1. The Skeletal System Chapter 6

2. The Skeletal System The skeletal system includes: Bones Cartilages
Joints (articulations)
Ligaments
Other connective tissues

3. The Skeletal System Functions of the Skeletal System Support
Protection
Movement (Leverage)
Storage
__________
Blood cell production

4. The Structure of a Typical Bone
All bones have a combination of spongy & compact bone tissue
Figure 6-3(a)

5. The Histological Features of Spongy Bone
Lamellae (layers) of matrix laid down in __________ -
criss-crossing network of bony tissue
Osteocytes located within lacunae
Canaliculi branch out from lacunae
Many marrow cavities which contain red marrow & small blood vessels

6. The Histological Features of Compact Bone
______________ - basic functional unit of compact bone
Concentric lamellae (layers) of matrix surrounding central (Haversian) canal
Osteocytes located within lacunae
Canaliculi branch out radially from lacunae
_____________ (containing BVs) run vertically down the length of the bone
_________________ (containing BVs) run horizontally across the width

7. Bone Cells
In addition to Osteocytes, the mature bone cells found within the matrix of bone tissue, there are three other cells that are associated with bones
Osteoprogenitor cells
Osteoblasts
Osteoclasts

8. Bone Cells Osteoprogenitor cells Derived from mesenchymal cells
Can undergo mitosis
Mature into osteoblasts

9. Bone Cells Osteoblasts Responsible for osteogenesis –
Mature into osteocytes

10. Bone Cells Osteoclasts Derived from embryological WBCs
Secrete enzymes for osteolysis –
Necessary for:

11. Anatomical Classification of Bones
Bones are classified by their basic shape
Long bones
(e.g. humerus, femur)

12. Anatomical Classification of Bones
Short bones
(e.g. carpals, tarsals)

13. Anatomical Classification of Bones
Flat bones
(e.g. parietal bone)

14. Anatomical Classification of Bones
Irregular bones
(e.g. vertebra)

15. Anatomical Classification of Bones
Sesamoid bones
(e.g. patella)
Not in text

16. The Structure of a Typical Long Bone
diaphysis (compact bone)
Figure 6-2

17. The Structure of a Typical Long Bone
diaphysis
epiphysis (spongy bone)
epiphysis

18. The Structure of a Typical Long Bone
diaphysis
epiphysis
articular cartilage

19. The Structure of a Typical Long Bone
epiphysis
metaphysis – location of
epiphyseal plate – in children
epiphyseal line – in adults
diaphysis
metaphysis
epiphysis
articular cartilage

20. The Structure of a Typical Long Bone
medullary cavity
filled with yellow marrow in adults
lined with endosteum

21. The Structure of a Typical Long Bone
Double layered membrane surrounding bone (except at articular cartilage)
Inner cellular layer contains: _______________
Outer fibrous layer of dense irregular CT for: ________________
periosteum

22. Bone Formation and Growth
Ossification - Process of converting other tissues to bone
Two types of ossification processes occur during embryological formation:
Intramembranous
Endochondral

23. Intramembranous Ossification
Forms flat bones of skull, mandible, clavicle
Replacement of mesenchymal membrane with osseous tissue
Mesenchymal cells differentiate to osteoprogenitor cells, which then become osteoblasts
Osteoblasts create spongy bone tissue, which then remodels into compact bone where necessary
Other mesenchymal cells around the developing bone form the periosteum
Mesenchymal tissue forms
Osteoblasts begin to secrete osteoid forming spongy bone tissue
Blood vessels infiltrate tissue. Calcium salts deposit in osteoid. Periosteum develops

24. Endochondral Ossification
Most bones formed this way
Mesenchyme creates Cartilage model, which gets replaced by bone
Replacement begins in middle (diaphysis) & follows in ends (epiphyses)
Enlarging
chondrocytes within
calcifying matrix
Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies.
Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.
Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center.
The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone.
Cartilage
model
Bone
formation
Epiphysis
Diaphysis
Marrow
cavity
Primary
ossification
center
Blood
vessel
Secondary
Epiphyseal
cartilage
Articular
perichondrium
periosteum
Perichondrium now called periosteum

25. Bone Growth Interstitial growth
Occurs throughout childhood as long as epiphyseal plate cartilage remains
Replacement of cartilage by osseous tissue (ossification) at __________ end of plate; replacement of cartilage cells at _________end of plate
eventually no more cartilagenous growth resulting in epiphyseal line
Appositional growth
Occurs throughout life through activity of cells in periosteum and endosteum
important in repair and remodeling

26. Injury and Repair Fracture - A crack or break in a bone
Steps in fracture repair
Fracture hematoma - bleeding in bone tissue causes a clot; occurs within hours
Callus formation - Mitoses in cells of periosteum, endosteum forms internal & external callus of spongy bone tissue; occurs within few days
Bone remodeling - replacement of spongy bone with compact bone; occurs over months to years

27. Steps in the Repair of a Fracture
Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hematoma, develops.
An internal callus forms as a network of spongy bone unites the inner edges, and an external callus of cartilage and bone stabilizes the outer edges.
The cartilage of the external callus has been replaced by bone, and struts of spongy bone now unite the broken ends. Fragments of dead bone and the areas of bone closest to the break have been removed and replaced.
A swelling initially marks the location of the fracture. Over time, this region will be remodeled, and little evidence of the fracture will remain.
Spongy bone
of internal
callus
Cartilage
of external
callus
Bone
fragments
External
callus
Fracture
hematoma
New
bone
Internal
callus
External
callus
Dead
bone
Periosteum

28. The Skeleton
Figure 6-8(a)

29. An Overview of the Skeleton
There are 206 bones in the adult human body
Skeletal Divisions
Axial skeleton (80 bones)
Skull
Thoracic cage and sternum
Vertebral column
Appendicular skeleton (126 bones)
Upper, lower limbs
Pectoral girdle
Pelvic girdle

30. Bone Markings (Surface Features)
Surface Features of Bones
Table 6-1 (in textbook)

31. Bone Markings (Surface Features)
Depressions/openings:
fossa
foramen (canal)
sulcus(groove)
meatus
Spinous process
Transverse process

32. Bone Markings (Surface Features)
Processes for articulations:
head
condyle
facet

33. Bone Markings (Surface Features)
Spinous process
Transverse process
Lateral epicondyle
Processes for attachment:
Trochanter (only on femur)
tubercle
tuberosity
epicondyle
crest
spine
spinous process (SP) (only on vertebrae)
transverse process (TP) (only on vertebrae)