Axial skeletal

AXIAL SKELETAL
Mrs. A. Brown
M.Sc (N)

The skeletal system
• The skeletal system is divided into-
 axial skeletal
 appendicular skeletal
• The skeletal system includes at least 206
separate bones and a number of associated
cartilages and ligaments.
2

The Axial Skeleton
3Figure 5.6

Axial skeletal
• Consist of bones of –
1. The skull
2. The vertebral column
3. The ribs
4. The sternum
4

Function of axial skeletel
1. Adjust the positions of the head, neck, and
trunk.
2. Perform respiratory movements
3. Stabilize or position structures of the
appendicular skeleton.
• The joints of the axial skeleton permit
limited movement, but they are very
strong and heavily reinforced with
ligaments
5

The Skull
• Two sets of bones
– Cranium
– Facial bones
• Bones are joined by
sutures
• Only the mandible is
attached by a freely
movable joint
6

The skull
• The bones of the skull protect
the brain and guard the
entrances to the digestive and
respiratory systems.
• The skull contains- 22 bones: 8
form the cranium, or
braincase, and 14 are facial
bone.
• Seven additional bones are
associated with the skull:
 The 6 auditory ossicles are
enclosed by the temporal
bones of the cranium.
 Hyoid bone is connected to
the inferior surfaces of the
temporal bone by a pair of
ligaments. 8

The cranium
• The cranium consist of the-
 Occipital bone
 Parietal bone2
 Temporal bone2
 Frontal bone
 Sphenoid bone
 Ethmoid bone
• Together these cranial bones encloses the cranial cavity, a
fluid filled chamber that cushions and supports the brain.
• Blood vessels, nerves and membrane that stabilize the
position of the brain are attached to the inner surface of
the cranium
• Its outer surface provide an extensive area for the
attachment of muscles that moves the eyes, jaws and
head.
10

sutures • The connection between the skull
bones of adults are immovable
joints called sutures.
• At a suture, the bones are tied
firmly together with dense fibrous
connective tissue.
• There are four major sutures-
1. Lamboidal suture- it across the
posterior surface of the skull.
This suture separates the
occipital bones from the two
parietal bone.
2. Coronal suture- it attaches the
frontal bone to the parietal bones
of either side. The occipital,
parietal and frontal bone form
the calvaria or skullcap.
3. Saggital suture- extends form
the lamboidal suture to the
coronal suture,between the
parietal bones. 11

Bones of the cranium
the occipital bone
• General function- forms
much of the posterior
and inferior surface of
the the cranium.
• Articulation- it
articulates with the
parietal bone, the
temporal bones, the
sphenoid bone, and the
first cervical vertebra.
12

• Regions/ landmarks- the external occipital protuberance is
a small bump at the midline on the inferior surface.
 the occipital crest, which begins at the external occipital
protuberance, marks the attachment of a ligament that
helps stabilize the neck.
 The inferior and superior nuchal lines are ridges that
intersect the crest. They mark the attachment sites of
muscles and ligaments that stabilize the articulation at the
occipital condyles and balance the weight of the head over
the vertebrae of the neck.
 The occipital condyles are the site of articulation between
the skull and the first cervical vertebra.
• Foramina: the foramen magnum connects the cranial
cavity with the spinal cavity, which is enclosed by the
vertebral column. It surrounds the connection between
the brain and the spinal cord.
 The jugular foramen- it lies between the occipital bone
and the temporal bone. The internal jugular vein passes
through this foramen, carrying venous blood from the
brain.
 The hypoglossal canal- it begin at the lateral base of each
occipital condyles and end on the inner surface of the
occipital bone near the formen magnum. The hypoglossal
nerves, the cranial nerves that control the tongue muscles
passes through these canal.
13

The Parietal bones
• General function- form part of
the superior and lateral
surfaces of the cranium.
• Articulation- it articulate with
one another and with
occipital,temporal,frontal and
sphenoid bones.
• Regions/ landmarks- the
superior and inferior temporal
lines are low ridges that mark
the attachment sites of the
temporalis muscle, a large
muscle that close the mouth.
• Grooves on the inner surface
of the parietal bones mark the
path of cranial blood vessels.
14

The frontal bone
• General function-
forms the anterior
portion of the
cranium and the roof
of the orbit; mucous
secretions of the
frontal sinuses help
flush the surfaces of
the nasal cavities.
articulates with the
parietal, sphenoid,
ethmoid, nasal,
lacrimal, maxillary
and zygomatic bones.
15

• Regions/landmarks-
 The frontal squama- or forehead,
forms the anterior, superior portion
of the cranium and provides surface
area for the attachment of facial
muscles.
 The supraorbital margin- helps
protect the eye.
 The lacrimal fossa- on the inner
surface of the orbit is a shallow
depression that marks the location
of the lacrimal gland, which
lubricates the surface of the eye.
 The frontal sinuses- are extremely
variable in size and time of
appearance. They appear after age
6, but some people never develop
them.( We will describe the frontal
sinuses and other sinuses of the
cranium and face in a later section).
16

• Foramina- the supraorbital foramen provides passage for
blood vessels that supply the eyebrow, eyelids and frontal
sinuses.
• Metopic suture- at birth, the fusion have not been
completed- there are two frontal bone that articulate along
the metopic suture. Although the suture generally disappears
by age 8 as the bone fuse, the adult skull commonly retains
traces of the suture line.
17

The temporal bone
• General function- form parts of
both:
 The lateral wall of the cranium
 The zygomatic arch
• Forms the only articulation
between the mandible and the
other facial bones.
• It surrounds and protects the
sense organs of the inner ear.
• Act as a attachment site for
muscles that close the jaws and
move the head.
18

• Articulation- the
temporal bone
articulate with the
 zygomatic bone
 Sphenoid bone
 Parietal bone
 Occipital bone
 and with
mandible bone
19

• Regions/ landmarks-
 The squamous portion-or squama, of the
temporal bone is the convex, irregular surface
that borders the squamosal suture.
 The zygomatic process- inferior to the
squamous portion,it is attached to the
temporal process of the zygomatic bone.
Together these process forms the zygomatic
arch or cheek bone.
 The mandibular fossa- on the inferior surface
marks the site of articulation with the
mandible.
 The mastoid process- is an attachment site for
muscles that rotate or extend the head.
 Styloid process- near the base of the mastoid
process, is attached to ligaments that support
the hyoid bone and to the tendon of the
several muscles associated with the hyoid
bone, the tongue, and the pharynx.
 The petrous portion- located on its internal
surface, encloses the structures associated with
the inner ear
20

• Regions/ landmarks-
 The squamous portion-or squama, of the
temporal bone is the convex, irregular surface
that borders the squamosal suture.
 The zygomatic process- inferior to the
squamous portion,it is attached to the
temporal process of the zygomatic bone.
Together these process forms the zygomatic
arch or cheek bone.
 The mandibular fossa- on the inferior surface
marks the site of articulation with the
mandible.
 The mastoid process- is an attachment site for
muscles that rotate or extend the head.
 Styloid process- near the base of the mastoid
process, is attached to ligaments that support
the hyoid bone and to the tendon of the
several muscles associated with the hyoid
bone, the tongue, and the pharynx.
 The petrous portion- located on its internal
surface, encloses the structures associated with
the inner ear
21

• Foramina- the jugular foramina,
between the temporal and occipital bones,
provides passage for the internal jugular
vein.
• The carotid foramen- the entrance to the
carotid canal, provides passage for the
internal carotid artery, a major artery to the
brain.
• The foramen lacerum- it is jagged slit
extending between the occipital and
temporal bone. It contains hyaline cartilage
and small arteries that supply the inner
surface of the cranium.
• The mastoid foramen-penetrates the
temporal bone and begins near the base of
the mastoid process. blood vessels travel
through this passage way to reach the
membrane surrounding the brain.
• The stylomastoid foramen- lies posterior
to the base of the styloid process. The
facial nerve passes through this foramen to
control the facial muscles.
22

• The external auditory
canal- on the lateral
surface ends at the
eardrum, which
disintegrates during the
preparation of a dreid
skull.
• Internal acoustic canal- begins
on the medial surface of the
petrous portion of the
temporal bone. It carries
blood vessels and nerves to
the inner ear, nad the facial
nerve to the stylomastoid
foramen.
23

The Sphenoid bone
• General functions-
 forms part of the floor of the cranium,
unites the cranial and facial bones.
 Act as a cross that strengthen the sides
of the skull.
 Mucous secretions of the sphenoidal
sinuses help flush surfaces of nasal
cavities.
• Articulation- with cranium bone:
 Frontal bone
 Occipital bone
 Parietal bone
 Ethmoid bone
 Temporal bone
And with the bone of the face:
 Palatine bone
 Zygomatic bone
 Maxillary bone
 Vomer
24

• Regions/ landmarks- it shape
is compared to a bat with its
wings extended.
 The body- it forms the central
axis of the sphenoid bone.
 The greater wings- extend
laterally from the body as a
part of the cranial floor.
Vertical extensions of each
wing contribute to the
posterior wall of each orbit.
 The lower wings- it extend
horizontally anterior to the
sella turcica
25

 The sella turcica- it resembles a
“Turkish saddle”, is a bony
enclosure on the superior
surface of the body.
 The hypophyseal fossa- it is the
depression within the sella
turcica. The pituitary glandsits
within this fossa.
 The sphenoid sinuses they are
on either side of the body,
inferior to the sella turcica.
 The pterygoid processes- they
are vertical projection that
begin at the boundary between
the greater wing and the body.
Each process form a pair of
petrygoid plates, which are
important an attachment sites
for muscles that moves the
lower jaw and soft palate.
26

• Foramina:
 the optic canals permit the passage of the optic nerve from
the eyes to the brain.
 The superior orbital fissure, foramen rotundum, foramen
ovale and foramen spinosum penetrate the greater wings.
These passage carry blood vessels and nerves to the orbit,
face, and jaws.
27

The ethmoid bone
• General function- forms:
 Anteromedial floor of the
cranium.
 Roof of the nasal cavity
 Part of the nasal septum
• Contributes to the medial
orbital wall.
• Secretions from the
ethmoidal sinuses flush the
surfaces of the nasal cavity.
28

• Articulation – it
articulate with:
a. Cranium bones:
 Frontal bone
 Sphenoid bone
b. Facial bone:
 Nasal bone
 Lacrimal bone
 Palatine bone
 Maxillary bone
 Inferior nasal
conchae
 Vomer
29

• Regions/landmark-the ethmoid
has three parts:
1. The cribriform plate
2. The paired lateral masses
3. The perpendicular plate
1. The cribriform plate-
(cribrum- sieve) forms the
anteromedial floor of the
cranium and the roof of the
nasal cavity.
• Crista galli-(cock’s comb)- is a
bony ridge that projects
superior to the cribriform plate.
• The flax cerebri, a membrane
that stabilizes the position of
the brain, attaches to the ridge
30

2. The lateral masses-
it contain the
ethmoidal sinuses,
or ethmoidal air
cells, which open
into the nasal cavity
on each side.
the superior nasal
conchae and the
middle nasal
conchae are delicate
projections of the
lateral masses.
31

3. The perpendicular plate-
Forms part of the
septum, along with the
vomer and a piece of the
hyline cartilage.
• Foramina- the olfactory
foramina in the
cribriform plate permit
passage of the olfactory
nerve which provide
your sense of smell.
32

Bones of the face
33Figure 5.11

The maxillary bones
• General functions: forms
 the inferior orbital rim
 The lateral margins of the
external nares.
 The upper jaw
 Most of the hard palates
• Supports the teeth
• Maxillary sinuses produce
mucous membrane that
flush the inferior surfaces
of the nasal cavities.
34

articulates with:
 Frontal bone
 Ethmoid bone
 With one another
 With all facial bones
except the mendible
35

 The orbital rim- protects the eye
and other structures in the orbit.
 The alveolar processes- that
border the mouth support the
upper teeth.
 The palatine process- forms most
of the hard palate, or bony roof of
the mouth.
 The maxillary sinuses- lighten the
portion of the maxillary bone
superior to the teeth.
 The lacrimal fossa- formed by the
maxillary and lacrimal bone,
protects the lacrimal sac and the
nasolacrimal duct, which carries
tears from the orbit to the nasal
cavity.
 The incisive fossa- is an
indentation in the anterior, inferior
portion of the hard palates.
36

• Foramina-
 The infraorbital foramen-
marks the enterance of a
major sensory nerve from
the face; that nerve exits the
skull through the formen
rotundum of the sphenoid
bone.
 The inferior orbital fissure-
which lies between the
maxillary bone and the
sphenoid bone, permits
passage of cranial nerves and
blood vessels.
37

The nasal bone • General Function-
 support the superior
portion of the bridge of the
nose.
 Form the superior border of
the external nares, the
entrance of the nasal cavity.
• Articulation- paired nasal
bone articulate with:
 One another
 frontal bone
 Ethmoid bone
 Maxillary bone
38

The vomer • General function- forms the
inferior portion of the nasal
septum.
• Articulations- it articulates
with:
 Sphenoid bone
 Ethmoid bone
 Palatine bone
 Maxillary bone with
cartilaginous portion of the
nasal septum, which extend
into the fleshy portion of the
nose.
39

The inferior nasal conchae
 Create terbulance through
nasal cavity.
 Increase epithelial surface area
to promote warming and
humidification of inhaled air.
• Articulation- it articulates
with:
 Maxillary bone
 Ethmoid bone
 Palatine bone
 Lacrimal bone
40

The zyg0matic bone
 forms the rim and lateral wall
of the orbit
 Form part of the zygomatic
arch.
with:
• Frontal bone
• Temporal bone
• Sphenoid bone
• Maxillary bone
41

• Regions/landmarks- the
temporal process curves
posteriorly to meet the
zygomatic process of the
temporal bone.
• Foramina- the
zygomaticofacial
foramen on the anterior
surface of each
zygomatic bone carries a
sensory nerve that
innervates the cheeks.
42

Palatine bone • General function- form the
posterior portion of the hard
palate and contribute to the
floor of each orbit.
• Articulation- the palatine
bones articulate with:
 One another
 maxillary bone
 Sphenoid bone
 Ethmoid bone
 Inferior nasal conchae
 Vomer
43

Regions/landmark
• These bones are ‘L’
shaped.
• The horizontal plate-
forms the posterior
portion of the hard palate.
• the vertical plate-
extends from the
horizontal plate to the
orbital process.
• the orbital process- forms
part of the floor of the
orbit.
• These process contains a
small sinus that normally
opens into the sphenoidal
sinuses.
44

foramina
• Greater palatine
foramen-
it permits passage of the
greater palatine nerve, a
sensory nerve supplying
the roof of the mouth.
• Lesser palatine foramina-
it permit the passage of
the lesser palatine nerve,
smaller branches of the
greater palatine nerve.
45

Lacrimal bone • General function- form part of
the medial wall of the orbit.
with :
 Frontal bone
 Maxillary bone
 Ethmoid bone
• Regions/landmarks:
 The lacrimal groove- it is a
depression along the edge of
the lacrimal bone where it
articulates with the maxillary
bone to form the nasolacrimal
canal, which opens into the
nasal cavity.
46

Mandible bone • General functions- it
forms the lower jaw.
• Articulation- it articulates
with the mandibular
fossae of the temporal
bone.
 The mandibular body is
the horizontal portion of
the mandible.
 The alveolar process
support the teeth.
47

• The mental protuberance-
or chin, is the attachment site
for several facial muscles.
A prominent depression on the
medial surface marks the
position of the submandibular
salivary gland.
• The mylohyoid line marks the
insertion of the mylohyiod
muscle, which support the floor
of the mouth.
• The mandibular ramus is the
ascending portion of the
mandible, that begin at the
mandibular angle on the either
side.
 On each ramus:
48

The condylar process
articulates with the temporal
bone at the
tempomandibular joint.
The coronoid process is the
insertion point for the
temporalis muscle, a
powerful muscle that closes
the jaws
 The mandibular notch is the
depression that separates the
condylar and coronoid
processes.
49

• Foramina-
 The mental foramina- are
openings for nerves that
carry sensory information
from the lips and chin to the
brain.
 The mandibular foramen is
the entrance to the
mandibular canal, a
passageway for blood
vessels and nerves that
service the lower teeth.
50

The hyoid bone • General functions:
 Support of larynx
 Attachment site for muscles of the larynx,
pharynx and tongue.
• Articulations: stylohyoid ligaments
connect the lesser cornua to the styloid
processes of the temporal bones.
• Regions/processes:
 The body is an attachment site for
muscles of larynx, tongue and pharynx.
 The greater cornua help support the
larynx and are attached to muscle that
move the tongue.
 The lesser cornua are attached to the
stylohyoid ligament
 From these ligaments, the hyoid and
larynx hang beneath the skull like a child’s
swing from the limb of a tree.
51

The Orbital and Nasal Complex
• Together, the cranial bone and facial bone forms
 the orbital complex, surrounds each eyes.
 Nasal complex, surrounds the nasal cavity.
• Orbits- the bony recesses that contain the eyes.
 Each orbit is made up of the seven bones of the orbital complex.
• Orbital complex- formed by:
 Roof- frontal bone
 Floor- maxillary bone
 Orbital rim and first portion of the Medial wall- maxillary bone and
the lateral mass of the ethmoid bone.
 Lateral mass articulates with the sphenoid bone and small process of
the palatine bone.
 Laterally- the sphenoid bone and maxillary bone articulate with the
zygomatic bone, which forms the lateral wall of the orbit.
52

• The nasal complex- includes the bones that encloses
the nasal cavities and the paranasal sinuses, air
filled chambers connected to the nasal cavities.
Superior wall- formed by frontal, sphenoid and
ethmoid bones
Lateral walls-formed by the maxillary and lacrimal
bones,the ethmoid bone (superior and middle nasal
conchae), and the inferior nasal conchae.
Anterior margin- much of it formed by the soft
tissue of the nose.
Bridge of the nose- it is supported by the maxillary
and the nasal bone.
54

Paranasal sinuses
• Paranasal sinuss are air
filled spaces present
within some bone
around the nasal
cavities.
• The frontal, sphenoid,
ethmoid, palatine and
maxilllary bones
contain the paranasal
sinuses.
• All of them open into
nasal cavity through its
lateral wall.
56

Paranasal sinuses- functions
• The sinuses lighten the various skull bones
• Warm up and humidify the inspired air
• These also add the resonence to the voice.
• It provide an extensive area of mucous epithelium.
• The mucus secretions are released into the nasal cavities.
• The ciliated epithelium passes the mucous back toward the
throat, where it eventually swallowed. Incoming air is
humidified and warmed as it flows across this thick carpet
of mucus.
• Foreign particles, such as microorganisms or dust becomes
trapped in the sticky mucus and is then swallowed. This
mechanism helps protect more delicate portions of the
respiratory tract.
57

Paranasal sinuses-
• The sinuses are rudimentary, or even absent
at birth. They enlarge rapidly during the age of
6-7 years, i.e time of eruption of permanent
theet and then after puberty. From birth to
adult life; the growth of sinuse is due to
enlargement of the bones; in old age it is due
to due to resorption of the surrounding
cancellous bone.
58

• Many different centres of ossification are involved in the
formation of the skull.
• As development proceeds the centres fused- for
example:
• The sphenoid bone begins as 14 separate ossification
centres
• At birth, fusion has not been completed:
 there are two frontal bone
 Four occipital bone
 several sphenoid and temporal elements.
• At birth, the cranial bones are connected by areas of
fibrous connective tissue, which are flexible and skull can
be distorted without damage.
• The fibrous area between the cranial bones are known
as fontanels.
62

The Fetal Skull
• Fontaneles – fibrous
membranes
connecting the cranial
bones
– Allow the brain
to grow
– Convert to bone
within 24 months
after birth
63Figure 5.13

The vertebral column
• The adult vertebral column
consist of 26 bones:
 The vertebrae 24
 sacrum and
 Coccyx
• Function of vertebral colmn:
 Support
 Bearing the weight of head,
neck, and trunk.
 Transferring the weight from
 the axial skeleton to the
appendicular skeletal.
 Protect the spinal cord.
 Help maintain an upright body
position, as sitting or standing.
67

Division of vertebral column
• It is divided into-
 7 cervical vertebrae- constitute the
neck and extend inferiorly to the
trunk.
 12 thoracic vertebrae- from the upper
back: each articulate with one or more
pairs of ribs.
 5 lumbar vertebrae- form the lower
back
- The 5th articulate with the sacrum.
 5 fused sacral vertebrae – forms
posterior portion of the pelvic cavity.
Originate as a group of five vertebrae,
and completely fused by the age of 25.
 The total length of the vertebral
column of an adult averages 71 cm.
68

Division of vertebral column
• Sometimes the vertbrae are also grouped according to their
mobility.
• The moveable or true vertebrae include:
 the seven cervical
 Twelve thoracic
 Five lumbar
• The fixed vertebrae include those of the sacrum and
coccyx.
• The length of the spine is about 70cm in males and 60 cm
in females.
• The intervertebral disc contribute 1/5th of the length of the
vertebral column.
69

Spinal curvature
• A lateral view of the
vertebral column shows 4
spinal curves;
 Cervical curvature
 Thoracic curvature
 Lumbar curvature
 Sacral curvature
• The sequence of
appearance of curvature is
first primary and then
secondary curvature.
71

Primary curve
• Also known as
accommodation curve,
because they
accommodate thoracic
and abdominopelvic
viscera.
• They appear late in the
foetal life.
• Only curve present in the
vertebral column of the
new born.
72

Secondary curve
• The lumbar and cervical curve
• Also known as compensation
curve, because they help shift
weight over the lower limbs.
• Cervical curve-It appears
during 4-5 after the birth
when the infant learn to
balance the head.
• The lumbar curve appears
during 12-13 months when
the child assumes the upright
posture.
• All four curves are fully
developed by age 10.
73

Structure of a Typical Vertebrae
• Each vertebrae consist of three basic parts:
 A body
 A vertebral arch
 Articular processes
74Figure 5.16

The vertebral body
• The body, or centrum is the
part of a vertebra that
transfers weight along the axis
of the vertebral column.
• It is shaped like a short
cylinder, being rounded from
side to side and having flat
upper and lower surfaces that
are attached to those of
adjoining vertebrae by
intervertebral discs.
• The bodies of adjacent
vertebra are interconnected
by ligaments but are
separated by pads of
fibrocartilage, the
intervertebral disc.
75
Body of the
vertebra
Intervertebral disc

The vertebral arch
• Also called the neural arch.
• Forms the posterior margin of the each
vertebral foramen.
• Together vertebral foramen encloses the
spinal canal, which contain the spinal
cord.
• The vertebral arch has walls called the
pedicles, which arise along the posterior
wall of the lateral margin of the body.
they are short rounded bars project
backwards, and some what laterally,
from the posterior aspect of the body.
• Each pedicles is continuous,
posteriomedially, with a vertical plates of
bone called the lamina
• The laminae of the two side s pass
backward and medially to meet in the
midline. The padicles and laminae
together constituet the vertebral or
neural arch.
76

• The vertebral foramen of the
successive vertebrae
collectively form the
vertebral canal.
• Vertebral canal encloses the
spinal cord.
• The spinous or spinal
process, project posteriorly
from the point where the
vertebral lamina fuse to
complete the vertebral arch.
• The transverse process
project laterally on the both
side from the point where
the lamina join the pedicles.
These process are the site of
muscle attachment, and
they may also articulate with
the ribs. 77

The articular processes
• Projecting upwards from
the junction of the
pedicle and the lamina,
there is on either side, a
superior articular
process; and projecting
downwards there is an
inferior articular process.
Each process bears a
smooth articular facet:
the superior facet of one
vertebra articulates with
the inferior facet of the
vertebra above
78

Cervical vertebrae
• IDENTIFICATON- the cervical vertebrae are identified by th presence of the transverse
foramen.
• There are seven cervical vertebrae, out of which the 3rd -6th are typical, while the first,
second and 7th are atypical.
• Typical cervical vertebrae-
• BODY- the body is small from side to side than from before backward.
• the superior surface is concave transversely with upward projecting lips on each side. the
anterior border of this surface may be bevelled.
• The inferior surface is saddle shaped, being convex from side to side and concave before
backwards. The lateral border are bevelled and form synovial joints with the projecting lips
of the next lower vertebrae.
80

• VERTEBRAL FORAMEN- vertebral foramen is larger than the body. It is triangular in shape
because the pedicles are directed backwards and laterally.
• VERTEBRAL ARCH-
1. the pedicles are directed backwards and laterally. the superior and inferior vertebral notches
are equal size.
2. The Laminae are relatively long and narrow, being thinner and than below.
3. The superior and inferior articular processes- they form articular pillars which project
laterally at the junction of pedicle and laminae.the superior articular facet are flat. They are
directed backwards and upwards. The inferior articular facet are also flat but are directed
forward and downwards.
81

• The transverse processes are pierced by foramina transversaria. Each process has
anterior and posterior roots which ends in the tubercle s joined by the costal
transverse bar.
• The spine is short and bifid. The notch is filled up by the ligamentum nuchae.
82

• the first two cervical vertebrae are
unique, and the 7th is modified.
• When C3-C7 articulate, their interlocking
bodies permit more flexibility than do
those of other regions.
• THE ALTAS- C1
 Ring shaped, Holds up head
 Articulating with the occipital condyles of
the skull. It permits nodding of the skull.
 Atlas can be distinguished from the other
vertebrae by the
1. Lack of a body or spinous process
2. It has shorter anterior and long
posterior vertebral arches, each
containing anterior and posterior
tubercles.
3. The anterior arch is marked by a
median anterior tubercle on its
anterior aspect. Its posterior surface
bears an oval facet which articulate
with the dens. The upper surface of the
arch is marked behind the lateral mass
by groove.
83

4. Lateral mass shows the following
feature:
• Its upper surface bears the superior
articular facet.this facet is elongated
concave, and is directed upwards and
medially. It articulates with the
corresponding condyles to form an
atlanto-occipital joint.
• The lower surface is marked by the
inferior articular facet. this facet is
nearly circular, more or less flat, and is
directed downwards. It articulates
with the corresponding facet on the
axis vertebra to form an atlantoaxial
joint.
 The atlas articulates with the 2nd
cervical vertebrae, the axis. This
articulation permits rotation (shakes
“no” )
5. The transverse process project
laterally form the lateral mass. They
are pierced by the foramen
transversarium. 84

• THE AXIS- C2
• During development,
the body of the atlas
fuses to the body of the
2nd cervical vertebra,
called the axis.
• this fusion creates the
prominent dens, or
odontoid process, of
the axis.
• A transverse ligament
binds the dens to the
inner surface of the
atlas, forming a pivot
joint for the rotation of
the atlas and skull.
85

• BODY AND DENS-
1. the superior surface of the
body is fused with the
dens, and is encroached
upon each side by the
superior articular facets.
The dens articulates
anteriorly with oval fact on
the posterior surface of
the anterior arch of the
atlas, and posteriorly with
the transverse ligament of
the atlas.
2. The inferior surface has a
prominent anterior margin
which project downwards.
3. The anterior surface
presents a median ridge
on each side of which
there is hollowed out
impression. 86

• Vertebral Arch-
1. The pedicles are concealed superiorly
by the superior articular process.
2. The laminae are thick and strong.
3. The superior articular facet occupied
the upper surfaces of the body and
of the massive pedicles. It is a large,
flat, circular facet which is directed
upwards and laterally. it articulates
with the inferior facet of the atlas
vertebra to form atlantoaxial joint.
Each inferior articular facet lies
posterior to the transverse process
and is directed downward and
forwards to articulate with the third
cervicle vertebrae.
4. The transverse processes are very
small and represent the true
posterior tubercles only. The
foramen transversium is directed
upwards and laterally.
5. The spine is large thick and very
strong. It is deeply grooved inferiorly.
Its tip is bifid, terminating in two
rough tubercles.
87

The vertebra prominens
(c7)
• It is also known as the vertebra
prominence because it has a
long, slender spinous process ,
the tip of which can be felt
beneath the skin at the base of
the neck.
• Its spine is thick, long and nearly
horizontal, it is not bifid, but
ends in a tubercle.
• The transverse processes are
comparatively large in size, the
posterior root is large than the
anterior.
• The anterior tubercle is absent.
• The foramen transversarium is
relatively small, sometimes
double, or may be entirely
absent. It does not transmit the
vertebral artery.
88

Thoracic vertebra
Identification-
• They are identified by the presence of
costal facet on the sides of the
vertebral bodies.
• The costal facets may be two or only
one on each sides.
• They are 12, out of which the 2nd-8th
are typical and the remaining five
(first, ninth ,tenth, eleventh and
twelfth) are atypical.
• Has heart shaped body, on each side,
it bears two costal demifacets.
• The superior demifacet is larger and
placed on the upper boarder of the
body near the pedicles. it articulates
with the head of the numerically
corresponding rib.
• The inferior demifacet is smaller and
placed on the lower border in front of
the inferior vertebral notch. It
articulates with the next lower rib. 89

• The vertebral foramen is comparivetly
small and circular.
• The vertebral arch shows:
a. The pedicles are directed straight
backwards
b. Superior vertebral notch is shallow
c. The inferior vertebral notch is deep
and conspicuous.
d. The Laminae overlap each other from
above.
e. The superior articular process project
upward from the junction of the
pedicle and the laminae. The articular
facets are flat and directed backwards.
This direction permits rotatory
movements of the spine.
90

• The inferior articular process are fused to the laminae. their articular facet are
directed forward.
• The transverse process are large, and are directed laterally and backwards from the
junction of the pedicles and laminae.
• The anterior surface of each process bears a facet near its tips, for articulation with
the tubercle of the corresponding rib. In the upper six vertebrae, the costal facet on
the transverse processes are concave, and face forward and laterally. In lower four ,
the facets are flat and face upwards, laterally and slightly forwards. In the last two
vertebrae, the articular facet are absent.
91

• The spine is long, and is directed downwards
and backwards. The 5th -9th spines are the
longest, more vertical and overlap each other.
the upper and lower spines are less oblique
in directions.
• The 1st rib originate at the body of T1,so that
has whole superior facet and an inferior
demifacet on each side.
• Vertebra 9 has only a superior demifacet on
each side.
• Where as T10, T11 and T12 have a single
whole facet on each side.
92

Lumbar vertebra
• There are five lumbar
vertebrae, of which
the first four are
typical, and the fifth is
atypical.
• A lumbar vertebrae is
identified by
a. Its large size
b. The absence of
costal facets on the
body
c. The absence of
foramen in
transverse process.
93

Lumbar vertebra
• The body is large, kidney – shaped and is
wider from side-to-side than from before
backwards. the height of the body is
slightly greater anteriorly than
posteriorly; this contributes to the
forward convexity of the lumbar spine.
• Vertebral foramen is triangular in shape.
• The pedicles are short and strong. They
project backwards from the upper part of
the body , so that the inferior vertebral
notches are much deeper than superior.
• The laminae are shorter, thick, broad.
They are directed backward and medially
to complete the vertebral foramen
posteriorly.
• The spines form a vertical quadrilateral
plate, directed almost backwards and
slightly downwards. It is thickened along
its posterior and inferior borders.
95

Lumbar vertebra • The transverse processes
are thin and tapering, and
are directed laterally and
slightly.
• The superior articular
processes lie further apart
than inferior. Each process
bears a concave facet facing
medially and backwards.
• The inferior articular
processes lie nearer to each
other than the superior. Each
process bearss a concave
facet facing laterally and
forwards.
96

The sacrum
• Consists of the fused
components of the 5 sacral
vertebrae.
• These vertebrae begin fusing
shortly after the puberty and in
general are completely fused
between age of 25 and 30.
• General function
 Sacrum provide protection for
reproductive, digestive and
urinary organs
 Paired articulations, attaches the
axial skeleton to the pelvic girdle
of the appendicular skeleton.
 Broad surface area of the sacrum
provides an extensive area for
the attachment of muscles,
especially those responsible for
movement of the thigh.
97

General feature
• Being triangular, the sacrum has a base or upper surface, an apex or
lower end and four surfaces- pelvic, dorsal, right and left lateral.
• The pelvic surface is smooth and concave.
• The dorsal surface is irregular and convex.
• The narrow, inferior portion os the sacral apex. Whereas the broad
superior surface forms the base.
• the base id directed upward and forwards. the body is lumbar in type, it
articulates with vertebrae L5 at the lumbosacral joint. The projecting
anterior margin is called sacral promontory.
• The vertebral foramina lies behind the body, and lead into the sacral
canal. It is triangular in shape.
• The pedicles are short and are idrected backwards and laterally.
• The laminae are oblique.
• The superior articular processes form synovial articulation with the last
lumbar vertebra.
98

• The spinous processes of the 5 fused
sacral vertebrae form a series of
elevations along the median sacral
crest.
• the laminae of the fifth sacral
vertebra fail to contact one another at
the midline, and they form the sacral
cornua.
• These Ridges establish the margin of
the sacral hiatus, the end of the sacral
canal.
• On either side of the median sacral
crest, the sacral formina represent
the intervertebral foramina, now
enclosed by the fused sacral bones.
• A broad sacral ala, or wing, extends
laterally from each lateral sacral crest.
• The median and lateral sacral crests
provide surface area for the
attachment of muscles of the lower
back and hip.
100

• The sacral curvature is more
pronounced in males than in
females.
• A thickened, flattened area,
the auricular surface, marks
the site of articulation with
the pelvic girdle, the sacroiliac
joint.
• Dorsal to the auricular suface
is the sacral tuberosity, a
roughened area marking the
attachment site of a ligament
that stabilizes this
articulation.
• The anterior surface of the
sacrum is concave.
• After fusion is completed,
prominent transverse lines
mark the former boundaries
of the individual vertebrae.
• At the apex, a flattened area
mark the site of articulation
with the coccyx 101

The coccyx
• It consists of 3-5(typically4)
• It start begun fusing by the age
26.
• The coccyx provides an
attachment site for a number
of ligaments and for a muscle
that constricts the anal
opening.
• The first 2 coccygeal vertebrae
have transverse processes and
unfused neural arches.
• The prominent laminae of the
first coccygeal vertebrae are
known as coccygeal cornua.
• The coccygeal vertebrae do not
fuse completely until late in
adulthood.
102

The Thoracic cage
• The thoracic cage, consist of the:
 Thoracic vertebrae
 Ribs
 The sternum
• The ribs and the sternum form
the rib cage and support the wall
of the thoracic cavity.
• Function:
a. It protects the heart, lungs,
thymus, and other structure in
the thoracic cavity.
b. It serves as an attachment
point for muscles involved in:
 Respiration
 The position of the vertebral
column
 Movements of the pectoral
girdle and upper extrimity.
103Figure 5.19a

• Ribs, or costae, are elongate,
curved, flattened bones that:
a. Originate on or between the
thoracic vertebrae.
b. End in the wall of the thoracic
cavity.
• There are 12 pairs of ribs.
• The first seven pairs are called
true ribs, or vertebrosternal
ribs.
• They reach the anterior body
wall and are connected to the
sternum by separate
cartilaginous extensions, the
costal cartilage.
• Beginning with the first rib, the
vertebrosternal ribs gradually
increase in length and in the
radius of curvature.
104Figure 5.19a
THE RIBS

• Ribs 8- 12 are called
false ribs because they
do not attach directly to
the sternum.
• The costal cartilage of
ribs 8-10, the
vertebrosternal ribs,
fuse together and merge
with the cartilages of rib
pair 7 before they reach
the sternum.
• The last two pairs of
ribs(11 and 12) are called
floating ribs, because
they have no connection
with the sternum, or
vertebral ribs, because
they are attached only to
the vertebrae. 105

• The vertebral end of the rib articulates with the vertebral column
at the head or capitulum.
• The interarticular crest divides the articular surface of the head
into superior and inferior articular facets.
• After a short neck, the tubercle, or tuberculum, projects dorsally.
• The inferior portion of the tubercle contains an articular facet that
contains an articular facet that contacts the transvese process of
the thoracic vertebra. 106

• The bend, or angle, of the rib is the site where the tubular body, or shaft,
begins curving toward the sternum.
• The internal rib surface is concave, and a prominent costal groove along its
inferior border marks the path of nerves and blood vessels.
• The superficial surface is convex and provides an attachment site for muscle
of the pectoral girdle and trunk.
• The intercostal muscles. Which move the ribs, are attached to the superior
and inferior surfaces. with their complex musculature, dual articulation at
the vertebrae, and flexible connection to the sternum, the ribs are quite
mobile.
107

The sternum
• The adult sternum, or breastbone, is a flat bone that
forms in the anterior midline of the thoracic wall.
• The sternum has three components:
1. The broad, triangular manubrium articulates with
the clavicles and the cartilages of the first pair of
ribs. this is the most superior portion of the
sternum. Only the first pair of the ribs is attached
by cartilage to this portion of the sternum.the
jugular notch, located between the calavicular
articulations, is shallow indentation on the
superior surface of the manubrium.
2. The tongue shaped body attaches to the inferior
surface of the manubrium and extends inferiorly
along the midline. Individual costal cartilages from
rib pair 2-7 are attached to this portion of the
sternum.
3. The xiphoid process, the smallest part of the
sternum, is attached to the inferior surface of the
body. The muscular diaphragam and rectus
abdominis muscles attach to the xiphoid process
108

Axial skeletal

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