Transcript Axial Skeletal System Notes

Guided Notes for the Axial
Skeleton
1. The axial skeleton can be
divided into three parts,
which are the skull, the
vertebral column, and the
bony thorax.
2. The skull is formed by two
sets of bones. The cranium
encloses and protects the
fragile brain tissue. The
facial bones hold the eyes in
an anterior position.
The Cranial Bones
Name of Bone
Frontal
Single or
Paired
Single
Description
Parietal
Paired
Superior and
lateral walls of the
cranium
Temporal
Paired
Inferior to the
parietal bones,
joined at
squamous sutures
Forms the
forehead, the bony
projections under
the eyebrows, and
the superior eye
orbit
The Cranial Bones
Occipital
Single
Most posterior
bone of the
cranium/ floor
and back of the
skull
Sphenoid
Single
Butterfly-shaped,
forms the floor of
the cranial cavity
Ethmoid
Single
Anterior to
sphenoid, forms
the roof of the
nasal cavity
4. 14 bones compose the face.
Twelve are paired; only the
mandible and vomer are
single.
5. The two maxilla fuse to form
the upper jaw. Like many other
facial bones, the maxillae contain
sinuses, which drain into the
nasal passages. They are called
paranasal sinuses.
6. The zygomatic bones are
commonly referred to as the
cheekbones.
7. The mandible, or lower jaw, is
the largest and strongest bone of
the face. It joins the temporal
bones on each side of the face,
forming the only freely movable
joints in the skull.
8. The hyoid bone is unique in that
it is the only bone of the body
that does not articulate directly
with any other bone. The hyoid
bone serves as a movable base
for the tongue and attachment
point for neck muscles.
9. In the newborn, the skull has
regions that have yet to be converted
to bone. These fibrous membranes
are called fontanels; they connect the
cranial bones. The fontanels allow
the fetal skull to be compressed
slightly during birth. They can no
longer be felt 22 to 24 months after
birth.
10. The vertebral column extends from
the skull to the pelvis, where it
transmits the weight of the body to
the lower limbs. The spine is formed
from 26 irregular bones connected
and reinforced by ligaments in such a
way that a curved, flexible structure
results.
11. The single vertebrae are
separated by pads of flexible
fibrocartilage called
intervertebral discs, which
cushion the vertebrae and
absorb shocks.
Common Structures of Vertebrae
A.
B.
Body: disc-like; weight-bearing part of vertebra
Vertebral Arch: formed from the joining of the
laminae and pedicles
C. Vertebral Foramen: canal through which the
spinal cord passes
D. Transverse Process: (2) lateral projection from
the vertebral arch
E. Spinous Process: single projection arising
posteriorly from vertebral arch
F. Articular Processes: paired projections lateral to
the foramen, allowing vertebrae to form joints
Types of Vertebrae
Name
Cervical
# of
bones
7
Single or
fused
Single
description
Thoracic
12
Single
heart-shaped
body; long,
hooked
spinous
process
Lumbar
5
Single
Massive,
block-like
bodies; short,
hatchet-
Form the neck
region of the
spine (atlas
and axis)
Types of Vertebrae
Name
# of
bones
Sacrum
5
Coccyx
3-5
Single or
fused
fused
fused
description
Articulate
with lumbar
vertebrae and
hips
The human
tail-bone;
function is
not certain,
but may aid
balance
14. The sternum, ribs, and
thoracic vertebrae make up
the bony thorax.
15. The sternum is a typical
flat bone, and is a result of
the fusion of the manubrium,
body, and xiphoid process.
16. Twelve pairs of ribs form
the walls of the thoracic
cage. All the ribs articulate
with the vertebral column
and then curve downward
and toward the anterior body
surface.
3 Different Types of Ribs
A. True ribs: the first 7 pairs, which
attach directly to the sternum by
costal cartilage
B. False ribs: the next 5 pairs attach
indirectly to the sternum by a shared
cartilage
C. Floating ribs: do not attach to the
sternum at all. They are the lowest
2 pairs of false ribs.