Skeletal System-2
Honors Anatomy
for copy
Essential Question
• What is the main contribution the axial
skeleton makes to homeostasis?
Divisions of the Skeleton
• AXIAL SKELETON
• Skull
– Cranium
– Face
•
•
•
•
Hyoid
Auditory Ossicles
Vertebral Column
Thorax
• APPENDICULAR
SKELETON:
• Pectoral Girdle
• Upper Limbs
• Pelvic Girdle
• Lower Limbs
Types of Bone
• bones fall into 1 of 5 main types based on
shape:
– Long
– Short
– Flat
– Irregular
– Sesamoid
Short Bones
• somewhat cube-shaped
• nearly equal in length as width
• consist of:
– spongy bone except @ surface
Flat Bones
• Composed of:
– 2 nearly parallel plates of compact bone
enclosing spongy bone inside
• Function:
– give considerable protection
– place for muscle attachment
Irregular Bones
• complex shapes (do not fit in other
categories)
• vary in amt spongy bone
Sesamoid Bones
• develop w/in certain tendons where there
is considerable friction, tension, &
physical stress
• function: protect tendon from excessive
wear & tear
• vary in # person to person but everyone
has 2 patella which develop in
quadriceps femoris tendon
Sutural Bones
• classified by location (w/in a suture: a
seam between 2 cranial bones)
• not everyone has them
Bone Surface Markings
• 2 major types:
1. depressions & openings
– form joints or allow passage of vessels &
nerves
2. processes
– projections or outgrowths that either help
form joints or serve as attachment points for
ligaments & tendons
Axial skeleton
Skull
• 22 bones in 2 categories:
1. Cranium
– 8 bones that form cranial cavity
1. 1 frontal bone
2. 2 parietal bones
3. 2 temporal bones
4. 1 occipital bone
5. 1 sphenoid bone
6. 1 ethmoid bone
Skull
2. Facial Bones
14 bones that form the face
•
2 nasal bones
» 2 maxillae
» 1 mandible
» 2 zygomatic
» 2 lacrimal
» 2 palantine
» 2 inferior nasal conchae
» 1 vomer
Skull: Cavities
1.
2.
3.
4.
5.
Cranial Cavity
Nasal Cavity
Orbits
Paranasal Sinuses
Middle & Inner Ear Cavities
Cavities of the Skull
Functions of Cranial Bones
1. protecting brain
2. stabilizing position of brain, vessels, &
nerves through attachments to the
meninges
3. outer surfaces provide large areas of
attachment for muscles that move parts
of the head & some for facial
expression
Frontal Bone
Parietal Bones
• form greater portion of sides & roof of
cranial cavity
Temporal Bones
• form inferior, lateral aspects of the
cranium & part of the cranial floor
• its zygomatic process forms the lateral
half of the zygomatic arch
• mandibular fossa: where condylar
process of mandible forms TMJ
(temporal mandibular joint)
Temporal Bones
• external auditory meatus: ear canal
• mastoid: posterior & inferior to external
auditory meatus, contains “air cells”
(mastoiditis: inflammation in air cells)
Temporal Bone: Petrous Portion
• base of skull between sphenoid &
occipital bones
• houses middle & inner ear
• Carotid foramen & Jugular foramen
Temporal Bones
• internal auditory meatus: passage of
Cranial nerves VII (facial n.) and VIII
(vestibulocochlear n.)
• styloid process: point of attachment for
muscles & ligaments of the tongue &
neck
Temporal Bone: Internal Surface
Occipital Bone
• forms back of head & most of base of
skull
• foramen magnum: large hole spinal cord
passes thru,
• occipital condyles: articulate with 1st
cervical vertebra (atlas)
Sphenoid Bone
• middle base of skull
• *articulates with all other cranial bones
• shape resembles a bat
Sphenoid Bone
• sella turcica: (Turkish saddle) the “seat”
of the saddle is the hypophyseal fossa:
where the pituitary gland sits
• optic foramen: between body & lesser
wings, cranial nerve II (optic n.) and
opthlamic artery pass thru
Ethmoid Bone
• “like a sieve”
• midline of anterior part of cranial floor,
anterior to sphenoid, posterior to nasal
bones
• cribiforme plate: forms roof of nasal cavity,
the holes of the sieve where olfactory
nerves pass from roof of nasal cavity to
brain
• crista galla: triangular process which serves
as pt of attachment for meninges of brain
Ethmoid Bone
Facial Bones
• shape of face changes dramatically
during 1st 2 yrs of life:
– brain & cranial bones expand
– 1st set of teeth erupt
– paranasal sinuses enlarge
– growth of face stops ~16 years old
Facial Bones
• 14 facial bones:
1. 2 nasal bones
2. 2 maxillae
3. 2 zygomatic bones
4. 1 mandible
5. 2 lacrimal bones
6. 2 palatine bones
7. 2 inferior nasal conchae
8. 1 vomer
Nasal Bones
• form part of the bridge of the nose (rest
is cartilage)
Maxillae
• = upper jaws
• *articulate with every bone in face except
the mandible
• form part of floor of orbits, parts of nasal
cavity, & most of the hard palate (bony
roof of mouth)
• each one has large maxillary sinus
• alveolar process is small arch that
contains the alveolar sockets for upper
set of teeth
Maxillae
Cleft Palate & Cleft Lip
• 10-12 wks gestation the palatine
processes of maxillae typically join
• not doing so  cleft palate +/- cleft lip
– speech & swallowing can be affected
– many ear infections
– reparative surgery recommended 1st few wks
of life / surgery needs to be completed by 12
– 18 mos b/4 speech: speech therapy &
orthodontic care frequently necessary
Zygomatic Bones
• “cheekbones”: the
temporal process of
the zygomatic bone
articulates with the
zygomatic process of
the temporal bone
• also part of floor of
orbit
Inferior Nasal Conchae
• inferior to the middle nasal conchae of
the ethmoid bone forming part of lateral
wall of nasal cavity
• same function as superior & middle
conchae: swirling inhaled air to deposit
particulates but not involved in sense of
smell
Vomer
• Δ shaped bone on the floor of nasal
cavity forming inferior portion of nasal
septum
Mandible
• largest & strongest facial bone (lower
jaw)
• alveolar processes hold lower teeth
sockets
• mental foramen: dentist numb mental
nerve
Sutures
• an immovable joint in an adult found
only between skull bones & holds most
skull bones together
• name generally reflects bones they unite
Newborn Skull
Hyoid Bone
• “U-shaped “
• *does not articulate with any other bone in
skeleton
• suspended by ligaments from styloid
process of temporal bone
• in anterior neck between mandible &
larynx
• function: supports tongue
• *frequently fractured during strangulation
Hyoid Bone
Vertebral Column
• Fetus has anteriorly
concave curve
• 3 mos old when holds
head cervical curve
develops
• lumbar curve develops
as infant sits up,
stands, walks
Intervertebral Discs
• between bodies of consecutive vertebra
– under compression they flatten & broaden
– harden, less elastic w/aging & narrow  loss
of height
• annulus fibrosus: outer fibrous ring
• nucleus pulposus: inner soft, highly
elastic
Parts of a Vertebra
• Body
– thicker, anterior portion, weight bearing portion
• Vertebral Foramina
– contains spinal cord, adipose, areolar CT, blood
vessels
• Spinous Process
– 1 of 7 processes, posterior, palpable on back of
body
Transverse Processes: on each side, extending
laterally
Vertebrae: 1st & 2nd Cervical
• Atlas
– ring-shaped
– articulates with
condyles of occipital
bone
– allows you to nod
head “yes”
• Axis
– 2nd cervical v.
– allows you to shake
head “no”
Typical Thoracic Vertebrae
• T-1 to T-12
• larger & stronger
than cervical v.
• distinguishing
feature: articulate
with ribs (facets on
transverse processes
of T-1 to T-10
Typical Lumbar Vertebrae
• L-1 to L-5
• largest & strongest of
the vertebrae
• processes are short &
thick
Sacrum
• triangular bone
formed by union of
S-1 to S-5
• fusion begins ~16,
complete by age 30
• female: shorter,
wider, more curved
S-2 to S-3
Coccyx
• small triangle
• formed by fusion of
4 coccygeal v. (Co-1
to Co-4), start
between 20 & 30
• females points
inferiorly; males it
points anteriorly
Thorax
• refers to entire chest
• skeletal part of thorax is thoracic cage
– Sternum
– Ribs
Sternum
• aka “breastbone”
• flat bone in center of anterior thorax
• 3 bones that fuse by age 25
Sternum
1.
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•
•
•
•
Manubrium
superior portion
suprasternal notch
clavicular notches
articulates with costal
cartilage of 1st & 2nd rib
sternal angle: where it
articulates with body
Sternum
2. Body
• middle & largest
portion
• articulates with
costal cartilage of 2nd
thru 10 ribs
Sternum
3. Xiphoid Process
• cartilagenous in
infancy
• not completely
ossified until ~age 40
• avoid it during CPR
Ribs: 12 Pair
• increase in length 1st thru 7th then
decrease in length to 12th
• 1st thru 7th ribs (true ribs) have direct
anterior attachment to sternum by strip
of hyaline cartilage which contribute to
elasticity of thoracic cage
• 8th thru 10th ribs attach to each other &
then to cartilages of 7th rib
• 11th & 12th ribs: floating ribs
Ribs
• all 12 attach posteriorly to vertebrae
• Parts of a Rib
1. Head
2. Neck
3. Tubercle
4. Body
5. Costal Angle
Abnormal Curvatures of Spine
• Scoliosis
• lateral bending
• usually in thoracic
region
Abnormal Curvature of Spine
• Kyphosis
• exaggeration of the
thoracic curve
• seen in TB of spine,
congenital
malformation,
elderly