1. Skeletal System Microanatomy

2. Functions of Bones

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

4. Shapes of Bones

5. Types of Bones
Long Bones - longer than wide, shaft with heads at both ends, mostly compact (Ex. femur, humerus)

6. Types of Bones
Short Bones - cube shaped, mostly spongy (ex. bones of the wrist and ankles)

7. Types of Bones
Flat bones – thin, flat, curved, compact bones sandwiching spongy (ex. bones of skull, ribs, sternum)

8. Types of Bones
Irregular bones – don’t fit other categories (ex. vertebrae)

9. Anatomy of a Long Bone Diaphysis – shaft, composed of compact bone
Epiphysis - ends of the bone, thin layer of compact enclosing an area filled with spongy

10. Anatomy of a Long Bone
Periosteum - membrane of connective tissue that covers diaphysis
Sharpey’s fibers - connective tissue fibers that connects periosteum to diaphysis

11. Anatomy of a Long Bone
Articular cartilage - covers epiphysis, decreases friction between bones
Epiphyseal Plate - growth plate, line of cartilage, (adults have epiphyseal line)

12. Anatomy of a Long Bone Medullary/Marrow Cavity – inside the diaphysis
In children, mostly red marrow which forms blood cells
In adults, mostly yellow marrow which stores adipose (red marrow in adults confined to epiphysis and flat bones

13. Surface Markings of Bones
Functions
Sites of attachments for muscles, tendons, and ligaments
Passageways for nerves and blood vessels

14. Surface Markings of Bones
Types
Projections and Processes – protrude out
Processes, tuberosities, crests, condyles, heads, facets

15. Surface Markings of Bones
Types
Depressions and Cavities – sink in,
foramen, fossa, fissure, sinus, sulcus

16. Microanatomy of a Bone
Osteocytes – mature bone cells

17. Microanatomy of a Bone
Lacunae - tiny cavities arranged in circles called lamellae
Haversian canals - center of lamellae, run lengthwise through bone,
Carry blood vessels and nerves
Osteon – complex of the above, many/bone

18. Microanatomy of a Bone
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

19. Ossification – formation of bone
In the fetus, skeleton is composed of cartilage
During development, cartilage is replaced with bone, using the cartilage as a model

20. Ossification – formation of bone
Osteoblasts – bone-forming cells, cover cartilage with a matrix of bone
Osteoclasts – cells that break down (consume) bone

21. Ossification – formation 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

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

23. Ossification – formation of bone
Bone remodeling - Necessary in response to calcium levels in the blood and the pull of gravity
Remember – osteoblasts build, osteoclasts consume/create cavities