1. The Skeletal System

2. Functions of Bones support - hard framework that supports organs
protection - cranium, vertebral column, thoracic cage
movement - place for attachment of skeletal muscles by tendons

3. adults - mostly in flat bones
3. storage - fat in marrow, calcium, phosphorus, and other minerals (K, Na, S, Mg, Cu)
4. blood cell formation - hematopoiesis - occurs in red marrow of certain bones
adults - mostly in flat bones
ex: ribs, pelvis, femur (flat and long bones)

4. Bone Classification by Shape and Size
1. long - longer than wide
shaft and 2 ends
ex: humerus, femur, metatarsals

5. 2. short - cube like
ex: carpals, tarsals

6. 3. flat - thin, flat, usually curved
ex: ribs, most cranial, scapula, sternum

7. 4. irregular - no other category describes them
ex: vertebrae, pelvic bones

8. Gross Anatomy of a Long Bone

10. Gross Anatomy of a Long Bone
diaphysis - shaft
epiphysis - end
medullary cavity - canal
periosteum - covering
endosteum - canal lining
articular cartilage - on ends
of bones for smooth movement
marrow - yellow - fat storage
- red - blood cell formation

12. Epiphyseal plate or cartilage is between diaphysis and epiphysis - and is an area of growth.
After growth has stopped (cartilage turned to bone) the epiphyseal line marks the area.

13. osteoclasts - bone destroying cells
The endosteum contains:
osteoclasts - bone destroying cells
osteoblasts - bone forming cells

14. The bone around the diaphysis is compact.
The epiphysis have thin layer of compact inside is spongy.

16. Flat bones are 2 thin plates of compact bone with spongy bone between.
Red marrow is located in spongy area.

17. Histology of Compact Bone

18. Harversion System = Osteon
Lamellae
Haversion Canal
Osteocyte in lacunae

19. osteocyte in lacunae
canaliculi

20. Osteocyte
Lacunae
Canaliculi

21. Histology of Compact Bone
very dense to naked eye
structural unit is Haversian system or osteon
lamellae - concentric rings of hard matrix around a central canal - Haversian canal
osteocytes are between lamella in cavities called lacunae
hair-like canaliculi connect lacunae to each other and Harversian canal allows nutrients, wastes, and gases to travel from blood vessels in Haversian canal to cells = diffusion

23. Spongy Bone Tissue
bone is arranged in trabeculae - partitions in an organ
arranged so stress points are well supported
contain irregular lamellae, osteocytes, and canaliculi
lack Haversian systems
nutrients diffuse through canaliculi from marrow spaces between trabeculae

24. Chemical Composition of Bone
organic - 1/3 of mass
- cells (blast, cytes, clasts)
- organic matrix
- tensile strength
inorganic - 2/3 of mass
- inorganic mineral salts
calcium phosphate
calcium hydroxide
calcium carbonate
- provides hardness
- bone is extremely strong but not brittle

25. If mineral removed, bone is too bendable
If collagen removed, bone is too brittle