lateral wall of the
posterior part of each
nasal cavity
Artiuclates with the
maxillae and the
sphenoid bone
Facial Bones
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Inferior nasal conchae
(turbinates)
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Form lower edge
projecting into the
nasal cavity and form
the nasal meati
Articulate with
ethmoid, lacrimal,
maxillary, and palatine
bones
Facial Bones
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Vomer bone (Figure 88, G)
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Forms posterior
portion of the nasal
septum
Articulates with the
sphenoid, ethmoid,
palatine, and maxillae
Hyoid bone (Figure 8-12)
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U-shaped bone
located just above the
larynx and below the
maxillae
Suspended from the
styloid processes of
the temporal bone
Only bone in the
body that articulates
with no other bones
Vertebral column (figure 8-13)
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Forms the flexible
longitudinal axis of the
skeleton
Consists of 24
vertebrae plus the
sacrum and coccyx
Vertebral column (figure 8-13)
3.
Segments of the vertebral column: (superior
to inferior – upper to lower)
Segments of the vertebral column
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Cervical vertebrae, 7
(skeletal framework of
the neck
Segments of the vertebral column
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Thoracic vertebrae, 12
Segments of the vertebral column
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Lumbar vertebrae, 5
Segments of the vertebral column
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Sacrum – in the adult,
results from the fusion
of five separate
vertebrae
Coccyx – in the adult,
results from the fusion
of four or five separate
vertebrae
Characteristics of the vertebrae
(Figures 8-14; Table 8-6)
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All vertebrae, except the first, have a flat, rounded
body anteriorly and centrally, a spinous process
posteriorly and two transverse processes laterally
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All but the sacrum and coccyx have a
vertebral foramen
Second cerival vertebrae has an upward
projection, the dens to allow rotation of the
head
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Seventh cerical vertebra has a long blunt
spinous process
Each thoracic vertebra has articulated facets
for the ribs
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Vertebral column as a whole
articulated with the head, ribs, and
iliac bones
Individual vertebrae articulate with
each other in joints between their
bodies and between their articular
processes
Sternum (Figure 8-15)
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Dagger – shaped bone in
the middle of the anterior
chest wall made up of
three parts
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Manubrium – the upper
handle part (most
superior part
Body – Middle blade part
Xiphoid process – blunt
cartilaninous lower tip
which ossifies during
adult life
Sternum (Figure 8-15)
1.
2.
Manubrium articulates with the clavicle
and first rib
Next nine ribs join the body of the sternum
either directly or indirectly by means of the
costal cartilages
Ribs (Figure 8-15-8-16)
1.
Twelve pairs of ribs,
with the vertebral
columns and sternum,
form
the thorax
Ribs (Figure 8-15-8-16)
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Ribs 2 through 9
articulate with the
body of the vertebra
above
From its vertebral
attachment, each rib
curves outward, then
forward and downward
Ribs (figure 8-15 and 8-16) – Thoracic
cage
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Rib attachment to the
sternum:
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Ribs 1 through 7 join a
costal cartilage that
attaches it to the sternum
(True ribs))
Costal cartilage of ribs 8
through 10 joins the
cartilage of the rib above to
be indirectly attached to the
sternum

Ribs 11 and 12 are
floating ribs, since they
do not attach even
indirectly to the
sternum
Appendicular Skeleton
Upper extremity (Table 8-7)
1.
Consists of the bones
of the shoulder girdle,
upper arm, lower arm,
wrist, and hand
Appendicular Skeleton
Upper extremity (Table 8-7)
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Shoulder girdle (figure
8-17)
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Made up of the scapula
and clavicle
Clavicle forms the only
bony joint with the
trunk, the sternoclaviclar
joint
At its distal end, the
clavicle articulates with
the acromion process of
the scapula
Appendicular Skeleton
Upper extremity (Table 8-7)
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Humerus (Figures 818) and 8-19)
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the long bone of the
upper arm
Appendicular Skeleton
Upper extremity (Table 8-7)
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Ulna
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The long bone found on
the little finger side of
the forearm
Articulates proximally
with the humerus and
radius and distally with a
fibrocartilaginous disk
Appendicular Skeleton
Upper extremity (Table 8-7)
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Radius
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The long bone found on
the thumb side of the
forearm
Articulates proximally
with the capitulum of the
humerus and the radial
notch of the ulna;
articulates distally with
the scaphoid and lunate
carpals and with the head
of the ulna
Appendicular Skeleton
Upper extremity
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Carpal bone (Figure 8-20)
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Eight small bones that form the
wrist
Carpals are bound closely and
firmly by ligaments and form
two rows of four carpals each
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Proximal row is made up of
the pisiform, triquetrum,
lunate, and scaphoid
Distal row is made up of the
hamate, capitate, trapezoids,
and trapezium
Appendicular Skeleton
Upper extremity
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Metacarpal bones
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Form the framework of
the hand
The thumb metacarpal
forms the most freely
movable joint with the
carpals (Makes us
different from other
animals)
Heads of the metacarpals
(the knuckles) articulate
with the phalanges
Lower Extremity
1.
Consists of the bones
of the hip, thigh, lower
leg, ankle, and foot
(Table 8-8)
Lower Extremity
1.
Pelvic girdle is made
up of the sacrum and
the two coxal bones
bound tightly by
strong ligaments
(figure 8-21)
Lower Extremity
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A stable circular base
that supports the trunk
and attaches the lower
extremities to it
Lower Extremity
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Each coxal bone is
made up of three bones
that fuse together
(figure 8-22)
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Ilium – largest and
uppermost
Lower Extremity
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Ischium – strongest
and lowermost
Pubis - anteriormost
Lower Extremity
1.
Femur – Longest and
heaviest bone in the
body (figure 8-23)
Lower Extremity
4. Patella – largest
sesamoid bone in the
body (knee)
Lower Extremity
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Tibia
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The larger, stronger,
and more medially and
superficially located of
the two leg bones
Articulates proximally
with the femur to form
the knee joint
Articulates distally with
the fibula and talus
Lower Extremity
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Fibula
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The smaller, more
laterally and deeply
placed of the two leg
bones
Articulates with the
tibia
Lower Extremity
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Foot (Figures 8-24 and
8-25)
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Structure is similar to
that of the hand with
adaptations for
supporting weight
Foot bones are held
together to form spring
arches
Figure 7.35a Arches of the foot.
Medial longitudinal arch
Transverse arch
Lateral longitudinal arch
Lateral aspect of right foot
© 2013 Pearson
Education, Inc.
Figure 7.35b Arches of the foot.
© 2013 Pearson
Education, Inc.
X ray, medial aspect of right foot
Skeletal differences
A.
Male skeleton is larger
and heavier than
female skeleton
Skeletal differences
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Male pelvis –
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deep and funnel
shaped with a narrow
pubic arch
Less than 90% angle
Males is more narrow
than female
Skeletal differences
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Female pelvis –
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shallow, broad, and
flaring with a wider
pubic arch
During childbirth, the
baby passes through an
imaginary plane called
the pelvic outlet
Iliac crest is more flared
in females than in males
Cycle of Life
A.
Changes in the skeletal framework
result from changes in bone, cartilage,
and muscle tissue
Cycle of Life
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Older adults
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Loss of bone
density
 prone to
fractures
Life Cycle
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Loss of skeletal
tissue density
 Compression of
weight – bearing
bones
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Loss of height
Postural changes
Abnormal Spinal Curvatures
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Kyphosis – a hunch
back appearance
Abnormal Spinal Cruatures
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Scholiosis is a lateral
curvature of the spine
Abnormal Spinal Curvatures
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Loss of motion – called false
motion
Pain
Deformity
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Degenerative of skeletal muscle tissue
 Loss of height
 Postural changes