1. The adult skeleton has 206 bones
The Skeletal System
NO BONES ABOUT IT!
Did you know?
The adult skeleton has 206 bones

2. Terminology:
Oste “bone” Art “joint” -blast “germ” or embryonic (creating/producing) -clast “broken” (destroying/break down) -cyte “cell” Peri- “around” Dia- “between or across” Epi- “upon” Hemat- “blood”

3. The Skeletal System Parts of the skeletal system Bones (skeleton)
Joints (flexibility)
Cartilages (cushion)
Ligaments (connect bone to bone)

4. Functions of Bones Support the body (internal framework)
Protect soft organs (vertebrae) L
Allow movement due to attached skeletal muscles
Store minerals and fats (fats, calcium, phosphorus)
Hematopoiesis (Blood cell formation)

5. Two subdivisions of the skeleton
2. Appendicular skeleton
(pectoral girdle, pelvic girdle, bones of limbs)
1. Axial skeleton
(skull, ribs, spine)

6. Classification of Bones by Shape

7. Have a shaft with heads at both ends
Long bones
Have a shaft with heads at both ends
Typically longer than they are wide
Contain mostly compact bone
Examples:
Femur (longest bone in the body)
Shaft
Head
Figure 5.1a

8. Anatomy of a Long Bone Diaphysis Epiphysis Compact bone
Protected by periosteum (membrane)
Epiphysis
Ends of the bone
Thin layer of compact bone
But mainly spongy bone in the middle
Protected by articular cartilage

9. Anatomy of a Long Bone Medullary cavity Cavity inside of the diaphysis
Contains yellow marrow
(mostly adipose) in adults
Contains red marrow
(for blood cell formation)
in infants

10. Contain mostly spongy bone
2. Short bones
Generally cube-shape
Contain mostly spongy bone
Example:
Carpals
Tarsals
Figure 5.1b

11. 3. Flat bones Thin, flattened, and usually curved
Two thin layers of compact bone inside
Layer of spongy bone inside
Example:
Skull
Ribs
Sternum

12. 4. Irregular bones Irregular shape
Do not fit into other bone classification categories
Example:
Vertebrae
Hip bones

13. 5. Sesmoid bones
Develop in some tendons where there is considerable friction, tension, and physical stress
Only one found in all normal human skeletons
Example:
Patella