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

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

3. Functions of the Skeletal System
Support the body (internal framework)
Protect soft organs (vertebrae)
Allow movement due to attached skeletal muscles
Store minerals and fats (fats, clacium, phosphorus)
Hematopoiesis (Blood cell formation)

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

5. Classification of Bones by Shape
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)
Head
Shaft
Head
Figure 5.1a

6. 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

7. 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

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

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

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

11. Review: Bone is a type of connective tissue 2 Parts: 1. Cells (living)
2. Matrix (nonliving substance released by cells)
A. Fiber
B. Ground Substance

12. 1. Cells 2. Matrix Osteocytes— mature bone cells
Osteoblasts— bone-forming cells (germ cells or “bud” cells)
Osteoclasts —bone-destroying cells (“breakers”)
A. primarily collagen fibers
flexibility
tensile strength (the strength to endure stretching forces)
B. calcium salts (hardness)
contain calcium and phosphorus
great compressional strength (the strength to endure squeezing forces)
2. Matrix

13. Classification of Bone by Tissue Type
Two basic types of Tissue
1. Compact bone
Homogeneous
Looks “smooth”
2. Spongy bone
Small needle-like pieces of bone
Many open spaces
(like sponge)
Keep bones light
Figure 5.2b

14. Microscopic Anatomy of Bone
Figure 5.3a

15. Microscopic Anatomy of Bone
Osteon (Haversian system)
A unit of bone containing central canal and matrix rings
Central (Haversian) canal
Opening in the center of an osteon
Carries blood vessels and nerves
Perforating (Volkman’s) canal
Canal perpendicular to the central canal

16. Microscopic Anatomy of Bone
Lacunae
Cavities containing bone cells (osteocytes)
Arranged in concentric rings
Lamellae
Rings around the central canal
Sites of lacunae

17. Microscopic Anatomy of Bone
Canaliculi
Tiny canals
Radiate from the central canal to lacunae
Form a transport system connecting all bone cells to a nutrient supply

18. Microscopic Anatomy of Bone
Figure 5.3b–c