Download Ch. 9 Skeletal System Notes

Anatomy & Physiology
Chapter 9: Skeletal System
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Introduction
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Skeletal tissues form bones—the
organs of the skeletal system
The relationship of bones to each
other and to other body structures
provides a basis for understanding the
function of other organ systems
The adult skeleton is composed of
206 separate bones
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Divisions of the Skeleton
(Figure 9-1; Table 9-1)
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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—the 126 bones
that form the appendages to the axial
skeleton; the upper and lower
extremities
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Axial Skeleton
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Skull—made up of 28 bones in two
major divisions: cranial bones and facial
bones (Figures 9-2 to 9-7; Table 9-3)
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Cranial bones
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Frontal bone (Figure 9-8, C)
 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
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Axial Skeleton
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Cranial bones (cont)
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Parietal bones (Figure 9-8, A)
 Form the bulging top of the cranium
 Form several sutures: lambdoid
suture with the occipital bone;
squamous suture with the temporal
bone and part of the sphenoid; and
coronal suture with the frontal bone
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Axial Skeleton
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Cranial bones (cont)
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Temporal bones (Figure 9-8, B)
Form the bulging top of the cranium
 Form several sutures: lambdoid suture with the
occipital bone; squamous suture with the
temporal bone and part of the sphenoid; and
coronal suture with the frontal bone
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Occipital bone (Figure 9-8, D)
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
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Axial Skeleton
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Cranial bones (cont)
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Sphenoid bone (Figure 9-8, E)
 A bat-shaped bone located in the
central portion of the cranial floor
 Anchors the frontal, parietal, occipital,
and ethmoid bones and forms part of
the lateral wall of the cranium and part
of the floor of each orbit (Figure 9-7)
 Contains the sphenoid sinuses
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Axial Skeleton
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Cranial bones (cont)
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Ethmoid bone (Figure 9-8, F)
 A complex, irregular bone that lies
anterior to the sphenoid and posterior
to the nasal bones
 Forms the anterior cranial floor, medial
orbit walls, upper parts of the nasal
septum, and sidewalls of the nasal
cavity
 The cribriform plate is located in the
ethmoid
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Axial Skeleton
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Skull (cont)
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Facial bones (Table 9-4)
 Maxilla (upper jaw) (Figure 9-8, H)
Two maxillae form the keystone of
the face
 Maxillae articulate with each other
and with the 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

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Axial Skeleton
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Facial bones (cont)
Mandible (lower jaw) (Figure 9-8, M)
 Largest, strongest bone of the face
 Forms the only movable joint of the
skull with the temporal bone
 Zygomatic bone (Figure 9-8, I)
 Shapes the cheek and forms the
outer margin of the orbit
 Forms the zygomatic arch with the
zygomatic process of the temporal
bones
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Axial Skeleton
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Facial bones (cont)
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Nasal bone (Figures 9-8, L and 9-10)
 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 bone, maxillae, and
the other nasal bone
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Axial Skeleton
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Facial bones (cont)
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Lacrimal bone (Figure 9-8, K)
 Paper-thin bone that lies just posterior
and lateral to each nasal bone
 Forms the nasal cavity and medial
wall of the orbit
 Contains a groove for the
nasolacrimal (tear) duct
 Articulates with the maxilla, frontal,
and ethmoid bones
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Axial Skeleton
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Facial bones (cont)
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Palatine bone (Figure 9-8, J)
 Two bones form the posterior part of
the hard palate
 Vertical portion forms the lateral wall
of the posterior part of each nasal
cavity
 Articulates with the maxillae and the
sphenoid bone
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Axial Skeleton
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Facial bones (cont)
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Inferior nasal conchae (turbinates)
 Form the lower edge projecting into the
nasal cavity and form the nasal meatus
 Articulate with ethmoid, lacrimal, maxillary,
and palatine bones
Vomer bone (Figure 9-8, G)
 Forms the posterior portion of the nasal
septum
 Articulates with the sphenoid, ethmoid,
palatine, and maxillae
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Axial Skeleton
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Eye orbits (Figure 9-7)
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Right and left eye orbits
 Contain eyes, associated eye
muscles, lacrimal apparatus,
blood vessels, and nerves
 Thin and fragile orbital walls
separate orbital structures from
the cranial and nasal cavities and
paranasal sinuses
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Axial Skeleton
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Fetal skull (Figure 9-11)
Characterized by unique anatomical
features not seen in adult skull
 Fontanels or “soft spots” (4) allow
the skull to “mold” during the birth
process and also allow for rapid
growth of the brain (Table 9-5)

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Axial Skeleton
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Fetal skull (cont)
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Permits differential growth or appearance of
skull components over time
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Face—smaller proportion of total cranium at
birth {1/8} than in adult {½}
Head at birth is {¼} the total height; at
maturity about {1/8} body height
Sutures appear with skeletal maturity (Table
9-5)
Paranasal sinuses—change in size and
placement with skeletal maturity (Figure 9-9)
Appearance of deciduous and, later,
permanent teeth
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Axial Skeleton
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Hyoid bone (Figure 9-12)
U-shaped bone located just above the
larynx and below the mandible
 Suspended from the styloid processes
of the temporal bone
 Only bone in the body that articulates
with no other bones

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Axial Skeleton
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Vertebral column (Figure 9-13)
Forms the flexible longitudinal axis
of the skeleton
 Consists of 24 vertebrae plus the
sacrum and coccyx

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Axial Skeleton
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Vertebral column (cont)
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Characteristics of the vertebrae (Figure 9-14; Table 9-6)
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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
All but the sacrum and coccyx have a vertebral foramen
Second cervical vertebrae has an upward projection, the
dens, to allow rotation of the head
Seventh cervical vertebra has a long, blunt spinous
process
Each thoracic vertebra has articular facets for the ribs
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Axial Skeleton
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Vertebral column (cont)
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

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Axial Skeleton
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Sternum (Figure 9-15)
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Dagger-shaped bone in the middle of the
anterior chest wall made up of three
parts:
 Manubrium—the upper handle part
 Body—middle blade part
 Xiphoid process—blunt cartilaginous
lower tip, which ossifies during adult
life
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Axial Skeleton
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Sternum (cont)
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
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Axial Skeleton
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Ribs (Figures 9-15 and 9-16)
Twelve pairs of ribs, with the vertebral
column and sternum, form the thorax
 Each rib articulates with the body and
transverse process of its corresponding
thoracic vertebra
 Ribs 2 through 9 articulate with the body of
the vertebra above
 From its vertebral attachment, each rib
curves outward, then forward and downward

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Axial Skeleton
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Ribs (cont)
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Rib attachment to the sternum:
 Ribs 1 through 8 join a costal
cartilage that attaches it to the
sternum
 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
because they do not attach even
indirectly to the sternum
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Appendicular Skeleton
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Upper extremity (Table 9-7)
Consists of the bones of the shoulder girdle,
upper and lower parts of the arm, wrist, and
hand
 Shoulder girdle (Figure 9-17)
 Made up of the scapula and clavicle
 Clavicle forms the only bony joint with
the trunk, the sternoclavicular joint
 At its distal end, the clavicle articulates
with the acromion process of the
scapula

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Appendicular Skeleton
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Upper extremity (cont)
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Humerus (Figures 9-18 and 9-19)
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The long bone of the upper part of the arm
Articulates proximally with the glenoid
fossa of the scapula and distally with the
radius and ulna
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
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Appendicular Skeleton
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Upper extremity (cont)
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Carpal bones (Figure 9-20)
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Eight small bones that form the wrist
Carpal bones are bound closely and firmly by
ligaments and form two rows of four carpals each
 Proximal row is made up of the pisiform,
triquetrum, lunate, and scaphoid
 Distal row is made up of the hamate, capitate,
trapezoid, and trapezium
The joints between the radius and carpal bones
allow wrist and hand movements
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Appendicular Skeleton
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Upper extremity (cont)
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Metacarpal bones
 Form the framework of the hand
 The thumb metacarpal forms the
most freely movable joint with the
carpal bones
 Heads of the metacarpal bones (the
knuckles) articulate with the
phalanges
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Appendicular Skeleton
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Lower extremity
Consists of the bones of the hip, thigh, leg,
ankle, and foot (Table 9-8)
 Pelvic girdle is made up of the sacrum and the
two coxal bones bound tightly by strong
ligaments (Figure 9-21)
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A stable circular base that supports the trunk
and attaches the lower extremities to it
Each coxal bone is made up of three bones that
fuse together (Figure 9-22):
 Ilium—largest and uppermost
 Ischium—strongest and lowermost
 Pubis—anterior most
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Appendicular Skeleton
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Lower extremity (cont)
Femur—longest and heaviest bone in the
body (Figure 9-23)
 Patella—largest sesamoid bone in the body
 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
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Appendicular Skeleton
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Lower extremity (cont)
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Fibula
 The smaller, more laterally and
deeply placed of the two leg
bones
 Articulates with the tibia
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Appendicular Skeleton
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Lower extremity (cont)
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Foot (Figures 9-24 and 9-25)
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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
 Medial longitudinal arch is made up of
the calcaneus, talus, navicular,
cuneiforms, and medial three metatarsal
bones
 Lateral longitudinal arch is made up of
the calcaneus, cuboid, and fourth and
fifth metatarsal bones
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Skeletal Differences Between
Men and Women
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Male skeleton is larger and heavier
than female skeleton
Pelvic differences (Figure 9-26; Table
9-9)
Male pelvis—deep and funnel-shaped
with a narrow pubic arch
 Female pelvis—shallow, broad, and
flaring with a wider pubic arch

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Cycle of Life: The Skeletal System
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Changes in the skeleton begin at
fertilization and continue over a lifetime;
changes can be positive or negative
Incompletely ossified skeleton in children
provides the resiliency needed to
withstand stress without breaking easily
Dense bone structure in young and
middle adulthood permits bearing heavy
loads
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Cycle of Life: The Skeletal System
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In later adulthood, reduced bone
density makes fractures more likely
and causes changes in posture and
overall height
Details of aging effects are found in
Mechanisms of Disease section
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The Big Picture: Skeletal System
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Skeletal system is a good example of
increasing structural hierarchy in the body
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Skeletal tissues grouped into discrete organs—
bones
Skeletal system consists of bones, blood vessels,
nerves, and other tissues grouped to form a
complex operational unit
Integration of skeletal system with other body
organ systems permits homeostasis to occur
Skeletal system more than a collection of
individual bones—it represents a complex and
interdependent functional unit of the body
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