1. Skeletal System Microanatomy

2. Functions of Bones Support Protection Movement Storage – fat, minerals
Blood cell formation (hematopoiesis)

3. Compact Bone – dense, smooth, homogeneous Spongy Bone – small, needle-like pieces with lots of open space

4. Long bones – longer than wide, shaft with heads at both ends, mostly compact,
Ex. femur, humerus

5. Short bones – cube shaped, mostly spongy,
Ex. bones of wrist and ankle

6. Flat bones – thin, flat, curved, compact bones sandwiching spongy
Ex. bones of skull, ribs, sternum

7. Irregular bones – don’t fit other categories
Ex. vertebrae, hip

8. Diaphysis – shaft, composed of compact bone
Periosteum – membrane of connective tissue that covers diaphysis
Sharpey’s fibers – connective tissue fibers that connects periosteum to diaphysis

9. Epiphyses – ends of the bone, thin layer of compact enclosing an area filled with spongy
Articular cartilage – covers epiphysis, decreases friction between bones
Epiphyseal Plate – growth plate, line of cartilage, (adults have epiphyseal line)

10. Cavity – inside the diaphysis
Adults – yellow marrow (medullary) cavity – stores adipose, red marrow confined to spongy bone of epiphysis and flat bones
Children – red marrow – forms blood cells

11. Projections/processes
Muscle and ligament attachment – tuberosity, crest,
Form joints – head, facet

12. Depressions/cavities – allow blood vessels and nerves to pass
Fossa, sinus, groove, fissure, foramen

13. Osteocytes – mature bone cells

14. Lacunae – tiny cavities arranged in circles called lamellae
Haversian canals – center of lamellae, run lengthwise through bone, carrying blood vessels and nerves
Osteon – complex of the above, many/bone

15. Canaliculi – radiate outward to connect all bone cells to the nutrient supply
Volkmann’s canals – run at right angle to the shaft to connect interior and outside areas of the bone

16. Ossification – formation of bone
In fetus, skeleton composed of cartilage, but it is replaced by bone during development (uses cartilage as model)

17. Osteoblasts – bone-forming cells – covers cartilage with a matrix of bone
Once enclosed, cartilage is digested away, leaving medullary cavity
By birth, most cartilage has been replaced by bone except articular cartilage and epiphyseal plates

18. Appositional growth – bone widens – add bone tissue to the external face and osteoclasts remove bone from inner surface
Controlled by growth hormones and sex hormones (during puberty)

19. Bone remodeling
Necessary in response to calcium levels in the blood and the pull of gravity

20. Simple fracture – bone does not break the skin (closed)
Compound fracture – bone breaks through skin (open)

21. Comminuted – many fragments

22. Compression – crushed

23. Depressed – pressed inwards (typical in skull)

24. Impacted – ends forced into each other (ex. break a fall)

25. Spiral – ragged break from twisting (sports, child abuse)

26. Greenstick – incomplete (more common in children)

27. reduction – realignment of bone

28. Hematoma forms
Break splintered by fibrocartilage callus – a mass of repair tissue, acts to close gaps

29. Bony callus forms – osteoblasts and osteoclasts migrate and work to replace fibrocartilage callus with spongy bone
Bone remodeling