Download SKELETAL DIVISIONS

The Axial Skeleton
• Forms the longitudinal axis of the body
• Divided into three parts
– Skull
– Vertebral column
– Bony thorax
The Axial Skeleton
Figure 5.6a
The Skull
• Two sets of bones
– Cranium
– Facial bones
• Bones are joined by sutures
• Only the mandible is attached by a freely
movable joint
SKELETAL DIVISIONS
I.
Skull
A. Cranium (8 bones)
1. frontal – forms forehead,
projections under eyebrows,
and superior part of eye socket
2. parietal (2) – superior and
lateral walls, joined together at
sagittal suture, joined with
frontal bone at coronal suture
3. temporal (2) – inferior to parietalsquamous sutures
a. external acoustic (auditory) meatus
(ear canal)
b. styloid process – attachment for
neck muscles
c. zygomatic arch (process)
d. mastoid process – contains
mastoid sinuses and provides for
neck muscle attachment
(mastoiditis)
e. jugular foramen – jugular vein
(“brain drain”)
f. carotid canal – internal carotid
artery (anterior to jugular foramen)
4. occipital – floor and back of skull, joins
parietals at lambdoid suture
a. foramen magnum – opening for
spinal cord
b. occipital condyles – articulates with
first vertebrae (atlas)
5. sphenoid – forms part of cranial floor, eye
orbits, and lateral part of skull
a. sella turcica – holds pituitary gland
b. sphenoid sinuses – air cavities
within the sphenoid bone
c. optic canal-optic nerve to pass to eye
d. superior orbital fissure- cranial
nerves controlling eye pass through
6. ethmoid – forms nasal cavity roof
and medial walls of orbits
a. crista galli – attachment for
outermost covering of the
brain
b. cribriform plates – holes
allowing impulses from smell
receptors to reach the brain
B. Facial bones (14 – only mandible &
vomer single)
1. mandible – lower jaw
a. alveolar margins (for lower teeth)
2. maxillae (2) – upper jaw, “keystone”
face bones
a. palatine processes – anterior
part of hard palate
b. alveolar margins (for upper teeth)
3. palatine (2) – posterior part of hard
palate
4. zygomatic (2) – cheekbones; lateral
walls of orbits
5. lacrimal (2) – medial walls of
orbits, contains passageway for
tears - lacrimal fossa (groove)
6. nasal (2) – bridge of nose
7. vomer – nasal septum
8. Nasal conchae (2) – curved
projections form lateral walls of
nasal cavity
C. Hyoid Bone (non-articulating)
1. movable base for tongue
2. attachment for neck muscles that raise &
lower larynx during swallowing & speaking
• Fetal Skull fontanels
II. Vertebral Column (spine – 26 irregular bones)
A. common features of vertebrae:
1. body/centrum
2. vertebral arch – laminae and pedicles
3. vertebral foramen – opening for spinal
cord
4. transverse processes (2) – lateral
projections
5. spinous process – projection (“spine”)
from vertebral arch
6. superior and inferior articular process –
joints with adjacent vertebrae
7. intervertebral disks – fibrocartilage
(herniated/slipped disks)
B. sections
1. cervical (C1-C7) – smallest and lightest
a. atlas – articulates with occipital condyles to
allow “yes” motion
b. axis – pivot point allowing rotation between
C1 and C2 to allow “no” motion
c. foramina – openings for vertebral arteries
and nerves
2. thoracic (T1-T12)
a. spinous process – long and hook-like
b. contain two costal facets – side for ribs
3. lumbar (L1-L5)
a. most massive
b. spinous process – hatchet-shaped
4. sacrum – fusion of 5 vertebrae
a. alae (wings) – articulate with hipbones to form
sacroiliac joints
b. forms posterior pelvic wall
* vertebral column continues in sacrum as sacral canal
5. coccyx (3-5 bones) – tailbone
B. curvatures
1. primary –
thoracic (convex) &
sacral (convex),
present at birth
2. secondary –
cervical (concave)
appears when baby
begins to raise head
& lumbar (concave)
when begins to walk
D. Abnormalities (text pg. 154)
1. scoliosis – abnormal side-to-side curvature
2. kyphosis – “hunchback,” abnormal thoracic
curvature
3. lordosis – “swayback,” exaggerated lumbar
curvature
III. Bony Thorax
A. sternum
1. consists of 3 bones:
a. manubrium
b. body
c. xiphoid process
2. sternal puncture – procedure where
needle is inserted into the marrow of
the sternum to withdraw hematopoietic
tissue (bone marrow)
B. ribs (12 pairs)
- attachments made by costal cartilage
- spaces between filled with intercostal
muscle
1. true ribs – first 7 pairs, attached to
sternum
2. false ribs – next 5 pairs, either indirectly
attached to sternum or not attached at
all
a. floating ribs – last 2 pair of false ribs,
have no attachment to sternum