The skeletal system includes bones and cartilage that provide structure, allow for movement, and protect organs. The medical specialty of orthopedics focuses on treating the skeleton and joints. Skeletal tissue includes cartilage and bone, which are types of dense connective tissue. Bones have important functions like support, protection, movement, mineral storage, and blood cell production. Bone is made up of osteogenic cells, osteoblasts that form bone, osteocytes embedded in bone matrix, and osteoclasts that resorb bone. There are different types of bones like long bones with a diaphysis, epiphyses, and metaphysis. Bone formation occurs through intramembranous ossification or endochondral ossification. Common bone

1. Skeletal tissue and system

2. Skeletal system
Bones and cartilage
Protect organs
Allow for motion

3. Orthopaedics
(Orthopedics)
Medical specialty for restorative treatment of skeleton
and articulations (joints) and associated connective
tissue

4. Skeletal system tissue
Cartilage
Bone
Dense connective

5. Skeletal system functions
Support
Protection
Movement (along with attached muscle)
Mineral Storage (calcium)
Storage and production of blood cell – red marrow
(hematopoiesis)
Energy storage -yellow marrow

6. Bone tissue cell types

8. Osteogenic (osteoprogenitor) cells
From mesenchyme
Can proliferate (mitosis)
Can differentiate
In periosteum, endosteum and canalicula

9. Osteoblasts
Form bone
Produce & secrete organic (collagenous)
components
Produce & secrete mineral salts (hydroxyapatite;
calcium phosphate, calcium carbonate)
Can no longer divide

10. Osteocytes
Major cell of bone tissue
“Mature” bone cells
Maintain bone
Trapped in their own secretions

11. Osteoclasts
Reabsorb bone (degrade bone)
Critical for remodeling and development and
repair
Located on bone surface

12. Types of bone

13. Long bone structure
Diaphysis – shaft / main portion
Epiphysis – ends
Metaphysis – btwn dia & epiphysis
Cartilage – hyaline for shock
absorption and friction reduction
Periosteum – dense covering of two
layers for growth, repair &
attachments
Elastic fibers and blood vessels
Osteogenic, -clast & -blast cells

14. Long bone structure
Medullary cavity (bone marrow)
Within diaphysis
Yellow bone marrow in adults
Fat and blood cells
Endosteum – lines medulla
Osteoblasts and clasts

15. Compact bone and spongy bone

16. Compact and spongy bone

17. Compact bone characteristics
Little space
Thick in diaphysis
Thin in epiphysis
Protection and support

18. Compact bone structure
Rings of bone material - Osteons
– Contain osteocytes
– Lacunae – space in which osteocytes are trapped
– Canaliculi – connect to lacunae, “little canals” for
nutrient and waste distribution
– Central canals – lead to perforating canals

19. Spongy bone

20. Spongy bone
No true osteons
Trabeculae – irregular thin bone plates
Red marrow between trabeculae
Produces blood cells
Osteocyte containing lacunae within trabeculae

21. Bone Formation
Intramembranous Ossification
Formation of bone within fibrous membranes
Forms flat bones of skull
Endochondral ossification
Most common type of bone formation
Bone forms from cartilage

22. Intramembranous
Ossification

23. Intramembranous
Ossification

24. Endochondral Ossification

25. Endochondral Ossification

26. Endochondral Ossification

31. Bone disorders
Osteoporosis

32. Bone disorders
Osteomalacia (rickets in children)

33. Bone disorders
Osteomyelitis

34. Bone disorders
Osteoarthritis

35. Bone disorders

36. Bone fractures

37. Bone repair

38. Calcium
Homeostasis
PTH
(parathyroid hormone)
Calcitonin