SKELETAL SYSTEM (AXIAL)

HUMAN ANATOMY AND PHYSIOLOGY SUMMER, 2002

AXIAL - long axis: ribs, breastbone, skull, backbone (80)

APPENDICULAR - free appendages (upper/lower) + girdle (126)

BONE TYPES (GENERAL)

• LONG - length > width; slightly curved (humerus, femur)

• SHORT - length = width; usually spongy with compact surface (wrist, ankle)

• FLAT - thin, 2 or more compact plates enclosing a spongy layer (ribs,
sternum)

• IRREGULAR - variable (vertebrae)

• SEASAMOID - tear drop; formed within tendon (patella)

SKELETAL TERMINOLOGY

• Elevations and projections - process, ramus

• Processes for tendon/ligament attachment – trochanter, tuberosity, tubercle, crest, line

• Processes formed bone articulations – head, neck, condyle, trochlea, facet, spine

• Depressions - fossa, sulcus

• Openings - foramen, fissure, sinus, antrum

I. SKULL

A. CRANIAL(8)

1. FRONTAL (1) - 'forehead', roofs eyesockets, forms ant part of cranial floor; FRONTAL SQUAM/ VERTICAL PLATE –forehead; FRONTAL SINUS - deep to forehead, mucus lined, sound chamber.

2. PARIETAL (2) -'sides', roof of cranial cavity; protects blood
vessels supplying Dura Matter.

3. TEMPORAL (2) - 'temple'; PETROUS PORTION - skull base between
sphenoid and occipital, houses internal ear, forms external auditory canal; has
carotid and jugular foramen; MANDIBULAR FOSSA - socket between
squamous & petrous portions ; ARTICULAR TUBERCLE - thin expanse
forming anterior & superior part of length; MF and AT articulate with
condylar process of mandible- Temporomandibular Joint (TMJ):
STYLOID PROCESS - projects downward from undersurface, attachment for
muscles/ligaments of tongue, neck.

4. OCCIPITAL (1) - posterior & major part of cranium base; FORAMEN

MAGNUM - inferior area has medulla oblongata, it's membranes, XI, vertebral and spinal arteries through it.

5. SPHENOID (1) - location middle part skull base, "keystone of cranial floor”, body contains SPENOIDAL SINUS- drains into

nasal cavity; SELLA TURCICA - depression on superior surfaces, houses pituitary gland.

6. ETHMOID (1) – light/spongy, at anterior floor of cranium between orbits

LABYRINTHS (lateral masses) - form wall between nasal cavities and orbits, has air spaces within - collectively ETHMOIDAL SINUS; PERPENDICULAR PLATE - superior part of nasal septum; SUPERIOR & MIDDLE NASAL CONCHAE (2 thin scroll shaped bones on each side of nasal septum) efficient circulation and filtration of inhaled air.

B. FACIAL (14)

1. NASAL (2) - meet at face's middle & superior area - forms nose
bridge: inferior part is cartilage.

2. MAXILLAE (2) - forms upper jaw; articulates with every face bone except
mandibular; MAXILLARY SINUS (within each) - drains into nasal cavity;
ALVEOLAR PROCESS - has ALVEOLI (bony sockets for upper teeth).

3. ZYGOMATIC (2) - 'cheekbone' + outer wall & floor of orbitals.

4. MANDIBLE (1) - 'lower jawbone', strongest/largest/only movable skull bone;
RAMI - perpendicular portion; has CONDYLAR PROCESS - articulates with
mandibular fossa and articular tubercle of temporal bone
(TEMPOROMANDIBULAR JOINT – TM); CORONOID PROCESS -
attachment for temporalis muscle; ALVEOLAR PROCESS - arch containing
ALVEOLI (sockets for lower teeth); MENTAL FORAMEN (below 1st molar) -
Mental Nerve and vessels pass through.

5. LACRIMAL (2) - thin/fingernail shaped; smallest facial bone; posterior and lateral
to nasal bone in middle wall of orbital.

6. PALANTINE (2)-‘L shaped', forms posterior part of hard palate, part of floor, lateral

wall of nasal cavity and some orbital floor.

7. INFERIOR NASAL CONCHA (2) - scroll-like, part of lateral wall of nasal cavity; projects into nasal cavity; inferior to superior & middle nasal conchae of ethmoid; helps with circulation and filtration of air.

8. VOMER (1) – triangular, forms interior and posterior part or nasal septum;

NASAL SEPTUM = perpendicular plate of ethmoid, septal cartilage and vomer.

HYOID - doesn't articulate with any other bone; suspended from styloid process of temporal bone by muscles/ligaments; supports tongue as attachment site for its muscles.

C. SUTURES (STITCHES)- immovable joints between skull bones

1. CORONAL - between frontal and parietal bones

2. SAGITTAL - between 2 parietal bones

3. LAMBDOIDAL - between parietal and occipital bones

4. SQUAMOSAL - between parietal and temporal bones

D. FONTANELS - membrane filled areas between cranial bones: pre-intra membraneous ossification sites

1. ANTERIOR (FRONTAL) - 2 parietal and 1 frontal bone; diamond shaped; 18-24 months.

2. POSTERIOR (OCCIPITAL)- 2 parietal and 1 occipital bone; diamond shaped;
2 months.

3. ANTEROLATERAL (SPHENOIDAL) - junction of frontal temporal and sphenoid
bones: 3 months.

4. POSTERIOLATERAL (MASTOID) - junction of parietal, occipital, and temporal;
Ossifies after 12 months

II. VERTEBRAL COLUMN (SPINE) - Functions as protection/house spinal cord, support head, attachment for ribs: flexibility (anterior, posterior and laterally)

A. VERTEBRAE - composite units for column

1. Divisions:

CERVICAL (7) - neck area 7

THORACIC (12)-post. to thoracic cavity 12
LUMBAR (5) - lower back 5

SACRAL (5) - fused as one bone (sacrum) 1

COCCYGEAL (4) - fused as 1 or 2 1

unfused - 33 fused - 26

2. COMPONENTS (GENERAL):

a. BODY - thick anterior (weight bearing), sup. and inf. roughened for disc
attachment

b. VERTEBRAL (NEURAL) ARCH - post, extension; surrounds spinal cord

c. LAMINA - flattened, forms post, part of arch

d. PEDICLE - forms medial part of arch

e. VERTEBRAL FORAMEN - area between body and arch, contains spinal cord

f. INTERVERTEBRAL FORAMEN - opening between vertebrae, passage for
spinal nerves (31 pr)

g. PROCESSES (7) -

Transverse (2) - area where pedicle and lamina join; side directed

Spinous (1) - laminae junction; post. and inf. directed

Sup. Articular (2) - adjacent vertebrae; superior directed

Inf. Articular (2) - adjacent vertebrae; inferior directed

3. TYPES

a. CERVICAL VERTEBRAE (7)

small body, large arch; BIFID (cleft) spinous process (2-6 only); 3 foramina: 1 vertebral, 2 transverse: for vertebral artery/vein/nerves

• ATLAS (C 1) - ring with bone with ant. and post. arch and larger lateral
mass; no spinous process

• AXIS (C2) - has body; DENS - peglike process thru ring of atlas

b. THORACIC VERTEBRAE (12)

larger, long spinous process, laterally flat, directed inf.; has transverse process with facets for ribs except for Tl & T2; bodies have whole or 1/2 facets (DEMIFACETS) to articulate with ribs

c. LUMBAR VERTEBRAE (5)

largest, strongest with short projections; sup. articular processes are medial rather than superior; inf. articular processes are lateral rather than inferior

d. SACRUM VERTEBRAE (5 into 1)

union of 5 vertebrae; foundation of pelvic girdle

• SACRAL HIATUS - area where S4 & S5 fail to meet - site of caudal
anesthesia

e. COCCYX VERTEBRAE (4 to 1)
triangular shaped; fusion of last 4 vertebrae

4. INTERVERTEBRAL DISC - cushion between adjacent vertebrae; from axis to sacrum; strengthens joint, permits movement, absorbs vertical shock

a. ANNULUS FIBROSUS – outer; fibrocartilage

b. NUCLEUS PULPOSUS – inner; pulpv/elastic

5. SPINAL CURVES - provides strength, balance, shock absorption

a. PRIMARY: THORACIC, SACRAL; anterior concave

b. SECONDARY: CERVICAL, LUMBAR; anterior convex

C. THORAX (CHEST)- bony cage formed by sternum, costal cartilage, ribs and bodies of thoracic vertebrae; encloses/protects thoracic cavity, supports girdle and upper extremities

1. STERNUM (BREASTBONE)- median line of ant. thoracic walls

a. MANUBRIUM - triangular sup. Portion; JUGULAR NOTCH -

b. BODY - middle, largest part; articulates with ribs 3-10

c. XIPHOID PROCESS – inf. smallest part; no ribs attach; initially hyaline cartilage,
ossifies at 40 yrs.