The Axial Skeleton Chapter 7

I. Skeletal Divisions (206 bones) Axial Skeleton (80 bones) Forms longitudinal axis of the body Consists of: Skull Vertebral column Ribs Sternum

Appendicular Skeleton (126 bones) Consists of Pectoral girdle Pelvic girdle Bones of the limbs

II. The Skull (22 bones) Functions Protects Guards entrances to digestive & respiratory systems

Cranium (braincase) (8 bones)

1. Occipital Bone (1 bone) Forms posterior & inferior surfaces

2. Parietal Bones (2 bones) Forms superior & lateral surfaces

3. Frontal Bone (1 bone) Forms anterior portion of skull & roof of orbits

4. Temporal Bones (2 bones) Surrounds & protects sense organs of inner ear

5. Sphenoid Bone (1 bone) Cross-brace that strengthens sides of skull (looks like a bat)

6. Ethmoid Bone (1 bone) Forms roof of nasal cavity, part of nasal septum

Facial Bones ( 14 bones)

1. Maxillary Bones (2 bones) Supports the teeth

2. Palatine Bones (2 bones) Forms portion of hard palate

3. Lacrimal Bones (2 bones) Forms medial wall of orbits

4. Nasal Bones (2 bones) Supports superior portion of bridge of nose

5. Zygomatic Bones (2 bones) Forms rim & lateral wall of orbits

6. Vomer Bone (1 bone) Forms interior portion of bony nasal septum

7. Inferior Nasal Conchae (2 bones) Creates turbulence in air passing through nasal cavity WHY???

8. Mandible Bone (1 bone) Lower jaw

Sinuses Makes bones lighter Produces mucus to moisten & clean air in and near the sinuses

E. Sutures- Immovable joints connected with dense fibrous connective tissue Lambdoidal Suture- between occipital & parietal bones Coronal Suture- between frontal and parietal bones Sagittal Suture- between parietal bones

4. Squamosal Sutures- between temporal & parietal bones 5. Fontanels- fibrous area between cranial bones in infants a. allow skull to be distorted/squished to ease delivery b. the frontal fontanel persists until a child is nearly 2 yrs. old

Sutures of the Skull

F. Associated Bones of the Skull (7) Auditory Ossicles (6 bones) 3 bones per ear malleus, incus & staples

Hyoid Bone (1 bone) Supports larynx Only free standing bone not connected to another bone

III. The Vertebral Column - 33 total bones

A. Functions of the V.C. Provide a column of support Bear the weight of the head, neck & trunk Protect the spinal cord Helps maintain an upright body position (Sitting/Standing)

B. Divisions of the V.C. Cervical Region a) Made of 7 vertebrae b) Constitutes the neck region c) Labeled C1-C7 (Superior to Inferior) i. C1 is called the Atlas -holds up the head - Articulates w/ occipital condyles - Allows “yes” movement ii. C2 is called the Axis - Pivots around the Atlas - Allows “no” movement

Thoracic Region a) Made of 12 vertebrae b) Constitutes the chest/upper back region c) Labeled T1-T12 (Superior to Inferior) d) Articulate with the ribs

Lumbar Region a) Made of 5 vertebrae b) Constitutes the lower back region c) Labeled L1-L5 (Superior to Inferior) d) Large, weight-bearing bones e) Provides site for muscle attachment

4. Sacrum a) Made of 5 fused vertebrae b) Constitutes the posterior portion of the pelvis c) Provides protection for reproductive, digestive, & urinary organs

5. Coccyx a) Made of 3-5 fused vertebrae b) Also known as the tailbone

5 Divisions of the V.C. Cervical Thoracic Lumbar Sacrum Coccyx

C. Spinal Curvatures 1) Thoracic Curvature 2) Sacral Curvature - 1) & 2) are known as Primary or Accommodation curves b/c they appear in fetal development

3) Cervical Curvature 4) Lumbar Curvature - 3) & 4) are known as Compensation curves b/c they develop as we learn to walk (help shift weight over legs)

4 Spinal Curvatures

A. Consists of the thoracic vertebrae, ribs, & sternum IV. The Thoracic Cage A. Consists of the thoracic vertebrae, ribs, & sternum

B. Functions Protects the heart, lungs, thymus & other structures Serves as an attachment point for muscles

C. The Ribs 12 pair of curved, flat bones Originate on or between thoracic vertebrae End in the wall of the thoracic cavity

D. Kinds of Ribs True/Vertebrosternal Ribs a) First 7 pairs, most superior b) Connected to sternum by cartilaginous extensions

False/Vertebrochondral Ribs a) Ribs 8-12 b) The cartilage on the ends of these ribs fuse together with rib 7

3) Floating Ribs a) Last 2 pairs (11th & 12th) b) Not connected to sternum at all

E. The Sternum (breastbone) Flat bone Forms the anterior midline of the thoracic wall

F. Divisions of the Sternum Manubrium a) Most superior part of the sternum b) Triangular shaped c) Articulates w/ the clavicles & the cartilage of the 1st pairs of ribs

Body a) Tongue shaped b) Costal Cartilage from pairs 2-7 attach here

Xiphoid Process a) Most inferior part of sternum b) Smallest part of sternum c) The diaphragm & some abdominal muscles attach here

The Thoracic Cage