The Skeleton
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Transcript The Skeleton
THE SKELETON
CHAPTER 7
Introduction
A strong, yet light, internal support for
the human body
The skeleton is adapted for the
protection, locomotor, and
manipulative functions
The upright stance increases the ability of
the skeletal muscle to resist gravity
Introduction
The skeleton maintains its upright
position through a series of
compensating curves
The skeleton accounts for approximately
20% of the body mass
The 206 bones of the body are grouped
into the axial and appendicular skeleton
Introduction
Axial skeleton
Forms the long axis
of the body
80 bones in three
major regions
– skull
– vertebral column
– bony thorax
• Ribs
• Sternum
Appendicular
Bones of upper &
lower extremities and
girdles
126 bones in three
major regions
– Girdles
• Shoulder girdle
• Pelvic girdle
– upper extremity
– lower extremity
THE SKULL
SECTION I
The Skull
The skull is the body’s most complex
bony structure
It is formed by two sets of bones, the
cranial bones and the facial bones
These 22 bones combine to form the
cranial cavity and the facial features
In addition, there are 3 bones of the inner
ear to assist in sound transmission
The Skull: Introduction
The bones of the skull provide . . .
– A case to house the brain, the cranium
– A framework for the face
– Cavities to house the organs of sight, taste,
and smell
– Passages for air and food
– Attachment sites for the teeth
– Attachment sites for muscle
The Skull: Introduction
Most bones of the skull are flat bones
Except for the mandible, all bones are
firmly united by interlocking sutures
The major sutures of the skull are . . .
–
–
–
–
Coronal
Sagittal
Squamosal
Lambdoidal
(Between Frontal & Parietal)
(Between Parietal bones)
(Between Parietal & Temporal)
(Between Parietal & Occipital)
Other skull sutures connect facial bones
and are named after these structures
________
________
Sagittal
Coronal
Lambdoid
Squamous
Overview of Skull Geography
Facial bones form the anterior aspect
The cranial bones enclose the brain
Vault
The cranial vault
or calvaria forms
the superior,
lateral, and
posterior aspects
of skull
The cranial base
forming the
inferior aspect of
skull
Cranial Base
Cranial base forms
the skull’s inferior
aspect
Three prominent
ridges divide the
base into fossae
The brain rests on
these cranial fossae
completely
enclosed by the
cranial vault
The brain occupies
the cranial cavity
Cavities of the Skull
In addition to the large cranial cavity
there are many smaller cavities
–
–
–
–
Middle and inner ear cavities
Nasal cavity
Orbits of the eyes
Several bones contain air filled sinuses
• Sinuses surrounding the nasal cavity are referred
to as the paranasal sinuses
Study Note
As you read about the bones of the skull,
locate each bone on the different skull
views in Figures 7.2, 7.3, 7.4
The skull bones and their important
markings and features are summarized in
Table 7.1 on pages 202-203
Cranium
The 8 cranial bones include; 2 parietal, 2
temporal frontal, occipital, sphenoid, ethmoid
Cranium is self- bracing allowing the bones to
be thin, yet strong
Frontal bone
Forms the
anterior
portion of
the cranium,
the forehead,
roofs of the
orbits, and
most of the
anterior
cranial fossa
Frontal bone - landmarks
Frontal
squama
Supraorbital
margins
Supraorbital
foramen
Orbits
Anterior
cranial fossa
Glabella
Frontal
sinuses
Parietal bones
Forms most of
the superior &
lateral aspects
of the skull
Articulates
with other
cranial bones
to form four
major sutures
Parietal bones - landmarks
The four largest sutures cranial sutures,
Coronal, Sagittal, Lambdodial, Squamosal
Occipital bone
Forms most of
the posterior wall
and base of skull
Articulates with
parietal &
temporal
Joins w/ sphenoid
in the cranial
floor
Forms internal
walls of posterior
cranial fossa
Occipital bone - Ext. landmarks
Foramen magnum, Occipital condyles, External
occipital protuberance, Nuchal lines, External
occipital crest
Occipital bone - Int. landmarks
Hypoglossal canal, Posterior cranial fossa
Temporal Bone
Forms the inferolateral aspects of
the skull
Parts of the
cranial floor
Divided into four
regions;
squamous
tympanic,
mastoid, and
petrous-(int)
Temporal Bone
The internal
petrous region
contributes to
the cranial base
The petrous
region and the
sphenoid bone
form the
middle cranial
fossa
Temporal Bone - landmarks
Zygomatic
process
– Meet the
zygomatic
bone
– Forms the
cheek
Mandibular
fossa
– Receives
condyle of
mandible
Temporal Bone - landmarks
External
Auditory
Meatus
– Middle and
inner ear
Styloid
process
– Muscle of
tongue
Mastoid
process
– Muscles of
neck
Temporal bones - landmarks
Jugular
foramen
– Entry point for
the Jugular
artery
Internal
acoustic meatus
– Entry point for
the auditory
nerve
Jugular foramen
Temporal bones - landmarks
Stylomastoid
foramen
– exit for facial
nerve
Carotid canal
– entrance for
the carotid
artery which
supplies blood
to cerebral
hemispheres
Sphenoid bone
Bone spanning the width of middle cranial fossa
Articulates as central wedge of all cranial bones
Consists of central body and three processes;
greater and lesser wings and pterygoid process
Sphenoid - landmarks
Sella turcica (enclosure for pituitary gland)
Optic foramina (passage of optic nerves)
Superior orbital fissure (Nerves III, IV, V enter orbit)
Foramen rotundum & ovale (Cranial Nerve V to face)
Foramen spinosum (Middle meningeal artery)
Ethmoid bone
Forms most of
the area between
the nasal cavity
& orbits of eyes
Lies between
nasal bones &
sphenoid
Complex shape
gives rise to
nasal septum,
sinuses and
cribiform plate
Ethmoid bone - landmarks
Cribiform plates
– Forms roof of
nasal cavity
Olfactory formina
– Olfactory nerves
enter brain
Crista galli
– Attachment of the
dura mater which
secures brain in
cavity
Ethmoid bone - landmarks
Perpendicular
plate
– Forms superior
part of nasal
septum
Lateral mass
– House ethmoid
sinuses
Nasal concha
– Project into nasal
cavity
Orbital plates
– Medial walls of
orbits
Facial bones
Consists of 14
bones w/ only
mandible and
vomer unpaired
Others include
maxillae,
lacrimals,
nasals,
zygomatics,
inferior nasal
conchae, and
palatines (not
pictured)
Mandible
Forms the lower
jaw
Largest,
strongest bone of
the face
It has a body
and two
upwardly
projecting
sections called
rami
Houses lower
dentition
Mandible - landmarks
Mandibular angle
Mandibular notch
Coronoid process
Mandibular
condyle
Alveolar margin
Mandible formina
Mental formina
Maxillary bone
Forms upper jaw
and central
portion of facial
skeleton
Fused medially
Articulates with
all facial bones
except mandible
Upper dentition
Forms 2/3 of
hard palate of
the mouth
Maxillary bones - landmarks
Alveolar margin
– Upper dentition
Frontal process
– Form lateral
aspects of nose
Zygomatic
process
– Articulates with
zygomatic bone
Maxillary
sinuses
– (Fig. 7.11)
Maxillary bones - landmarks
Palatine
processes
– Forms roof of
mouth
Incisive fossa
– Passage of
nerves and
blood vessels
Infraorbital
foramen
– Infraorbital
nerve and blood
vessel to face
Palatine Process
Maxillary bones - landmarks
Inferior
orbital fissure
– Located deep
within the
orbit
– Permits
passage of the
zygomatic
nerve,
maxillary
nerve, and
blood vessels
to reach face
Zygomatic bones
Commonly called
the cheekbones
Form prominences
of cheeks and
inferolateral
margins of orbits
Articulate with the
Zygomatic process
of temporal bone
and Zygomatic
process of maxallae
Zygomatic
Process of
Temporal
Zygomatic
bone
Nasal bones
Forms bridge
of the nose
Thin,
rectangular
shape
Fused medially
Articulate with
the frontal bone
and maxillary
bones laterally
Nasal cartilages
– (Fig. 6.1)
Lacrimal Bones
Forms part of
the medial
border of each
orbit
Articulates with
frontal, ethmoid
& maxillae
Forms part of
Lacrimal fossa
– Permits tears to
drain from orbit
to nasal cavity
Lacrimal Bones
Lacrimal fossa
– Permits tears to
drain from orbit
to nasal cavity
Palatine bones
The horizontal
plates forms the
posterior portion
of hard palate
Vertical plate
forms part of the
posterolateral
wall of nasal
cavity and a
small portion of
orbit
Palatine bones - landmarks
Horizontal plate
Vertical plate
Orbital surface
Vomer
Forms part of
the nasal
septum
Located with
nasal cavity
Vomer - landmarks
Plow shape
– Divides nasal
septum into
right and left
parts
Vomer
Inferior Nasal Conchae
Form lateral
walls of nasal
cavity
Project
medially from
the lateral
walls of nasal
cavity
Largest of
nasal conchae
Inferior Nasal Conchae - Landmark
The Inferior
nasal conchae
is just one of
three in the
nasal cavity
Superior and
middle concha
are on the
Ethmoid bone
The Orbits
The orbits are bony cavities within which
the eyes are encased and cushioned by fatty
tissue
The muscles that move the eyes and the tear
producing lacrimal glands are housed
within the orbit
Formed by frontal, sphenoid, maxilla,
zygomatic, lacrimal palatine & ethmoid
Contain superior & inferior orbital fissures
Optic foramina
The Orbits
Nasal cavity
The nasal cavity is constructed of bone
and hyaline cartilage
The cavity is divided into right and left
parts by the nasal septum
Superior, middle and inferior nasal
concha project into the cavity
The nasal septum and conchae are lined
with mucus-secreting mucosa
Nasal cavity
Roof of the
cavity is the
cribriform
plates of
ethmoid
Lateral walls
are the superior,
middle, and
inferior
conchae, and
vertical plates of
palatines
Cribriform
plate
Nasal cavity
Floor of cavity is
formed by
palatine
processes of the
maxillae and the
palatine bones
Septum is
formed by vomer
and the
perpendicular
plate of ethmoid
Paranasal sinuses
Five skull bones; frontal, sphenoid,
ethmoid, and the paired maxillary
contain mucus-lined, air-filled sinuses
Cluster around nasal cavity
Connected to nasal cavity to allow air to
enter and mucus to drain
Lighten skull, warm and humidify air,
enhance voice resonance
Paranasal sinuses
Note positioning
around nasal
cavity
Paranasal sinuses
Sphenoid sinus
Frontal sinus
Ethmoid sinus
Maxillary
sinuses
Hyoid bone
Not really a part of the skull, it is unique
in that it is the only bone that does not
articulate with any other bone
Positioned just inferior to the mandible
Anchored by stylohyoid ligaments to the
styloid processes of temporal bone
Acts as a movable base for the tongue
Hyoid bone
Body
– Neck muscle
attachment
Greater horn
– Neck muscle
attachment
Lesser horn
THE VERTEBRAL COLUMN
SECTION II
Vertebral Column:
General Characteristics
Formed from 26 irregular bones
It contains four distinct curvatures
It provide axial support for the trunk
Transmits weight of trunk to lower limbs
Protects spinal cord
Attachment site for ribs and muscles
Separated by intervertebral discs
There are 24 vertebrae, a sacrum (5 fused)
and a coccyx (4 fused)
General
Characteristics
Alignment
– Anterior/ posterior
– Lateral
Curvatures
– Compensatory
curves
Features
– Weight bearing
– Muscle attachment
– Protection
Regional
Characteristics
Cervical C1-C7
– Neck / movable
Thorasic T1-T12
– Rib cage / limited
movement
Lumbar L1-L5
– Low back / movable
Sacral 5 fused
– Joins the pelvis
Coccyx 4 fused
– Terminus
Clinical
deviations
Scoliosis
– An abnormal lateral
curvature of the
spinal column
– Curvature can
occur in an “S” or
“C” deviation
Clinical
deviations
Kyphosis
– An exaggerated
dorsal curvature
in the dorsal
region
– Common is aged
individuals
because of
osteoporosis
Clinical
deviations
Lordosis
– Accentuated
lumbar curvature
– Being overweight
or pregnant
causes an
excessive load up
front
Curves develop in response to:
Upright posture
Weight bearing
Musculature
Characteristics - Ligaments
Ligaments hold the
vertebral column in
an upright position
– The broad Anterior
Longitudinal
Ligament prevents
hyperextension and
is quite strong
– The cord like
Posterior
Longitudinal
Ligament prevents
hyperflexion and is
relatively weak
Characteristics - Ligaments
Ligaments
also connect
specific
vertebra and
support disc
position
– Supraspinos
ligament
– Ligamentum
flavum
– Interspinous
ligament
Intervertebral Discs
Intervertebral discs are cushion like pads
interposed between vertebra
The discs provide elasticity and
compressibility
Compression flattens discs
Discs are thickest in the cervical and
lumbar to provide flexibility
Characteristics - discs
Annulus fibrosus
surrounds the
outer margin
– Collagen fibers
Nucleus pulposus
is the semi fluid
substance which
shifts under body
weight &
pressure
Herniation of
disc
Herniation
of disk
General structure of vertebrae
Common pattern
– Body or centrum
– Vertebral arch
• lamina
• pedicle
– Vertebral
foramen
– Spinous process
• Muscles attach
– Transverse
process
• Muscles attach
General structure of vertebrae
Interlocking
pattern
– Superior and
inferior processes
interlock
– The inferior from
above and the
superior from the
vertebrae below
form a movable
joint
– The movement
contributes to
spinal rotation
Superior Articular
Process
General structure
Pedicles have
notches on their
superior and
inferior borders
Lateral openings
are called
intervertebral
foramen
– Spinal nerves
from spinal cord
exit through
these foramina
Regional Characteristic: Cervical
Body is oval, but wide
side to side C3 - C7
Spinous process is
short and bifid (split)
except in C7
Vertebral foramen is
triangular
Transverse processes
contain foramina for
blood vessels leading
to brain
Cervical Vertebrae C1 and C2
The first two cervical vertebrae are named
the atlas and axis respectively
There is no intervertebral disc between
them
They are highly modified for carrying the
skull on top of the vertebral column
The atlas (C1) functions are a cradle to
support the head
The axis (C2) functions as a pivot point for
the rotation of the atlas
Cervical Vertebrae C1
Lateral masses articulates with the occipital
condyles of the skull
Cervical Vertebrae C1
Body of the
Vertebrae is
missing
Inferior articular surface articulates with C2
below
Cervical Vertebrae C2
The axis has the
odontoid process
or dens is its
unique feature
The dens is the
missing body of
the atlas which
fuses with the
atlas during
embryonic
development
Regional Characteristic: Cervical
Spinous processes
project directly
posteriorly
Superior facets
directed
superoposteriorly
Inferior facets
directed
inferoanteriorly
Flexion/extension,
lateral flexion and
rotation
Regional Characteristic: Thoracic
Body is larger than
cervical; heart
shaped
Spinous process is
long and sharp
Vertebral foramen is
circular
Transverse processes
project posteriorly
and bear facets for
ribs
Regional Characteristic: Thoracic
Body bears two
costal demifacets
Spinous processes
projects inferiorly
Superior facets
directed posteriorly
Inferior facets
directed anteriorly
Rotation, limited
lateral flexion,
flexion/extension
prevented
Regional Characteristic: Lumbar
Body is massive and
kidney shaped
Spinous processes are
short and blunt
Vertebral foramen is
triangular
Transverse processes
are perpendicular to
spinous process but
has no special
features
Regional Characteristic: Lumbar
Spinous process
projects posteriorly
Superior facets
directed medially
Inferior facets
directed laterally
Flexion/extension,
some lateral flexion,
rotation prevented
Sacrum
The triangular shaped structure formed
by five fused vertebrae
Forms the posterior wall of the pelvis
Articulates with L5 of the vertebral
column
Articulates with the iliac bone of the
pelvic girdle
Transfers the weight of the upper torso
and limbs to the lower extremities
Sacral
Ala are fused remnants
of transverse processes
that articulate with hip
bones to form the sacro
iliac joints of the pelvis
Sacral promontory
– Center of gravity is 1 cm
posterior of this point
Transverse line are sites
of vertebral fusion
Sacral foramina
transmit blood vessels
and nerves
Ala
Sacral
promontory
Sacral
On the posterior aspect
median sacral crest are
fused spinous processes
The vertebral canal
continues inside the
sacrum as the sacral
canal
Sacral hiatus is at the
inferior end of the
sacral canal
Superior articular
surface form a joint
with the spinal column
Coccyx
Coccyx articulates with sacrum
The Bony Thorax
The thorax is the chest which includes
– Thoracic vertebrae posteriorly
– The ribs laterally
– The sternum and costal cartilages anteriorly
It is cone shaped with its broad opening
inferiorly
The thorax forms a bony cage around the
heart, lungs and major blood vessels
Functions of The Bony Thorax
Protection
Attachment point for muscles of the
back, chest, and shoulders
The intercostal muscles attach to the
thorax to lift and depress the thorax
during respiration
The Sternum
The sternum lies in the
anterior midline of the
thorax
It is three fused bones
– Manubrium
• Jugular notch
• Clavicular notch
– Sternal body
• Sternal angle
– Xiphoid process
• Xiphisternal joint
Bony Thorax
Thorax is the chest and its bony
underpinnings is called the thoracic cage
Elements consist of the thoracic vertebrae,
ribs, sternum, and costal cartilages which
secure ribs to the sternum
A cone opening inferiorly, the thorax provides
a protective cage around the vital organs of
the thoracic cavity (heart, lungs, great blood
vessels)
Bony Thorax - continued
Provides support for the shoulder girdles
Bony attachment points for muscles of the
back, chest and shoulders
Intercostal spaces between ribs are occupied
by the intercostal muscles which lift and
depress the thorax during breathing
Sternum
Located on the anterior
midline of the thorax
Consists of three fused
bones; manubrium,
body, and xiphoid
process
Manibrium articulates
with clavicle & 2 ribs
Body with ribs 2 - 7
Xiphoid attachment
site for abdominal
muscle
Thorax to Vertebral Column
Ribs
Ribs
Twelve pairs forming thoracic cage
All attach posteriorly to thoracic vertebrae
Curve inferiorly toward anterior body surface
Ribs 1-7 attach directly to sternum by
separate costal cartilages and are referred to
as true ribs
Ribs 8-10 attach indirectly to sternum by
attaching to costal cartilages immediately
above
Ribs 11-12 have no anterior attachments and
are referred to as floating ribs
Ribs
Ribs are bowed
flat bones
Long shaft
Tear drop shaped
with a costal
groove on inner
surface
Head of rib has 2
facets to
articulate with its
vertebrae as well
as the one above
Ribs
Neck is just
beyond the head
Angle of rib
Costal cartilages
attach rib to
sternum
Attachments are
secure but
flexible
Ribs
Tubercle of rib
articulates with
transverse process
Ligaments secure
rib to transverse
process
Note how the
transverse
processes of
thoracic vertebrae
are angled
posteriorly
The Appendicular Skeleton
Appended to the axial skeleton
Pectoral girdle is for manipulation and is
a lighter, less heavily reinforced
structures
Pelvic girdle is for weight bearing and
locomotion and is a heavier, more robust
structure
Differences appear in bone structure,
joint structure, ligaments and muscle
THE PECTORAL GIRDLE
SECTION IV
Pectoral or Shoulder Girdle
Consists of two bones, the anteriorly
positioned clavicle and the posteriorly
positioned scapula
Pectoral girdle is a loosely attached, held
in place largely by musculature attached
to the thorax and the vertebral column
Only direct ligament attachment exists at
the sternoclavicular joint
Frees girdle to move over the thorax as
the need arises
Pectoral Girdle
Flexible and Mobile
Pectoral girdle is very light to allow the
upper limb flexibility and mobility not
allowed anywhere else in body
This is possible because only the sternal
end of clavicle is attached to axial skeleton
thus allowing the scapula to move across
thorax and the arm with it
The socket of the shoulder joint is shallow
and poorly reinforced
Although this arrangement does not
restrict movement it is less stable
Clavicles
Clavicles are double curved bones extending along the
superior thorax
Attached on the sternal end to sternum and the
acromial
Attachment site or muscles of the thorax and shoulder
Position scapula away from thorax
THE UPPER LIMB
SECTION V
The Upper Limb
Arm
– Humerus
Forearm
– Ulna
– Radius
Hand
Wrist (8 carpal bones)
Palm (5 metacarpal bones)
Fingers (14 phalanges)
The Humerus
Radius and ulna
Carpals, Metacarpals, & Phalanges
THE PELVIC GIRDLE
SECTION VI
The Pelvic (Hip) Girdle
Attaches the lower limbs to axial skeleton
Transfers the weight of the torso, head,
and upper extremities to lower limbs
Supports the visceral organs of the pelvis
Secured by strong ligaments and deep
sockets the joint is reinforced for stability
Less range of motion in all planes of
movement
Female pelvic structure to facilitate
childbearing
Pelvis
Pelvis
Pelvic girdle is formed by a pair of coxal
bones, each called an os coxae
Each os coxae unites anteriorly at the
pubic symphysis and with the sacrum
posteriorly
Each coxa is formed by the ilium, ischium
and pubic which were separate during
childhood but fused in adulthood
Collectively the os coxae, sacrum and
coccyx is called the pelvis
Os Coxa
Ilium
– Superior
Ishium
– Posterior
Pubis
– Anterior
Os Coxa
Ilium
– Superior
Ishium
– Posterior
Pubis
– Anterior
Pelvic Structure and Childbearing
The female pelvis reflects modifications
for child bearing
It tends to be wider, shallower, lighter,
and rounder than the male
Pelvic modifications accommodate the
growing fetus as well as providing a birth
canal wide enough to allow the infants
head to exit at birth
Pelvic inlet and outlet are critical to
delivery
Male and Female Pelvic Structures
THE LOWER LIMB
SECTION VII
The Lower Limb
Thigh
– Femur
Leg
– Tibia
– Fibula
Foot (7 Tarsal bones)
Instep (5 Metatarsal bones)
Toes (14 Phalanges)
Femur
Tibia
Fibula
Bones of
Right Foot
Right Foot - Medial View
Right Foot - Lateral View
Arches of the Foot
DEVELOPMENTAL ASPECT
OF THE SKELETON
SECTION VIII
Developmental Aspects of the
Skeleton
Fontanels
Spinal Curvatures
Long Bone Ratio
Changes in Female Pelvis
Adult Skeletal Changes