Bones & Muscles Of The Axial Skeleton

Front 1

Osteology of Axial Skeleton

Back 1

the axial skeleton consists of:
a) skull
b) vertebral column - cervical, thoracic, & lumbar vertebrae, sacrum & coccyx
c) rib cage - ribs, sternum, thoracic vertebrae

Front 2

Vertebral Column
(spinal column, spine)

Back 2

1) Consists originally of 33 vertebrae:
a) 7 cervical (C1-C7)
b) 12 thoracic (T1-T12)
c) 5 lumbar (L1-L5
d) 5 fused into the sacrum
e) coccyx - 3 fused together, 1 seperate (all vertebrae are small & rudimentary)

Front 3

Vertebral Curves
- Normal
- Primary
- Secondary

Back 3

1) In adult, the vertebral column has 4 curves:
a) primary curves - curves develop in fetus; directed posteriorly (outside of "C" is posterior)
1) thoracic curve
2) sacrococcygeal curve - formed by fused vertebrae of sacrum & coccyx
b) secondary curves - develop after birth; both directed anteriorly
1) cervical curve - develops when infant begins to hold head up
2) lumbar curve - develops when infant begins to sit up & later to stand
c) curves add supporting strngth and spring to vertebral column

Front 4

Vertebral Curves
- Abnormal

Back 4

a) kyphosis - excessive posterior curvature; usually seen in thoracic region (humpback)
b) lordosis - excessive anterior curvature; usually seen in lumbar region (swayback)
c) scoliosis - lateral curvature; most common abnormal curvature; due to unequal growth of 2 sides ov vertebral column

Front 5

Structure of typical vertebrae

1) Body
2) Arch
3) Projections from Arch

Back 5

1) body - weight supporting region of vertebrae
2) vertebral arch
a) formed by 2 pedicles (body of transverse process) and 2 lamina (transverse process to spinous process)
b) arch surrounds vertebral foramen
c) successive vertebral foramen make up vertebral canal - for passage of spinal cord
3) projections from vertebral arch
a) spinous process - prokects posteriorly
b) transverse process (2) - project laterally
c) superior articular processes (2) - project upward from superior side of lamina
d) inferior articular processes (2) - project downward from inferior side of lamina
e) superior & inferior articular processes from adjacent vertebrae articulate together; form synovial joint & define intervertebral foramen (for passage of spinal nerve)

Front 6

Modifications of Vertebrae by Region
x4
1) Cervical

Back 6

a) transverse process has transverse foramen - allows for passage of vertebral artery
b) transverse process grooved by spinal nerve - forms anterior & posterior tubercles
c) have small body with bifid spinous process (Y-Shaped)
d) C1 (atlas) - ring-shaped (lacks body); inside of anterior arch articulates with dens of axis
e) C2 (axis) - has dens (odontoid process) - superior projection that articulates with atlas

Front 7

Modifications of Vertebrae by Region
x4
2) Thoracic

Back 7

a) long, inferiorly directed spinous processes - overlap succeeding vertebrae
b) have articulation sites for rib on body (2 sites) and on transverse process (1 site)

Front 8

Modifications of Vertebrae by Region
x4
3) Lumbar

Back 8

a) large, thick body and short, blunt spinous process

Front 9

Modifications of Vertebrae by Region
x4
4) Sacrum

Back 9

- formed by fusion of 5 sacral vertebrae
a) median sacral crest - at midline; formed by fusion of spinous processes
b) lateral sacral crest - formed by fusion of transverse processes
c) dorsal & ventral sacral foramen - for exit of dorsal or ventral branches of sacral spinal nerve

Front 10

Joints (Articulation) of Vertebral Column

Back 10

1) atlanto-occipital joints
a) between superior articular processes of atlas & ocipital condyles of skull
b) have deep anterior-posterior curve - allow for flexion/extension of head only (no rotation)
2) atlantoaxial joints
a) 2 parts: between superior articular facet of axis & inferior articular facet of atlas, and between dens of axis & anterior arch of atlas
b) dens & flattened articular facets allow for rotation (side to side motion) of head only (no flexion-extension)
3) all other vertebrae articulate between adjacent superior-inferior articular facets
a) allow varying degrees of flexion/extension, lateral flexion 9bending to side), or rotation

Front 11

Intervertebral Discs:

Back 11

1) strongest attachment between adjacent vertebrae, but still allow for movement
a) responsible for 25% of total vertebral column length (height of body trunk from sacrum to skull)
2) consists of 2 parts:
a) anulus fibrosus - tough, fibrous outer layer
b) nucleus pulposus - softer (gelatinous) central portion
3) weakening of anulus fibrosus allows for protrusion or rupture of nucleus pulposus part of disc
a) can press on spinal nerve as it exits through intervertebral foramen - may produce pain, numbness, ,uscle spasms - affected area corresponds to dermatome/myotome

Front 12

Ligaments of Vertebral Column

Back 12

1) supraspinous ligament - runs length of vertebral column; connects spinous processes
a) supraspinous ligament serves to resist hyperflexion of vertebral column
b) ligamentum nuchae - posterior expansion of supraspinous ligament in neck
1) attaches to cervical spinous processes & to external occipital protuberence at base of skull
2) serves to support head (weight of head is in front of vertebral column; ligamentum nuchae resists forward fall of head)
2) Anterior longitudinal ligament - runs down anterior side of vertebral bodies
a) protects against hyperextension (whiplash injury), particularly in neck region

Front 13

Rib Cage

Back 13

consists of 12 pairs of ribs, sternum, & 12 thoracic vertebrae
2) provides protection for heart & lungs and functions as part of the mechanism for respiration

Front 14

Sternum

Back 14

1) consists of manubrium, body & xiphoid process
a) jugular notch - superior border of manubrium
b) clavisular notch - for articulation between manubrium of sternum & clavicle (sternoclavicular joint)
2) sternal angle - junction between manubrium & body, attachment site of rib 2

Front 15

Ribs

Back 15

a) head - for most ribs, head articulates with body of same numbered vertebrae plus (to lesser degree), to body of next higher vertebrae
b) neck
c) tubercle - articulates with transverse process of same numbered vertebrae
d) angle of rib - sharper bend in curve of rib; most dorsal (posterior) point of rib
e) costal groove - on inferior margin of rib; for passage of intercostal artery, vein, & nerve
f) costal cartilage - cartilage extension attached to anterior end of all ribs
1) true ribs - ribs 1-7: united by cartilage directly to sternum
a) angle of attachment for ribs 5-7 runs sharply upward to join sternum
2) false rib - ribs 8-10: connected by costal cartilage to cartilage of next higher rib
3) floating ribs - ribs 11-12: costal cartilage ends in abdominal musculature

Front 16

Deep Back Muscles

1) has 3 layers of muscle

Back 16

a) superficial - muscles associated with movement of upper limb
b) intermediate - muscles associated with respiratory movements
c) deep - muscles associated with movements of vertebral column

Front 17

Deep Back Muscles

2) Deep back muscles group

Back 17

- erector spinae muscle
a) runs longitudinally - forms large muscular bulges parallel to sides of vertebral column
b) arises from single common origin - broad aponeurosis from posterior sacrum, posterior iliac crest, & spines of all lumbar vertebrae
c) just inferior to last rib, divides into 3 vertical columns of muscle

Front 18

Deep Back Muscles

3) Erector Spinae Muscle

Back 18

a) iliocostalis muscle - most lateral column of muscle
1) runs from area of common origin up to all ribs (near angle of rib) and to lower cervical vertebrae
b) longissimus muscle - middle muscle column
1) runs entire length of vertebral column, attaching to transvers processes
2) ends at base of skull
c) spinalis muscle - most medial muscle column
1) thin muscle layer that attaches to spinous processes of thoracic vertebrae

Front 19

Deep Back Muscles

4) Actions of Erector Spinae Muscle

Back 19

a) unilateral - lateral flexion of head, neck, or trunk of body
b) bilateral - chief extensors of vertebral column
1) most common muscles in lower back strain
c) postural - maintain upright stance & stabilize vertebral column during other movements

- innervated by dorsal branches from spinal nerves