Skeletal system
Divisions of Skeleton
• Axial Skeleton- 80 bones
that make up the center axis
of the skeleton. (green)
• Appendicular skeleton-126
bones that make up
appendages to axial
skeleton (legs, arms, etc.)
(purple)
Axial Skeleton-Skull
• Made up of 28 irregularly shaped bones
• 2 major divisions
– Cranium (brain case)-8 bone
– Face-14
Cranial Bones
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Frontal
2 parietal
2 temporal
Occipital
Sphenoid
Ethmoid
Cranial bone
• Frontal-forms forehead & anterior part of
cranium.
– Contains FRONTAL PARANASAL SINUSES.
– Forms orbit (eye space) and nasal cavity.
• Parietal bones- give shape to bulging topside of
cranium.
Cranial Bones
• Temporal Bones-lower sides of cranium &
part of its floor
– House middle & inner ear structures
– Mastoid sinuses
• Occipital bone- lower posterior part of skull
– Forms movable joint with first cervical
vertebrae
Cranial Bones
• Sphenoid bones-resemble a bat with
outstretched wings
– Located in central portion of cranial floor.
– Lines orbit & nasal cavity.
– Sphenoid sinuses
– Protects the pituitary gland.
• Ethmoid bone- Irregular bone, lying anterior to
sphenoid but posterior to nasal bones
– Fashions posterior nasal septum, nasal cavity
sidewalls, nasal roof, & sides of orbit.
– Contains ethmoid sinuses .
– Functions in olfaction.
Sutures of the Cranium
• Sutures are immovable joints where two
cranial bones meet.
• Coronal
• Lambdoidal
• Squamous
• Sagittal
Fontanels
• “Soft spots” in infants before ossification (bone
formation).
• Allows compression of skull during birth.
Flash cards
• Using the pictures provided, create a set
of flash cards for the cranial bones.
• On the front of the card, glue the picture
provided, as well as a description of the
bone
• On the back side, write the name of the
bone.
Frontal Bone
Contains muscosa lined,
air filled spaces called sinuses
Connects with parietal bones
in a suture (immovable joint)
called coronal suture
Facial Bones
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2 maxilla
2 zygomatic (malar)
2 nasal
Mandible
2 lacrimal
2 palatine
vomer
2 inferior nasal conchae (turbinates)
Facial Bones
• 2 Maxillae- form part of the floor with
orbits, roof of mouth, floor and sidewall of
nose.
– Maxillary sinuses
• Mandible-lower jaw & only movable joint in
the skull
Facial Bones
• Zygomatic bone-forms outer margin of orbit.
• 2 nasal bones- form upper bride of nose and
with septal cartilage, lower bridge of nose.
• Lacrimal bone-paper thin bone that is posterior
and lateral to each nasal bone.
– Lines the orbit.
– Contains the foramen (hole) for the tear ducts.
– Lines the nasal cavity.
Facial Bones
• 2 palatine bones- join each other like 2 L’s
facing each other.
– Form posterior portion of palate (roof of mouth).
– Form lateral wall of nasal cavity
• Inferior nasal conchae- scroll shaped bone
projecting into nasal cavity.
– Important in the ventilation of lungs by warming &
humidifying.
• Vomer bone- fashions posterior septum
Palatine
Vomer
Paranasal Sinuses
• Muscosa lined, air filled spaces
– maxillary sinuses, the largest of the paranasal
sinuses, are under the eyes, in the maxillary
bones.
– frontal sinuses, superior to the eyes, in the
frontal bone.
– ethmoid sinuses are within the ethmoid bone
between the nose and the eyes.
– sphenoid sinuses, in the sphenoid bone at the
center of the skull base.
Mastoid
External Auditory
Meatus
•Tube running from
outer ear to middle
ear.
•Extends from pinna
(visible ear) to ear
drum.
•Sound enters
through here.
Foramen
• Holes in the bone.
• Foramen magnum is the hole in the cranial
floor that allows passage of spinal cord.
Axial skeleton- Hyoid Bone
• A single bone in the neck.
• Part of axial skeleton
• U shape felt just above
larynx and below
mandible.
• Many muscles of the
mouth floor attached to it
(including tongue).
• Only bone in the body
that does not articulate
with any other.
Axial skeleton- Vertebral Column
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Forms the longitudinal axis of the skeleton.
Flexible because of segmentation.
24 vertebrae plus the sacrum and coccyx.
7 cervical vertebrae: framework of neck
12 thoracic vertebrae: posterior to thoracic
region (chest)
• 5 lumbar vertebrae: small of the back.
Characteristics of vertebral Column
• All but 1st cervical vertebrae
have flat rounded body; sharp
spinous markings at the
anterior; & transverse process.
• All but the sacrum & coccyx
have central opening (vertebral
foramen).
• An upward projection (dens) on
the 2nd cervical vertebrae
provides an axis for rotating the
head.
occipital condyles
• The occipital condyles on the skull are the
articulation point for the skull to the vertebrae.
Ribs & Vertebrae
• The thoracic
Vertebrae have
articular facets for
ribs.
• This is where ribs
and vertebrae
connect.
• There are also facets
between vertebrae
for other vertebrae as
well.
Axial skeleton- Sternum
• Medial portion of the
anterior chest wall.
• 3 parts
– Upper- manubrium:
articulates with
clavicle and first rib.
– Middle- body:
articulates with ribs 210
– Lower- xiphoid
process: cartilage that
ossifies during adult
life
Axial Skeleton- Ribs
• 12 ribs form thoracic cage or thorax along
with sternum & vertebrae.
• Rib’s head articulate with body and ribs
tubercle articulates with vertebrae
• True ribs: first 7 ribs joins a coastal cartilage
that attaches to the sternum directly.
• False ribs do not attach directly to sternum.
• Floating ribs do not attach to sternum at all.
1
2
true
3
4
5
6
false
7
8
11
12
9
10
floating