ch 7 - axial skeleton s2009
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Chapter 7:
The Axial Skeleton
part 1
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Structures of Bones
Articulations:
contacts with other bones
Marks:
areas of muscle and ligament attachment
Foraminae:
openings for nerves and blood vessels
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The Axial Skeleton - longitudinal axis
Supports and protects organsin body cavities
Attaches to muscles of:
head, neck, and trunk
respiration
appendicular skeleton
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Bones of the Axial Skeleton - 80 The skull:
8 cranial bones 14 facial bones
Bones associated
with the skull: 6 auditory ossicles
the hyoid bone
The vertebral column:
24 vertebrae
the sacrum
the coccyx
The thoracic cage:
24 ribs the sternum
Th Sk ll
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The Skull The skullprotects:
the brain
entrances torespiratory system
entrance to digestive
system
Has 22 bones:
8 cranial bones:
form the braincase or cranium 14 facial bones:
protect and support entrances
to digestive and respiratory
tracts
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Cranial Bones Enclose the cranial cavity
Which contains the brain:
and its fluids, blood vessels, nerves, membranes
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The Facial Bones Superficial facial bones
for muscle
attachment Maxillary
Lacrimal
Nasal
Zygomatic Mandible
Deep facial bones
separate the oral and
nasal cavities & form the
nasal septum Palatine bones
Inferior nasal conchae
Vomer
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The 4 Major Sutures (immovable joints of the skull)1. Lambdoid suture-
separates occipital from
parietal bones2. Coronal suture-attaches
frontal bone to parietal
bones (calvaria consists
of occipital, parietal,and frontal bones)
3. Sagittal suture-between
the parietal bones
lambdoid suture to
coronal suture
4. Squamous suture-form
boundaries between
temporal bones and
parietal bones
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The Hyoid Bone (assoc w/facial bones) Functions
Supports the larynx
Attaches muscles of the
larynx, pharynx, and tongue
Articulations
Does not articulate with anyother bone
Connects lesser hornsto
styloid processes of
temporal bones
Marks Body- attaches muscles of larynx, tongue, and pharynx
Greater hornssupport larynx & attach muscles of the tongue
Lesser hornsattach stylohyoid ligaments & support hyoid andlar nx
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The Infant Skull
Figure 715
Grows rapidly
Is large compared to the body
Has many ossification centers
Fusion is not complete at birth:
2 frontal bones
4 occipital bones
several sphenoid and temporal elements
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Fontanels Are areas of fibrous connective tissue (soft spots)
Cover unfused sutures in the infant skull Allow the skull to flex during birth
Anterior fontanel-frontal, sagittal, and coronal
sutures soft spot
Occipital fontanel-lambdoid and sagittal sutures
Th A i l Sk l 2
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The Axial Skeleton part 2
The Vertebral Column
The spine or vertebral column:
protects the spinal cord
supports the head and body
26 bones:
24 vertebrae, the sacrum,and coccyx
Regions
Cervical(C) 7 v
Thoracic(T) 12 v
Lumbar(L) 5 v
Sacral(S)
Coccygeal(Co)
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Curvatures
Cervical curve
Thoracic curve
Lumbar curve
Sacral curve
Primary Curves Thoracicand sacral curves present during fetal development
aka accommodation curves-
accommodate internal organs
Secondary Curves Lumbarand cervical curves-appear after birth
Aka compensation curves-shift body weight for upright
posture
V b
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Vertebrae
3 Parts of a Vertebra
vertebral body (centrum)-transfers weight along
the spine
vertebral arch-posterior margin of vertebral
foramen
articular processes-lateral projections between
laminae and pedicles
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Figure 717d,e
Intervertebral
Discs Are pads of
fibrocartilage
Separate the
vertebralbodies
Absorb shocks
V b l R i
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Vertebral Regions
Figure 716
Vertebrae are numbered: by region, from top to bottom
C1 articulates with skull, L5
with sacrum Vertebrae of each region:
have characteristics
determined by functions
Th C i l V t b
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Characteristics of C1C7:
small body (support only head)
large vertebral foramen (largest part of spinal
cord)
C1(atlas) has no spinous process all others have
short spinous processes tip of each spinous process is notched (bifid)
The Cervical Vertebrae
l
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Atlas(C1):
articulates with occiptal condyles of skull
has no body or spinous process
has a large, round foramen within anteriorand posteriorarches
Axis(C2):
supports the atlas
has heavy spinous process to attach muscles of head and neck
Axis and atlas bodies fuse during development to
form the dens
V b i (C )
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Vertebra prominens(C7):
transitions to thoracic vertebrae
has a long spinous process with a broad tubercle
Whiplash:
a traumatic dislocation of cervical vertebrae
Th Th i V t b
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The Thoracic Vertebrae
Characteristics T1T12:
have heart-shaped bodies
larger bodies than in C1C7
smaller vertebral foramen thanin C1C7
long, slender spinous processes Dorsolateral surfaces of body
have costal facets-whicharticulate with heads of ribs
T T
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T1T10:
Ribs at T1T10:-contact costaland transverse costal
facets T1T8articulate with 2 pairs of ribs-at superiorand
inferiorcostal facets
T9T11articulate with 1 pair of ribs
T10T12transition to lumbar vertebrae
Th L b V t b
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The Lumbar Vertebrae
Characteristics L1L5: largest vertebrae
oval-shaped bodies
thicker bodies than T1T12
no costal or transverse
costal facets
triangular vertebral
foramen
Transverse processes-
slender
Spinous process-short,
heavy
for attachment of lower
back muscles
C i g V t b
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Comparing Vertebrae
Table 72
The Sac m and Cocc
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The Sacrum and Coccyx
Characteristics -
sacrum:
is curved, more in
males than in females
protects reproductive,
urinary, and digestive
organs
attaches-the axial
skeleton to pelvic girdle
of appendicular
skeleton broad muscles that
move the thigh
The adult sacrum:
consists of 5 fused sacral
vertebrae fuses between puberty
and ages 2530
leaving transverse lines
S l l
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Sacral canal:
replaces the vertebral canal
Sacral cornua:
horn-shaped formed by laminae of the 5th sacral vertebra
which do not meet at midline
Sacral hiatus:
opening at the
inferior end of the
sacral canal
formed by ridges
of sacral cornua
covered by
connective tissues
M di l t
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Median sacral crest:
fused spinous processes
Lateral sacral crest:
attach to muscles of lower back and hip Auricular surface:
articulates with pelvic girdle (sacroiliac joint)
Sacral tuberosity:
attaches ligaments of the sacroiliac joint
4 R i f th S
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4 Regions of the Sacrum
Base-the broad superior surface
Ala-wings at either side of the base to attach
muscles
Apex-the narrow inferior portion articulates with
the coccyx
Ch t i ti
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Characteristics - coccyx:
attaches ligaments and a constricting muscle of
the anus
mature coccyx-consists of 3 to 5 fused coccygealvertebrae
first 2 coccygeal vertebrae-have transverse
processes and have unfused vertebral arches
Th Th i C
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The Thoracic Cage The skeleton of the chest-supports the
thoracic cavity
Consists of:
thoracic vertebrae
ribs
sternum (breastbone)
Rib Cage - formed of
ribs and sternum
A ti l ti f Rib d V t b
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Articulations of Ribs and Vertebrae
Figure 722b
Functions
Protects organs of
the thoracic cavity-
heart, lungs, and
thymus
Attaches muscles: for respiration
of the vertebral column
of the pectoral girdle
of the upper limbs
Th Rib
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The Ribs Functions
are flexible
are mobile
can absorb shock
Rib movements
(breathing): affect width and depth
of thoracic cage
changing its volume
Ribs(costae)-12 pairs of long, curved, flat
bones extending from the thoracic vertebrae
Ribs 1 7 (true ribs)
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Ribs 17 (true ribs)
vertebrosternal ribs
connected to the sternum by costal cartilages
Ribs 812 (false ribs):
do not attach directly to the sternum Vertebrochondral ribs(ribs 810):
fuse together
merge with cartilage before reaching the sternum
Floatingor vertebral ribs(ribs 1112):
connect only to the vertebrae have no connection with the sternum
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Structures of the Ribs The head(capitulum):
at the vertebral end of the rib
has superior and inferior
articular facets
The neck:
the short area between thehead and the tubercle
The tubercle(tuberculum):
a small dorsal elevation
has an auricular facet that
contacts the facet of its
thoracic vertebra (at T1
T10
only)
The tubercular body(shaft): attaches muscles of the
pectoral girdle and trunk
attaches to the intercostal
muscles which move the ribs
The Sternum
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The Sternum The sternum-a flat bone in the midline of the
thoracic wall
3 parts 1-manubrium:
superior portion of
sternum
broad, triangular
shape
articulates with
collarbones (clavicles)
& cartilages of 1st rib
pair
has a jugular notch
between clavicular
articulations
2-sternal body:
tongue-shaped
attaches to the
manubrium& costal
cartilages of ribs 27
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3-xiphoid process:
smallest part of the
sternum
attaches to thesternal body &
diaphragmand
rectus abdominis
muscles Development
Sternum
completes fusion about age 25
Xiphoid process:
last part of sternum to fuse
can easily be broken away
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