Download Chapter 7 Body Systems

Chapter 8
Skeletal System
Mosby items and derived items © 2007, 2003 by Mosby, Inc.
Slide 1
Introduction
• 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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Slide 2
Divisions of Skeleton
(Figure 8-1; Table 8-1)
• 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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Slide 3
Axial Skeleton
• 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
• Frontal bone (Figure 8-8, 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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Slide 4
Axial Skeleton

Cranial bones (cont.)
• Parietal bones (Figure 8-8, A)

Form the bulging top of the cranium

Form several sutures: lambdoidal suture with occipital
bone; squamous suture with temporal bone and part of
sphenoid; and coronal suture with frontal bone
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Slide 5
Axial Skeleton

Cranial bones (cont.)
• Temporal bones (Figure 8-8, B)

Form the lower sides of the cranium and part
of the cranial floor

Contain the inner and middle ears
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Slide 6
Axial Skeleton

Cranial bones (cont.)
• Occipital bone (Figure 8-8, 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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Slide 7
Axial Skeleton

Cranial bones (cont.)
• Sphenoid bone (Figure 8-8, 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 8-7)

Contains the sphenoid sinuses
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Slide 8
Axial Skeleton

Cranial bones (cont.)
• Ethmoid bone (Figure 8-8, F)

A complicated, 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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Slide 9
Axial Skeleton

Facial bones (Table 8-4)
• Maxilla (upper jaw) (Figure 8-8, H)

Two maxillae form the keystone of the face

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
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Slide 10
Axial Skeleton

Facial bones (cont.)
• Mandible (lower jaw) (Figure 8-8, M)

Largest, strongest bone of the face

Forms the only movable joint of the skull with the temporal
bone
• Zygomatic bone (Figure 8-8, 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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Slide 11
Axial Skeleton

Facial bones (cont.)
• Nasal bone (Figures 8-8, L, and 8-10)

Both nasal bones form the upper part of the bridge of the
nose, whereas cartilage forms the lower part

Articulates with the ethmoid bone, nasal septum, frontal
bone, maxillae, and the other nasal bone
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Slide 12
Axial Skeleton

Facial bones (cont.)
• Lacrimal bone (Figure 8-8, 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 groove for the nasolacrimal (tear) duct

Articulates with the maxilla and the frontal
and ethmoid bones
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Slide 13
Axial Skeleton

Facial bones (cont.)
• Palatine bone (Figure 8-8, 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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Slide 14
Axial Skeleton

Facial bones (cont.)
• Inferior nasal conchae (turbinates)

Form lower edge projecting into the nasal cavity and form
the nasal meati

Articulate with ethmoid, lacrimal, maxillary, and palatine
bones
• Vomer bone (Figure 8-8, G)

Forms posterior portion of the nasal septum

Articulates with the sphenoid, ethmoid, and palatine
bones and maxillae
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Slide 15
Axial Skeleton
• Eye orbits (Figure 8-7)

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 cranial and nasal cavities and paranasal sinuses
• Traumatic injuries may result in “blowout fractures”
(Figure 8-7, C)
• “Raccoon eyes”—clinical sign of blowout fracture
(Figure 8-7, D)
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Slide 16
Axial Skeleton
• Fetal skull (Figure 8-11)

Characterized by unique anatomic features not
seen in adult skull

Fontanels or “soft spots” (4) allow skull to “mold”
during birth process and permit rapid growth of
brain (Table 8-5)
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Slide 17
Axial Skeleton
• Fetal skull (cont.)

Permits differential growth or appearance of skull
components over time
• Face—smaller proportion of total cranium at birth (1/8) than in
adult (1/2)
• Head at birth is ¼ total body height; at maturity is about 1/8
body height
• Sutures appear with skeletal maturity (Table 8-5)
• Paranasal sinuses—change in size and placement with skeletal
maturity (Figure 8-9)
• Appearance of deciduous and, later, permanent teeth
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Slide 18
Axial Skeleton
• Hyoid bone (Figure 8-12)

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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Slide 19
Axial Skeleton
• Vertebral column (Figure 8-13)

Forms the flexible longitudinal axis of the skeleton

Consists of 24 vertebrae plus the sacrum and coccyx

Segments of the vertebral column:
•
•
•
•
•
Cervical vertebrae, 7
Thoracic vertebrae, 12
Lumbar vertebrae, 5
Sacrum—in adult, results from fusion of five separate vertebrae
Coccyx—in adult, results from fusion of four or five separate
vertebrae
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Slide 20
Axial Skeleton
• Vertebral column (cont.)

Characteristics of the vertebrae (Figure 8-14; Table 8-6)
• 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 vertebral foramen
• Second cervical vertebra has upward projection, the dens, to
allow rotation of the head
• Seventh cervical vertebra has long, blunt spinous process
• Each thoracic vertebra has articular facets for the ribs
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Slide 21
Axial Skeleton
• Vertebral column (cont.)

Vertebral column as a whole articulates 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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Slide 22
Axial Skeleton
• Sternum (Figure 8-15)

Dagger-shaped bone in the middle of the anterior
chest wall made up of three parts:
• Manubrium—the upper, handle part
• Body—the middle, blade part
• Xiphoid process—the blunt cartilaginous lower tip, which
ossifies during adult life
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Slide 23
Axial Skeleton
• 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 cartilage
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Slide 24
Axial Skeleton
• Ribs (Figures 8-15 and 8-16)

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
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Slide 25
Axial Skeleton
• Ribs (cont.)

From its vertebral attachment, each rib curves outward, then
forward and downward

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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Slide 26
Appendicular Skeleton
• Upper extremity (Table 8-7)

Consists of the bones of the shoulder girdle, upper
arm, lower arm, wrist, and hand

Shoulder girdle (Figure 8-17)
• Made up of scapula and clavicle
• Clavicle forms only bony joint with trunk, the
sternoclavicular joint
• At its distal end, clavicle articulates with the acromion
process of the scapula
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Slide 27
Appendicular Skeleton
• Upper extremity (cont.)

Humerus (Figures 8-18 and 8-19)
• The long bone of the upper arm
• Articulates proximally with the glenoid fossa of the
scapula and distally with the radius and ulna
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Slide 28
Appendicular Skeleton
• Upper extremity (cont.)

Ulna
• Long bone found on little finger side of forearm
• Articulates proximally with humerus and radius and
distally with a fibrocartilaginous disk
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Slide 29
Appendicular Skeleton
• Upper extremity (cont.)

Radius
• Long bone found on thumb side of forearm
• Articulates proximally with capitulum of humerus and
radial notch of ulna; articulates distally with scaphoid
and lunate carpals and with head of ulna
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Slide 30
Appendicular Skeleton
• Upper extremity (cont.)

Carpal bones (Figure 8-20)
• Eight small bones that form wrist
• Carpals are bound closely and firmly by ligaments and
form two rows of four carpals each

Proximal row is made up of pisiform, triquetrum, lunate,
and scaphoid

Distal row is made up of hamate, capitate, trapezoid,
and trapezium
• The joints between radius and carpals allow wrist and
hand movements
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Slide 31
Appendicular Skeleton
• Upper extremity (cont.)

Metacarpal bones
• Form framework of hand
• Thumb metacarpal forms the most freely movable joint
with the carpals
• Heads of metacarpals (knuckles) articulate with
phalanges
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Slide 32
Appendicular Skeleton
• Lower extremity

Consists of the bones of hip, thigh, lower leg,
ankle, and foot (Table 8-8)
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Slide 33
Appendicular Skeleton
• Lower extremity (cont.)

Pelvic girdle is made up of the sacrum and the two coxal
bones, bound tightly by strong ligaments (Figure 8-21)
• 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 8-22):

Ilium—largest and uppermost

Ischium—strongest and lowermost

Pubis—anteriormost
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Slide 34
Appendicular Skeleton
• Lower extremity (cont.)

Femur—longest and heaviest bone in the body
(Figure 8-23)

Patella—largest sesamoid bone in the body

Tibia
• 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 the talus
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Slide 35
Appendicular Skeleton
• Lower extremity (cont.)

Fibula
• The smaller, more laterally and deeply placed
of two leg bones
• Articulates with tibia
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Slide 36
Appendicular Skeleton
• Lower extremity (cont.)

Foot (Figures 8-24 and 8-25)
• 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 calcaneus, talus,
navicular, cuneiforms, and medial three metatarsals

Lateral longitudinal arch is made up of calcaneus, cuboid,
and fourth and fifth metatarsals
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Slide 37
Skeletal Differences
in Men and Women
• Male skeleton is larger and heavier than
female skeleton
• Pelvic differences (Figure 8-26; Table 8-9)

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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Slide 38
Cycle of Life: The Aging Skeleton
• Aging changes begin at fertilization and continue
over a lifetime

Changes can be positive or negative
• Normal bone development is a skeletal aging process

Intramembranous ossification

Endochondral ossification

Appearance of ossification centers and closure of epiphyseal
plates can be used to estimate potential growth and height
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Slide 39
Cycle of Life: The Aging Skeleton
• Characteristics of bone during age
• Bone produced early in life is properly
calcified but not brittle
• Osteoblastic activity during early periods of bone
remodeling results in deposition of more bone than is
resorbed

Prior to puberty results in growth of bones

After puberty and until early thirties, replaced bone
is stronger
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Slide 40
Cycle of Life: The Aging Skeleton

Negative outcomes of skeletal aging begin
between 30 and 40 years of age
• Decrease in osteoblast numbers with production of lower
quality matrix
• Increase in osteoclast numbers and activity with
increased bone loss
• Mature osteocytes coalesce and shrink, producing a
honeycomb of tiny holes in the compact bone
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Slide 41
Cycle of Life: The Aging Skeleton

Negative outcomes (cont.)
• Skeleton as a whole loses strength, and fracture risk
increases
• Decrease in number of trabeculae in spongy bone in
vertebral bodies and other bones results in
“spontaneous” as well as compression fractures
• Overall height decreases beginning at about age 35
• Osteoporosis is a common and very serious bone
disease in old age
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Slide 42
The Big Picture
• Skeletal system is a good example of increasing
structural hierarchy in the body

Skeletal tissues are 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 is more than an assemblage of individual
bones—it represents a complex and interdependent
functional unit of the body
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Slide 43
Mechanisms of Disease—
Bone Fractures
• Fracture defined as partial or complete break in
continuity of a bone

Mechanical stress and traumatic injury are most common
causes

Pathological or spontaneous fractures occur in absence of
trauma

Stress fractures may not be apparent in clinical examination
or standard x-ray images but can be seen in bone scans
• Bone damage is microscopic
• Caused by repetitive trauma (e.g., marathon runners)
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Slide 44
Mechanisms of Disease—
Bone Fractures
• Fracture defined (cont.)

Displaced, open or compound fractures—do not produce a break in
the skin and pose less danger of infection

Nondisplaced, closed or simple fractures—do not produce a break
in the skin and pose less danger of infection

Fracture types:
•
•
•
•
Impacted—one end of fracture driven into diaphysis of other fragment
Complete—break extends across entire section of bone
Incomplete—some fracture components still partially joined
Dentate—fracture components jagged and fit together like teeth on a
gear
• Comminuted—crushed, small, crumbled bone fragments near fracture
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Slide 45
Mechanisms of Disease—
Bone Fractures

Fracture types (cont.)
• Avulsion—bone fragments pulled away from underlying bone
surface or bone totally torn from body part
• Linear—fracture line parallel to the bone’s long axis
• Transverse—fracture line at right angle to long axis of bone
• Oblique—fracture line slanted or diagonal to longitudinal axis
• Spiral—fracture line spirals around long axis
• Hairline—common in skull—fracture components small and
aligned; if fracture is pushed downward, called a depressed
fracture
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Slide 46
Mechanisms of Disease—
Bone Fractures

Fracture types (cont.)
• Greenstick—bone bent but broken only on one side
(common in children)
•
•
•
•
Pott’s—fracture of lower tibia
Colles’—fracture of distal radius
LeFort—fracture of face and/or base of skull
Hangman’s—fracture of posterior elements in upper
cervical spine, especially the axis
• Blowout—fracture of the eye orbit
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Slide 47
Mechanisms of Disease—
Bone Fractures

Osgood-Schlatter disease

Avulsion fracture of tibial tuberosity fragments the
surface
• Caused by powerful contraction of quadriceps muscle
group pulling on patellar ligament attached to tibial
tuberosity
• Common in adolescent athletes in whom patellar
ligament is stronger than underlying bone
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Slide 48
Mechanisms of Disease—
Treatment of Fractures
• Clinical signs of fracture include pain, loss of function,
false motion, soft tissue edema, deformity, and crepitus
• Initial treatment is realignment and immobilization of bone
fragments

Closed reduction—alignment completed without surgery

Open reduction—surgery required to align and internally
immobilize bone fragments with screws, wires, plates, or other
orthopedic devices

After reduction, immobilization generally accomplished by casts,
splints, and bandages

Traction sometimes used—especially in children

Restoration of function is treatment priority following healing
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Slide 49
Mechanisms of Disease—Mastoiditis
• Inflammation of air spaces within mastoid portion of
temporal bone

Pus may enter mastoid air spaces from middle ear infection
or otitis media

Mastoid air cells do not drain into nose as do paranasal
sinuses

Infectious material may erode thin, bony partition separating
air cells from cranial cavity, causing intracranial infection

Treatment is antibiotic therapy and surgical incision of
eardrum to drain pus from middle ear

Surgical removal of part of mastoid process of temporal
bone—mastoidectomy—is rare
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Slide 50
Mechanisms of Disease—
Abnormal Spinal Curvatures
• Normal curvature of spine is convex through
the cervical and lumbar regions

Normal curves give spine strength for support of
body and balance required to stand and walk
• Abnormal curvatures

Lordosis—abnormally accentuated lumbar curve
(“swayback”)
• Frequently seen during pregnancy
• May be secondary to traumatic injury
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Slide 51
Mechanisms of Disease—
Abnormal Spinal Curvatures
• Abnormal curvatures (cont.)

Kyphosis—abnormally accentuated thoracic
curvature (“hunchback”)
• Frequent consequence of vertebral compression
fractures in osteoporosis
• Sign of Scheuermann’s disease, which may develop
in children at puberty
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Slide 52
Mechanisms of Disease—
Abnormal Spinal Curvatures
• Abnormal curvatures (cont.)

Scoliosis—abnormal side-to-side spinal curvature
• Often appears before adolescence
• Treatments vary with severity of curvature

Milwaukee brace

Transcutaneous stimulation

Surgical grafting to the deformed vertebrae of bone from
elsewhere in skeleton or of metal rods
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Slide 53